JP2017065201A - Plunger type injection unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plunger type injection unit which has large injection pressure and large injection speed, and which is optimal for injection of a fiber-reinforced resin.SOLUTION: A plunger type injection unit (1) is comprised of: a heating cylinder (2); a plunger (4) provided in the heating cylinder (2); a melter (5); and a transport piston (8) provided in the heating cylinder (2). The melter (4) is integrated with the plunger (4), and the transport piston (8) is configured to be driven in a reciprocating manner in the heating cylinder (2) independent from the plunger (4). When the plunger (4) is driven forward, during injection, the transport piston (8) is also driven in an integrated manner. The transport piston (8) is comprised of an annular body and is provided in a shaft portion (18) having a certain diameter which is formed in a prescribed zone near a rear side of the plunger (2).SELECTED DRAWING: Figure 2

Description

  The present invention comprises a heating cylinder, a plunger that is reciprocatingly driven in the heating cylinder, a backflow prevention device, and a melter provided with a plurality of injection material melting holes or grooves. The plunger-type injection device is designed to be driven integrally with the plunger. The plunger-type injection device is suitable for injecting a fiber-reinforced resin including a reinforcing fiber such as a glass fiber, but not limited thereto. The present invention relates to an injection device.

  The injection device can be roughly classified into an inline screw type and a plunger type. The in-line screw type is composed of a heating cylinder, a screw that can be driven in the rotation direction and the axial direction in the heating cylinder, a drive device that drives the screw in the rotation direction and the axial direction, and the like, as is conventionally known. Has been. An injection nozzle is provided in front of the heating cylinder, a hopper is provided at the rear end, and a band heater is provided at the outer periphery of the heating cylinder. Therefore, when the screw is rotated and the resin material is supplied from the hopper, the resin material is melted by the heat from the band heater, the frictional heat due to the rotation of the screw, the shear heat, etc. in the process of being sent forward, and the front of the heating cylinder. Accumulated in the weighing chamber or storage chamber. As a result, the screw is retracted by the pressure of the accumulated molten resin and the measurement is completed. When the screw is driven in the axial direction, molten resin is injected and filled into a mold that has been clamped, and after cooling and solidification, the movable mold is opened to obtain a molded product.

  In such an inline screw type injection device, a backflow prevention device is provided at the tip of the screw so that the molten resin does not flow back through the heating cylinder during injection. The backflow prevention device includes a backflow prevention ring that is loosely fitted to a shaft portion formed in a small diameter at the tip of the screw, and a presser on which the backflow prevention ring is seated. The backflow prevention ring can be moved back and forth at a predetermined stroke in the shaft portion, and at the time of measurement, it receives the pressure of the molten resin and moves forward away from the presser. If it does so, molten resin will be sent ahead through the resin flow path which consists of the internal diameter of a backflow prevention ring, and the clearance gap between shaft parts. On the other hand, when the screw is driven forward at the time of injection, the backflow prevention ring moves backward and is seated on the presser and the resin flow path is closed. This prevents the back flow of the molten resin. By the way, although it describes also in patent document 1, in the in-line screw type injection device provided with the backflow prevention device, when the fiber reinforced resin containing reinforcing fibers such as glass fiber is melted and injected, the stroke of the backflow prevention ring Becomes a problem. That is, if the stroke of the backflow prevention ring is short, the molten resin passes through a narrow gap between the presser and the backflow prevention ring, and the reinforcing fibers are damaged and shortened. Therefore, it is necessary to ensure a long stroke in order to prevent damage to the reinforcing fibers. However, when the stroke of the backflow prevention ring is long, the amount of the molten resin flowing back at the start of injection becomes unstable, and there is a problem that the weight of the molded product varies.

  In contrast to such an inline screw type injection device that requires a backflow prevention device, the plunger type injection device does not necessarily require a backflow prevention device. As is well known in the art, a plunger-type injection device includes a heating cylinder, a plunger provided in the cylinder so as to be driven, a melter for melting pellets, a drive device for driving the plunger, and the like. Plunger-type injection devices are of various types and have been proposed in various patent documents.

Japanese Patent No. 4272502 JP-A-53-106765 Japanese Patent No. 4817402

  As shown in FIG. 4, Patent Document 2 discloses a plunger type injection device that includes a heating cylinder 50 having a predetermined length in the axial direction and a plunger 56 that is driven forward in the cylinder 50. ing. An injection nozzle 51 is provided in front of the heating cylinder 50, and a hopper 52 is provided in the rear. Further, between the injection nozzle 51 and the hopper 52, a melter, that is, first and second stage torpedos 53 and 55 are fixedly provided to the heating cylinder 50 at a predetermined interval. The first stage torpedo 53 is heated by a heater, and a plurality of small diameter gradient holes at the tip, that is, tapered resin passage holes 54, 54,... Yes. On the other hand, a plurality of spiral grooves 56, 56,... Are formed on the outer peripheral surface of the second stage torpedo 55. Therefore, when the plunger 56 is driven forward, the pellets P, P,... Supplied from the hopper 52 are pushed forward and pass through the plurality of resin passage holes 54, 54,. pass. At this time, the pellets P, P,... Are pressed against the inner peripheral walls of the passage holes 54, 54,. When passing through the spiral grooves 56, 56,... Of the second torpedo 55, it is further melted by heat generated by shearing or kneading action, and then injected and filled from the injection nozzle 51 into the mold cavity that has been clamped. The When the movable mold is opened after cooling and solidification, a molded product is obtained.

  As shown in FIG. 5, the plunger-type injection device proposed in Patent Document 2 is provided with a heating cylinder 60 provided with an injection nozzle 61 at its tip, and is driven in the heating cylinder 60. The plunger 66, the melter 63 in which a plurality of resin passage holes 64, 64,... Are formed, the air vent 67 provided in the vicinity of the resin supply port, and the like. A heater 68 is attached to the outer peripheral portion of the heating cylinder 60, and the resin passage holes 64, 64,... Therefore, when the plunger 66 is driven downward, that is, forward, the pellets supplied from the hopper 62 are pushed forward and consolidated when passing through the plurality of resin passage holes 64, 64,... 64, and so on. At this time, it is efficiently melted by heat applied from the heating cylinder 60, frictional heat generated when passing through the resin passage holes 64, 64,. When melted in this way, the air retained between the pellets is exhausted from the air vent 67. Next, the mold is clamped and filled from the injection nozzle 61. When the movable mold is opened after cooling and solidification, a molded product is obtained in the same manner.

  In the plunger type injection devices described in Patent Documents 1 and 2, since the resin does not flow backward at the time of injection, a backflow prevention device is not required. Therefore, it can be said that it is advantageous that the reinforcing fibers are not cut in the backflow prevention device when molding is performed with the fiber reinforced resin including the reinforcing fibers.

  There are inline screw type and plunger type in the injection device, and each has advantages and disadvantages, and if it is better, it can not be determined immediately, but with the inline screw type, the amount of pellets in contact with the inner peripheral wall of the heated cylinder is small, It takes time to melt. Therefore, there is a problem that the screw or the heating cylinder must be elongated in the axial direction in order to melt the pellet. Further, when molding with fiber reinforced resin, there is also a problem that the reinforcing fiber is easily damaged in the backflow prevention device. In the backflow prevention device, if the stroke of the backflow prevention ring is increased, damage to the reinforcing fibers can be prevented, but the problem that the amount of molten resin to be injected becomes unstable remains. On the other hand, since the pellet type or the molten resin passes through the plurality of passage holes of the melting device, the plunger type has a wide contact area between the pellet and the melting device and is easily melted. Therefore, it is not necessary to lengthen the heating cylinder and the plunger in the axial direction, and an advantage that the injection device can be configured compactly is recognized. Further, since a backflow prevention device is not essential, there is an advantage that damage of the reinforcing fiber can be prevented. Although the present invention is directed to such a plunger type injection device, there is a problem with the plunger type injection device. The plunger-type injection device described in Patent Documents 2 and 3 will be described as an example. Both of them perform resin melting and injection simultaneously when the plungers 56 and 66 are driven forward. In other words, since the melting and the injection are performed simultaneously by driving in one direction, the pressing force of the plungers 56 and 66 is distributed to the pressure loss and the injection pressure when the pellets are melted. That is, in order to increase the injection pressure, it is necessary to increase the pressing force of the plungers 56 and 66. However, as the pressing force of the plungers 56 and 66 increases, the pressure loss of the melters 53 and 63 also increases. The conventional plunger-type injection device that performs the above simultaneously has a problem that it is difficult to obtain a high injection pressure. There is also a problem with the injection speed. The injection speed may be increased by increasing the driving speed of the plungers 56 and 66, but the pellets must be reliably melted in the melters 53 and 63. However, there is a limit in trying to shorten the melting time in the melting units 53 and 63. That is, there is a problem that the melters 53 and 63 are rate limiting and the injection speed cannot be increased sufficiently.

  An object of the present invention is to provide a plunger type injection device that solves the above-mentioned conventional drawbacks or problems. Specifically, a plunger that can increase the injection pressure and the injection speed by taking advantage of the advantages of the plunger type. An object of the present invention is to provide a plunger type injection device suitable for molding with a fiber reinforced resin, although not limited thereto.

  In order to achieve the above object, the present invention provides a heating cylinder, a plunger provided in the heating cylinder, a melter in which a plurality of injection material melting holes or melting grooves are formed, and a heating cylinder. A plunger-type injection device is constituted by the transport piston provided. The melter is provided integrally with the plunger. The transport piston is configured to be able to reciprocate dynamically within the heating cylinder independently of the plunger. However, when the plunger is driven forward, the transport piston is driven integrally with the plunger. The transport piston is preferably composed of an annular body, and is provided on a shaft portion having a constant diameter formed in a predetermined section near the rear of the plunger. The plunger is provided with a backflow prevention device.

That is, in order to achieve the above-mentioned object, the invention according to claim 1 is a heating cylinder in which a tip end portion serves as a storage portion for molten injection material and a rear end portion serves as a supply portion for injection material to be supplied. And a plunger provided in the heating cylinder, a melter in which a plurality of injection material melting holes or melting grooves are formed, and a transport piston provided in the heating cylinder. The container is provided integrally with the plunger, and the transport piston can be reciprocally driven in the heating cylinder independently of the plunger, and the plunger is driven when the plunger is driven forward. It is comprised as a plunger type injection device characterized by being driven integrally.
According to a second aspect of the present invention, in the plunger-type injection device according to the first aspect, the plunger includes a shaft portion in which a predetermined section near the rear is formed with a constant diameter, and the transport piston is the shaft portion. It is comprised as a plunger type injection device characterized by comprising an annular body provided coaxially.
According to a third aspect of the present invention, in the plunger type injection device according to the first or second aspect, the number of the injection material melting holes or the melting grooves of the melter increases toward the tip. It is comprised as a plunger type injection device characterized by this.

  As described above, according to the present invention, a heating cylinder is provided in the heating cylinder in which the front end portion serves as a storage portion for the molten injection material and the rear end portion serves as a supply portion for the injection material supplied. And a plunger having a plurality of injection material melting holes or melting grooves, and a transport piston provided in a heating cylinder. The melter is provided integrally with the plunger, and the transport piston is reciprocally driven in the heating cylinder independently of the plunger, and when the plunger is driven forward, It is designed to be driven integrally. Since such a transport piston is provided, when the transport piston is driven in the axial direction in the heating cylinder, the pellets can be fed forward, and the pellets can be melted in the melter and metered in the accumulator. At this time, it is not necessary to drive the plunger. When the plunger is driven in the axial direction during injection, the transport piston is integrally driven, so that the transport piston has an effect of preventing the backflow of the molten resin. That is, the plunger type injection device according to the present invention does not require a backflow prevention device having a backflow prevention ring. Although the backflow prevention device causes damage to the reinforcing fibers, such a backflow prevention device is not necessary, so that it can be said that the plunger type injection device of the present invention is suitable for molding with fiber reinforced resin. In the present invention, since there is no resistance in the melter at the time of injection, the axial force of the plunger acts as the injection pressure as it is. That is, the injection pressure can be applied efficiently. And since it is not necessary to melt a pellet with a fuser at the time of injection, the injection speed can be increased. That is, the plunger type injection device according to the present invention has an effect of increasing the injection pressure and the injection speed. According to another invention, the plunger includes a shaft portion in which a predetermined section near the rear is formed with a constant diameter, and the transport piston is formed of an annular body provided coaxially with the shaft portion. That is, the transport piston is provided coaxially with the plunger. Then, when the pellets are fed forward by the transport piston, a pressing force acts on the pellets in a well-balanced manner in the heating cylinder, and the pellets can be efficiently melted by the melter and the injection material can be measured. The transport piston is driven integrally with the plunger at the time of injection to prevent the reverse flow of the molten resin, but since the transport piston is formed in an annular body, the pressure is applied uniformly to the molten resin and the balance is achieved. good. According to still another invention, the number of injection material melting holes or melting grooves of the melting device increases toward the tip. The pellets are melted in contact with the injection material melting holes and the wall of the melting groove, but as the number of injection material melting holes and melting grooves increases, the area of the wall surface increases. As a result, the injection material is easily melted.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows typically the plunger type injection device which concerns on embodiment of this invention, The (a) is front sectional drawing of a plunger type injection device, The (a)-(D) is the (a), respectively. It is sectional drawing of the plunger seen in arrow AA, BB, CC direction in FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the effect | action of the plunger type injection device which concerns on embodiment of this invention typically, (a)-(d) is front sectional drawing of the plunger type injection device in each process of injection | emission. It is front sectional drawing of the plunger type injection device which concerns on the 2nd Embodiment of this invention. It is sectional drawing which shows the conventional plunger type injection device. It is sectional drawing which shows the other conventional plunger type injection device.

  Embodiments of the present invention will be described below. As shown in FIG. 1A, the plunger injection device 1 according to this embodiment includes a heating cylinder 2 having a predetermined length in the axial direction and a screw provided inside the heating cylinder 2. A plunger 4 having a head, a melter 5 provided in the plunger 4, a transport piston 8 which is a member unique to the present invention and will be described later, and the like. The heating cylinder 2 is a storage portion where the injection material in a molten state is measured at the tip, and an injection nozzle 10 is provided at the tip. The rear part is a supply part to which pellets of the injection material are supplied, and a hopper 11 is provided in the supply part. Although not shown in the drawing, a plurality of band heaters are wound around the outer peripheral surfaces of the heating cylinder 2 and the injection nozzle 10 so that the heating cylinder 2 and the injection nozzle 10 can be heated.

  The melter 5 includes fins 13, 14, and 15 fixedly provided in a predetermined section of the plunger 4, and when the plunger 4 is driven, the melter 5 is driven back and forth integrally with the plunger 4. The fins 13, 14, 15 are provided on the plunger 4 so as to be parallel to the axial direction and even in the circumferential direction, but the fins 13, 14, 14 provided in the respective sections of the melter 5 are provided. The number of 15 is different. That is, six fins 13, 14, 15,... Are provided in the section closer to the rear of the melter 5, as shown in FIG. 1D, and in FIG. As shown in FIG. 1, 8 sheets are provided, and in the section closer to the front, 12 sheets are provided as shown in FIG. The injection material is melted when it flows through a groove between adjacent fins 13, 14, 15,. That is, the heat of the heating cylinder 2 heated by the band heater is conducted to the fins 13, 14, and 15 and is efficiently melted by this heat. Since the injection material is supplied as pellets, the number of fins 13, 13,... Is small and the gap between the melt grooves is large so that the pellets can easily pass through the rear part. In order to melt reliably, the number of sheets is increased so that the contact area between the injection material and the fins 15, 15,. That is, the number of the melt grooves increases as it approaches the tip. As a result, the injection material is sufficiently melted as it is sent to the tip.

  The transport piston 8 according to the present embodiment will be described. The transport piston 8 is made of an annular body having a predetermined thickness. A predetermined section in the rear portion of the plunger 4 is a shaft portion 18 having a constant diameter, and the transport piston 8 is slidably provided on the shaft portion 18. Although the drive mechanism is not shown in FIG. 1A, the transport piston 8 is reciprocally driven in a predetermined section in the heating cylinder 2 independently of the plunger 4. When such a transport piston 8 is driven in the axial direction, the pellets of the injection material supplied from the hopper 11 can be sent forward in the heating cylinder 2, whereby the injection material is melted in the melter 5 and heated. 2 is stored in the storage unit.

  As will be apparent from the description of the operation, the transport piston 8 according to the present embodiment is driven integrally with the plunger 4 when driving the plunger 4 forward during injection. Thereby, the transport piston 8 prevents the backflow of the injection material. Therefore, in the plunger-type injection device 1 according to the present embodiment, no backflow prevention device is provided at the tip of the plunger 4. A groove 20 is formed at the tip of the plunger 4 in place of the backflow prevention device so that the injection material flows smoothly.

  The operation of the plunger type injection device 1 according to the present embodiment will be described with reference to FIG. The plunger-type injection device 1 according to the present embodiment can inject various injection materials. In the following, an example will be described in which a fiber reinforced resin containing reinforcing fibers such as glass fibers and carbon fibers is injected. . The heating cylinder 2 is heated by a band heater, and fiber reinforced resin pellets are supplied from the hopper 11 as shown in FIG. Then, the transport piston 8 is driven in the axial direction as shown in FIG. Then, the pellets are sent forward in the heating cylinder 2 by the pressing force of the transport piston 8. The pellets are melted when passing through the melter 5 to become a molten injection material. That is, it becomes an injection material containing reinforcing fibers. When the transport piston 8 is driven in the axial direction, the molten injection material including the reinforcing fibers is measured in the accumulation portion at the tip of the heating cylinder 2. At this time, since the injection material flows smoothly through the groove 20, the injection material is measured without damaging the reinforcing fibers. The driving of the transport piston 8 in the axial direction may be performed only once or may be repeated a plurality of times. As described above, the number of times of driving of the transport piston 8 is not limited, but after the drive, the transport piston 8 is moved back to the original position. As shown in FIG. 2C, when the metering proceeds, the plunger 4 is retracted by the pressure of the injection material. When the predetermined position is reached, the weighing is completed. The plunger 4 is driven in the axial direction as shown in FIG. At this time, the transport piston 8 is also driven integrally with the plunger 4. Alternatively, although not shown in the drawing, the transport piston 8 is temporarily fixed to the plunger 4 by a predetermined locking mechanism, and the transport piston 8 is driven integrally when the plunger 4 is driven forward. To be. Then, the backflow of the injection material including the reinforcing fibers is prevented by the transport piston 8 driven together with the plunger 4, and is injected from the injection nozzle 10 under the pressing force of the plunger 4. Although not shown in the drawing, a molded product made of fiber reinforced resin is obtained by being injected into a clamped mold.

  The plunger-type injection device 1 according to the present embodiment includes a transport piston 8 that is driven independently of the plunger 4 in the heating cylinder 2, so that the injection material is sent forward without driving the plunger 4. Can be melted. When the plunger 4 is driven at the time of injection, most of the pressing force of the plunger 4 can act as the injection pressure. Since the transport piston 8 has a backflow prevention function, a backflow prevention device is unnecessary, and damage to the reinforcing fibers can be prevented when the fiber reinforced resin is measured or injected. As described above, the plunger injection device 1 according to the present embodiment can naturally handle general resin materials that do not include reinforcing fibers.

  The plunger-type injection device 1 according to the present embodiment can be variously modified. For example, FIG. 3 shows a plunger-type injection device 1 ′ according to the second embodiment. In this embodiment, the transport piston 8 ′ is not an annular body. In the heating cylinder 2 ′, an extended section 20 having a wide bore in a predetermined rear section is formed, and a transport piston 8 ′ is provided in the expanded section 20. Those skilled in the art can easily understand that, as long as the cross-sectional shapes of the expansion section 20 and the transport piston 8 ′ are equal, these may be any shape, and the transport piston 8 ′ can be pivoted. If driven in the direction, the pellets can be fed forward in the heating cylinder 2 'to melt it and the injection material can be weighed. If the transport piston 8 'is driven integrally with the plunger 4 at the time of injection, backflow of the injection material can be prevented. Other modifications are possible, and the melter 5 can also be modified. In this embodiment, the melter 5 is composed of fins 13, 14, 15,... And is melted when the injection material flows through these grooves, that is, the melt grooves. On the other hand, the melter 5 can be configured to include a plurality of axial holes, that is, injection material melting holes.

DESCRIPTION OF SYMBOLS 1 Plunger type injection apparatus 2 Heating cylinder 4 Plunger 5 Melting machine 8 Transport piston 10 Injection nozzle 11 Hopper 13, 14, 15 Fin 18 Shaft part

Claims (3)

A heating cylinder that serves as an injection material supply unit to which the front end portion is a molten injection material accumulation portion and a rear end portion is supplied, a plunger provided in the heating cylinder, and a plurality of injection materials A melter in which a melt hole or a melt groove is formed, and a transport piston provided in the heating cylinder,
The melter is provided integrally with the plunger;
The transport piston can be driven reciprocally in the heating cylinder independently of the plunger, and is driven integrally with the plunger when the plunger is driven forward. A plunger-type injection device.   2. The plunger-type injection device according to claim 1, wherein the plunger includes a shaft portion in which a predetermined section near the rear is formed with a constant diameter, and the transport piston is an annular body provided coaxially with the shaft portion. A plunger type injection device comprising:   3. The plunger type injection device according to claim 1, wherein the injection material melting hole or the melting groove of the melter increases in number toward the tip. .

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