JP2602189Y2 - Injection molding equipment - Google Patents

Description

[Detailed description of the invention]

[0001]

The present invention relates to an injection molding apparatus,
The present invention relates to an injection molding apparatus that can prevent excessive filling or poor filling caused by the compression characteristics of various compressible molding materials such as rubber materials.

[0002]

BACKGROUND OF THE INVENTION Injection molding is a molding material, such as heated and melted plastics or rubber injected and filled into the mold cavity is carried out by taking out the crosslinking after completion formed molded article. This type of injection molding machine includes a plasticizing device that heats and melts a molding material, an injection device that injects a molding material, a mold clamping device that holds a mold, and opens and closes and clamps.
And a control device for automatically controlling the operation of each of these devices.

[0003]

Problems to be Solved by the Invention Rubber and plastic materials used as molding materials have compression characteristics, and the compression characteristics differ depending on the type (material) of the material and the conditions of measurement (weight measurement). I do.

For example, when measuring the weight of a material,
Various conditions such as the screw back pressure, the screw rotation speed, and the preheating temperature of the heating cylinder affect the degassing effect of the material at the stage of material measurement. Therefore, the amount of gas having compression characteristics, such as air and water vapor, included in the material varies depending on these conditions, and the compression characteristics of the entire material also vary.

[0005] Such fluctuations in the compression characteristics of the material affect the injection amount. If the compression characteristics are different even if the injection screw has the same stroke amount, the amount of molding material actually injected will be different. As a result, for example, when the compressibility is high, the injection amount decreases, and insufficient filling occurs. On the contrary, when the compressibility is low, the injection amount increases, and the filling problem (burr leakage) occurs. Had.

However, in the conventional injection molding apparatus,
It was not possible to verify such abnormalities regarding the compression characteristics in advance, and after obtaining a molded product, it was a fact that an abnormality in the molding material was noticed only after performing, for example, an appearance inspection or a functional inspection of the molded product. . For this reason, many defective products are generated, and there has been a demand for the development of an injection molding apparatus that can always achieve a set injection amount even if the compression characteristics are different.

[0007] In the case of a material having a remarkable compression characteristic, such as rubber, in particular, when the injection screw starts to move, the material pressure in the heating cylinder first increases, and then the filling starts.
The time lag from the start of the movement of the injection screw to the start of the filling of the rubber material is large, and the above-mentioned problem has been prominent.

The present invention has been made in view of such problems of the prior art, and can achieve a set injection amount regardless of the compression characteristics of a molding material. The purpose is to prevent occurrence.

[0009]

In order to achieve the above object, the injection molding apparatus of the present invention moves an injection screw (8) of an extruder (3) in a cylinder (11) to form a molten state. In an injection molding apparatus for injecting the material (M),
A position sensor (15) for detecting a movement position of the injection screw, and a pressure value (P) of a molding material in the cylinder.
Pressure sensor (9) for detecting pressure and molding from the cylinder
Installation position of the pressure sensor when material is started to be injected
A reference pressure setting unit (1) for setting a reference pressure value (P ₀ ) in (1), and an injection amount setting unit (2) for inputting the injection amount of the molding material in terms of the travel distance (L) of the injection screw. Determining means (13, 14) for determining whether or not the actual pressure value (P) of the molding material detected by the pressure sensor has reached a reference pressure value (P ₀ ) set in the reference pressure setting section. ) And the actual pressure value (P)
The position of the injection screw when it is determined that has reached the reference pressure value (P ₀ ) is taken from the position sensor, and this position is input to the injection amount setting unit as the origin (L ₀ ) of the filling start. Computing means (17, 18) for operating the injection screw by the moved distance (L) of the injection screw.

[0010]

In the injection molding apparatus of the present invention, the material pressure in the heating cylinder is actually detected in order to compensate for the time lag between the start of the movement of the injection screw and the start of the filling of the molding material.
When a pressure that can be recognized as the start of injection is reached, the movement position of the injection screw at this time is set as the origin of the filling start, and the injection screw is moved by a predetermined movement amount from this origin. That is, regular injection molding is performed by pressing a nozzle of an extruder against an injection port of a molding die, supplying a pressure fluid to an injection pressure cylinder of the extruder, and moving an injection screw at a predetermined pressure in a nozzle direction. Do.

At this time, whether or not the molding material in the cylinder has reached a predetermined reference pressure value is monitored by a pressure sensor, and the position of the injection screw when the molding material reaches the reference pressure value is confirmed by a position sensor. Then, the position of the injection screw confirmed by the position sensor is recognized as the origin of the filling start, and the injection screw is moved by a predetermined movement amount from the origin.

When injection molding a molding material having a remarkable compression characteristic, such as rubber, the material is compressed in the cylinder from the time when the injection screw starts moving until the material is injected from the nozzle. become. This time
In this invention, since the starting point of the filling is based on the actual pressure value of the molding material, the filling amount is different even if the compression characteristics of the molding material are different. Can be controlled to a desired value.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an injection molding apparatus according to one embodiment of the present invention, FIG. 2 is a flowchart illustrating a control procedure of the embodiment, and FIG. 3 illustrates compression characteristics of a molding material in an extruder of the embodiment. FIG.

The injection molding apparatus according to the present embodiment includes a molding die, a mold clamping device for opening and closing the molding die, an extruder 3 for injecting a molding material into the molding die, and supplying the extruder 3. A hydraulic device 6 for controlling hydraulic pressure and oil flow, plasticizing devices 11 and 12 for plasticizing a molding material, and
And a control device 10 for automatically controlling the operation of the extruder 3. In the present invention, the molding die, the mold clamping device, and the plasticizing device have conventionally known configurations and do not cause any trouble. Therefore, detailed drawings thereof are omitted, and only the outline of the configuration will be described.

The molding die includes an upper die and a lower die, and a cavity is formed inside by combining the upper and lower dies. The upper die and the lower die are mounted on a die plate via a heating plate and a heat insulating plate, respectively, and one of the die plates is configured to be able to move toward and away from another die plate. In addition, in order to make the tip of the nozzle 4 of the extruder 3 contact the injection port formed in the upper mold,
The heating plate, the heat insulation plate, and the die plate are formed with through holes for passing the nozzle 4.

The upper and lower die plates are provided so as to be able to move toward and away from each other, and the die is fixed so that the die fixed to the die plate is not pushed open by injection pressure. And is constituted by, for example, a mold clamping cylinder or the like.

The extruder 3 is a device for injecting a molding material from a nozzle 4 into a cavity formed between an upper die and a lower die. An injection screw 8 is inserted therein so as to be movable in the axial direction. And a heating cylinder 11. The heating cylinder 11 is provided with a flow path 12 for flowing a heating medium whose temperature has been adjusted. The molding material introduced into the heating cylinder is heated by the rotation of the injection screw 8 to plasticize the molding material. It constitutes a plasticizing device that maintains the state.

On the other hand, the injection screw 8 moves in the heating cylinder 11 by moving the injection pressure cylinder 7 forward and backward while being rotated by a screw drive hydraulic motor (not shown). The hydraulic device 6 for driving the injection pressure cylinder 7 includes, for example, a variable displacement pump, a direction switching valve for switching the pressure feeding direction of the pressure fluid fed from the variable displacement pump, and a pressure of the pressure fluid at a predetermined pressure. And an electromagnetic relief valve for maintaining the pressure.

A pressure fluid is sent from the hydraulic device 6 to the front and rear of the piston 22 of the injection pressure cylinder 7 via a direction switching valve, whereby the injection screw 8 is driven up and down in the axial direction. An electromagnetic relief valve is mounted between the hydraulic device 6 and the direction switching valve, and is sent from the hydraulic device 6 based on a signal from the injection control device 10 (via a D / A converter or the like). The pressure of the pressure fluid is adjusted.

In FIG. 1, reference numeral 15 denotes a position sensor which detects the position of the injection screw 8 in the axial direction and outputs the detected position to the position monitor 16. The position monitoring unit 16 sequentially outputs the position information of the injection screw 8 to the calculation unit 17 according to the input of the injection molding start signal.

The heating cylinder 11 of the extruder 3 is provided with a pressure sensor 9, which detects the pressure of the molding material in the heating cylinder 11 and outputs this information to the pressure monitoring unit 5. The pressure monitoring unit 5 outputs the pressure of the molding material detected by the pressure sensor 9 to the comparison unit 13. This pressure sensor 9 is preferably provided near the nozzle 4, that is, at the tip of the heating cylinder 11. This is because, when observing the compression behavior of the molding material in the heating cylinder, the material pressure increases from near the tip of the injection screw 8 as shown in FIG. This is because the material pressure in the heating cylinder 11 becomes uniform when filling is started.

The reference pressure setting unit 1 previously inputs the material pressure in the heating cylinder 11 at the start of filling shown in FIG. 3, ie, the reference pressure P ₀ , and compares this value with the comparison unit 13.
Are output sequentially. Further, the injection amount setting unit 2 previously sets an injection amount according to a molding material or a molded product, and sequentially outputs this value to the calculation unit 17. However, in the injection amount setting unit 2 in the present embodiment, each set injection amount is converted into the moving distance L of the injection screw corresponding to the molding material and the volume of the heating cylinder and input.

In the control device 10 according to the present embodiment, the actual pressure value P of the molding material detected by the pressure sensor 9 is
The comparison unit 13 and the determination unit 14 that determine whether or not the reference pressure value P ₀ input to the reference pressure setting unit 1 has been reached.
Are provided, and the comparing section 13 and the judging section 14 constitute judging means of the present invention.

The comparison unit 13 compares the actual pressure value P sequentially input from the pressure sensor 9 via the pressure monitoring unit 5 with the reference pressure value P ₀ sequentially input from the reference pressure setting unit 1. When the actual pressure value P reaches the reference pressure value P ₀ , a signal to that effect is output to the determination unit 14. In the present embodiment, the comparison unit 13 and the determination unit 14 are configured separately, but may be configured by one element.

The control unit 10 is provided with a calculation unit 17. When the determination unit 14 determines that the actual pressure value P has reached the reference pressure value P ₀ , the injection screw 8 at this moment is determined. From the position sensor 15. Then, the injection screw position is recognized as the origin L ₀ start filling takes a moving distance information of the injection screw which is input simultaneously to the injection quantity setting section 2.

Since the moving distance information L of the injection screw input to the injection amount setting section 2 is the moving distance after actually starting the filling, if the actual filling start position is known, the injection amount becomes Should be optimized. In this embodiment, based on such viewpoint, the origin L ₀ start filling that is recognized by the arithmetic unit 17, the origin of the movement distance of the injection screw, which is input to the injection quantity setting section 2. That is, the stop position of the injection screw is obtained by adding the moving distance L input to the injection amount setting unit 2 to the position information L ₀ of the injection screw captured via the position monitoring unit 16.

The start / stop position output unit 18 outputs the injection screw stop position information calculated by the arithmetic unit 17 to the hydraulic device 6 in addition to outputting the injection molding start signal to the hydraulic device 6.

Next, the operation will be described. In the reference pressure setting unit 1 of the control device 10 according to the present embodiment, first, the heating cylinder 11 at the start of filling when a standard molding material is used is used.
Material pressure of the inner, i.e. should enter the reference pressure P ₀ (Step 1). In addition, the injection amount setting unit 2 includes a moving distance L of the injection screw 8 corresponding to the molding material and the item of the molded product.
Is input (step 1).

Next, the molding material M is placed in the heating cylinder 11.
To start injection molding (step 2),
The position information from the position sensor 15 is taken into the position monitor 16, and the information is sequentially output from the position monitor 16 to the arithmetic unit 17 (step 3). Further, the pressure information from the pressure sensor 9 is taken into the pressure monitoring unit 5, and this information is sequentially output from the pressure monitoring unit 5 to the comparison unit 13 (step 4). At this time, the injection screw 8 and the heating cylinder 11
3 is in a state indicated by “A” in FIG. 3, which is a state before being compressed.

While the movement of the injection screw 8 proceeds,
The comparison unit 13 compares the actual pressure P captured from the pressure sensor 9 with the reference pressure P ₀ input to the reference pressure setting unit 1.
Are sequentially compared (step 5). Until the actual pressure P reaches the reference pressure P ₀ , the molding material M in the injection screw 8 and the heating cylinder 11 is in a state indicated by “B” in FIG. It is a state before being ejected from the nozzle 4 though it goes on.

When the injection screw 8 further advances, the pressure P of the molding material in the heating cylinder 11 starts to increase.
When the actual pressure P reaches the reference pressure P ₀ , the comparison unit 13 outputs a signal to that effect to the determination unit 14. The judging unit 14 recognizes that the filling is actually started based on the signal from the comparing unit 13 (step 6), and subsequently calculates a signal indicating that the actual pressure P has reached the reference pressure P ₀ by the calculating unit 17. Output to At this time, the injection screw 8 and the heating cylinder 1
The molding material in 1 is in a state indicated by “C” in FIG. 3 and is in a state in which filling is started against the fluid resistance of the nozzle 4.

The calculating section 17 fetches the position information L ₀ of the injection screw 8 from the position sensor 15 via the position monitoring section 16 (step 7), and at the same time, calculates the moving distance L of the injection screw 8 from the injection amount setting section 2. Capture (step 8). Then, the stop position (= L ₀ + L) of the injection screw 8 is calculated and obtained by adding the position information L of Step 8 to the position information L ₀ recognized in Step 7 (Step 9). It outputs to the stop position output part 18 and further outputs from the start / stop position output part 18 to the hydraulic device 6 (step 10).

The embodiments described above are described to facilitate understanding of the present invention, but not to limit the present invention. Therefore, each element disclosed in the above-described embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

[0034]

The injection molding apparatus according to the present invention recognizes the time point when the filling is actually started from the extruder based on the material pressure in the cylinder, and determines the stop position of the injection screw using this time point as the origin. Therefore, a predetermined injection amount can be filled regardless of the compression characteristics of the molding material. As a result, problems such as overfilling and underfilling can be eliminated, and the occurrence of a large number of defective molded products can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an injection molding apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a processing procedure in the embodiment.

FIG. 3 is a cross-sectional view and a graph illustrating compression characteristics of a molding material in the extruder according to the embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reference pressure setting part 2 ... Injection amount setting part 3 ... Extruder 4 ... Nozzle 5 ... Pressure monitoring part 6 ... Hydraulic device 7 ... Injection pressure cylinder 8 ... Injection screw 9 ... Pressure sensor 10 ... Control device 11 ... Heating cylinder DESCRIPTION OF SYMBOLS 12 ... Flow path 13 ... Comparison part (judgment means) 14 ... Judgment part (judgment means) 15 ... Position sensor 16 ... Position monitoring part 17 ... Calculation part (calculation means) 18 ... Start / stop position output part (calculation means) 22 ... piston M ... molding material P ... origin of the movement distance L ₀ ... start filling pressure value P ₀ ... reference pressure value L ... injection screw of the molding material

Claims (1)

(57) [Scope of request for utility model registration] An injection molding apparatus for moving an injection screw (8) of an extruder (3) in a cylinder (11) to inject a molten molding material (M), wherein a movement position of the injection screw is detected. a position sensor for (15), a pressure sensor (9) for detecting the pressure value (P) of the molding material in the cylinder, said when the molding material is injected starting from the cylinder
Setting the reference pressure value at the installation location of the pressure sensor (P ₀₎
A reference pressure setting unit constant to (1), the injection quantity setting unit that inputs by converting the injection quantity to the moving distance of the injection screw (L) of the molding material and (2), detected by the pressure sensor forming Judging means (13, ₁ ) for judging whether the actual pressure value (P) of the material has reached the reference pressure value (P ₀ ) set in the reference pressure setting section.
4) and taking in the position of the injection screw from the position sensor when the determination means determines that the actual pressure value (P) has reached the reference pressure value (P ₀ ), and starts filling this position. And an operation means (17, 18) for operating the injection screw moving distance (L) inputted to the injection amount setting section as an origin (L ₀ ) of the injection molding apparatus.