JP2002337187A - Injection molding device and injection molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection molding device which prevents a failure such as stringing from generating by inhibiting an increase in the temperature of a valved gate part in the injection molding device, and thereby manufactures a molded product with a highly qualitative appearance, and an injection molding method. SOLUTION: The injection molding device is provided with a nozzle cooling means 7 such as an air hose 71 or an oil hose 72 which guides a compressed gas or a part of an oil as a medium for activating the opening/closing of a valve pin 11 in response to a timely action to supply a molten resin into a cavity 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding apparatus and an injection molding method for performing injection molding without troubles such as stringing by cooling a tip of a nozzle for injecting a molten resin.

[0002]

2. Description of the Related Art A conventional hot runner type injection molding apparatus 1 'is shown in FIG. The injection molding apparatus 1 'includes a mold and a mold clamping device, an injection device, a drive source, and a control device. The injection resin (a hopper, an injection plunger, etc.) supplied with a molten resin supplied from a primary sprue 14, hot Runner block 9
Through the runner 10 to the gate in a molten state,
The molten resin is injected into the cavity according to the opening and closing of the gate. As the gate opening / closing method, there is a heating control method using a spear tip extending into the gate or a valve gate method for mechanically opening / closing the gate. In the injection molding apparatus 1 ′ shown in FIG. 7, the valve gate method is used. Has been adopted. When a predetermined amount of the molten resin is injected, the valve pin 11 is set at an appropriate timing during the injection or after the completion of the pressure holding process.
Closes the valve gate 4 and a molded product is obtained after cooling.

Incidentally, the nozzle diameter of the valve gate 4 is:
8 is smaller than the nozzle diameter of the general portion of the flow path 6 of the nozzle.
As shown in the figure, the nozzle diameter in the AA cross section (the flow path 6 of the nozzle)
Nozzle diameter) is about 5mm to 18mm,
The nozzle diameter in the BB section (nozzle diameter of the valve gate portion 4) is about 2 mm to 7 mm. The reason why the tip of the flow path 6 of the nozzle is relatively thinner than the other parts is that the operating force for opening and closing the valve gate 4 is reduced, the size of the gate nozzle 61 is reduced, and the gate mark is reduced. This is for making it less noticeable.

[0004]

However, if the cross-sectional area at the tip of the flow path 6 of the nozzle is smaller than the cross-sectional area of the general portion of the flow path 6 of the nozzle, the molten resin passes through the narrowed portion of the flow path. At times, the pressure rises, and accordingly, the temperature near the valve gate 4 rises excessively. In particular, when molding a large molded product such as a bumper, the injection time of the resin becomes longer, so that the temperature near the valve gate 4 becomes even higher. When the mold is opened with the temperature in the vicinity of the valve gate 4 being high as described above, a stringing phenomenon occurs between the molded product and the gate chip 5, and if this yarn adheres to the molded product, the appearance quality of the product is deteriorated. There was a problem of inviting. Although it is conceivable to increase the contact area between the gate chip 5 and the fixed mold 22 or to lengthen the mold cooling time in order to suppress the temperature rise, in the former case, the gate chip at the time of injection is required. Since the temperature rise of 5 is insufficient, the resin is solidified in the gate chip 5, and this cold slag may be mixed into the molded product and deteriorate the appearance quality of the product. In the latter case, the cooling time is prolonged, resulting in a decrease in production efficiency. The present invention has been made in view of such problems of the related art, and by cooling the tip of a nozzle for injecting a molten resin, stringing,
An object of the present invention is to provide an injection molding apparatus and an injection molding method that can prevent a cold slag defect or the like.

[0005]

According to the first aspect of the present invention, a molten resin is injected into a cavity formed by a relatively close mold. A nozzle that guides the molten resin to the tip of the nozzle, a valve pin that is inserted into the nozzle and opens and closes the tip of the nozzle by reciprocating motion along the insertion direction, and an opening / closing operating medium for opening and closing the valve pin And a nozzle cooling means for guiding a part of the nozzle to the tip of the nozzle. In the present invention, although not particularly limited, it is preferable that the opening / closing operating medium is a driving fluid for driving the valve pin (claim 2).

The present inventor has focused on the fact that the timing of the temperature rise at the tip of the nozzle of the injection molding apparatus depends on the timing at which the molten resin is supplied to the cavity (ie, the opening and closing timing of the valve pin). Nozzle cooling means for guiding a part of the medium to the nozzle tip is provided. In the present invention, the driving fluid for driving the valve pin is a power medium for supplying energy for reciprocating the valve pin, and specifically refers to compressed air, oil or other fluid.

According to the present invention, the heat generated at the nozzle tip can be absorbed by a part of the opening / closing operating medium of the valve pin guided to the nozzle tip by the nozzle cooling means, and the temperature rise can be suppressed. Furthermore, since the tip of the nozzle is cooled using the opening / closing operation medium, the opening / closing of the tip of the nozzle and the cooling of the tip of the nozzle can be performed by one system (supply of the opening / closing operation medium). The tip of the nozzle can be cooled accordingly. By cooling the tip of the nozzle in this way, there is no possibility of causing troubles such as stringing at the time of opening the mold, and it is possible to provide an injection molding apparatus for producing a resin molded product having high appearance quality.

(2) In order to achieve the above object, according to the third aspect of the present invention, although not particularly limited, the tip of the nozzle is synchronized with the supply timing of the opening / closing operating medium for driving the valve pin. And an injection molding apparatus for supplying the opening / closing working medium to the injection molding apparatus. In order to achieve the above object, according to the fifth aspect of the present invention, a molten resin is fed through a flow path and a predetermined amount of molten resin is melted toward a cavity formed by a relatively close mold. Injecting resin through a nozzle, synchronizing with the timing of the start of the injection, feeding the cooling medium to the tip of the nozzle, synchronizing with the timing of ending the injection, and stopping the feeding of the cooling medium. A molding method is provided. Regarding the invention of claim 5, although not particularly limited,
The cooling medium is preferably a fluid that opens and closes the tip of the nozzle (claim 6).

In the present invention, the opening and closing operation medium is supplied such that the driving of the valve pin and the supply of the opening and closing operation medium (cooling medium) to the nozzle tip are synchronized. Accordingly, the nozzle tip can be cooled in accordance with the timing of injection of the molten resin, that is, the timing at which the temperature of the nozzle tip rises.

The term "synchronous" in the present invention does not mean a narrow meaning of substantially the same timing with respect to a certain timing, but also refers to a second timing (time) having a predetermined relationship with the first timing (time). In a broad sense, including. Therefore, in the present invention, the opening / closing operating medium may be supplied to the tip of the nozzle substantially simultaneously with the supply timing of the opening / closing operating medium for driving the valve pin, or the opening / closing operating medium may be supplied to the tip of the nozzle before or after a predetermined time. May be supplied. In addition, the first timing referred to here can be arbitrarily determined. For example, any one of a time when the valve pin starts to be opened (a time when the supply of the molten resin starts), a time when the valve pin is opened to some extent, and a time when the valve pin is fully opened, and the like. Timing.

The timing and degree of the temperature rise at the nozzle tip may vary depending on physical properties such as the temperature or viscosity of the molten resin to be injected or various conditions such as injection pressure or injection time. In such a case, it is preferable to measure the timing of temperature rise for each supplied resin in advance, and to match the injection timing of the molten resin with the cooling timing of the nozzle tip.

Thus, the timing of injection of the molten resin,
That is, since the opening / closing operating medium can be supplied to the nozzle tip in accordance with the timing of the temperature rise at the nozzle tip, poor threading at the time of opening the mold, or poor cold slag that solidifies and mixes into the molded product before injection. It is possible to provide an injection molding apparatus and an injection molding method for producing a resin molded product having high appearance quality without the risk of occurrence of the like.

(3) According to the fourth aspect of the present invention, there is provided an injection molding apparatus in which a pipe of the nozzle cooling means is disposed outside the apparatus. Since the inside of the apparatus is provided with a flow path for guiding the molten resin to the cavity, there are high temperature parts. On the other hand, it is preferable that the open / close operating medium has a low temperature in order to efficiently absorb the heat at the nozzle tip. In this invention, since the pipe of the nozzle cooling means is arranged outside the apparatus so as not to be affected by the heat inside the apparatus, the temperature of the open / close operating medium guided to the nozzle tip is kept low, and the nozzle tip is efficiently cooled. Thus, an injection molding apparatus having the same effects as the above invention can be provided.

[0014]

According to the first to sixth aspects of the present invention, the opening / closing operating medium can be supplied to the nozzle tip in synchronization with the timing of injection of the molten resin, that is, the timing of temperature rise at the tip of the nozzle. Provided are an injection molding apparatus and an injection molding method for producing a resin molded product having a high appearance quality without the risk of poor stringing or cold slag defect mixed in the molded product before injection. Can be.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 to 4 are views for explaining the first to fourth embodiments of the injection molding apparatus 1 of the present invention. The injection molding apparatus 1 according to these embodiments includes a hopper, an injection cylinder, a plunger, a nozzle, and the like having functions of plasticizing, measuring, and injecting a resin, and FIGS. 1 to 4 illustrate a gate nozzle having an injection function. Reference numeral 61 is mainly shown, and a basic configuration common to the first to fourth embodiments will be described in the first embodiment.

First, an overall configuration of an injection molding apparatus 1 according to a first embodiment will be described with reference to FIG. The injection molding apparatus 1 according to the present embodiment includes a runner 10 that guides at least molten resin, a gate nozzle 61 that communicates with the runner 10, and a fixed mold 2 in which the gate nozzle 61 is fitted.
2 and a movable mold 21 that forms a cavity 3 in a pair with the fixed mold 22, and further has an air hose 71 provided alongside the gate nozzle 61.

By closing the pair of the movable mold 21 and the fixed mold 22, a hermetically sealable cavity 3 is formed therebetween. In this example, a rigid injection molding apparatus 1
Since the fixed mold 22 in which the gate nozzle 61 is fitted is fixed, the movable mold 21 is moved up and down with respect to the fixed mold 22 by a mold clamping device (not shown). Of course, the molding die 2 may be a horizontal type, and the fixed die 22 may be replaced with the movable die 2.
1 may be moved. Incidentally, although the cavity 3 shown in FIG. 1 is plate-shaped, it is actually shaped according to the shape of a molded product such as an automobile body.

A plurality of valve gates 4 are formed in the fixed mold 22 that forms the cavity 3, and the cavity 3 is filled with molten resin supplied from a hopper, a heating cylinder and the like (not shown) through the fixed gate 22. It is the primary sprue 14 and the runner 10 provided inside the hot runner block 9 that guide the molten resin to the valve gate 4. The runner 10 communicates with the flow path 6 of the nozzle and feeds an amount of resin necessary for injection.

The gate nozzle 61 for injecting the molten resin is
The valve gate 4 at the tip is buried in a fixed form with the valve gate 4 facing the opening of the cavity 3, and a nozzle channel 6 is disposed at the center of the fixed gate nozzle 61, and the nozzle flow is A valve pin 11 is inserted into the center of the passage 6. The valve pin 11 opens and closes the valve gate 4 by reciprocating, and the valve pin 11 is driven by compressed air sent from the cylinder 13 under the control of the opening and closing work medium supply controller. Here, the opening / closing operation of the valve gate 4 will be described. When the compressed air is sent from the path a, the cylinder 13 moves downward (the direction in which the valve pin 11 is moved away from the valve gate 4).
And the valve gate 4 is opened. On the other hand, when the compressed air is sent from the path b, the cylinder 13 moves upward (in a direction in which the valve pin 11 approaches the valve gate 4) and closes the valve gate 4. The cylinder 13
As the driving fluid for driving the motor, not only compressed air but also compressed gas or oil can be used, and these are supplied from supply means (not shown).

Next, the air hose 71 (nozzle cooling means 7) particularly provided in the present embodiment will be described. FIG.
As shown in FIG. 5, the tip of the flow path 6 of the nozzle surrounded by the gate chip 5 is formed to be thinner than a general part. For this reason, when the molten resin passes through the narrow portion of the flow path 6 of the nozzle during injection, the pressure at the tip of the flow path 6 of the nozzle rapidly rises, and the temperature of the valve gate 4 and the gate chip 5 becomes excessive. To rise. In this embodiment, the valve gate 4
An air hose 71 (nozzle cooling means 7) for cooling the vicinity is arranged along the gate nozzle 61. This air hose 7
1 (nozzle cooling means 7) has a tubular supply path and supplies compressed air or other compressed gas. One end of the air hose 71 is connected to the cylinder 13, and the other end is open near the valve gate 4. With such a configuration, a part of the driving medium such as the compressed air sent from the cylinder 13 is guided to the air hose 71 and is sprayed on the gate chip 5.

The drive fluid as a cooling medium guided by the air hose 71 is a part of the drive fluid serving as an opening / closing operation medium of the valve pin 11. Therefore, the opening and closing of the valve pin 11 and the cooling of the valve gate 4 are controlled by a single system of supplying or stopping the supply of the driving fluid (compressed air or oil) by the opening and closing operation medium supply controller.

The injection molding apparatus 1 of the present invention can be modified as follows. The second to fourth embodiments relate to the injection molding apparatus 1 provided with the nozzle cooling means 7 corresponding to various driving media. The second embodiment shown in FIG. 2 is an injection molding apparatus 1 in a case where the driving fluid is oil.
Is shown. The main configuration is the same as that of the first embodiment shown in FIG. 1, except that an oil hose 72 communicating between the cylinder 13 and the valve gate 4 is provided. With the use of the driving fluid as oil, a sealing for preventing oil leakage is provided at each joint, and a circulation path for circulating the oil is provided to collect the oil to the drain port.

FIG. 3 shows a third embodiment, and FIG.
Has been shown. These basic configurations are common to the first and second embodiments described above. The difference is that the nozzle cooling means 7 (air hose 71, oil hose 72) for supplying the driving fluid to the valve gate 4 is arranged outside the apparatus. The third embodiment shown in FIG. 3 is an example in which the driving fluid is compressed air, and the fourth embodiment shown in FIG. 4 is an example in which the driving fluid is oil. In the fourth embodiment shown in FIG. 4, an oil hose 72 is arranged so as to surround the periphery of the valve gate 4 when the driving fluid is oil, and the oil hose 72 is in contact with the valve gate 4. The configuration is such that heat of the nozzle tip 6 is absorbed. Further, a circulation path for circulating the oil is provided to collect the oil to the drain port. In this example, the tube portion of the nozzle cooling means 7 is disposed outside the apparatus so as not to be affected by the heat inside the apparatus. This is because it is preferable that the temperature of the driving fluid blown to the valve gate 4 is low, so that the driving fluid is prevented from passing near the hot runner block 9, the runner 10, and the like heated by the molten resin.

FIG. 5 shows a fifth embodiment. In this example, the driving fluid supplied to the valve gate 4 and the driving fluid for driving the valve pin 11 are compressed air, and both are supplied from a main compressor (not shown). The supplied compressed air is branched into two paths and the valve gate 4
A relief valve for supplying compressed air for cooling the valve gate 4 after securing the pressure of the compressed air for operating the valve pin 11 to a predetermined value or more is provided on the circuit side for cooling the valve pin 11.

Next, the operation will be described. here,
The operation of the nozzle cooling means 7 (air hose 71, oil hose 72) particularly provided in the present embodiment will be mainly described. As described above, since the distal end of the flow path 6 of the nozzle is reduced in diameter, the temperature near the valve gate 4 increases due to a rise in pressure at the distal end of the flow path 6 of the nozzle during injection. Air hose 71 and oil hose 7 as nozzle cooling means 7
2 guides compressed air or oil, which is a driving fluid, to the valve gate 4 at the timing of effectively cooling this portion.

In this embodiment, the cooling of the valve gate 4 is performed in synchronization with the driving of the valve pin 11. In this embodiment, the cooling is performed based on the time when the valve pin 11 is opened (when the molten resin is injected). The valve gate 4 is cooled in synchronization with the timing, that is, at a timing having a predetermined relationship with the timing. For example, the cooling of the valve gate 4 may be started at the same time as the timing when the valve pin 11 is opened, or the cooling of the valve gate 4 may be started before or after a predetermined time has passed since the valve pin 11 was opened. The compressed air or oil guided under such control deprives the gate chip 5, the gate nozzle 61, and the like of heat at the timing when the temperature rises,
The vicinity of the valve gate 4 is cooled.

In this embodiment, when the valve gate 4 is closed, cooling is not performed, but the injection of the molten resin is started, and the valve gate 4 is cooled at the timing when the temperature of the valve gate 4 rises. I made it. This is because in the molding according to the present embodiment, the temperature rise has not yet started at the time when the valve gate 4 is closed, so if the valve gate 4 is cooled at this time, the flow path of the nozzle 6 This is because cold slag in which the resin at the tip portion is partially solidified is mixed into the molded product. Therefore, in this example, the driving of the valve pin 11 and the supply of compressed air or oil to the tip of the flow path 6 of the nozzle are performed simultaneously, that is, only when the valve pin 11 is open, the compressed air (or (Oil) for cooling. However, since the timing at which the temperature at the tip of the flow path 6 of the nozzle rises differs depending on the physical properties of the molten resin, the temperature, the difference in the molding method, and the like, it is preferable that the synchronized cooling timing be considered separately.

An example of the timing control of the cooling of the valve gate 4 will be specifically described with reference to FIG. FIG. 6A shows a state in which the valve pin 11 closes the valve gate 4 and the valve gate 4 is fully closed (before the start of injection).
FIG. 6B shows a state in which the valve pin 11 has retreated slightly and the valve gate 4 has begun to open (immediately after the start of injection). FIG.
(C), the valve pin 11 retreats from the valve gate 4,
The valve gate 4 is fully open (during injection).
When the valve gate 4 is fully closed (FIG. 6A) and when the valve gate 4 is partially opened (FIG. 6B), the supply of compressed air (or oil) has not been started. The cooling of the valve gate 4 has not been started. On the other hand, when the valve gate 4 is fully opened (FIG. 6C), the supply of the compressed air (or oil) from the air hose 71 is started, and the cooling of the valve gate 4 is started.

The temperature rise at the tip of the flow path 6 of the nozzle is as follows:
The timing of the temperature rise and the degree of the temperature rise vary depending on physical properties such as the temperature or viscosity of the molten resin to be injected or conditions such as the injection pressure or the injection time. It is preferable to measure and match the injection timing of the molten resin with the cooling timing of the tip of the flow path 6 of the nozzle.

As a result, in the present embodiment, only the vicinity of the valve gate 4 is cooled at the time when the temperature rises, the temperature of the valve gate 4 is appropriately maintained, and poor threading at the time of opening the mold, defective cold slag, etc. It is possible to provide an injection molding apparatus for producing a resin molded product having a high appearance quality without the risk of occurrence of the resin molding.

The embodiments described above are described for the purpose of facilitating the understanding of the present invention, and are not described for limiting the present invention. Therefore, each element and each numerical value disclosed in the above embodiment are intended to include all design changes and equivalents belonging to the technical scope of the present invention.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a first embodiment of an injection molding apparatus.

FIG. 2 is a diagram illustrating a second embodiment of the injection molding device.

FIG. 3 is a diagram illustrating a third embodiment of the injection molding apparatus.

FIG. 4 is a diagram illustrating a fourth embodiment of the injection molding apparatus.

FIG. 5 is a diagram illustrating a fifth embodiment of the injection molding apparatus.

FIG. 6 is a diagram illustrating an embodiment of the operation of the injection molding apparatus. 6A shows a state in which the valve gate 4 is fully closed, FIG. 6B shows a state in which the valve gate 4 has begun to open, and FIG. 6C shows a state in which the valve gate 4 is fully opened. Indicates the status.

FIG. 7 is a view showing a conventional injection molding apparatus.

FIG. 8 is a diagram showing a difference in nozzle diameter of a conventional injection molding apparatus.

[Explanation of symbols]

 1, 1 '... injection molding apparatus 2 ... mold 21 ... movable mold 22 ... fixed mold 3 ... cavity 4 ... valve gate 5 ... gate chip 6 ... nosle flow path 61 ... gate nozzle 7 ... nozzle cooling means 71 ... air hose (nozzle Cooling means) 72 Oil hose (nozzle cooling means) 8 Heater 9 Hot runner block 10 Runner 11 Bubble pin 12 Bubble pin bush 13 Cylinder 14 Primary sprue

Claims (6)

[Claims] 1. A nozzle for injecting a molten resin toward a cavity formed by a relatively close mold, a flow path for guiding the molten resin to a tip of the nozzle, and a nozzle inserted into the nozzle. An injection molding apparatus comprising: a valve pin that opens and closes the tip of the nozzle by reciprocating movement along an insertion direction; and a nozzle cooling unit that guides a part of the opening and closing operation medium of the valve pin to the tip of the nozzle. 2. The injection molding apparatus according to claim 1, wherein said opening / closing operating medium is a driving fluid for driving said valve pin. 3. The injection molding apparatus according to claim 1, wherein the opening / closing operation medium is supplied to a tip of the nozzle in synchronization with a supply timing of the opening / closing operation medium for driving the valve pin. 4. The injection molding apparatus according to claim 1, wherein the tube of the nozzle cooling means is disposed outside the apparatus. 5. A molten resin is fed through a flow path, and a predetermined amount of the molten resin is injected through a nozzle toward the inside of a cavity formed by a relatively close molding die. An injection molding method in which a cooling medium is fed to the tip of the nozzle in synchronization with the injection of the cooling medium, and the feeding of the cooling medium is stopped in synchronization with the end timing of the injection. 6. The injection molding method according to claim 5, wherein the cooling medium is a fluid for opening and closing the tip of the nozzle.