JP5752404B2 - Injection molding machine - Google Patents

Description

  The present invention relates to an injection molding machine that injects a resin melted by a heating cylinder into a mold cavity, and in particular, an injection for manufacturing a molded body using a material in which a reinforcing fiber is mixed with a thermoplastic resin. It relates to a molding machine.

  In a general injection molding machine that has been used in the past, a granular thermoplastic resin as a raw material is fed into a heating cylinder, and the nozzle at the tip of the screw is melted by the rotation of a screw provided in the heating cylinder. The molten resin is injected into the mold cavity closed from the injection nozzle provided on the tip side of the screw by advancing to the side, and the molten resin is cooled and solidified in the cavity. The molded body is manufactured by opening the mold and taking out the molded body stuck to the inner surface of the mold with a protruding pin or the like.

  By the way, in recent years, in order to achieve high strength of a molded body, not only a thermoplastic resin but also a glass fiber reinforced plastic (GFRP) in which a glass fiber is mixed with a thermoplastic resin or a thermoplastic resin is used as a material of the molded body. A technique for producing a molded body made of a composite material such as carbon fiber reinforced plastic (CFRP) in which carbon fiber is mixed with carbon fiber is becoming widespread. As related to such a conventional technique, Patent Document 1 discloses a thermoplastic resin and A fiber reinforced thermoplastic resin (pellet) mixed with reinforcing fibers is kneaded by rotating a screw in a heated cylinder, and then injected into a cavity of a mold to form a molded product of fiber reinforced thermoplastic resin. Techniques for manufacturing are disclosed.

Japanese Patent No. 3755293

  However, when the above-mentioned molded article made of glass fiber reinforced plastic is no longer necessary and incinerated, there is a current situation that incineration is practically difficult because the incinerator is damaged. In the case of producing a molded body, since fossil fuel is used for obtaining carbon fibers, there is a problem that it leads to depletion of resources.In recent years, as reinforcing fibers mixed with thermoplastic resins, Adoption of natural fibers is attracting attention, but pellets (mixed with natural fiber reinforced heat) are mixed with thermoplastic resin and natural fibers for reinforcement by the rotation of a screw that can rotate in the heating cylinder of an injection molding machine. When melting and kneading a plastic resin), for example, as a reinforcing natural fiber, a material that is relatively easy to break, such as bamboo fiber, is used. That when, with rotation of the screw, in a relatively low strength bamboo fiber, there is a problem that the remaining fiber length and the like easily broken is shortened. Therefore, as in Patent Document 1, for example, in order to reduce the shearing force that causes breakage of the reinforcing fiber, natural fiber reinforced heat is used by using a screw having a shallow groove depth Hm of the screw of the measuring section Sm. When kneading a plastic resin, natural fibers, which are different from fibers such as glass fibers and carbon fibers, are difficult to disentangle with the melting of the resin, so the dispersibility of the natural fibers with respect to the thermoplastic resin is poor. There was a problem that a molded article having a predetermined strength could not be obtained.

  The present invention has been made in view of the above problems, and suppresses breakage of reinforcing fibers contained in a fiber-reinforced thermoplastic resin that is injected and filled into a cavity of a mold, and improves dispersibility, and has a predetermined strength. It aims at providing the injection molding machine which can obtain a molded object.

The invention of the injection molding machine according to claim 1
An injection molding machine for injecting a fiber reinforced thermoplastic resin composed of a thermoplastic resin and reinforcing fibers into a mold cavity closed from an injection nozzle attached to the tip of a heating cylinder,
The heating cylinder, and a variable pitch dull mage screw provided rotatably in the heating cylinder,
The variable pitch dull mage screw includes a compression unit that melts and kneads the fiber-reinforced thermoplastic resin supplied from a supply port while transferring the fiber-reinforced thermoplastic resin to the injection nozzle side, and the melt / kneaded material that is conveyed from the compression unit. A measuring unit for measuring the kneaded fiber-reinforced thermoplastic resin,
The pitch of the flight formed in the compression part is formed so as to gradually narrow toward the injection nozzle side,
A dull image part for dispersing the reinforcing fibers within a range of 1 to 2 times the diameter of the variable pitch dull image screw is formed between the measuring part and the compression part.

Invention of the injection molding machine according to claim 2, Oite to claim 1,
The reinforcing fiber may be any one of bamboo, jute, or hemp, or a natural fiber containing at least one of bamboo, jute, or hemp.

According to the present invention, since the dull image portion is formed between the metering portion and the compression portion of the variable pitch dull image screw, it is melted in the heating cylinder immediately before being injected and filled into the mold cavity via the injection nozzle. -Among the kneaded fiber reinforced thermoplastic resins, the fiber dispersibility is improved because the defibrating action of the reinforcing fibers can be increased. Therefore, a molded article having a predetermined strength can be obtained by improving the dispersibility of the reinforcing fibers.

Furthermore, in the variable pitch dalmage screw, the formation of the dalmage part between the metering part and the compression part makes it possible to effectively disperse the reinforcing natural fiber, but it is relatively easy to break or break. Even if it is a weak natural fiber for reinforcement (natural fibers such as bamboo, jute, hemp, etc.), it can be suppressed so as not to be shorter than a predetermined dimension. Accordingly, it is possible to achieve both the suppression of the remaining fiber length of the reinforcing natural fiber so as not to be shortened and the kneading dispersibility of the reinforcing natural fiber with respect to the thermoplastic resin, thereby obtaining a molded body having a predetermined strength. it can.

Furthermore, the dull image part of the variable pitch dalmage screw is not a compression part separated from the injection nozzle, but is formed between the metering part and the compression part close to the injection nozzle, so that the compression part is rotated along with the rotation of the variable pitch dalmage screw. Even if the reinforcing fibers are entangled with each other, the reinforcing fibers entangled in the dalmage portion are unwound and dispersed, and the fiber-reinforced thermoplastic resin containing the dispersed reinforcing fibers is injected into the mold cavity via the injection nozzle. Since injection filling can be performed, a molded body having a predetermined strength can be obtained more reliably.

It is a schematic block diagram which shows the injection molding machine of an example of this invention. It is a schematic side view which shows the variable pitch dull mage screw rotatably provided in the heating cylinder of an injection molding machine. It is explanatory drawing which shows schematic structure of various screws, Fig.3 (a) shows a standard screw, FIG.3 (b) shows a dalmage screw, FIG.3 (c) shows a variable pitch screw. 4A is a graph corresponding to the variable pitch dull screw, FIG. 4B is a standard screw, FIG. 4C is a dull image screw, and FIG. 4D is a graph corresponding to the variable pitch screw. The average shear stress when each screw is applied and driven to rotate is shown on the horizontal axis, and the frequency is shown on the vertical axis.

  Embodiments of the present invention will be described below with reference to FIGS. Of course, it goes without saying that the present invention can be easily applied to configurations other than those described in the embodiments without departing from the spirit of the invention.

  An injection molding machine 1 according to an example of the present invention shown in FIG. 1 manufactures a molded body using pellets as a granular natural fiber reinforced thermoplastic resin composed of a thermoplastic resin and a bamboo fiber which is a large number of natural fibers for reinforcement. The injection molding machine 1 includes a machine base 2, and an injection unit 3 and a mold clamping unit 4 are disposed on the machine base 2.

  The mold clamping unit 4 includes a mold opening / closing mechanism that moves the movable mold 6 forward and backward with respect to the fixed mold 5 to perform mold clamping (mold closing) and mold opening. As the mold opening / closing mechanism in the present embodiment, The toggle link mechanism 7 is bent using the driving force of the motor as a drive source, so that the movable mold 6 fixed to the movable die plate 9 is repeatedly opened and closed with respect to the fixed mold 5 fixed to the fixed die plate 8. To do.

  The injection unit 3 includes a cylindrical heating cylinder 10, an injection nozzle 11 provided at the tip of the heating cylinder 10, a variable pitch dull image screw 12 provided inside the heating cylinder 10, and a variable pitch dull image screw 12. A support member 13 that is rotatably supported, a hopper 14 into which pellets of a natural fiber reinforced thermoplastic resin are charged, a hopper block 15 provided with the hopper 14, and the like are configured, and a variable provided inside the heating cylinder 10. When the pitch dalmage screw 12 is rotated, the natural fiber reinforced thermoplastic resin supplied from the supply port 16 to the rear side of the heating cylinder 10 is sent to the front end side of the heating cylinder 10 provided with the injection nozzle 11. And is supplied into the heating cylinder 10 and is heated and melted in the heating cylinder 10. However, the fiber reinforced thermoplastic resin is measured by a measuring unit 22 which will be described later by rotating the variable pitch dull mage screw 12 by a rotation driving means such as a measuring motor (not shown), and then is not shown. The variable pitch dull mage screw 12 is advanced by an advancing / retracting drive means comprising a motor, a ball screw mechanism, etc., whereby a predetermined amount of molten natural fiber reinforced thermoplastic resin is injected into the closed mold cavity. As shown in FIG. 1, a heater 17 is provided outside the heating cylinder 10, and the pellets supplied to the inside of the heating cylinder 10 are melted when the heater 17 is heated to a high temperature. The

  Here, the variable pitch dull mage screw 12 for kneading and transferring the natural fiber reinforced thermoplastic resin supplied into the heating cylinder 10 will be further described with reference to FIG.

  In FIG. 2, the variable pitch dull image screw 12 has a leading end on the left side and a trailing end on the right side, and a natural fiber reinforced thermoplastic resin supplied from the supply port 16 is transferred to the injection nozzle 11 side on the rear end side. On the front end side (injection nozzle side), the measuring unit 22 for measuring the melted and kneaded natural fiber reinforced thermoplastic resin conveyed from the compressing unit 20 is configured. Yes.

In addition, as schematically shown in FIG. 2, the dull image portion is between the metering portion 22 and the compression portion 20 of the variable pitch dull image screw 12 within the range of 1 to 2 times the screw diameter D. 21 is formed. Moreover, the pitch of the flight formed in the compression part 20 is formed so that it may become narrow gradually as it goes to the injection nozzle 11 side.

  Moreover, since the main body (shaft part) of the variable pitch dull screw 12 is formed in a cylindrical shape with the same radius throughout, the outer periphery of the screw main body corresponding to each of the compression part 20 and the measuring part 22. And the dimension H1, H2 of the depth of the screw groove, that is, the screw groove depth, have the same relationship, and if the diameter of the screw is Dmm, the length of the compression part is 16.325 Dmm, the length dimension of the weighing part 22 is 2 Dmm, the length dimension L of the variable pitch dull image screw 12 is 20 Dmm, and the length dimension L1 of the dull image part 21 in the same direction as the length direction is the screw diameter The length of the dull image portion 21 of the present embodiment is 1.675 Dmm.

  Here, various screws having different forms from the variable pitch dull image screw 12 of the present embodiment will be further described with reference to FIG.

  3A shows the standard screw 102, FIG. 3B shows the dalmage screw 202, and FIG. 3C shows the variable pitch screw 302. FIG. Each screw 102, 202, 302 in FIG. 3 has a leading end on the left side and a trailing end on the right side as in FIG. 2, and in FIGS. 3 (a) and 3 (b), in order from the trailing end side to the leading end side, A supply unit 24 that transfers the natural fiber reinforced thermoplastic resin supplied from the supply port 16 to the injection nozzle 11 side, and further transfers the natural fiber reinforced thermoplastic resin that is transferred from the supply unit 24 to the injection nozzle 11 side. A compressing unit 20 that melts and kneads, and a measuring unit 22 that measures the melted and kneaded natural fiber reinforced thermoplastic resin conveyed from the compressing unit 20 are configured.

  The general standard screw 102 in FIG. 3A is formed such that the pitches of the flights 23 are all equally spaced, and the compression portion 21 is formed in a tapered shape with a diameter larger in front than in the rear.

  3 (b), a dull image portion 21 is formed between the measuring portion 22 and the compression portion 20, and the pitches of the flights 23 excluding the dull image portion 21 are all formed at equal intervals. It is a thing.

  The variable pitch screw 302 in FIG. 3C is composed of the compression unit 20, and the pitch of the flight 23 is gradually narrowed from the rear end side toward the front end side. Part) is formed in a cylindrical shape with the same radius throughout, but does not have a dull image part.

  Here, in addition to the variable pitch dull image screw 12 of the present embodiment, various screws (standard screw 102, dull image screw 202, variable pitch screw 302) are provided in the heating cylinder 10, and the injection molding machine 1 is operated. Table 1 shows the results of taking out bamboo fiber as reinforcing natural fiber after the measuring step and conducting experiments on the state of bamboo fiber. (In addition, the original bamboo fiber contained in the pellets has a fiber length of 8 mm and a fiber diameter of 0.15 mm.)

※上記「フラクタル値」は、繊維分散性を定量化した値であり、フラクタル値が大きいほど、分散性が良好であると判断できる。

* The above-mentioned “fractal value” is a value obtained by quantifying fiber dispersibility. It can be determined that the greater the fractal value, the better the dispersibility.

  According to the experimental results shown in Table 1, the initial bamboo fiber had a fiber length of 8 mm and a fiber diameter of about 0.15 mm, but when taken out and measured after the measuring step, the variable pitch screw 302 was adopted, It was preferable because it was closest to the original size of the original bamboo fiber, and the result was that the variable pitch dull image screw 12, standard screw 102, and dull image screw 202 of this embodiment were in this order. The value of the variable pitch dull mage screw 12 of the present embodiment is the result that the value is secondly preferable although it is slightly inferior to the variable pitch screw 302.

  Further, from the viewpoint of the dispersibility of the bamboo fiber, as apparent from the fractal value, the dalmage screw 202 is most preferable. Next, the variable pitch dalmage screw 12, the standard screw 102, and the variable pitch screw 302 of the present embodiment. The result was that Although the value of the variable pitch dull mage screw 12 of this embodiment is slightly inferior to that of the dull mage screw 202, it is the result that it is second preferred.

  From the above experimental results, in order to produce a molded body having a predetermined strength using natural fiber-containing pellets, it is possible to suppress the remaining fiber length of bamboo fibers from being shortened and to have good fiber dispersibility. The conclusion was found that it is most preferable to adopt the variable pitch dull image screw 12 of the present embodiment that combines the above.

  Further, in the graph relating to the bamboo fiber of FIG. 4, FIG. 4 (a) is the variable pitch dull image screw 12 of this embodiment, FIG. 4 (b) is the standard screw 102, and FIG. 4 (c) is the dull. The image screw 202, FIG. 4 (d) shows the case where the variable pitch screw 302 is applied. The vertical axis indicates the frequency (%), the horizontal axis indicates the average shear stress, and the average shear stress is small. The left side of the horizontal axis represents the case where the residual fiber length of the bamboo fiber is long and the dispersibility is poor, and the right side of the horizontal axis where the average shear stress is large, the short residual fiber length of the bamboo fiber is short and the dispersibility is good. Represents the case.

  According to the graph of FIG. 4, when the standard screw 102 (b) and the dalmage screw 202 (c) are applied, the distribution is concentrated from the center of the horizontal axis to the left side, and the remaining fibers of the bamboo fiber. Since it is difficult to leave the length for a long time, it is not necessary to consider dispersibility and is not suitable for producing a molded article having a predetermined strength. In addition, when the variable pitch dull screw 12 of (a) and the variable pitch screw 302 of (d) are applied, since the distribution exists on the left side, the remaining fiber length of the bamboo fiber is left in a long state. However, in the variable pitch screw 302 of (d), since there is also a distribution near the right side of the horizontal axis, it can be understood that bamboo fibers having a short remaining fiber length are generated, and the strength is high. It is not suitable for producing shaped bodies. Further, in the graph of (c) to (d), when the variable pitch dull mage screw 12 of (a) is applied, all distributions exist on the left side of the center of the horizontal axis. From the viewpoint of the remaining fiber length of the bamboo fiber, it can be grasped that the remaining fiber length can be suppressed so as not to be shortened, and from the viewpoint of dispersibility, more than a majority can be aggregated in the approximate center of the horizontal axis. It can be understood that the dispersion of bamboo fiber can be realized while suppressing the remaining fiber length of the bamboo fiber from being shortened.

  As described above, according to the injection molding machine 1 of the present embodiment, the thermoplastic resin and the reinforcing natural fiber such as bamboo fiber are placed in the mold cavity closed from the injection nozzle 11 attached to the tip of the heating cylinder 10. An injection molding machine 1 for injecting a natural fiber reinforced thermoplastic resin comprising a heating cylinder 10 and a variable pitch dull image screw 12 rotatably provided in the heating cylinder 10, and this variable pitch dull image In the screw 12, a natural fiber reinforced thermoplastic resin supplied from the supply port 16 is melted and kneaded while being transferred to the injection nozzle 11 side, and the melted and kneaded material conveyed from the compressing unit 20 is mixed. A measuring unit 22 for measuring the natural fiber reinforced thermoplastic resin, and between the measuring unit 22 and the compression unit 20, the variable pitch dull image screw 1 is provided. In the range of from 1 screw diameter D of the double length is obtained by forming a Dulmage portion 21 for dispersing the natural reinforcing fibers. Then, by forming the dull image portion 21 between the measuring portion 22 near the injection nozzle 11 side of the variable pitch dull image screw 12 and the compression portion 20, the mold cavity is injected and filled via the injection nozzle 11. Of the natural fiber reinforced thermoplastic resin previously melted and kneaded in the heating cylinder 10, the reinforcing natural fibers can be dispersed so as not to form a bundle. Therefore, the molded object of predetermined intensity | strength can be obtained by improving the dispersibility of the natural fiber for reinforcement | strengthening.

  Furthermore, since the variable pitch dalmage screw 12 is formed with the dalmage part 21 only within the range of 1 to 2 times the screw diameter D, the natural fiber for reinforcement can be dispersed effectively. On the other hand, even if it is a natural fiber for reinforcement (natural fibers such as bamboo, jute, hemp, etc.) having a weak strength that is relatively easy to break or break, it can be prevented from becoming shorter than a predetermined dimension. Accordingly, it is possible to achieve both the suppression of the remaining fiber length of the reinforcing natural fiber so as not to be shortened and the kneading dispersibility of the reinforcing natural fiber with respect to the thermoplastic resin, thereby obtaining a molded body having a predetermined strength. it can.

  Furthermore, the dull image portion 21 of the variable pitch dull image screw 12 is not the compression portion 20 separated from the injection nozzle 11 but is formed between the measuring portion 22 and the compression portion 20 which are closer to the injection nozzle 11 than the compression portion 20. Even if the natural fiber for reinforcement is entangled in the compression part 20 with the rotation of the dalmage screw 12, the natural fiber for reinforcement entangled in the dalmage part 21 between the measuring part 22 and the compression part 20 is unwound and dispersed. Since the natural fiber reinforced thermoplastic resin containing the reinforcing natural fiber can be injected and filled into the cavity of the mold through the injection nozzle 11, a molded body having a predetermined strength can be manufactured more reliably.

  As mentioned above, although an example of this embodiment was explained in full detail, as a natural fiber for reinforcement, not only flat bamboo fiber but jute, hemp, or corn fiber may be sufficient, bamboo, jute, hemp, corn fiber A composite natural fiber including two or more natural fibers may be employed. Moreover, since the injection molding machine 1 of this embodiment can disperse | distribute effectively even natural fibers, such as bamboo, whose fiber is difficult to be disentangled, it is not limited to natural fibers, and glass fibers that are easier to disentangle than that. Ordinary reinforcing fibers such as carbon fibers may be employed, and even in such a case, the above-described effects can be obtained.

1 Injection molding machine 5 Fixed mold (mold)
6 Movable mold (mold)
10 Heating cylinder 11 Injection nozzle 12 Variable pitch dull mage screw (screw)
16 Supply Port 20 Compression Unit 21 Dalmage Unit 22 Weighing Unit 23 Flight 24 Supply Unit

Claims (2)

An injection molding machine for injecting a fiber reinforced thermoplastic resin composed of a thermoplastic resin and reinforcing fibers into a mold cavity closed from an injection nozzle attached to the tip of a heating cylinder,
The heating cylinder, and a variable pitch dull mage screw provided rotatably in the heating cylinder,
The variable pitch dull mage screw includes a compression unit that melts and kneads the fiber-reinforced thermoplastic resin supplied from a supply port while transferring the fiber-reinforced thermoplastic resin to the injection nozzle side, and the melt / kneaded material that is conveyed from the compression unit. A measuring unit for measuring the kneaded fiber-reinforced thermoplastic resin,
The pitch of the flight formed in the compression part is formed so as to gradually narrow toward the injection nozzle side,
Wherein between the metering section and the compression section, an injection, characterized in that the formation of the variable pitch dull image Dulmage portion dispersing the reinforcing fibers in the range of 1 to 2 times the length of the diameter of the screw Molding machine. The reinforcing fibers, bamboo, jute, or any one of hemp, or bamboo, jute, according to claim 1, characterized in that the natural fibers comprise at least one of a hemp Injection molding machine.

Images