JP3725802B2 - Injection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an injection apparatus.
[0002]
[Prior art]
Conventionally, in an injection molding machine, a resin heated and melted in a heating cylinder is injected at a high pressure into a cavity space of a mold apparatus, and cooled and solidified in the cavity space. Thus, a molded product can be obtained.
[0003]
For this purpose, the injection molding machine has a mold clamping device and an injection device, and the mold clamping device includes a fixed platen and a movable platen, and the mold clamping cylinder moves the movable platen forward and backward to close the mold of the mold apparatus. Then, mold clamping and mold opening are performed.
[0004]
On the other hand, the injection device is generally an in-line screw type, and includes a heating cylinder that heats and melts the resin supplied from the hopper, and an injection nozzle that injects the molten resin, and the heating cylinder A screw is rotatably disposed in the interior of the screw. Then, the resin is injected from the injection nozzle by moving the screw forward by a drive unit connected to the rear end, and the resin is weighed by moving backward by the drive unit.
[0005]
FIG. 2 is a cross-sectional view showing a main part of a conventional injection apparatus.
[0006]
In the figure, 11 is a heating cylinder, an injection nozzle 12 is attached to the front end (left end in the figure) of the heating cylinder 11, and a heater (not shown) is disposed around the heating cylinder 11. Further, a screw 14 is disposed in the heating cylinder 11 so as to be freely rotatable and movable back and forth (movable in the left-right direction in the figure). The screw 14 includes a flight part 15 and an injection part 16, and is connected to a drive part (not shown) via a shaft part 21 at the rear end (right end in the figure). The injection portion 16 includes a screw head 41, a rod 42 formed behind the screw head 41 (right side in the drawing), a check ring 43 disposed around the rod 42, and a front end of the flight portion 15. The seal ring 44 is attached to. The check ring 43 and the seal ring 44 function as a backflow prevention device that prevents the resin from flowing back during the injection process. The drive unit includes an injection motor and a metering motor. In addition, a spiral flight 23 is formed around the flight portion 15, and a spiral groove 24 is formed by the flight 23.
[0007]
A resin supply port 25 is formed in the vicinity of the rear end of the heating cylinder 11, a funnel-shaped hopper (not shown) is disposed in the resin supply port 25, and the pellet-shaped resin accommodated in the hopper is: It is supplied into the heating cylinder 11 through the resin supply port 25.
[0008]
In the state where the screw 14 is placed at the forward limit position (the position shown in the drawing) in the forefront (left side in the drawing) of the heating cylinder 11, the resin supply port 25 has a rear end portion (in the drawing in the drawing). It is formed at a location facing the right end). The flight part 15 is melted from the rear to the front by a resin supply part P1 to which the resin is supplied via the resin supply port 25, a compression part P2 for melting the supplied resin while compressing it, and A metering portion P3 for metering a resin by a certain amount is formed in order.
[0009]
In the injection apparatus having the above configuration, when the screw 14 is rotated by driving the metering motor during the metering step, the resin supplied from the hopper into the heating cylinder 11 advances along the groove 24. (Moved to the left in the figure) and heated and melted by the heater, and accordingly, the screw 14 is moved backward (moved to the right in the figure). As the screw 14 moves backward, the check ring 43 is moved relatively forward with respect to the rod 42, so that the resin that has reached the front end of the flight portion 15 does not check with the rod 42. It passes through the resin flow path between the ring 43 and the front of the screw head 41. Accordingly, the melted resin for one shot is stored in front of the screw head 41 in a state where the screw 14 is placed at the retreat limit position.
[0010]
Next, when the injection motor is driven and the screw 14 is advanced during the injection process, the resin stored in front of the screw head 41 is injected from the injection nozzle 12 and is not shown in the figure of the mold apparatus. The cavity space is filled.
[0011]
Incidentally, since the resin injected from the injection nozzle 12 is stored in front of the screw head 41, the amount of resin injected from the injection nozzle 12, that is, the injection amount Iq is the diameter of the screw 14. When the cross-sectional area of As is As and the stroke of the screw 14 is St,
Iq = As · St
become. Therefore, when the dimension of the molded product changes, the injection amount Iq is changed by adjusting the stroke St.
[0012]
[Problems to be solved by the invention]
However, in the conventional injection device, for example, when a molded product having a small size is molded, the quality of the molded product is deteriorated.
[0013]
That is, when molding a molded product having a small size, it is necessary to reduce the injection amount Iq by reducing the stroke St. Therefore, the resin in the heating cylinder 11 when the screw 14 is placed in the retreat limit position is used. When the volume of the space to be accommodated is Q and the period of the molding cycle is T, the residence time Ta from when the resin is supplied to the resin supply part P1 until it is injected from the injection nozzle 12
Ta = (Q / Iq) · T
Becomes longer, the resin deteriorates or burns, and the quality of the molded product is lowered.
[0014]
Further, since the stroke St of the screw 14 becomes small, it becomes difficult to achieve the injection speed, pressure, etc. set for each position of the screw 14 during the injection process, and the controllability of the injection device is lowered.
[0015]
Therefore, when molding a molded product having a small size, it is conceivable to reduce the diameter of the screw 14. However, as the diameter of the screw 14 is reduced, the groove 24 becomes shallower, and the depth of the groove 24 becomes relatively smaller than the size of the pellet-shaped resin. And the resin feed becomes unstable. As a result, the density of the melted resin tends to be non-uniform and the injection amount Iq becomes unstable, causing short shots, sink marks, chips, burrs, and the like, resulting in a deterioration in the quality of the molded product.
[0016]
Further, when the biting property is lowered, the number of rotations of the screw 14 necessary for measuring is increased, and wear generated between the heating cylinder 11 and the check ring 43 is increased. As a result, it becomes impossible to prevent the resin from flowing back due to the generated wear, the injection amount Iq becomes more unstable, and the quality of the molded product is further deteriorated.
[0017]
An object of the present invention is to solve the problems of the conventional injection device and to provide an injection device capable of improving the quality and controllability of a molded product when molding a molded product having a small size. To do.
[0018]
[Means for Solving the Problems]
Therefore, in the injection apparatus of the present invention, a cylinder body having a large inner diameter, a heating cylinder having a cylinder head having a small inner diameter and detachably disposed in front of the cylinder body, and a front end of the heating cylinder are attached. An injection nozzle, a screw main body having a large outer diameter, and an injection portion disposed in front of the screw main body and having a small outer diameter. Screw.
In addition, the outer peripheral surface between the screw body and the injection portion has a tapered surface so that a cross-sectional area gradually changes, and an inner periphery in front of an attachment portion to the cylinder body at a rear end portion of the cylinder head. Tapered surfaces are formed on the surfaces so that the cross-sectional area of the resin flow path gradually changes.
[0019]
In the metering step, the injection part is retracted in the cylinder head as the screw is retracted, and the molding material is stored in front of the injection part in the cylinder head.
[0020]
Further, in the injection process, as the screw is advanced, the injection part is advanced in the cylinder head, and the molding material is injected from the injection nozzle.
[0021]
In the injection step, the screw is rotated in the opposite direction to the rotation direction in the metering step in order to move the molding material present in the space formed between the injection portion and the screw body backward. It is done.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0023]
FIG. 1 is a cross-sectional view showing the main part of the injection apparatus when the metering process in the embodiment of the present invention is completed, and FIG. 3 shows the main part of the injection apparatus when the injection process in the embodiment of the present invention is completed. It is sectional drawing shown.
[0024]
In the figure, 51 is a heating cylinder as a cylinder member. The heating cylinder 51 is disposed in front of the cylinder main body 52 and the cylinder main body 52 (left side in the figure), and is attached by a bolt or the like (not shown). A cylinder head 53 is provided. The cylinder head 53 is set over a predetermined distance at the front end portion (left end portion in the drawing) of the heating cylinder 51. The distance is calculated and set based on the injection amount Iq corresponding to the dimension of the molded product.
[0025]
The injection nozzle 12 is attached to the front end (left end in the figure) of the heating cylinder 51, and the heater 13 is disposed around the heating cylinder 51. In the heating cylinder 51, a screw 14 as an injection member is rotatably disposed and can be moved back and forth (moved in the left-right direction in the figure). The screw 14 includes a flight part 15 and an injection part 16, and is connected to a drive part (not shown) via a shaft part 21 at the rear end (right end in the figure). The drive unit includes an injection motor as a first drive means and a metering motor as a second drive means. The flight portion 15 is formed in the main body of the screw 14 having a spiral flight 23 formed therearound, that is, a large-diameter portion 54 as a screw main body, and a front portion of the large-diameter portion 54. And the flight 23 forms a spiral groove 24.
[0026]
The injection portion 16 includes a screw head 41 having a conical shape, a rod 42 that is integrally formed with the screw head 41 and connects the screw head 41 and the small diameter portion 55, and is arranged around the rod 42. An annular check ring 43 provided, and a seal ring 44 that is disposed so as to be in contact with the check ring 43 and is attached to the small diameter portion 55. In the injection part 16, the check ring 43 and the seal ring 44 function as a backflow prevention device that prevents the resin as the molding material from flowing back during the injection process.
[0027]
A resin supply port 25 as a molding material supply port is formed at a predetermined position near the rear end of the heating cylinder 51, and a funnel-shaped hopper (not shown) is connected to the resin supply port 25. The accommodated pellet-shaped resin is supplied into the heating cylinder 51 through the resin supply port 25.
[0028]
The resin supply port 25 faces the rear end portion (right end portion in the drawing) of the groove 24 in a state where the screw 14 is placed at the foremost forward limit position (position shown in FIG. 3) in the heating cylinder 11. It is formed in the place to do. The flight part 15 has a resin supply part P1 to which resin is supplied via the resin supply port 25 from the rear (right side in the drawing) to the front, and a compression part P2 for melting the supplied resin while compressing it. , And a metering part P3 for metering the molten resin by a certain amount is formed in order.
[0029]
In the injection device having the above configuration, when the screw 14 is rotated in the forward direction by driving the metering motor in the forward direction during the weighing step, the resin supplied into the heating cylinder 11 from the hopper is While moving forward (moving leftward in the figure) along the groove 24, the heater 13 is heated and melted by the heater 13, and the screw 14 is moved backward (moved rightward in the figure). As the screw 14 moves backward, the check ring 43 is moved relatively forward with respect to the rod 42, so that the resin that has reached the front end of the flight portion 15 does not check with the rod 42. It passes through a resin flow path as a molding material flow path with the ring 43 and is sent to the front of the screw head 41. Therefore, the melted resin for one shot is stored in front of the screw head 41 in a state where the screw 14 is placed at the retreat limit position (position shown in FIG. 1).
[0030]
Next, when the injection motor is driven and the screw 14 is advanced during the injection process, the resin stored in front of the screw head 41 is injected from the injection nozzle 12 and is not shown in the figure of the mold apparatus. The cavity space is filled.
[0031]
By the way, when molding a molded product having a small size, if the injection amount Iq is reduced by reducing the stroke St of the screw 14, the resin is supplied from the injection nozzle 12 until it is supplied to the resin supply part P1. The residence time Ta becomes long, the resin is deteriorated or the burn is generated, and the quality of the molded product is deteriorated.
[0032]
Therefore, the outer diameter of the injection portion 16 is made smaller than that of the large diameter portion 54. That is, when the outer diameter of the injection part 16 is d1 (for example, 14 [mm] equal to the diameter of a conventional thin in-line screw) and the outer diameter of the large-diameter part 54 is d2 (for example, 25 [mm]). The outer diameters d1 and d2 are
d1 <d2
To be. The outer diameter d1 is expressed by the outer diameters of the screw head 41, the check ring 43, and the seal ring 44.
[0033]
Further, the inner diameter of the cylinder head 53 is made smaller than the inner diameter of the cylinder body 52. That is, when the inner diameter of the cylinder head 53 is e1, and the inner diameter of the cylinder body 52 is e2, the inner diameter e1 is slightly larger than the outer diameter d1, the inner diameter e2 is slightly larger than the outer diameter d2, and the inner diameters e1, e2 Is
e1 <e2
To be.
[0034]
When the screw 14 is advanced and retracted in the heating cylinder 51, the injection part 16 is advanced and retracted in the cylinder head 53, and the outer peripheral surface of the check ring 43 and the cylinder head 53 in the entire stroke of the injection part 16. The inner peripheral surface is moved by sliding to measure and inject. That is, when the metering process is started and the screw 14 is retracted, the screw head 41 is retracted in the cylinder head 53, and when the metering process is completed and the screw 14 is placed at the retreat limit position, the screw head 41 is When the screw head 41 is advanced in the cylinder head 53 when the injection process is started and the screw 14 is advanced, the screw head 41 is advanced in the cylinder head 53. The screw head 41 is placed at the forward limit position in the cylinder head 53. Therefore, the outer diameter of the small diameter portion 55 is made smaller than the outer diameter d1, and the axial length of the small diameter portion 55 is set so that the stroke of the screw head 41 can be secured.
[0035]
In the injection apparatus configured as described above, the outer diameter d1 of the injection portion 16 and the inner diameter e1 of the cylinder head 53 are reduced. Therefore, when forming a molded product with a small size, the stroke of the screw head 41 and the stroke of the screw 14 are reduced. The injection amount Iq can be ensured without reducing.
[0036]
And it is not necessary to make the outer diameter d2 of the large diameter part 54 small as the outer diameter d1 of the injection part 16 is made small. Therefore, for example, when the outer diameter of the conventional small-diameter inline screw is 14 [mm] and the outer diameter d2 of the large-diameter portion 54 in the present embodiment is 25 [mm], it is larger than the conventional small-diameter inline screw. The cross-sectional area ratio γ of the diameter portion 54 is
γ = 25 ^{2/14 2}
≒ 3
Thus, even if the screw 14 is rotated at the same rotational speed in the measurement process, the time required for measurement is reduced to about one third. As a result, the cycle of the molding cycle can be shortened.
[0037]
Thus, since the injection amount can be ensured and the cycle of the molding cycle can be shortened without reducing the stroke of the screw 14, the residence time Ta can be shortened. Therefore, the resin does not deteriorate or burn does not occur, and the quality of the molded product can be improved.
[0038]
Moreover, since the stroke of the screw 14 does not become small, the injection speed, pressure, etc. set for each position of the screw 14 can be easily achieved during the injection process, and the controllability of the injection device can be improved.
[0039]
And since the outer diameter d2 of the large diameter part 54 can be made large enough, the depth of the groove | channel 24 can be enlarged relatively with respect to the dimension of pellet-shaped resin. Therefore, the biting property of the resin in the screw 14 can be improved, and the feeding of the resin can be stabilized. As a result, the density of the melted resin can be made uniform and the injection amount Iq can be stabilized, so that short shots, sink marks, chips, burrs, etc. do not occur and the quality of the molded product is improved. be able to.
[0040]
Further, since the biting property can be improved, the number of rotations of the screw 14 necessary for measuring is reduced, and the wear generated between the cylinder head 53 and the check ring 43 is reduced. As a result, it is possible to sufficiently prevent the resin from flowing backward, and the injection amount Iq can be further stabilized, so that the quality of the molded product can be further improved. Moreover, since the biting property can be improved, the biting when the pulverized material is used as the resin can be stabilized.
[0041]
Furthermore, since the outer diameter d2 of the large diameter portion 54 is large, the volume in the groove 24 is increased. Accordingly, the axial dimension of the screw 14 can be reduced.
[0042]
Further, since the cylinder head 53 is detachably disposed on the cylinder body 52, when the cylinder head 53 is worn, it is not necessary to replace the entire heating cylinder 51, and the cylinder head 53 is replaced. Just do it. Therefore, the cost of the injection device can be reduced.
[0043]
By the way, a tapered surface S1 is formed on the outer peripheral surface between the small diameter portion 55 and the large diameter portion 54 so that the cross-sectional area gradually changes, and on the inner peripheral surface at the rear end portion of the cylinder head 53, The tapered surface S2 is formed so that the cross-sectional area of the resin flow path gradually changes. Accordingly, as the screw 14 is retracted during the metering step, as shown in FIG. 1, between the tapered surfaces S1, S2, that is, on the outer periphery between the injection portion 16 and the large diameter portion 54, A space having a predetermined volume is formed, and as the screw 14 is advanced during the injection process, the space becomes smaller. When the injection process is completed, the space is almost eliminated as shown in FIG. At this time, when the resin is compressed, a predetermined resistance force is generated and injection cannot be performed smoothly.
[0044]
Therefore, from the start to the end of the injection process, a control unit (not shown) drives the metering motor in the reverse direction, rotates the screw 14 in the reverse direction with respect to the rotation direction in the measurement process, and the groove 24. The resin inside is caused to flow backward, and the resin existing in the space is moved backward. When the forward speed of the screw 14 is Vs and the pitch of the flight 23 is Pf, the rotational speed Ns when rotating the screw 14 in the reverse direction is
Ns = Vs / (Pf · 60)
To be.
[0045]
Therefore, injection can be performed smoothly.
[0046]
In addition, this invention is not limited to the said embodiment, It can change variously based on the meaning of this invention, and does not exclude them from the scope of the present invention.
[0047]
【The invention's effect】
As described above in detail, according to the present invention, in the injection device, a cylinder body having a large inner diameter, and a heating cylinder provided with a cylinder head having a small inner diameter, which is detachably disposed in front of the cylinder body, An injection nozzle attached to the front end of the heating cylinder, a screw body that is rotatable and reciprocating in the heating cylinder, has a large outer diameter, and is disposed in front of the screw body. And a screw having an injection portion having a small outer diameter.
In addition, the outer peripheral surface between the screw body and the injection portion has a tapered surface so that a cross-sectional area gradually changes, and an inner periphery in front of an attachment portion to the cylinder body at a rear end portion of the cylinder head. Tapered surfaces are formed on the surfaces so that the cross-sectional area of the resin flow path gradually changes.
[0048]
In the metering step, the injection part is retracted in the cylinder head as the screw is retracted, and the molding material is stored in front of the injection part in the cylinder head.
[0049]
Further, in the injection process, as the screw is advanced, the injection part is advanced in the cylinder head, and the molding material is injected from the injection nozzle.
In the injection step, the screw is rotated in the opposite direction to the rotation direction in the metering step in order to move the molding material present in the space formed between the injection portion and the screw body backward. It is done.
[0050]
In this case, the inner diameter of the cylinder head is made smaller than the inner diameter of the cylinder main body, and the outer diameter of the injection part is made smaller than the outer diameter of the screw main body. The injection amount can be ensured without any problem.
[0051]
And since the injection quantity can be secured and the cycle of the molding cycle can be shortened without reducing the stroke of the screw, the residence time of the molding material can be shortened. Therefore, the molding material is not deteriorated or burned, and the quality of the molded product can be improved.
[0052]
Moreover, since the stroke of the screw does not become small, the injection speed, pressure and the like set for each screw position can be easily achieved during the injection process, and the controllability of the injection device can be improved.
[0054]
Furthermore, in the injection process, the screw is rotated in the opposite direction to the rotation direction in the metering process, the molding material in the groove is caused to flow backward, and the molding material present in the space formed between the injection part and the screw body Is moved rearward, so that injection can be performed smoothly.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a main part of an injection device when a weighing process is completed in an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a main part of a conventional injection apparatus.
FIG. 3 is a cross-sectional view showing a main part of the injection apparatus when an injection process is completed in the embodiment of the present invention.
[Explanation of symbols]
12 Injection nozzle 14 Screw 16 Injection part 51 Heating cylinder 52 Cylinder body 53 Cylinder head 54 Large diameter part

Claims (1)

(A) a cylinder body having a large inner diameter, and a heating cylinder including a cylinder head having a small inner diameter, which is detachably disposed in front of the cylinder body;
(B) an injection nozzle attached to the front end of the heating cylinder;
(C) a screw body that is rotatably and reciprocally disposed in the heating cylinder and has a large outer diameter, and a screw that is disposed in front of the screw body and includes an injection portion having a small outer diameter; And having
(D) The outer peripheral surface between the screw main body and the injection portion has a tapered surface so that a cross-sectional area gradually changes, and an inner portion of the rear end portion of the cylinder head in front of the attachment portion to the cylinder main body. A taper surface is formed on the peripheral surface so that the cross-sectional area of the resin flow path gradually changes,
(E) In the measuring step, as the screw is retracted, the injection part is retracted in the cylinder head, and the molding material is stored in front of the injection part in the cylinder head,
(F) In the injection step, the injection part is advanced in the cylinder head as the screw is advanced, and the molding material is injected from the injection nozzle ,
(G) In the injection step, the screw rotates in the opposite direction to the rotation direction in the metering step in order to move the molding material present in the space formed between the injection portion and the screw body backward. allowed are injection device according to claim Rukoto.

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