JP3047214B2 - Mold clamping force control device for injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a mold clamping force control device used for a mold clamping device of an injection molding machine.

[0002]

2. Description of the Related Art Conventionally, as a mold clamping device of an injection molding machine,
For example, as shown in FIG. 3, there is a toggle-type mold clamping device 20 having a tie bar 22, a movable platen 23, an arm 24, a toggle support 25, and a crosshead 28. By the way, there is a case where it is required to measure a distortion amount of a constituent member for the purpose of, for example, inspecting the characteristics and performance of the mold clamping device. In this case, for example, a strain measurement method may be used in which a strain gauge 31 is attached to the tie bar 22 of the mold clamping device 20 with an adhesive or the like. The strain gauge 31 is a sensor component that detects and outputs the strain amount of the tie bar 22 whose strain amount changes relatively largely. The output signal is a signal representing the magnitude of the distortion amount as, for example, the level of electric resistance.

By the way, regarding a mold clamping device of an injection molding machine,
Techniques for controlling the mold clamping force have been proposed and implemented. The mold clamping force control device needs to detect the mold clamping force when performing feedback control of the mold clamping force by the mold clamping device. As a method of detecting the mold clamping force, for example, the state of the source of the mold clamping force is detected, for example, the hydraulic pressure is detected if the mold clamping force source is a hydraulic circuit, or the torque is detected if the electric motor is an electric motor. There is a method of controlling the mold clamping force according to the magnitude of the detection value. However, these methods have a problem that, in the case of a mold clamping device having a toggle, the toggle efficiency varies depending on the state of the link and the like, so that an accurate mold clamping force cannot be obtained.

[0004]

As a method of detecting a mold clamping force other than the above-described method, for example, the above-described strain gauge is used, the amount of distortion represented by the output signal is converted into the mold clamping force, and the mold clamping force is converted. A detection method is conceivable. However, in practice, the method using the strain gauge is used only for inspection at the time of shipping the mold clamping device, and cannot be practically used for permanent mold clamping force control. That is, in order to perform accurate and precise mold clamping force control in the mold clamping force control device, it is necessary to accurately detect the mold clamping force. The state of attachment,
The durability after pasting greatly affects the detection accuracy. In detail, in the method using a strain gauge, the tie bar strain amount is usually polished, and the tie bar strain amount can be accurately detected on the surface of the tie bar where lubricating oil or the like often adheres. It is difficult to securely attach the strain gauge. In addition, if the state of attachment is not reliable, there is a possibility that an accurate detection cannot be performed due to a positional shift with the passage of time. Further, as a characteristic of the conventional pasting-type strain gauge itself, it is a fact that it is easily affected by external electric noise and its durability is not sufficient.

As another method of detecting a mold clamping force, as shown in FIG. 4, for example, a tie bar 2 fixed to a fixed platen 21 'by a fixing nut 29' is used.
A groove is formed inside the tie bar 22 'at the end of 2', and a mold clamping force sensor 41 is provided in this groove. The output signal is amplified by a charge amplifier 43 connected via a cable 42 to control mold clamping force. There is also a method of outputting to a unit or the like. However, in the method in which the mold clamping force sensor is provided inside the tie bar, it is necessary to machine a relatively thin and deep groove in the tie bar, and it is difficult to mount the mold clamping force sensor in such a place. . Furthermore, this type of clamping force sensor is generally expensive.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a mold clamping force control device for an injection molding machine that can detect a mold clamping force with a simple structure and accurately control the mold clamping force by using the value. It is.

[0007]

According to the present invention, there is provided a metal part fixed by bolts to an outer surface of a component of a mold clamping device, and a sensor attached to the metal part for detecting an amount of distortion of the component. And a strain sensor unit comprising: a mold clamping unit that detects a mold clamping force by converting a strain amount detected by the strain sensor unit into a mold clamping force, and forms a mold by the mold clamping device based on the detected mold clamping force. According to the present invention, there is provided a mold clamping force control device for an injection molding machine, wherein the clamping force is feedback-controlled.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will now be given, with reference to the drawings, of a mold clamping force control device for an injection molding machine according to an embodiment of the present invention.

FIG. 1 is a diagram showing a main mold clamping force control device. In the figure, the same or similar parts as in the conventional example are denoted by the same reference numerals. In FIG. 1, the mold clamping force control device includes a fixed platen 21, a tie bar 22, a movable platen 23, an arm 24, a toggle support 25, a mold clamping servo motor 26, a ball screw 27, a crosshead 28, a strain sensor unit 11, an amplifier 12, a mold clamping force control unit 13, a servo amplifier 14, and an absolute encoder 15, which are applied to a toggle type mold clamping device 20 having have. Although not shown in FIG. 1, an output signal from the absolute encoder 15 is input to a general control unit (not shown) of the mold clamping device. Then, the position of the crosshead 28 (movable platen 23) is obtained from this signal and used for controlling the mold clamping device. However, in the present embodiment, description of control of the mold clamping device using an output signal from the absolute encoder 15 is omitted.

When a mold clamping force is generated by the mold clamping device 20, the upper portion of the movable platen 23, the arm 24, the upper portion of the toggle support 25, and the like are members which are easily elastically deformed and easily distorted. The strain sensor unit 11 is fixed to such a member, which is distorted by the mold clamping force, using a bolt as described later (particularly on the movable platen 23 and on the toggle support 25 in the figure). The provided states are indicated by broken lines). Referring to FIGS. 2A and 2B showing the strain sensor unit 11 in detail, the strain sensor unit 11 outputs a small current having a magnitude corresponding to the amount of strain when the strain sensor unit 11 itself generates a strain. And the sensor part 111 is supported so as to support the sensor part 111 from both sides.
Fitting 1 with holes for bolting to distorted members
12 are provided. Of course, a screw hole for a bolt is formed in a constituent member of the mold clamping device on the side where the strain sensor unit 11 is mounted. The strain sensor section 11 is deformed in accordance with the deformation of the object to be measured, and has a structure such that it is distorted in the same manner as the object to be measured. Sensor part 111 of laminated structure having strain detection sensitivity
have. Therefore, although the amount of change in strain according to the mold clamping force is smaller than that of the tie bar 24, it can be attached to the arm 24 or the like having a flat portion suitable for attaching an article. Note that the output signal of the strain sensor unit 11 may be a signal representing the amount of distortion by the magnitude of the resistance value.
Since the output signal itself from the strain sensor unit 11 is a very small current, it is amplified through the amplifier 12.

The clamping force and the amount of distortion of the above-mentioned distorted member are in a proportional relationship of a predetermined proportional constant. The predetermined proportionality constant is obtained from the material and shape of the member, the results of experiments and simulations performed in advance, and the like. The obtained proportional constant is
It is set in the mold clamping force control unit 13. Mold clamping force controller 1
3 converts the output signal representing the amount of strain from the strain sensor unit 11 amplified by the amplifier 12 into a mold clamping force using a proportional constant. Further, this mold clamping force is used as the actual mold clamping force at that time, an amount to be adjusted of the mold clamping force is calculated according to a predetermined mold clamping force control program, and the drive of the mold clamping servo motor 26 is performed in accordance with the calculated amount. Drive signal indicating the amount is sent to servo amplifier 1
Output to 4. The servo amplifier 14 which has received the drive signal from the mold clamping force control unit 13 converts the drive signal into a predetermined signal form for driving the servo motor, and
Output to The mold clamping servomotor 26 is connected to a shaft (or a nut) of the ball screw portion 27, and the rotational movement of the mold clamping servomotor 26 based on a drive signal from the mold clamping force control device 13 is linear. Is converted to
This linear motion is transmitted to the crosshead 28, and the movable platen 23 is driven by the toggle support 25 and the arm 24 that forms a toggle structure together with the crosshead 28.

Incidentally, the mold clamping force control section 13 may be configured to be included in an injection molding machine control device of the entire injection molding machine (not shown). In this case, comprehensive control of the injection molding machine using various parameters (mold clamping force, injection pressure, time, resin temperature, etc.) in injection molding becomes possible.

When the mold receives the injection pressure, the mold clamping force increases by the amount corresponding to the reaction force. Changes in the mold clamping force during injection molding affect the flow of the resin, and a good product may not be obtained depending on the molded product. On the other hand, in the present invention, the mold clamping force can be controlled to be constant. Further, the mold clamping force during the injection molding can be multi-stage, and the pattern of the mold clamping force according to the molded product can be set.

[0014]

According to the present invention, a mold clamping force control device for an injection molding machine has a strain sensor unit which is fixed to an outer surface of a component of the mold clamping device by a bolt and detects a distortion amount of the component.
The mold clamping force is obtained based on the amount of strain detected by the strain sensor,
Since the mold clamping force is feedback-controlled in accordance with the obtained mold clamping force, the mold clamping force can be detected with high accuracy with a simple structure, and the value can be used to control the mold clamping force.

[Brief description of the drawings]

FIG. 1 is a diagram showing a mold clamping force control device of an injection molding machine according to an embodiment of the present invention.

FIGS. 2A and 2B are diagrams each showing a strain sensor unit shown in FIG. 1;

FIG. 3 is a diagram for explaining a mold clamping force control device of an injection molding machine according to a conventional example.

FIG. 4 is a diagram for explaining a mold clamping force control device of an injection molding machine according to another conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Strain sensor part 12 Amplifier 13 Mold clamping force control part 14 Servo amplifier 15 Absolute encoder 20 Mold clamping device 21, 21 'Fixed platen 22, 22' Tie bar 23 Movable platen 24 Arm 25 Toggle support 26 Servo motor for mold clamping 27 Ball screw part 28 Crosshead 29 'Fixing nut 31 Strain gauge 41 Mold clamping force sensor 42 Cable 43 Charge amplifier 111 Sensor part 112 Metal fitting part

Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) B29C 45/76-45/80 B29C 45/64-45/68 B29C 33/20-33/24 B22D 17 / 26,17 / 32 G01L 1 / 00,1 / 22

Claims (1)

(57) [Claims] 1. A mold and metal parts that will be fixed to the outer surface by a bolt of the components of the clamping device, mounted et the gold tool part
And a sensor portion for detecting a strain amount of the constituent member.The strain sensor portion detects a mold clamping force by converting a strain amount detected by the strain sensor portion into a mold clamping force. A mold clamping force control device for an injection molding machine, wherein the mold clamping force by the mold clamping device is feedback-controlled based on the detected mold clamping force.