JPH0651329B2 - Injection molding machine - Google Patents

Description

The present invention relates to an injection molding machine, and more particularly to BMC (Bulk Molding).
The present invention relates to an injection molding machine suitably used for a molding material containing a glass fiber such as a compound.

[Prior Art and Prior Art] A molding material in which a synthetic resin such as unsaturated polyester is mixed with glass fiber has various compositions depending on the use and the molding method.
There is a property.

The mechanical properties of the molded product have a strong correlation with the state of the glass fiber of the molded product, the longer the fiber length and the more unbent,
Mechanical strength is improved.

The length of the glass fiber in the molded product is of course related to the length of the raw material glass fiber, but it is also related to the molding method, and it is important to use a molding method with as few breakages as possible. It is necessary to improve mechanical properties.

Plunger type molding machine has less breakage of glass fiber and less bending than screw type. However, in spite of these advantages, the plunger type molding machine is rarely adopted in practice. This is because of the structural drawbacks described below. The general structure of the plunger type is shown in FIGS.

FIG. 11 is a schematic configuration diagram of a conventional plunger type injection molding machine. The molding machine 1 includes a stuffer 3 and a barrel 4 connected by an elbow 2, and an inner hole of the stuffer 3 has: The plunger 6 of the supply cylinder 5 is reciprocally inserted. Further, the plunger 8 of the injection cylinder 7 is fitted into the inner hole of the barrel 4, and the stuffer 3
The material supply port 9 from is opened in the middle part of the inner hole near the nozzle 10. Reference numeral 11 is a check valve for preventing backflow of material. With this structure, when the material 12 is charged into the stuffer 3 and the plunger 6 of the supply cylinder 5 is advanced, the material 12 is supplied through the elbow 2 into the barrel 4 through the material supply port 9. The check valve 11 regulates backflow. Then, by moving the plunger 8 of the injection cylinder 7 forward, the material 1 in the barrel 4 is
2 can be injected from the nozzle 10 into the mold.

Further, FIG. 12 is a schematic configuration diagram showing another example of a conventional plunger type injection molding machine, and the components denoted by the same reference numerals as those in FIG. 11 have the same structure, and therefore the description thereof will be omitted.
This example is different from the example shown in FIG. 11 in that the material supply port 9A from the stuffer 3 is opened at the end of the barrel 4A on the side opposite to the nozzle 10 and the check valve 11 is not provided. . The material 12 is supplied into the barrel 4A by the advance of the plunger 6, and the injection is performed by the advance of the plunger 8, as in the example shown in FIG.

However, in the conventional molding apparatus shown in FIG. 11, since the material supply port 9 is provided near the nozzle 10, the back pressure can be applied by the injection cylinder 7 when the material 12 is metered and supplied from here. However, on the other hand, the material 12 that has entered from the material supply port 9 to the inner hole of the barrel 4 faces the plunger 8 side, and the material 12 that has entered afterwards is the nozzle 1
The material 1 that entered first when it was ejected
Since 2 comes out later, there is a drawback that the material 12 tends to stay. Moreover, since the seal portion of the plunger 8 passes through the material supply port 9 during injection, the seal portion is easily damaged.

Further, in the case shown in FIG. 12, the material supply port 9A
Is provided near the plunger 8 and the material 8 is supplied by retracting the plunger 8 for each shot, so the material 12 that has entered first comes out first, but since back pressure is not applied, it is supplied. The measured material 12 becomes unstable,
In addition, there is a drawback that it is easy to entrap air.

The present applicant has proposed a rotary plunger type injection molding machine shown in FIG. 13 in Japanese Patent Application Nos. 60-79197, 60-168898 and 61-77309 as means for solving these drawbacks. .

In FIG. 13, a cylindrical barrel 2 having a nozzle 21 at its tip and a temperature control device at a relatively low temperature on its outer periphery.
2 is disposed so that the nozzle 21 faces the material injection port of the mold.

In the barrel 22, a plunger 24 having an outer diameter smaller than the inner diameter of the barrel 22 and having a backflow prevention mechanism including a check ring 23, a ball and the like near the tip is provided so as to be able to move forward and backward and to rotate. Between the inner peripheral surface of the barrel 22 and the outer peripheral surface of the plunger 24.
Are formed. At the material inlet portion on the rear side of the barrel 22, for example, a stuffer type material supply device having a stuffer plunger 30 in a stuffer 27 having a material inlet 31 as shown in the drawing is provided. (The material supply device may be another type of device, such as a type having a sufficient material supply capacity such as a screw feeder.) As shown in the drawing, the plunger 24 has a rear end side substantially equal to the barrel inner diameter. The convex portion 25 has a diameter increased so as to have the same diameter. The convex portion 25 slides on the inner peripheral surface of the barrel 22, and holds the plunger 24 so that the plunger 24 is arranged substantially coaxially with the barrel 22. The further rear end side of the plunger 24 projects from the barrel 22 and is connected to a plunger rotation and forward / backward movement mechanism (not shown).

In the injection molding machine having such a configuration, when the stuffer plunger 30 for material supply is advanced with the plunger 24 located in the front of the barrel 22 of the injection cylinder being rotated, the material is supplied while being metered. Mouth 28,
The material is supplied to the tip of the barrel of the injection cylinder through the material passage 70 and the backflow prevention mechanism 23. When the desired amount of BMC or the like is accumulated in front of the barrel 22, the measurement is finished, and when the plunger 24 is advanced thereafter, the material is injected from the nozzle 21, but in this case, the material that has entered the material passage 70 first comes out. . Also, the rotation of the plunger 24 makes the material flow extremely smooth and uniform. This plunger type injection molding machine has a characteristic that the metering capacity increases almost in proportion to the number of rotations, although there is no portion corresponding to a screw type flight.

[Problems to be Solved by the Invention] According to the above structures proposed in Japanese Patent Application Nos. 60-79197 and 60-168898, a glass fiber is less damaged and a molded article having excellent performance can be obtained. But
It has been found that this type has the following improvement problems.

That is, when the material is supplied from the material supply device (stuffer 27) into the barrel 22, bending stress is generated in the plunger 24 due to the force of pushing the plunger downward from above. If this bending stress is excessive, the plunger 24 may be damaged by repeated bending stress. Further, this bending stress is received by the convex portion 25 at the rear portion of the stuffer, but excessive bending stress causes galling. In addition, the resistance of the plunger 24 for retracting becomes large at the time of weighing, and if it is excessively large, it causes breakage of the glass fiber.

In addition, this type of injection molding machine is different from the screw type in that most of the material metering action is performed by pressurization from the material supply device. Supply pressure) is several times to several tens of times higher than that of a normal screw type. This point also contributes to an increase in the galling of the convex portion 25 and the damage phenomenon of the glass fiber.

[Means for Solving Problems] An injection molding machine of the present invention is provided with a barrel having an injection port at a tip and a material inlet at a rear side, and a barrel rotatably provided in the barrel. A plunger having a diameter that forms a material passage between the peripheral surface and the inner peripheral surface of the barrel, and having its rear end side connected to a drive device and reciprocating in the barrel, is connected to the material inlet portion of the barrel. A material pressure supply device provided, a material backflow prevention mechanism provided in the plunger for preventing backflow of material in the material flow passage, and a plunger provided on the inner peripheral surface of the barrel provided in the material flow passage. And a support member for supporting it. The support member may be integrated with the barrel or the plunger, or may be a structure that can move freely with respect to the barrel or the plunger.

[Operation] In the injection molding machine of the present invention employing the above structure,
The stress state generated in the plunger changes from "cantilever" to "both ends supported" or "equal distribution", and bending stress is reduced. Further, the force generated on the convex portion at the rear part of the plunger is reduced, the occurrence of bulging is prevented, the backward resistance of the plunger is reduced, and the damage of the glass fiber can be reduced.

Embodiments Embodiments will be described below with reference to the drawings.

FIG. 1 is an overall cross-sectional view showing the structure of an injection molding machine according to an embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view of the relevant part, and FIG.
A sectional view taken along the line III-III in FIG. 4, and FIG. 4 is a plan view of the plunger portion in FIG.

1 and 2, a cylindrical barrel 22 having a nozzle 21 at its tip and a heater at a relatively low temperature on its outer periphery.
Are arranged so that the nozzle 21 can be exposed to the material injection port of the fixed mold 61 attached to the fixed platen 60. 62 is a column, 63 is a column nut, 62 is a machine base on the mold clamping device side, 65 is a machine base on the injection device side, and 66 is a block provided on the machine base 65 so as to be slidable in the axial direction. The barrel 22 is fixed to the front of the above, and the motor holding member 67 is slidably attached to the rear of the above. 68 is a fixed plate 60
A cylinder for moving the block 66, which is fixed to the block 66, 69 is a piston rod, and the tip of the piston rod 69 is fixed to the central portion of the outer surface of the block 66.
The nozzle 21 can be brought into contact with the fixed mold 61 or retracted to the state shown in the drawing by the operation of.

In the barrel 22, a plunger 24 having an outer diameter smaller than the inner diameter of the barrel 22 and having a backflow prevention mechanism including a check ring 23, a ball and the like near the tip is provided so as to be able to move forward and backward and to rotate. . The material passage 70 is provided between the inner peripheral surface of the barrel 22 and the outer peripheral surface of the plunger 24.
Was set up. A shaft of a rotary drive device such as a hydraulic motor 35 fixed to the motor holding member 67 is connected to the rear of the plunger 24 via a bearing 71 in the motor holding member 67. An injection cylinder 72 and a piston rod 73 are attached between the barrel 22 and the lower side of the motor holding member 67.

At the center of the plunger 24, a convex portion 25 that is in contact with the inner peripheral surface of the barrel 22 is provided. In addition, the convex portion 2 of the plunger 24
On the rear side of No. 5, a screw 29 for discharging the leak material was provided. The screw 29 includes the outer peripheral surface of the convex portion 25 and the barrel 2
The leak material leaked rearward from the clearance between the inner peripheral surfaces of the two is smoothly discharged rearward of the barrel 22, and is provided in a direction opposite to the rotational direction of the plunger 24.

Reference numeral 27 denotes a stuffer vertically provided in the material inlet portion 28 on the rear side of the barrel 22, and a stuffer plunger 30 for pushing down the material is provided therein. Reference numeral 31 is a material supply inlet provided on the side surface of the stuffer 27. 74
Is a cylinder for the stuffer plunger 30, which has a built-in piston 74a and is vertically attached to a part of the barrel 22 in an upward direction. 75 is a piston rod, and 76 is a connecting member.

Thus, the third and fourth parts are provided on the part of the plunger 24 near the tip.
As shown in the enlarged view of the drawing, a support member A made of a pin-shaped projection is provided so as to project, and the tip end portion of the plunger 24 is held against the inner peripheral surface of the barrel 22. Therefore, the plunger 24 has the convex portion 25 and the support member A.
It is installed in a state where it is held by both.

In the apparatus shown in FIG. 1, the material such as BMC is loaded into the stuffer 27 while the plunger 24 is positioned at the forward limit and rotated at, for example, 25 to 150 rpm, and the material is fed by the stuffer plunger 30. Push down. Then, the material is sent forward through the outer peripheral portion of the plunger 24, and passes through the check ring 23 portion to make the plunger 2
4 are sequentially accumulated in the barrel 22. Of course, in this measuring process, the plunger 24 is gradually retracted.

At this time, the back pressure can be applied to the material by controlling the hydraulic pressure in the rod end side chamber of the injection cylinder 72 connected to the rear of the plunger 24. Note that the back pressure can be applied to the material by friction between the outer peripheral surface of the convex portion 25 of the plunger 24 and the inner peripheral surface of the barrel 22, which retracts.

Due to the rotation of the plunger 24, the resin material around the plunger 24 is homogenized and a short circuit of the flow path of the material is prevented. Further, the pressing action of the stuffer plunger 30 and the rotating action of the plunger 24 cause the material to be
4, the material is pushed in such a manner that it does not pass only through the upper material passage 70 of the plunger 24 but also around the lower material passage 70 of the plunger 24, and the material is pushed from the lower side to the upper side of the plunger 24 or the upper side. Since it is sent while also wrapping around from the bottom to the lower side, the entire circumference of the barrel 22 can be smoothly transferred without staying in the barrel 22 even if the material is difficult to flow or the material is hard to flow.

Thus, even if the material is pressed and supplied from the stuffer 27 into the barrel 22 at a high supply pressure, the plunger 24 will not protrude.
5 and the support member A are supported on both sides, the bending stress on the plunger 24 is reduced. Further, the stress of the convex portion 25 is also reduced, the galling thereof is prevented, the backward resistance of the plunger 22 is reduced, and the damage of the glass fiber contained in the material is also reduced.

In the above embodiment, a support member composed of a pin-shaped protrusion is adopted, but this support member has a wing shape (Fig. 5) and a movable wing shape (Figs. 6 and 7) as shown in Figs. Note that FIG. 7 shows a sectional view taken along line VII-VII of FIG. One, two or more of these support members are provided in the circumferential direction. Further, one or two or more are provided in the axial direction.

8 to 10 are cross-sectional views of main parts of an injection molding machine according to different embodiments.

FIG. 8 shows an example in which the support member A is fixed to the barrel 22. When the support member is fixed to the barrel as in this embodiment, it is fixed to the inner surface of the barrel so that there is no hindrance when the plunger is pulled out. In this case, the shape, the installation position, the number, etc. of the support members may be various as shown in FIGS.

FIG. 9 shows an example in which the support member A is provided in a state where it is not fixed to either the plunger 22 or the barrel 24.
Note that FIG. 9 (a) shows a cross section taken along the line aa of FIG. 9 (b).

In the case of the embodiment shown in FIG. 9, in order to stop the support member A at a predetermined position, a groove for receiving a support may be formed on the inner peripheral surface of the barrel 22 or the outer peripheral surface of the plunger 24.

FIG. 10 shows an example in which the screw flight B is provided as a support member around the entire circumference of the plunger 22, but in order to eliminate the measuring action of the screw flight B, the pitch thereof should be made as large as possible, the plunger diameter d and the barrel inner diameter. Ratio is set to d / D ≦ 0.75, the groove depth is increased, and L / D is decreased as much as possible. (L / D has a minimum value determined by how much the measuring stroke is set. ) Is desirable. Further, L / D ≦ 3 is desirable in order to prevent damage to the glass fiber in the screw groove.

[Effect] As is clear from the above embodiments, in the injection molding machine of the present invention, since the support member that supports the plunger is provided, the bending stress of the plunger is reduced. As a result, the galling phenomenon of the plunger is prevented, the retracting resistance of the plunger is reduced, and the glass fiber contained in the material is prevented from being damaged.

[Brief description of drawings]

1 is an overall sectional view of the apparatus of the embodiment, FIG. 2 is a partial sectional view of the same, FIG. 3 is a sectional view taken along line III-III of FIG. 2, and FIG.
Partial plan views, FIG. 5, FIG. 6 and FIG. 7 are shape explanatory views showing different support members, FIG. 8, FIG. 9 and FIG.
FIG. 0 is a partial sectional view showing a different embodiment, FIG. 11 and FIG.
2 and 13 are sectional views showing the prior art. 22 ... Barrel, 23 ... Check ring, 24 ... Plunger, 27 ... Staffer, 30 ... Staffer plunger, 70 ... Material passage.

Claims (1)

[Claims] 1. A barrel having an injection port at the tip and a material inlet at the rear side, and a barrel rotatably provided in the barrel, the material passage being between the peripheral surface and the barrel inner peripheral surface. A plunger that has a diameter that forms a rear end side and is reciprocally moved in the barrel with its rear end side connected to a drive device; a material pressing and supplying device that is connected to a material inlet portion of the barrel; And a support member that is provided in the material flow passage and that supports the plunger against the inner peripheral surface of the barrel. Machine.