JP3288147B2 - Nozzle for injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nozzle for injecting a molten molding resin material in a heating cylinder of an injection molding machine into a cavity of a mold, and more particularly to a nozzle caused by heating of a molding resin material flow path. The present invention relates to an improved nozzle for an injection molding machine that can prevent resin burn by a simplified structure.

[0002]

2. Description of the Related Art When molding a resin material using an injection molding machine, the resin material is supplied into a heating cylinder of the injection molding machine, and the measured and melted resin material is supplied to a nozzle attached to the heating cylinder. , The resin material in the mold is cooled and solidified, and then the mold is opened to remove the molded product.

Around the nozzle, there are provided heating means provided with a heater for maintaining the molten state of the resin material and temperature detecting means for maintaining a constant temperature in the resin flow path inside the nozzle. FIG. 1 shows a cross-sectional structure of a nozzle having such a known heating / heating mechanism.

In FIG. 1, a nozzle indicated by reference numeral 1 is a base 2 attached to a heating cylinder (not shown).
A resin flow path 4 is formed by a thick cylindrical body portion 3 extending forward from the front, and a discharge port 5 is provided at the tip of the resin flow path 4 to be in contact with a sprue portion of a mold (not shown).
In order to keep the molten resin material flowing in the resin flow path 4 at a high temperature,
A heating means 6 composed of a nozzle heater is mounted over the entire circumference of substantially the entire length of the body 3. Reference numeral 7 denotes a thermocouple for detecting the resin temperature of the body 3, and reference numeral 8 denotes a cable including a signal line for extracting an output signal of the thermocouple 7. Reference numeral 9 denotes a lead wire for supplying heating power to the nozzle heater 6, which is connected to a heating control device (not shown) together with the cable 8, and supplies heating power controlled to maintain the resin temperature at a set temperature. Used to supply to nozzle heaters.

[0005] By using the nozzle having the above structure, the temperature control of the molten resin material flowing in the resin flow path 4 can be achieved for the time being, but the resin temperature in the flow path is controlled over the entire length of the nozzle. There is a problem that it is difficult to keep it uniform.

That is, the portion near the discharge port 5 at the tip of the nozzle originally has a large heat radiation surface area, and when the peripheral portion of the discharge port comes into contact with the mold, heat is directed toward the relatively low temperature mold. The phenomenon that escapes occurs. Therefore, when controlling the temperature of the molten resin, the heating temperature is set in consideration of this point in order to maintain the fluidity of the molten resin.

However, when the temperature is detected using the thermocouple 7 near the nozzle tip and power is supplied to the heating means (heater) 6 so as to keep the resin temperature at the optimum set temperature, the temperature is close to the nozzle base 2. In the portion (the portion indicated by A in the figure), the heat is too small and the heat is too small, so that the heating tends to be excessive and the resin temperature greatly exceeds the set temperature (for example, the setting of 10 to several tens of degrees Celsius) Over temperature).

Therefore, in a nozzle having a structure as shown in FIG. 1 (hereinafter referred to as a conventional nozzle structure), deterioration of resin quality due to so-called “resin burning” occurs in the portion A near the nozzle base 2. In addition, there is a risk that the molded product may suffer from a phenomenon of burning, mixing of carbides, and deterioration of quality such as silver.

As a solution to the above drawback, a nozzle structure as shown in FIG. 2 has been proposed. In FIG. 2, portions common to FIG. 1 are denoted by common reference numerals, and a nozzle 1 forms a resin flow path 4 by a thick cylindrical body 3 extending from a base 2, and has a discharge port at its tip. The point where the outlet 5 is provided is not different from the structure shown in FIG. The feature of the nozzle structure shown in FIG. 2 lies in the arrangement of the heating means and the temperature detecting means, and the heating means (heaters) 6a and 6b and the temperature detecting means (thermocouples) 7a and 7b are connected to the nozzle body as shown. The front and rear portions of the section 3 are separately provided so that the set temperatures of the front and rear sections can be independently determined.
Reference numerals 8a and 8b denote cables including signal lines for extracting output signals of the thermocouples 7a and 7b. Reference numerals 9a and 9b denote lead wires for individually supplying heating power to the nozzle heaters 6a and 6b. The lead wires 9a and 9b are connected to a heating control device (not shown) together with the cables 8a and 8b. It is used to supply heating power controlled to keep the temperature at the set temperature to the nozzle heaters 6a and 6b.

According to a nozzle structure obtained by improving the conventional structure (hereinafter referred to as an improved nozzle structure), the resin temperature of the portion A on the side close to the nozzle base 2 is determined by the thermocouple 8b provided on the rear side. Is monitored, and the electric power suppressed so that the resin temperature in the portion A does not become excessively high is supplied to the heater 6b, thereby preventing the occurrence of resin burning.

[0011]

However, when the energization time of the fuselage rear heater 6b in the improved type structure shown in FIG. 2 was investigated, only a very short time was passed, and the fuselage rear heater 6b was effective. It turned out that it was hard to say that he worked. In the structure of FIG. 2, the heating sections 6a and 6b, which are heating heaters, thermocouples 7a and 7b, attached cables 8a and 8b, and heating power supply leads 9a and 9
b and two or two heating control units are required, which is obviously disadvantageous in terms of economy.

Accordingly, an object of the present invention is to provide a resin which has arisen when the conventional nozzle structure of FIG. 1 is employed with a simpler and less expensive structure without providing such two heating and heating control systems. It is to solve the problem of burning.

[0013]

According to the present invention, a heating means is provided around the front of the fuselage, and a heat insulating material is provided around the rear of the fuselage.
In addition to attaching only the heat insulating means including the heating means, the above problem is solved by the nozzle for the injection molding machine in which the temperature detecting means for controlling the supply of the heating power to the heating means is arranged in the area receiving the heat supply from the heating means. It is a solution.

[0014]

According to the present invention, it is possible to sufficiently maintain the molten resin temperature and secure the fluidity only by preventing heat radiation from the outer surface of the body of the nozzle body without particularly actively supplying heat to the rear part of the nozzle body. It is based on this new knowledge. In the improved nozzle structure shown in FIG. 2, the idea of providing a heating unit and a temperature detecting mechanism dedicated to the rear of the fuselage in order to prevent resin burning due to excessively high temperature in the rear fuselage flow path of the conventional nozzle structure of FIG. This is a breakthrough from the old idea that resin heating is indispensable over the entire resin flow path in order to ensure the flowability of the molten resin flowing through the nozzle. It tells you that you did not get.

On the other hand, the present invention pays attention to the fact that the power supply time of the rear heater 6b in the structure of FIG. 2 is extremely short and does not function as a positive heating means. Instead, the heat insulation means only performing a heat retaining function is employed to simplify the structure and succeed in reducing costs.

According to the structure of the present invention, active heating of the molten resin is performed exclusively by heating means (a nozzle heater or a heating element instead of the nozzle heater) disposed around the front of the fuselage. At the rear of the fuselage, only heat insulation is performed by heat insulating means including a heat insulating material around. When the resin heated and melted to an appropriate temperature in the heating cylinder communicating with the nozzle base 2 side is fed into the nozzle by the screw means, it first passes through the flow path portion (the portion corresponding to A in FIG. 1) at the rear of the nozzle body. However, in this portion, there is no large heat dissipation as in the front portion of the nozzle, and the surroundings are surrounded by a heat insulating material. Since the heat transfer effect from the heating means at the front of the fuselage is also considered to contribute to the direction of preventing the resin temperature from fluctuating, the heat supply-demand balance does not significantly collapse even without active heating.

As the molten resin that has passed through the resin flow path at the rear of the fuselage enters the flow path at the front of the fuselage, the positive heating effect of the heating means provided around the front of the fuselage begins to take effect.
The molten resin passes through the resin flow path at the front of the fuselage while maintaining the balance with the heat dissipation that increases as approaching the nozzle tip.

After all, according to the present invention, the heating means provided over the entire length of the conventional nozzle (see FIG. 1) is provided only at the front of the nozzle body, and the heating means is simply provided at the rear of the body. With a simple configuration in which a simple heat insulating structure is provided, it is possible to avoid resin burning while maintaining sufficient molten resin temperature. In order to maintain the temperature of the molten resin at the set temperature, a thermocouple or a temperature detecting means instead of the thermocouple may be arranged facing an appropriate position in the resin flow path as in the related art. It is preferable that the temperature is selected in the front part of the body as in the case of the heating means. However, there is no particular limitation as long as the temperature fluctuates depending on the amount of heat supplied from the heating means.

It is preferable that the heat insulating means including the heat insulating material is disposed uniformly over the entire periphery of the rear portion of the nozzle body.
As long as the heat retaining action is not substantially impaired, the arrangement mode may have a degree of freedom. Similarly, the heating means (typically, a nozzle heater) is also preferably arranged evenly over the entire circumference of the front part of the nozzle body, but as long as the uniform heating action is not substantially impaired, the nozzle means is heated. It is also acceptable that there is a difference in the arrangement density of the heating means in the circumferential direction or the length direction of the body. Some space may be provided between the heating means and the heat insulating means (see the embodiment).

In the present invention, the term "front of the body" or "rear of the body" of the nozzle is used for the purpose of relatively dividing the nozzle body, and the length of the nozzle body is not necessarily 50%. It does not mean that it is divided into front and rear parts.

[0021]

FIG. 3 is a view showing a sectional structure of a nozzle for an injection molding machine according to a first embodiment of the present invention. Elements common to the nozzle structure shown in FIG. 1 or 2 are the same. Reference numerals are given. The nozzle 1 has a resin flow path 4 formed therein by a thick cylindrical body 3 extending from a base 2, and a discharge port 5 is provided at the tip thereof. A nozzle heater 6c is provided around the front part of the body part 3, and a covering part 10c made of a heat insulating material is provided over the entire circumference from the rear part of the body part 3 to the periphery of the base part 2. Insulation material
Generally, any material can be used as long as it can withstand the temperature of the molten resin material, for example,
Use of a heat insulating material made of a material using glass fiber or aramid fiber can be considered.

Reference numeral 7c denotes a thermocouple for detecting the temperature of the region to be heated, and reference numeral 8c denotes a cable including a signal line for extracting an output signal of the thermocouple 7c. Reference numeral 9c denotes a lead wire for supplying electric power for heating to the nozzle heater 6c. Cable 8c
The lead wire 9c is connected to a control device (not shown), and the power supplied to the nozzle heater 6c is controlled based on the detection output of the thermocouple 7c so as to maintain the heated area at a set temperature.

On the other hand, in the rear portion and the base portion 2 of the nozzle body, a coating portion 10c made of a heat insulating material prevents a temperature decrease due to heat radiation from the outer surface of the nozzle. Also, if a temperature difference occurs between the rear part of the body and the front part of the body, a heat flow due to heat conduction is generated from the high temperature part to the low temperature part in order to eliminate the temperature difference, so that some heat dissipation was performed through the heat insulating material. However, there is no possibility that a large temperature drop occurs.

When the resin heated and melted to an appropriate temperature in the heating cylinder communicating with the nozzle base 2 side is fed into the nozzle by the screw means, it first passes through the flow path portion (a portion corresponding to A) at the rear of the nozzle body. However, due to the heat insulating effect of the covering portion 10 made of the above-described heat insulating material and the heat transfer effect from the heating means at the front portion of the body, the flow at the front portion of the nozzle body portion 3 is maintained while the molten resin temperature is kept at an appropriate temperature. You will be heading for the road.

As the molten resin enters the flow path at the front of the fuselage, the positive heating effect of the nozzle heater 6c provided around the front of the fuselage begins to take effect, and the heat dissipation and balance increase with approaching the nozzle tip. While maintaining the temperature set by the heating control unit, it passes through the resin flow path at the front of the body and reaches the discharge port 5.

In this manner, the temperature of the molten resin is maintained at an appropriate temperature over the entire length of the nozzle. Therefore, as in a conventional type nozzle (see FIG. 1), a flow path portion (region A) at the rear of the body is formed. Does not cause resin burning. Also, compared to the improved type (FIG. 2), two heating means, a heating power supply lead wire, a temperature detecting means (thermocouple), a signal line (cable) for extracting a temperature detecting signal, and the like are provided. Since there is no need to use each of them and only one control system for properly supplying power to the two heating means is required, the entire configuration is simplified, which contributes to a reduction in manufacturing cost and adjusts the temperature control unit. Will also be easier.

FIG. 4 is a view showing a sectional structure of a nozzle for an injection molding machine according to a second embodiment of the present invention.
Elements common to the nozzle structures shown in FIGS. 3 to 3 are denoted by the same reference numerals. The nozzle of the second embodiment has a structure similar to the nozzle of the first embodiment described above. Briefly, a thick cylindrical body 3 extends from the base 2 of the nozzle 1, and a resin flow path 4 reaching the discharge port 5 is formed inside the body 1, and the front of the body 3 is surrounded by a resin flow path 4. The nozzle heater 6d is provided. A covering 10d made of a heat insulating material such as glass fiber or aramid fiber is provided all around the rear portion of the body 3, and a thermocouple 7 for detecting the temperature of the region to be heated.
d, a cable 8d, and a lead wire 9d are arranged as shown.

The cable 8d and the lead wire 9d are connected to a control device (not shown), and the power supplied to the nozzle heater 6d is controlled based on the detection output of the thermocouple 7d so as to maintain the heated area at a set temperature. Is exactly the same as in the first embodiment.

The difference between the nozzle of the second embodiment and that of the first embodiment is that, in the latter, the nozzle heater 6c is provided with the coating portion 10c.
Are formed separately and the covering portion 10 extends over a part of the base portion 2, and the lead wire 9 c is drawn out from near the center of the body portion 3, whereas the former has a nozzle heater 6 d
This is that a member 11 is provided for integrating the body and the covering portion 10d, and the lead wire 9d is drawn out from the base side of the body portion 3 with the center of the body portion 3. Further, in the second embodiment, the covering portion 10d has a structure that covers only the rear portion of the body (a heat insulating material may be separately applied to the base portion 2 in order to further improve the heat retaining effect).

One advantage of the second embodiment is that the lead wire 9d
Is drawn out from a position distant from the nozzle tip, so that the possibility of contact or interference between the die or the fixed platen and the lead wire can be reduced. Note that a metal member may be used for the integration member 11, but a heat retaining effect can be further improved by using a tubular member made of a heat-resistant material having heat insulation. Further, the shape of the integration member 11 is not limited to a tubular shape.
A shape surrounding d may be used.

[0031]

According to the present invention, the heating means provided over the entire length of the conventional nozzle is limited to the front portion of the nozzle body, and a simple heat insulating structure is provided at the rear portion of the body. With this simple configuration, it is possible to avoid resin burning while maintaining sufficient molten resin temperature.

Heating means, heating power supply lead wires, temperature detecting means (thermocouple), two signal lines (cables) for extracting a temperature detecting signal, etc. are used two by two to supply electric power to the two heating means. Since the configuration is simpler than that of the improved type in which two control systems are separately provided, the manufacturing cost can be reduced, and there is an advantage that handling such as adjustment of the temperature control unit is facilitated.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross-sectional structure of a nozzle having a conventional heating / heating mechanism.

FIG. 2 is a diagram showing a cross-sectional structure of a known nozzle obtained by improving the conventional nozzle shown in FIG.

FIG. 3 is a diagram showing a cross-sectional structure of a nozzle for an injection molding machine according to a first embodiment of the present invention.

FIG. 4 is a diagram showing a cross-sectional structure of a nozzle for an injection molding machine according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Nozzle 2 Base part 3 Body part 4 Resin channel 5 Discharge port 6, 6a-6d Nozzle heater (heating means) 7, 7a-7d Thermocouple (temperature detecting means) 8, 8a-8d Cable 9, 9a-9d Lead wire 10c , 10d covering portion 11 integrated member A flow path region at the rear of the nozzle body

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-62848 (JP, A) JP-A-3-211028 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 45/00-45/84

Claims (1)

(57) [Claims] 1. A heating means is provided around a front part of a fuselage.
Attach only insulation means including insulation material around the rear
A nozzle for an injection molding machine, wherein a temperature detecting means for controlling the supply of heating power to the heating means is disposed in a region receiving the heat supply from the heating means.