JPH0464493B2 - - Google Patents

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 inside of the heating cylinder, and a screw drive unit that controls the rotation and movement of the screw. In the metering process, the screw is rotated to accumulate molten resin material in front of the screw, and in the injection process, the screw is moved forward to inject and fill the mold.

The screw drive unit built into a conventional injection device adopts a configuration in which one system of a rotation control system or a forward/backward 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, by moving the rotation control system itself forward and backward using the forward and backward control system, the screw can be controlled to move forward and backward.

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, quickness, 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 existing 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
has a cylindrical outer shaft 2 arranged coaxially in the main part,
An inner shaft 3 is rotatably inserted into the outer shaft 2. 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. Also,
The inner shaft 3 is rotated by the second motor 7, and also rotates the screw 6. 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.

[Function] Next, the function of the injection device 1 according to the present invention will be explained.

In the injection device 1 according to the present invention, the advance/retreat control system and the rotation control system of the screw 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 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, due to the rotation of the second motor 7, the inner shaft 3
, and further rotate the screw 6.
That is, it can mainly be used for weighing.

〔Example〕

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

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

Reference numeral 11 denotes a heating cylinder, which is equipped with an injection nozzle 12 at its front end and a hopper 13 for supplying molding material into the heating cylinder 11 at its rear upper end. 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 horizontally at the rear. The tie bars 15 are equipped with a sliding member 16 that can be slid forward and backward, and inside this sliding member 16 is a bearing pressing member 16 that applies pressure to the bearing and also functions as a retainer for the bearing.
A is inserted into the member 16a, and the member 16a is further provided with a rotatable coupling member 17 via a radial bearing and a thrust bearing. A ring-shaped load cell 18 is interposed between the rear end surface of the thrust bearing and the sliding member 16. On the other hand, the coupling member 17
The rear end of the screw 6 is connected to the front end of the screw 6. Also,
An inner shaft 3 extending rearward is coupled to the rear end of the coupling member 17. It is inserted into a cylindrical outer shaft 2 which is rotatable internally, and a ball screw mechanism 5 for injection is interposed between the outer periphery of the outer shaft 2 and the sliding member 16. Note that this ball screw mechanism 5 includes a ball screw shaft 5a using the outer peripheral surface of the outer shaft 2 and a sliding member 16.
It consists of a ball screw nut 5b connected to the rear end of. Further, 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 to a drive gear 2 attached to a screw rotation servo motor 27 (second motor 7) via a timing belt 26.
Connect to 8.

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

First, due to the forward rotation of the servo motor 27, the rotational force of the motor 27 is transferred from the drive gear 28 to the driven gear 2.
5 → spline mechanism 24 → inner shaft 3 → coupling member 17
→Transmitted through the route of Screw 6. Therefore, the screw 6 rotates forward and the molten resin material can be measured. Note that by rotating the servo motor 27 in the reverse direction, the screw 6 can be rotated in the reverse direction along the same path.

On the other hand, due to the forward rotation of the servo motor 22, the rotational force of the motor 22 is transferred from the drive gear 23 to the driven gear 2.
0 → Outer shaft 2 → Ball screw mechanism 5 → Sliding member 16 →
The signal is transmitted along the path of the coupling member 17. Therefore, the screw 6 moves forward, and the measured amount of molten resin material can be injected and filled into the mold. Note that if the servo motor 22 is rotated in the opposite direction, the screw 6 will be rotated in the same way.
can be set back.

FIGS. 2 to 4 clearly show a structure that embodies the main parts of the injection device 1 (FIG. 1). In addition, Fig. 2 is a vertical cross-sectional view clearly showing the rotation control system of the screw in the injection device, Fig. 3 is a longitudinal cross-sectional view clearly showing the vicinity of the motor of the screw advance/retreat control system in the moving device, and Fig. 4 is a partial view. It is a broken view taken along the line A--A in FIG. 3, and the same parts as in FIG. 1 are given the same reference numerals to clarify the structure.

Next, an example of the operation of the injection device 1 will be described 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 to perform weighing.

On the other hand, when the metering process is completed, the process moves to the injection process. In the injection process, an injection speed command signal based on an injection command signal from the central control unit 32 and a setting value set by the injection speed setter 34 is sent to the servo motor 22 based on the completion of closing of the mold (not shown).
is given to the control circuit 36 that controls the. As a result, the servo motor 22 rotates to advance the screw 6, and at the same time, a detection signal from the tachometer generator 38 that detects the speed of the motor connected to the motor 22 is applied to the control circuit 36, which matches the injection speed command signal. Closed-loop control is performed to ensure that

By the way, at this time, the setting signal set in the screw reverse rotation speed setting device 39 is transmitted to the control circuit 33.
is applied, 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 sent to the control circuit 33.
and performs closed-rose control 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, thereby 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 control signal for each servo motor 22, 27 is turned OFF, and the entire injection process is 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 can be obtained.

The rotation control system and advance/retreat control system of the screw can be constructed as independent systems, and one system does not include the motor of the other system as in the conventional system (two-motor system). As a result,
Not only can each system be quantized, but the inertia can be significantly reduced, resulting in improved responsiveness, quickness, stability, and
Improved accuracy and reproducibility can be achieved.

The drive unit can be simplified, and the entire injection device can be made smaller and lower in cost.

[Brief explanation of drawings]

Fig. 1: A vertical side view showing the basic configuration of the injection device according to the present invention, Fig. 2: A longitudinal side view showing the rotation control system of the screw embodying the injection device according to the present invention, Fig. 3: The same Vertical side view clearly showing the vicinity of the motor of the advance/retreat control system of the screw in the device, No. 4
Figure: A partially cutaway view in the direction of A-A in Figure 3,
FIG. 5: A block circuit diagram showing only the main parts of the overall control system in the same device. In the drawing, 1: injection device, 2: outer shaft, 3: inner shaft, 4: first motor, 5: ball screw mechanism,
6: Screw, 7: Second motor.

Claims (1)

[Scope of Claims] 1. A cylindrical outer shaft that is rotated by a first motor and moves the screw forward and backward via a ball screw mechanism provided on the outer periphery; An injection device for an injection molding machine, comprising an inner shaft rotatably inserted into the screw to rotate the 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.