JP6875959B2 - Manufacturing method of injection molding equipment and reinforced resin molded product - Google Patents

Description

The present invention relates to an injection molding apparatus and a method for manufacturing a reinforced resin molded product.

Reinforced resin molded bodies whose material properties have been improved by reinforcing materials such as glass fiber and carbon fiber are generally manufactured by injection molding of thermoplastic resin pellets (reinforced resin pellets) containing the reinforcing material inside. Is. However, since the material cost of reinforced resin pellets is high, in recent years, in order to reduce the material cost, a technique has been developed in which resin pellets and reinforced materials are separately supplied to an injection molding machine to form a reinforced resin molded body. ing. This technique is also called direct blend molding.

Patent Document 1 discloses an injection molding apparatus that injects a fiber reinforced resin by direct blend molding. Further, the injection screw disclosed in Patent Document 1 includes a first stage provided on the upstream side (rear end side) and a second stage provided on the downstream side (front end side) of the first stage. The first stage will have a main flight and a secondary flight with a smaller outer diameter than the main flight. By providing the secondary flight, the solid resin and the molten resin are separated, and the resin is compressed with a relatively weak force. Therefore, clogging of the solid resin in the screw groove of the first stage is prevented.

Japanese Patent No. 5889493

(Problems to be solved by the invention)
Generally, a full flight screw is used as an injection screw in an in-line screw type injection molding apparatus. Further, the injection screw is provided with a material supply unit, a compression unit, and a measuring unit from the rear end side (upstream side) to the front end side (downstream side). Then, the material is supplied from the hopper to the material supply unit. Further, when the injection screw rotates and the resin is transported to the front end side (downstream side) of the injection screw, the injection screw retracts due to the resin back pressure. The flight of the injection screw then crosses the opening formed in the injection cylinder to supply the material into the interior space of the injection cylinder. Therefore, a part of the material supplied from the opening is supplied to the material supply unit over the flight trying to cross the opening. However, the clearance between the flight and the inner peripheral wall of the injection cylinder is generally about 0.2 mm to 0.5 mm, which is very small, so that there is a risk that a reinforcing material may be caught in the clearance when the material gets over the flight. .. When the reinforcing material is sandwiched in the clearance, a large shearing force acts on the reinforcing material and the reinforcing material is broken. This shortens the length of the reinforcing material.

FIG. 10 is a graph showing the relationship between the fiber length of the glass fiber as a reinforcing material contained in the glass fiber reinforced resin molded body and the material properties (rigidity, strength, impact resistance) of the glass fiber reinforced resin molded body. (Source: Automotive technology, [3] (2010)). In FIG. 10, the horizontal axis represents the fiber length of the glass fiber, and the vertical axis represents the magnitude of the material characteristics of the glass fiber reinforced resin molded product. As shown in FIG. 10, as the fiber length of the glass fiber becomes longer, the material properties such as rigidity (modulus), strength (strength), and impact resistance (impact resistance) of the glass fiber reinforced resin molded body can be improved. Understand.

Therefore, in order to improve the material properties of the reinforced resin molded product, it is preferable that the reinforcing material is long, but according to the prior art, the reinforcing material is sandwiched by the clearance and broken at the material supply section as described above. Therefore, the material properties of the molded product cannot be sufficiently improved.

In this regard, by reducing the diameter of the flight and setting the clearance between the flight and the inner peripheral wall of the injection cylinder to be large, the possibility that the reinforcing material is pinched in the clearance can be reduced. However, in this case, the material near the inner peripheral wall of the injection cylinder is not transported but stays at that position, so that the material transporting capacity is reduced. In addition, the resin in the retained material is carbonized and the carbide is mixed with the material to be transported, which causes deterioration of the quality of the molded product. Therefore, simply reducing the diameter of the flight may not be a fundamental solution because there is a concern that another problem may occur.

An object of the present invention is to provide an injection molding apparatus and a method for manufacturing a reinforced resin molded product, which can suppress breakage of a reinforcing material in a material supply unit without lowering the material transport capacity.

(Means to solve problems)
The present invention comprises a screw shaft (321) having a rear end (321a) and a front end (321b), a flight screw portion (32) having a flight (322) provided on the outer periphery of the screw shaft, and a rear end of the screw shaft. A coil screw portion (33) having a coil body (332) spirally extended from the rear end in a direction (rear) opposite to the extending direction (front) of the screw shaft. The injection screw (3) provided with the above and the cylindrical internal space (2a) are formed in a tubular shape, and the injection screw is coaxially arranged in the internal space, and the resin (R) and the resin (R) and An injection cylinder (2) having an opening (2c) for supplying the material containing the reinforcing material (S) to the internal space is provided, and the position of the opening is determined so that the material is supplied to the coil screw portion. The injection molding apparatus (1) is formed so that the clearance between the coil body and the inner peripheral wall (2d) constituting the internal space of the injection cylinder is larger than the clearance between the flight and the inner peripheral wall. I will provide a.

According to the present invention, the injection screw included in the injection molding apparatus includes a flight screw portion having a flight and a coil screw portion having a coil body. The coil screw portion is connected to the rear end of the flight screw portion. Further, the injection screw is coaxially arranged in the injection cylinder. The injection cylinder is formed with an opening for supplying a material containing a resin and a reinforcing material to the internal space thereof. The position of this opening is determined so that the material is fed to the coil screw section. Therefore, the material is supplied to the coil screw portion. That is, the coil screw portion corresponds to the material supply portion. When the coil screw portion rotates, the material on the inner peripheral side of the coil body is transported along with the rotation of the coil body. At this time, the propulsive force acting on the material on the inner peripheral side of the coil body propagates to the material on the outer peripheral side of the coil body, so that the materials on the inner peripheral side and the outer peripheral side of the coil body are transported. According to the transportation principle of such a material, the clearance between the coil body and the inner peripheral wall of the injection cylinder can be set within a range in which the propulsive force related to the transportation is propagated to the material on the outer peripheral side of the coil body.

The clearance between the coil body and the inner peripheral wall of the injection cylinder, which can be set within the range in which the propulsive force related to transportation is propagated to the material on the outer peripheral side of the coil body, is the clearance between the conventional flight and the inner peripheral wall of the injection cylinder (0. 2 mm to 0.5 mm). Therefore, the coil body can be formed so that the clearance between the coil body and the inner peripheral wall of the injection cylinder is larger than the clearance between the flight and the inner peripheral wall of the injection cylinder. In other words, the coil body can be formed so that the outer diameter of the coil body is smaller than the outer diameter of the flight. Even when the coil body is formed in this way, the material transporting capacity is secured. Further, since the clearance can be set large in this way, the possibility that the reinforcing material is caught in the clearance can be reduced, and thereby the breakage of the reinforcing material in the material supply part (coil screw part) can be suppressed. it can. That is, according to the present invention, it is possible to suppress breakage of the reinforcing material in the material supply section without lowering the material transport capacity.

The coil screw portion is connected to the rear end of the screw shaft and is connected to the connecting shaft (331) extending from the rear end in the direction opposite to the extending direction (front) of the screw shaft (rear). It is preferable to include a fixing member (333) for connecting the shaft and the coil body. Then, the coil body may be fixed to the connecting shaft via a fixing member in a state of being coaxially arranged around the outer circumference of the connecting shaft. According to this, the coil body is fixed to the connecting shaft, so that the elastic deformation of the coil body is suppressed. Therefore, deformation of the coil body is prevented when the resin pressure is applied, whereby the material can be stably transported.

Further, it has been confirmed by the inventors and the like that when the clearance between the coil body and the inner peripheral wall of the injection cylinder is 6 mm or less, the material transport capacity due to the rotation of the coil body is sufficiently secured. Therefore, the clearance is preferably 6 mm or less. Further, if the clearance is larger than 0.5 mm, the possibility that the reinforcing material is sandwiched in the clearance can be reduced as compared with the case where the conventional full flight screw is used. Therefore, the clearance is preferably larger than 0.5 mm. That is, the clearance between the coil body and the inner peripheral wall of the injection cylinder is preferably larger than 0.5 mm and 6 mm or less. Further, it has been confirmed by the inventor and the like that when the clearance is 3 mm or more, the breakage of the reinforcing material in the material supply part (coil screw part) due to the reinforcing material being sandwiched in the clearance is sufficiently suppressed. Has been done. Therefore, the clearance is more preferably 3 mm or more. The clearance may be larger than 0.5 mm and 3 mm or less.

Further, the injection screw has a material supply unit (3A) to which the material is supplied, a compression unit (3B) for compressing the material supplied to the material supply unit, and a measuring unit (3C) for measuring the material compressed by the compression unit. ) Are provided along the longitudinal direction of the injection screw in this order, and it is preferable that the flight screw portion constitutes the measuring portion and the compression portion, and the coil screw portion constitutes the material supply portion. According to this, the material supplied to the coil screw portion is compressed by the compression portion and weighed by the measuring portion. Then, a reinforced resin molded product is manufactured by injecting a fixed amount of the measured material.

Further, the present invention is a method for manufacturing a reinforced resin molded product using the injection molding apparatus according to the present invention, which comprises a material supply step of supplying a material containing a resin and a reinforcing material to a coil screw portion, and a coil screw. A transport process for transporting the material supplied to the section to the flight screw section, a compression / melting step for compressing the material transported to the flight screw section and melting the resin in the material, and a compression / melting process for compression. Provided is a method for producing a reinforced resin molded product, which comprises an injection step of injecting a material containing a molten resin into a mold.

According to the above invention, it is possible to provide a method for producing a reinforced resin molded product capable of suppressing breakage of a reinforcing material in a material supply portion (coil screw portion) without lowering the material transport capacity.

It is the schematic which shows the injection molding apparatus which concerns on embodiment of this invention. It is a side view of the injection screw which concerns on embodiment. It is a side view of a coil screw part. It is the A direction arrow view of FIG. It is a figure which shows the state which the reinforcing material which enters into an injection cylinder through an opening is sandwiched by a clearance when a material supply part is composed of a flight screw. It is a figure which shows the state which the reinforcing material which enters into an injection cylinder through an opening is not sandwiched by a clearance when a material supply part is composed of a coil screw part. It is a figure which shows the graph which shows the relationship between a screw rotation speed and a transport capacity. It is a graph which shows the change of the weight average fiber length of a glass fiber. It is a side view of the injection screw which concerns on a modification. It is a graph which shows the relationship between the fiber length of the glass fiber as a reinforcing material contained in a glass fiber reinforced resin molded body, and the material property (rigidity, strength, impact resistance) of a glass fiber reinforced resin molded body.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing an injection molding apparatus according to the present embodiment. As shown in FIG. 1, the injection molding apparatus 1 according to the present embodiment includes an injection cylinder 2, an injection screw 3, a hopper 4, a drive unit 5, and a heater 6. In FIG. 1, the configurations of ancillary equipment such as the mold clamping device and the operation control device of the injection cylinder 2 are known and are omitted.

The injection cylinder 2 is a tubular member having a tip end (left end in FIG. 1) and a base end (right end in FIG. 1), and a columnar internal space 2a is formed inside the injection cylinder 2. A material containing a resin pellet R and a reinforcing material S, which will be described later, is supplied into the injection cylinder 2. Further, a nozzle 2b that can be opened and closed is attached to the tip of the injection cylinder 2.

A heater 6 is attached to the outer circumference of the injection cylinder 2. The injection cylinder 2 is heated by operating the heater 6. By heating the injection cylinder 2, the material in the injection cylinder 2 is heated. A temperature sensor is installed at an appropriate position in the injection cylinder 2, and the temperature information detected by the temperature sensor is input to a heater control device (not shown). The heater control device controls the operation of the heater 6 so that the detected temperature matches the set temperature.

The hopper 4 is arranged above the injection cylinder 2. The hopper 4 has a container shape capable of receiving a material containing the resin pellet R and the reinforcing material S, and a material storage space 4a in which the material is stored is formed therein. Further, an outlet passage 4b communicating with the material storage space 4a is formed at the lower end of the hopper 4, and the outlet passage 4b communicates with the opening 2c communicating with the internal space 2a provided in the injection cylinder 2. Therefore, the material storage space 4a communicates with the internal space 2a of the injection cylinder 2 via the outlet passage 4b and the opening 2c. Here, the opening 2c is provided near the base end of the injection cylinder 2. Therefore, the material storage space 4a of the hopper 4 communicates with the portion of the internal space 2a of the injection cylinder 2 near the base end of the injection cylinder 2.

The resin pellet R supplied to the hopper 4 may be spherical, columnar, or powdery. Further, the main resin component constituting the resin pellet R may be any thermoplastic resin (including general-purpose resin, engineering plastic, super engineering plastic) generally used for injection molding.

The reinforcing material S supplied to the hopper 4 may be any material as long as it improves the material properties of the molded product by mixing it with the resin. Examples of the reinforcing material S include fiber reinforcing materials such as glass fiber and carbon fiber, and fillers such as calcium carbonate and talc. Typically, the reinforcing material S is a fiber reinforcing material. When the reinforcing material is a fiber reinforcing material, the form of the fiber reinforcing material supplied to the hopper 4 may be in the form of a bundle (chopped strand shape), or before the roving-like fiber is supplied to the hopper 4. It may be cut to a desired length.

Further, in addition to the resin pellet R and the reinforcing material S, the hopper 4 contains other additives such as a modifier, a colorant, and a heat stabilizer, if necessary (for example, depending on the required characteristics of the product to be manufactured). Etc. can be supplied.

The supply form of each material (resin pellet, reinforcing material, additive, etc.) to the hopper 4 may be any as long as each material is supplied individually. That is, any form may be used as long as it is a supply form of a material that can be directly blend-molded. For example, each material (resin pellet, reinforcing material, additive, etc.) may be weighed by a quantitative feeding device based on a desired compounding ratio, and each weighed material may be individually supplied to the hopper 4. Alternatively, after blending (dry blending) each material in advance, the blended material may be supplied to the hopper 4.

The injection screw 3 is arranged in the injection cylinder 2. FIG. 2 is a side view of the injection screw 3 according to the present embodiment. The injection screw 3 has a rear end 3a and a front end 3b, and is formed in an elongated shape. Coaxially with the injection cylinder 2 in the cylindrical internal space 2a in the injection cylinder 2 so that the front end 3b side is located on the tip side of the injection cylinder 2 and the rear end 3a is located on the base end side of the injection cylinder 2. Arranged. When the direction is used in explaining the structure of the injection screw 3, the direction from the rear end 3a to the front end 3b (left side in FIG. 2) is referred to as the front, and the direction from the front end 3b to the rear end 3a. (To the right in FIG. 2) may be referred to as the rear. The front is the direction in which the material is transported when the injection screw 3 rotates in the injection cylinder 2, and the rear is the opposite direction.

The injection screw 3 has four portions that can be functionally separated along the axial direction (longitudinal direction). These functional parts are a material supply part 3A, a compression part 3B, a measuring part 3C, and a mixing part 3D, and the above-mentioned parts are provided in the above-mentioned order from the rear end 3a to the front end 3b of the injection screw 3.

Further, the injection screw 3 has three portions that can be structurally separated along the axial direction (longitudinal direction). These structural parts are a coil screw part 33, a flight screw part 32, and a mixing element 31, and the above-mentioned parts are provided in the above-mentioned order from the rear end 3a to the front end 3b of the injection screw 3.

A mixing element 31 is attached to the mixing unit 3D. Examples of the mixing element 31 include a Dalmage type mixing element and a Maddock type mixing element, but the present invention is not limited to this. Further, the mixing element 31 (mixing unit) may be provided as needed, and may be omitted in some cases.

The measuring unit 3C and the compression unit 3B are composed of a flight screw unit 32. The flight screw portion 32 has the same structure as a portion constituting a measuring portion and a compression portion of a full flight screw usually used as an injection screw.

The flight screw portion 32 has a screw shaft 321 and a plurality of flights 322 having the same shape. The screw shaft 321 has a rear end 321a and a front end 321b, and is formed in a round bar shape. The portion of the screw shaft 321 closer to the rear end 321a constitutes the compression portion 3B, and the portion closer to the front end 321b constitutes the weighing portion A. The front end 321b of the screw shaft 321 is connected to the rear end of the mixing element 31.

The diameter of the first screw shaft 321B, which is a portion of the screw shaft 321 that constitutes the compression portion 3B, increases toward the front. The front end of the first screw shaft 321B is coaxially connected to the rear end of the second screw shaft 321C, which is a portion of the screw shaft 321 that constitutes the measuring portion 3C. The diameter of the second screw shaft 321C is constant along the longitudinal direction. The diameter of the second screw shaft 321C is equal to the diameter of the front end of the first screw shaft 321B.

The plurality of flights 322 are coaxially provided on the outer circumference of the screw shaft 321 and are arranged at equal pitch intervals over the compression unit 3B and the measurement unit 3C. Further, as described above, the diameter of the first screw shaft 321B provided in the compression portion 3B increases toward the front. Therefore, the screw groove depth of the compression portion 3B (the length from the outer peripheral surface of the first screw shaft 321B to the outer peripheral surface of the flight 322 in the direction orthogonal to the axial direction of the first screw shaft 321B) increases toward the front. It becomes shallow. On the other hand, the diameter of the second screw shaft 321C provided in the measuring unit 3C is constant over the longitudinal direction. Therefore, the screw groove depth of the measuring unit 3C is constant over the longitudinal direction.

The material supply portion 3A of the injection screw 3 is composed of a coil screw portion 33. FIG. 3 is a side view of the coil screw portion 33, and FIG. 4 is an arrow view in the A direction of FIG. 3 when the coil screw portion 33 is viewed from the front. As shown in FIGS. 3 and 4, the coil screw portion 33 has a connecting shaft 331, a coil body 332, and a fixing member 333 (see FIG. 4).

The connecting shaft 331 is formed in the shape of a round bar having a constant diameter, and its front end 331b is coaxially connected to the rear end 321a of the screw shaft 321 (the rear end of the first screw shaft 321B) with the screw shaft 321 and rearward. It extends from the end 321a along a direction (rear) opposite to the extending direction (front) of the screw shaft 321. The rear end 331a of the connecting shaft is connected to the drive unit 5. Therefore, the driving force from the drive unit 5 is transmitted to the connecting shaft 331, and further transmitted from the connecting shaft 331 to the screw shaft 321.

The coil body 332 is a member that extends spirally along a predetermined direction and has a space formed on the inner peripheral side that penetrates in the extending direction (axial direction). In the present embodiment, the coil body 332 is made of a long member formed in a spiral shape, and is coaxially arranged with respect to the connecting shaft 331 so as to cover the outer periphery of the connecting shaft 331 in the longitudinal direction. .. One (front) end of the coil body 332 is connected to the front end 331b of the connecting shaft 331, and the other (rear) end of the coil body 332 is connected to the rear end 331a of the connecting shaft 331. As a result, the coil body 332 is connected to the rear end 321a of the screw shaft 321 via the connecting shaft 331, and is in a direction opposite to the extending direction (front) of the screw shaft 321 from the rear end 321a of the screw shaft 321. It is formed so as to extend spirally along (rear).

Further, as can be seen from FIG. 2, the coil body 332 is formed so that the outer diameter of the spirally formed coil body 332 is smaller than the outer diameter of the flight 322 provided in the flight screw portion 32. The outer diameter of the coil body 332 is the diameter of a virtual cylinder that is coaxial with the coil body 332 and whose peripheral surface is in contact with the coil body 332. In other words, the outer diameter of the coil body 332 is the length of the coil body 332 in the direction orthogonal to the axial direction of the coil body 332. The outer diameter of the flight 322 is a so-called screw diameter, which is the diameter of a virtual cylinder that is coaxial with the screw shaft 321 and whose peripheral surface is in contact with the flight 322. In other words, the outer diameter of the flight is the length of the flight in the direction orthogonal to the axial direction of the screw shaft 321.

As shown in FIG. 4, the fixing member 333 is attached to the outer peripheral surface of the connecting shaft 331. The fixing member 333 extends from the outer peripheral surface of the connecting shaft 331 to the outside of the diameter of the connecting shaft 331, and the tip thereof is connected to the coil body 332. As a result, the coil body 332 is fixed to the connecting shaft 331 via the fixing member 333 in a state of being coaxially arranged around the outer circumference of the connecting shaft 331. Further, by fixing the coil body 332 to the connecting shaft 331 in this way, elastic deformation of the coil body 332 is prevented as much as possible. In FIG. 4, three fixing members 333 are provided at equal intervals along the circumferential direction from the connecting shaft 331, but the number of fixing members 333 is not limited to this example. When a plurality of fixing members 333 are provided, they may be attached to the connecting shaft 331 at equal intervals along the circumferential direction of the connecting shaft 331. Further, it is preferable that the fixing member 333 is attached to the connecting shaft 331 at a plurality of positions different in the longitudinal direction of the connecting shaft 331.

As can be seen from the above description, the injection screw 3 according to the present embodiment has a structure in which the material supply portion of the normal flight screw is replaced with the coil screw portion 33. Such an injection screw creates a measuring section and a compression section (mixing section if necessary) of a normal flight screw, or cuts a material supply section from a normal flight screw, and then compresses the flight screw. It can be manufactured by attaching the coil screw portion 33 to the rear end of the. The flight screw portion 32 constituting the compression portion 3B and the measuring portion 3C of the injection screw portion 33 is preferably integrally formed from the viewpoint of strength. Further, each portion of the injection screw 3 may be integrally formed.

As described above, the injection screw 3 having the above configuration is arranged coaxially with the injection cylinder 2 in the internal space 2a of the injection cylinder 2. In this case, as shown in FIG. 1, the injection screw 3 is arranged in the internal space 2a of the injection cylinder 2 so that the opening 2c provided in the injection cylinder 2 faces the coil screw portion 33 (material supply portion 3A). Will be set up. That is, the opening 2c is such that the material in the hopper 4 is supplied to the coil screw portion 33 of the injection screw 3 in the injection cylinder 2 via the opening 2c regardless of the position of the injection screw 3 in the axial direction. The position of is determined.

Further, the injection cylinder 2 forms an inner peripheral wall 2d that constitutes the internal space 2a. A minute amount is formed between the inner peripheral wall 2d and the flight 322 of the flight screw portion 32, and between the inner peripheral wall 2d and the coil body 332 of the coil screw portion 33 along the direction orthogonal to the axial direction of the injection screw 3. A gap is provided. This gap is called clearance. Here, as described above, since the outer diameter of the coil body 332 is smaller than the outer diameter of the flight 322, the clearance between the coil body 332 and the inner peripheral wall 2d of the injection cylinder 2 is the inner peripheral wall of the flight 322 and the injection cylinder 2. 2d, which is larger than the clearance. That is, the coil body 332 is formed so that the clearance between the coil body 332 and the inner peripheral wall 2d forming the internal space 2a of the injection cylinder 2 is larger than the clearance between the flight 322 and the inner peripheral wall 2d.

The rear end 3a of the injection screw 3 (that is, the rear end 331a of the connecting shaft 331) arranged in the internal space 2a of the injection cylinder 2 is connected to the drive unit 5. Therefore, when the drive unit 5 is driven, the injection screw 3 rotates in the injection cylinder 2. That is, the injection screw 3 is rotatably arranged in the injection cylinder 2. Further, the injection screw 3 is configured to be able to move forward (forward) and backward (backward) in the injection cylinder 2 along the axial direction.

Next, a method of manufacturing a reinforced resin molded product using the injection molding apparatus 1 having the above configuration will be described. First, the material containing the resin pellet R and the reinforcing material S is put into the material storage space 4a of the hopper 4, and the injection molding apparatus 1 is driven. Then, the injection screw 3 rotates in the injection cylinder 2 which is heated to a desired temperature by the heater 6. At the same time, the material containing the resin pellet R and the reinforcing material S in the material storage space 4a of the hopper 4 passes through the outlet passage 4b of the hopper 4 and the opening 2c of the injection cylinder 2 in the internal space 2a of the injection cylinder 2. Is supplied to. Here, as described above, since the opening 2c of the injection cylinder 2 is arranged to face the coil screw portion 33 (material supply portion 3A) of the injection screw 3 in the injection cylinder 2, the opening 2c is passed through the opening 2c. The material that has entered the injection cylinder 2 is supplied to the coil screw portion 33 (material supply portion 3A) of the injection screw 3 in the injection cylinder 2 (material supply step).

Further, when the injection screw 3 rotates, the coil body 332 of the coil screw portion 33 translates from the rear to the front. Along with this, the material supplied to the coil screw portion 33 moves forward. That is, the material is fed forward. The material sent forward from the coil screw portion 33 (material supply portion 3A) is transported to a portion of the flight screw portion 32 located in front of the coil screw portion 33 that constitutes the compression portion 3B (transportation step).

In the compression section 3B, the material is fed forward by the rotation of flight 322. Further, as described above, since the screw groove depth in the compression portion 3B becomes shallower toward the front, a strong compressive force acts on the material as the material in the compression portion 3B moves forward in the compression portion 3B. Therefore, the material is compressed and kneaded in the compression unit 3B and heated by the heat from the heater 6. As a result, the resin melts (compression / melting step).

The material sent forward from the compression portion 3B is transported to the portion of the flight screw portion 32 that constitutes the weighing portion 3C. In the measuring unit 3C, the material is weighed. The material weighed by the measuring unit 3C is transported to the mixing unit 3D in front of the measuring unit 3C. In the mixing unit 3D, the material is further kneaded and the reinforcing material S is uniformly dispersed in the molten resin.

The material kneaded in the mixing section 3D and the reinforcing material S is uniformly dispersed in the molten resin is further sent to the front of the injection screw 3 and filled in front of the injection screw 3. Then, when the quantitative material measured by the measuring unit 3C is filled in front of the injection screw 3, the rotation of the injection screw 3 is stopped. The nozzle 2b of the injection cylinder 2 is closed while the injection screw 3 is rotating. Therefore, the material filled in front of the injection screw 3 does not flow out from the nozzle 2b and accumulates in front of the injection screw 3. At this time, the pressure of the resin stored in front of the injection screw 3 (resin back pressure) causes the injection screw 3 to move backward while rotating even if a force in the forward direction is applied to the injection screw 3.

After the rotation of the injection screw 3 is stopped, the nozzle 2b of the injection cylinder 2 is opened at a predetermined timing, and the injection screw 3 is driven forward. As a result, the material stored in front of the injection screw 3 is injected from the injection cylinder 2 into the cavity of the mold MO (injection step). The material injected into the cavity of the mold MO is cooled and solidified in the mold MO. Then, after a lapse of a predetermined time, the mold MO operates to open the mold, and the molded product is taken out from the cavity. In this way, a resin molded body (reinforced resin molded body) containing a reinforcing material is manufactured.

By the way, as described above, during the rotation of the injection screw 3, the injection screw 3 moves backward due to the pressure of the resin stored in front of the injection screw 3. At this time, when the material supply unit 3A is composed of a flight screw like a conventional injection screw, the flight crosses the opening 2c formed in the injection cylinder 2 by the rearward movement of the injection screw. Therefore, by the time the material through the opening 2c reaches the material supply section 3A, some of the material must survive the flight across the opening 2c. That is, a part of the material that has passed through the opening 2c passes through the clearance between the flight and the inner peripheral wall 2d of the injection cylinder 2 and reaches the material supply unit 3A.

If the clearance between the flight and the inner peripheral wall 2d of the injection cylinder 2 is large, the material passing through the opening 2c can easily get over the flight and reach the material supply unit 3A. However, when a conventional flight screw is used, the material is sent forward so as to be carried to the flight. Therefore, if the clearance between the flight and the inner peripheral wall 2d of the injection cylinder 2 is large, the material located in the clearance is carried to the flight. Instead, it stays in place, which reduces the transport capacity of the material. Therefore, in order to secure the material transport capacity, the clearance is set to be very small when a conventional flight screw is used. Generally, the clearance between the flight of the full flight screw and the inner peripheral wall of the injection cylinder is set to 0.2 mm to 0.5 mm. When such a very small clearance is set, the reinforcing material S among the materials that have passed through the opening 2c cannot get over the flight that crosses the opening 2c and is sandwiched in the clearance. The reinforcing material S sandwiched between the clearances receives a strong shearing force due to the rotation of the injection screw and breaks. In FIG. 5, when the material supply unit 3A is composed of a flight screw, the reinforcing material S that enters the injection cylinder 2 from the hopper 4 via the opening 2c is the flight and the inner peripheral wall 2d of the injection cylinder 2. It is a figure which shows the state which is sandwiched by the clearance between. In the portion indicated by the region A surrounded by the broken line in FIG. 5, the reinforcing material S1 is sandwiched between the flight F and the inner peripheral wall 2d of the injection cylinder 2.

When the material supply portion 3A is composed of the coil screw portion 33 as in the present embodiment, the coil body 332 of the coil screw portion 33 crosses the opening 2c of the injection cylinder 2 during the rotation of the injection screw 3. However, the outer diameter of the coil body 332 is smaller than the outer diameter of the flight 322, and the clearance between the coil body 332 and the inner peripheral wall 2d of the injection cylinder 2 is the clearance between the flight and the inner peripheral wall 2d of the injection cylinder 2 (generally). Is larger than 0.2 mm to 0.5 mm). Therefore, the possibility that the reinforcing material S is sandwiched between the coil body 332 and the inner peripheral wall 2d of the injection cylinder 2 is reduced. In FIG. 6, when the material supply portion 3A is composed of the coil screw portion 33, the reinforcing material S that enters the injection cylinder 2 from the hopper 4 via the opening 2c is the coil body 332 and the injection cylinder 2. It is a figure which shows the state which is not sandwiched by the clearance with the inner peripheral wall 2d. In the portion indicated by the region B surrounded by the broken line in FIG. 6, the reinforcing material S2 passes through the clearance between the coil body 332 and the inner peripheral wall 2d of the injection cylinder 2 without being sandwiched.

Further, as shown in FIG. 6, it has been confirmed by a confirmation experiment described later that the material transport capacity can be secured even when the clearance between the coil body 332 and the inner peripheral wall 2d of the injection cylinder 2 is set large. Therefore, the material supply portion 3A is composed of the coil screw portion 33, and the clearance between the coil body 332 and the inner peripheral wall 2d is larger than the clearance between the flight 322 and the inner peripheral wall 2d (that is, the coil body 332). By forming the coil body 332 (so that the outer diameter is smaller than the outer diameter of the flight 322), the reinforcing material S is sandwiched in the clearance in the material supply unit 3A without reducing the material transport capacity. It is possible to prevent or suppress breakage of the reinforcing material S.

The inventors conducted an experiment to visualize the transport state of the material supplied to the coil screw portion 33 (material supply portion A) using a transparent injection cylinder. According to this, when the coil screw portion 33 rotates, the coil body 332 moves forward in translation, and the material located on the inner peripheral side of the coil body 332 moves forward by the translation movement of the coil body 332. Then, the material located on the outer peripheral side of the coil body 332 is dragged to the inner peripheral side of the coil body 332 by the movement of the material on the inner peripheral side of the coil body 332. The material on the inner peripheral side of the coil body 332 is pushed out to the outer peripheral side of the coil body 332 by the material dragged from the outer peripheral side to the inner peripheral side of the coil body 332. In this way, the material supplied to the coil screw portion 33 moves forward while moving between the inner peripheral side and the outer peripheral side of the coil body 332.

That is, the propulsive force related to the movement of the material on the inner peripheral side of the coil body 332 accompanying the translational operation of the coil body 332 is also propagated to the material on the outer peripheral side of the coil body 332, so that it is supplied to the coil screw portion 33. The material moves as a whole. Therefore, as long as the movement propulsion force is propagated to the material on the outer peripheral side of the coil body 332, the material transport capacity is secured even if the clearance between the coil body 332 and the inner peripheral wall 2d of the injection cylinder 2 is increased. can do.

Further, according to an experiment by the inventors, if the clearance between the coil body 332 and the inner peripheral wall 2d of the injection cylinder 2 is 6 mm or less, the propulsive force related to the movement is propagated to the material on the outer peripheral side of the coil body 332. It has been confirmed that. Therefore, in the range where the clearance between the coil body 332 and the inner peripheral wall 2d of the injection cylinder 2 is 6 mm or less, the clearance is made larger than the clearance between the flight 322 and the inner peripheral wall 2d of the injection cylinder 2 so that the coil body 332 By forming the above, it is possible to effectively prevent or suppress breakage of the reinforcing material S due to the reinforcing material S being sandwiched in the clearance in the material supply unit 3A without lowering the material transporting capacity.

Further, if the clearance between the coil body 332 and the inner peripheral wall 2d of the injection cylinder 2 is larger than 0.5 mm, there is a possibility that the reinforcing material S is sandwiched in the clearance as compared with the case where the conventional flight screw is used. It can be reduced, and as a result, breakage of the reinforcing material S due to the reinforcing material S being sandwiched in the clearance can be suppressed. Therefore, it is preferable that the clearance between the coil body 332 and the inner peripheral wall 2d of the injection cylinder 2 is larger than 0.5 mm. In particular, as shown in the confirmation experiment described later, when the clearance between the coil body 332 and the inner peripheral wall 2d of the injection cylinder 2 is 3.0 mm, the material supply unit 3A does not reduce the material transport capacity. It has been confirmed that breakage of the reinforcing material S in the above can be sufficiently prevented or suppressed. Therefore, the clearance between the coil body 332 and the inner peripheral wall 2d of the injection cylinder 2 is preferably 3 mm or more, and more preferably, the clearance is 3 mm or more and 6 mm or less.

Further, since the coil body 332 is fixed to the connecting shaft 331 via the fixing member 333, elastic deformation of the coil body 332 is suppressed. Therefore, when the resin pressure acts on the coil body 332, the coil body 332 is prevented from being deformed. Therefore, it is possible to prevent a decrease in the material transport capacity due to the deformation of the coil body 332. That is, the material can be transported stably.

Further, if the resin in the material supplied to the material supply unit 3A melts in the material supply unit 3A, there is a risk that the material cannot be transported by the coil screw unit 33. Therefore, the temperature of the internal space 2a in the portion where the material supply unit 3A is located is preferably set to a temperature 20 ° C. or more lower than the melting point of the resin in the material. Along with this, the resin melting process shifts to the front side of the injection screw 3. That is, the resin is melted at the flight screw portion 32 of the injection screw 3. Therefore, the overall length of the flight screw portion 32 of the injection screw 3 should be long, and at least the ratio (L / D) of the effective length (L) of the flight screw portion 32 to the outer diameter (screw diameter D) of the flight 322 is 20 or more. It is good to be. Further, in order to suppress breakage of the reinforcing material S in the compression portion 3B, it is preferable that the compression ratio of the flight screw portion 32 constituting the compression portion 3B is smaller. In this case, the compression ratio of the flight screw portion 32 constituting the compression portion 3B is preferably 2 or less.

Further, it is preferable that the material transporting capacity of the coil screw portion 33 and the material transporting capacity of the flight screw portion 32 are the same. Therefore, the pitch of the coil body 332 of the coil screw portion 33 is preferably the same as the pitch of the flight 322 of the flight screw portion 32.

<Confirmation experiment>
(Example 1)
Using polypropylene resin pellets with a compounding ratio of 58 wt% and chopped strand-shaped (bundle-shaped) glass fibers with a compounding ratio of 42 wt% as materials, injection molding is performed by the injection molding apparatus 1 shown in FIG. 1 using the injection screw 3 shown in FIG. Was carried out. In this case, polypropylene resin pellets and glass fibers were individually supplied to the hopper 4. Further, the cross-sectional shape of the coil body 332 of the coil screw portion 33 of the injection screw 3 is a round shape having a diameter of 8 mm. The outer diameter of the coil body 332 is φ62.5 mm, and the inner diameter of the injection cylinder 2 is φ68.5 mm. Therefore, the clearance between the coil body 332 and the inner peripheral wall 2d of the injection cylinder 2 is 3.0 mm. The outer diameter of the flight 322 of the flight screw portion 32 is φ67.5. Therefore, the clearance between the flight 322 and the inner peripheral wall 2d of the injection cylinder 2 is 0.5 mm. Therefore, the clearance (3.0 mm) between the coil body 332 and the inner peripheral wall 2d of the injection cylinder 2 is larger than the clearance (0.5 mm) between the flight 322 and the inner peripheral wall 2d of the injection cylinder 2.

(Example 2)
Using polypropylene resin pellets having a blending ratio of 58 wt% and chopped strand-shaped glass fibers having a blending ratio of 42 wt% as materials, injection molding was carried out by an injection molding apparatus 1 shown in FIG. 1 using the injection screw 3 shown in FIG. In this case, polypropylene resin pellets and glass fibers were individually supplied to the hopper 4. Further, the cross-sectional shape of the coil body 332 of the coil screw portion 33 of the injection screw 3 is a round shape having a diameter of 8 mm. The outer diameter of the coil body 332 is φ56.5 mm, and the inner diameter of the injection cylinder 2 is φ68.5 mm. Therefore, the clearance between the coil body 332 and the inner peripheral wall 2d of the injection cylinder 2 is 6.0 mm. The outer diameter of the flight 322 of the flight screw portion 32 is φ67.5. Therefore, the clearance between the flight 322 and the inner peripheral wall 2d of the injection cylinder 2 is 0.5 mm. Therefore, the clearance (6.0 mm) between the coil body 332 and the inner peripheral wall 2d of the injection cylinder 2 is larger than the clearance (0.5 mm) between the flight 322 and the inner peripheral wall 2d of the injection cylinder 2.

(Comparison example)
Injection molding was carried out using a normal full flight screw using polypropylene resin pellets having a compounding ratio of 58 wt% and chopped strand-shaped glass fibers having a compounding ratio of 42 wt% as materials. In this case, polypropylene resin pellets and glass fibers were individually supplied to the hopper. The injection molding apparatus is the same as the injection molding apparatus 1 shown in FIG. 1, except that the injection screw is a normal full flight screw. The outer diameter of the flight is φ67.5 mm, and the inner diameter of the injection cylinder 2 is φ68.5 mm. Therefore, the clearance between the flight and the inner peripheral wall of the injection cylinder 2 is 0.5 mm.

<Confirmation of transportation capacity>
In the injection molding apparatus according to Examples 1 and 2 and Comparative Example, when the rotation speed of the injection screw is 36 rpm, 72 rpm, 108 rpm, 144 rpm, 180 rpm, the weight of the material delivered (transported) per second [g]. / Sec. ] Was measured as the transport capacity. The measurement results are shown in Table 1.

Further, FIG. 7 shows a graph showing the relationship between the screw rotation speed and the transport capacity. In FIG. 7, the horizontal axis is the screw rotation speed [rpm], and the vertical axis is the transport capacity [g / sec. ]. Further, in FIG. 7, the line connecting the points indicated by the circles is a graph (graph A) showing the relationship between the screw rotation speed and the transport capacity when the injection molding apparatus according to the first embodiment is used, and is represented by a triangle. The line connecting the indicated points is a graph (graph B) showing the relationship between the screw rotation speed and the transport capacity when the injection molding apparatus according to the second embodiment is used, and the line connecting the points indicated by the squares is 6 is a graph (graph C) showing the relationship between the screw rotation speed and the transport capacity when the injection molding apparatus according to the comparative example is used.

As can be seen from Table 1 and FIG. 7, the material transport capacity when the injection molding apparatus according to the first and second embodiments is used is the same as the material transport capacity when the injection molding apparatus according to the comparative example is used. It's almost the same. Further, even when the injection molding apparatus according to the first and second embodiments is used, the transport capacity is proportional to the increase in the screw rotation speed as in the case where the injection molding apparatus according to the comparative example is used. Can be seen to increase. From this, it can be seen that even when the injection screw 3 according to the present embodiment is used, a transport capacity equal to or higher than that when the full flight screw is used can be secured. Further, in the injection molding apparatus according to the first embodiment, the clearance between the coil body 332 and the inner peripheral wall 2d of the injection cylinder 2 is 3.0 mm, and in the injection molding apparatus according to the second embodiment, the coil body 332 and the injection cylinder 2 The clearance with the inner peripheral wall 2d is 6.0 mm. Therefore, it can be seen that if the clearance between the coil body 332 and the inner peripheral wall 2d of the injection cylinder 2 is 6.0 mm or less, a sufficient transport capacity can be secured.

なお、表２における位置の欄の「材料（素材）」とは、ホッパーに供給するガラス繊維の重量平均繊維長である。 <Measurement of weight average fiber length of glass fiber>
In the case of injection molding by the injection molding apparatus according to Example 1, Example 2 and Comparative Example, the glass fiber contained in the material located at each of the material supply part, the compression part, the measuring part, and the nozzle outlet of the injection cylinder of the injection screw. , And the weight average fiber length of the glass fiber contained in the fiber reinforced resin molded product (molded product) injected into the mold is measured, and the change in the weight average fiber length of the glass fiber as the molding process progresses is measured. investigated. The weight average fiber length of the glass fibers in the material located in each part (material supply part, compression part, measuring part) of the injection screw is injected from the injection molding apparatus during injection molding (however, the operation of the injection screw is stopped). The measurement was performed by pulling out the screw and collecting the material located at each site. Table 2 shows the measurement results of the weight average fiber length at each position for Examples and Comparative Examples.

The "material" in the position column in Table 2 is the weight average fiber length of the glass fibers supplied to the hopper.

Further, FIG. 8 is a graph showing changes in the weight average fiber length of the glass fibers at each of the above positions. The horizontal axis of FIG. 8 is the position where the weight average fiber length of the glass fiber is measured, and the material forming process proceeds from right to left. The vertical axis of FIG. 8 is the weight average fiber length of the glass fiber at each position. Further, in FIG. 8, the line connecting the points indicated by the circles is a graph (graph D) showing the change in the weight average fiber length of the glass fiber when the injection molding apparatus according to the first embodiment is used, and is represented by a triangle. The line connecting the indicated points is a graph (graph E) showing the change in the weight average fiber length of the glass fiber when the injection molding apparatus according to the second embodiment is used, and the line connecting the points indicated by the squares is It is a graph (graph F) which shows the change of the weight average fiber length of the glass fiber at the time of using the injection molding apparatus which concerns on a comparative example.

As can be seen from Table 2 and FIG. 8, whether the injection molding apparatus according to Examples 1 and 2 is used or the injection molding apparatus according to Comparative Example is used, as the molding process progresses (on the horizontal axis of FIG. 8). From right to left), the weight average fiber length of the glass fiber becomes shorter. However, the weight average fiber length of the glass fiber in the material supply section when the injection molding apparatus according to Examples 1 and 2 is used is the glass fiber in the material supply section when the injection molding apparatus according to Comparative Example is used. Much longer than the weight average fiber length of. From this, it can be seen that the breakage of the glass fiber in the material supply section (or up to the material supply section) is sufficiently suppressed by using the injection molding apparatus according to Examples 1 and 2. Further, in the injection molding apparatus according to the first embodiment, the clearance between the coil body 332 and the inner peripheral wall 2d of the injection cylinder 2 is 3.0 mm, and in the injection molding apparatus according to the second embodiment, the coil body 332 and the injection cylinder 2 The clearance with the inner peripheral wall 2d is 6.0 mm. Therefore, it can be seen that if the clearance between the coil body 332 and the inner peripheral wall 2d of the injection cylinder 2 is 3.0 mm or more, the breakage of the glass fiber can be sufficiently suppressed.

Although the embodiments of the present invention have been described above, the present invention should not be limited to the above embodiments. For example, in the above embodiment, the coil screw portion 33 constituting the material supply portion 3A of the injection screw 3 includes the coil body 332, the connecting shaft 331, and the fixing member 333. For example, as shown in FIG. , The coil screw portion 33 may be formed only by the coil body 332. Further, the cross-sectional shape of the coil body 332 may be circular or other shape (for example, a quadrangle).

Further, in the present invention, the material supply portion is composed of the coil screw portion, and the clearance between the coil body of the coil screw portion and the inner peripheral wall of the injection cylinder is larger than the clearance when a normal full flight screw is used. It is characterized by. Therefore, the screw shape in the functional part other than the material supply part does not need to be caught in the above embodiment and may be deformed if necessary. For example, in the above embodiment, the diameter of the first screw shaft 321B, which is a portion of the screw shaft 321 that constitutes the compression portion 3B, is increased toward the front. However, the diameter of the screw shaft of the portion constituting the rear side of the compression portion 3B (the rear portion of the compression portion) is made constant, and the diameter of the screw shaft of the portion constituting the front side (the front portion of the compression portion) is increased toward the front. It may be increased. In this case, the screw groove depth of the compression portion rear portion of the compression portion 3B is constant. Therefore, the rear portion of the compression portion fulfills the material transport function and the melting function. On the other hand, the depth of the screw groove in the front portion of the compression portion of the compression portion 3B becomes shallower toward the front. Therefore, the front portion of the compression portion fulfills the compression function and the melting function of the material. That is, the compression unit 3B may have other functions as long as it has a function of compressing the material.

Further, in the above embodiment, an example is shown in which the coil body 332 included in the coil screw portion 33 constituting the material supply portion 3A is formed of a long member formed in a spiral shape. However, if the coil body is configured to have a spiral shape and a space penetrating in the extending direction (axial direction) is formed on the inner peripheral side, the coil body may have a shape other than the coil body 332 shown in the above embodiment. Can be adopted. For example, the coil body and the fixing member of the present invention can be provided by a plurality of flights having a diameter smaller than that of the flight 322 and having through holes formed along the axial direction of the injection screw 3 (hereinafter referred to as a small diameter flight with a through hole). It may be configured. When the coil body and the fixing member are composed of a small-diameter flight with a through hole, a propulsive force is applied to the material in the small-diameter flight with a through hole by the translational operation of the small-diameter flight with a through hole accompanying the rotation of the injection screw. As a result, the material in the through hole is transported, and the propulsive force is propagated to the material on the outer peripheral side of the small diameter flight with a through hole, and the material on the outer peripheral side of the small diameter flight with a through hole is also transported. Such a configuration is also included in one embodiment of the present invention. As described above, the present invention can be modified as long as it does not deviate from the gist thereof.

1 ... Injection molding device, 2 ... Injection cylinder, 2a ... Internal space, 2b ... Nozzle, 2c ... Opening, 2d ... Inner peripheral wall, 3 ... Injection screw, 3A ... Material supply part, 3B ... Compression part, 3C ... Weighing part, 3D ... mixing part, 3a ... rear end, 3b ... front end, 4 ... hopper, 4a ... material storage space, 4b ... outlet passage, 5 ... drive unit, 6 ... heater, 31 ... mixing element, 32 ... flight screw part, 321 ... Screw shaft, 321B ... First screw shaft, 321C ... Second screw shaft, 321a ... Rear end, 321b ... Front end 322 ... Flight, 33 ... Coil screw part, 331 ... Connecting shaft, 332 ... Coil body, 333 ... fixing member, R ... resin pellet, S ... reinforcing material

Claims (6)

A screw shaft having a rear end and a front end, a flight screw portion having a flight provided on the outer circumference of the screw shaft, and a flight screw portion connected to the rear end of the screw shaft and extending from the rear end to the screw shaft. An injection screw comprising a coil screw portion having a coil body spirally extended in the direction opposite to the above.
In order to form a cylinder so that a columnar internal space is formed, the injection screw is coaxially arranged in the internal space, and a material containing a resin and a reinforcing material is supplied to the internal space. With an injection cylinder with an opening
With
The position of the opening is defined so that the material is supplied to the coil screw portion.
An injection molding apparatus in which the coil body is formed so that the clearance between the coil body and the inner peripheral wall forming the internal space of the injection cylinder is larger than the clearance between the flight and the inner peripheral wall. In the injection molding apparatus according to claim 1,
The coil screw portion includes a connecting shaft connected to the rear end of the screw shaft and extended from the rear end along a direction opposite to the extending direction of the screw shaft, and the connecting shaft and the connecting shaft. It is equipped with a fixing member that connects to the coil body.
An injection molding apparatus in which the coil body is fixed to the connecting shaft via the fixing member in a state of being coaxially arranged around the outer circumference of the connecting shaft. In the injection molding apparatus according to claim 1 or 2.
An injection molding apparatus in which the clearance between the coil body and the inner peripheral wall is 6 mm or less. In the injection molding apparatus according to claim 3,
An injection molding apparatus in which the clearance between the coil body and the inner peripheral wall is larger than 0.5 mm. In the injection molding apparatus according to any one of claims 1 to 4.
The injection screw includes a material supply unit to which the material is supplied, a compression unit that compresses the material supplied to the material supply unit, and a measurement unit that measures the material compressed by the compression unit, in this order. It is provided along the longitudinal direction of the injection screw and is provided.
An injection molding apparatus in which the measuring section and the compressing section are configured by the flight screw section, and the material supply section is configured by the coil screw section. A method for manufacturing a reinforced resin molded product using the injection molding apparatus according to claims 1 to 5.
A material supply process for supplying a material containing a resin and a reinforcing material to the coil screw portion, and
A transportation process for transporting the material supplied to the coil screw portion to the flight screw portion, and
A compression / melting step of compressing the material transported to the flight screw portion and melting the resin in the material.
An injection step of injecting the material containing the resin compressed and melted in the compression / melting step into a mold, and an injection step.
A method for producing a reinforced resin molded product, including.

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