JP7587839B2 - Injection Molding Equipment - Google Patents

Description

The present invention relates to a rubber injection molding device capable of high-speed vulcanization.

As shown in FIG. 1 of Patent Document 1, a conventional injection molding device is a pre-plasticization type injection molding device that is composed of a plunger 3 that can slide up and down inside an injection pot 2 that stores a plasticized rubber material, which is a molding material, by an injection cylinder 1, a heating cylinder 4 whose tip is connected to the side end face of the injection cylinder 1, and a plasticizer (extruder) 6 into which a rotating screw 5 is inserted. In this injection molding device, the injection pot 2, an injection nozzle 8 connected via a passage 7 provided at the tip of the injection pot 2, and an input port 9 that supplies the plasticized rubber material in a plasticized state from the side to the storage space in the injection pot are formed, and the plunger 3 is lowered into the injection pot 2, and the molding material is fed into the storage space in the injection pot 2 through the passage 7 at the tip of the injection pot and the injection nozzle 8 into the mold 10, and the molding material is pressed into the cavity 14 in the mold 10 through the sprue 11, runner 12, and gate 13, and vulcanized.

In this type of pre-plasticizing injection molding device, when the plunger 3 retracts, the forward space of the storage space in the injection pot 2 increases, and the amount of stored plasticized rubber material increases. Just before injection, the plunger 3 retracts sufficiently, and a sufficient amount of plasticized rubber material is stored in front of the plunger 3. The first plasticized rubber material enters retracts together with the plunger 3, and the next plasticized rubber material is stored next, so that the last plasticized rubber material entered is stored in the area farthest from the plunger 3.
Therefore, when the plunger 3 is advanced, the last plasticized rubber material is injected first, and the first plasticized rubber material is injected last. In other words, a first-in, last-out system (the first plasticized rubber material is ejected last) is implemented.

In contrast, the injection molding machine has a so-called first-in, first-out system, in which the plasticized rubber material that entered first is discharged first. When comparing the first-in, first-out system with the first-in, last-out system, the first-in, last-out system has the advantage that the screw and plunger can be freely combined and the screw can be easily changed, including the change of L (length)/D (diameter), but the properties of the plasticized rubber material are easily changed over time. The plasticized rubber material that entered first is retained in the space in front of the plunger for a long time, while the plasticized rubber material that entered last has a short residence time. The properties of the plasticized rubber material are easily changed over time, and there is a disadvantage that the properties of the plasticized rubber material liquid that entered first and the plasticized rubber material liquid that entered last differ due to the time difference.
On the other hand, FIFO has limitations in the combination of the screw and plunger, and also has the disadvantage that it is difficult to change the screw or the L (length)/D (diameter) due to many practical restrictions. Also, FIFO has a problem with the limit of the increase in the amount of shear heat generated due to differences in thermal history, but with FIFO, there is no problem even if the amount of heat generated increases.

In addition, there is an in-line screw type injection molding machine (for example, Patent Document 2) that uses a first-in, first-out method, in which the screw is built into the plunger, but there is a limit to the combination of the screw and plunger, making such a combination practically difficult, and the parts shared with the pre-plastication type are minimal. It is also practically impossible to modify the in-line screw to a vent type with a degassing hole (vent hole) that is effective for degassing and removing monomer gas, and there are other issues such as the relatively high manufacturing cost.

Generally, in rubber injection molding, the rubber is finally molded in a mold, and the vulcanized rubber is exposed to high temperatures for a certain period of time, causing a crosslinking reaction and hardening. By shortening this hardening time, it is possible to produce the product in a short time, improving productivity. There are two ways to shorten this time: by increasing the temperature of the rubber in the mold and by reducing the vulcanization temperature.
(1) Temperature rise of rubber in the mold The temperature of rubber injected into the mold gradually rises due to heat transfer from the mold surface, and becomes the same as the mold temperature. Rubber has extremely low thermal conductivity, so it takes a long time to heat up. This is particularly noticeable in thick-walled products. For this reason, the closer the temperature of the plasticized rubber material is to the mold temperature when it is injected into the mold, the shorter this time can be, but keeping it at a high temperature may cause the vulcanization reaction to proceed, and vulcanization may progress before it is injected into the mold. Therefore, it is ideal to raise the temperature of the plasticized rubber material just before it is injected into the mold. This also makes the thermal history of the surface and center of the molded product uniform.
(2) Vulcanization temperature Generally, the vulcanization time of plasticized rubber material is shortened by half with a 10°C increase in temperature according to the Arrhenius law. However, the temperature at which vulcanization is performed is also affected by the physical properties of the plasticized rubber material, so it is largely left to the discretion of the customer. For this reason, it cannot be achieved by simply raising the mold temperature.

For high-speed vulcanization, there is a high-frequency heating method in which high-frequency waves are irradiated from a waveguide to heat the plasticized rubber material as it passes through an applicator installed near the nozzle, but this requires large-scale additional equipment. There is also an induction heating method in which an induction heating coil is installed at the tip of the nozzle to heat the plasticized rubber material, but this requires additional equipment just like the high-frequency heating method.
In contrast to these, there is the shear heating type, in which friction occurs between the rubber material plasticized by injection and the wall surfaces of the nozzle, runner, etc., which generates heat and raises the temperature of the plasticized rubber material.This type does not require additional equipment and can be constructed inexpensively.

In addition, the temperature rise of plasticized rubber material due to shear heat generation is determined only by the physical properties of the rubber (density, specific heat) and the injection pressure. Therefore, in order to increase the temperature rise due to shear heat generation, it is possible to achieve this by setting the injection pressure to a high pressure. In other words, after the plasticized rubber material is injected into the mold, the temperature rises due to heat transfer from the mold surface, but since rubber generally has a low thermal conductivity, this takes a long time, especially when molding thick products. The feature of injection molding equipment is that it shortens the molding time by increasing the temperature of the rubber injected into the mold due to shear heat generation, and this capacity can be greatly improved by increasing the injection pressure.

JP 2007-30498 A JP 2014-117889 A

The present invention was made to solve these problems, and aims to realize a new injection molding device that combines the advantages of both first-in, first-out and first-in, first-out, and is capable of high-pressure injection and capable of injecting high-temperature molding material into a mold with a high shear heat generation.

In order to achieve this object, the injection molding apparatus of the first invention is an injection molding apparatus comprising: a plasticizing device having a rotatably incorporated screw which transports while plasticizing a rubber material fed into a heating barrel, and extruding the plasticized rubber material toward its tip; and an injection unit which has a communication passage at a connecting portion with the plasticizing device, and which injects the plasticized rubber material supplied from the communication passage and filled into a storage space in the injection pot as a plunger moves within the injection pot,
The connecting portion connects the leading end of the plasticizer and the side surface of the rear end of the injection pot,
a first check ring that moves within the injection pot in response to pressure exerted by the plasticized rubber material within the injection pot;
a second check ring that is inserted and fitted to the plunger closer to the rear end than the first check ring and moves together with the plunger,
an injection molding apparatus characterized in that, when the plunger is at its maximum retraction position within the injection pot, the first check ring and the second check ring come into close contact with each other to stop the supply of the plasticized rubber material from the communicating passage.
A second aspect of the present invention is the injection device according to the first aspect of the present invention, wherein the communication passage is formed in the injection pot of the injection unit,
The present invention is characterized in that it has a guide member which is fixed to the inner peripheral surface of the injection pot near the communicating passage, is cylindrical as a whole, and has a guide curved surface formed at the tip portion thereof, which guides the plasticized rubber material supplied from the communicating passage into the injection pot along a curved surface.
The third invention is characterized in that, in the first or second invention, the injection nozzle in the injection unit is equipped with a temperature control nozzle having a spiral medium passage through which a medium for heating and cooling the plasticized rubber material can flow.

The present invention makes it possible to realize a new injection molding device that combines the advantages of both first-in, first-out and first-in, first-out, and is capable of high-pressure injection, with high shear heat generation and the ability to inject high-temperature molding material into a mold.

1 is a perspective view of an overall appearance of an injection molding apparatus according to an embodiment of the present invention; 1 is a vertical sectional view showing an overall configuration of an embodiment of an injection molding apparatus of the present invention. 1 is a conceptual explanatory diagram of an overall configuration of an embodiment of an injection molding apparatus of the present invention; FIG. 2 is a schematic cross-sectional view of a main part of a plunger of the injection unit of the present invention. FIG. 2 is a bottom view of a main portion of the plunger nozzle of the injection unit of the present invention. 3 is a schematic cross-sectional view of a main portion of a tip of a plunger of the injection unit of the present invention. FIG. 4 is a schematic cross-sectional view of a main portion showing an operation during metering of vulcanized rubber in the injection molding apparatus of the present invention. 4 is a schematic cross-sectional view of a main portion showing an operation before completion of metering of vulcanized rubber in the injection molding apparatus of the present invention. 4 is a schematic cross-sectional view of a main portion showing a vulcanized rubber metering completion operation in the injection molding apparatus of the present invention. 2 is a schematic cross-sectional view of a main portion showing a vulcanized rubber injection operation in the injection molding apparatus of the present invention. 2 is a schematic cross-sectional view of a main portion around an injection nozzle in the injection molding apparatus of the present invention. FIG. 2 is a perspective view of an injection nozzle in the injection molding apparatus of the present invention. 2 is a schematic cross-sectional view of an injection nozzle in the injection molding apparatus of the present invention. FIG. FIG. 2 is a flow diagram of the operation state of the injection nozzle and the like in the injection molding apparatus of the present invention. FIG. 1 is a vertical cross-sectional view showing an example of a conventional injection molding apparatus.

The following describes in detail an embodiment of the present invention when applied to a rubber injection molding device, with reference to the drawings. Note that this embodiment is one embodiment of the present invention, and is not to be construed as being limited thereto, and design changes are possible within the scope of the present invention.

Figure 1 shows an overall schematic of an injection molding apparatus 15 according to one embodiment of the present invention, Figure 2 is a vertical cross-sectional view showing the entire injection molding apparatus 15 from the side, and Figure 3 is a conceptualization of the vertical cross-sectional view of Figure 2 for explaining the configuration of the injection molding apparatus 15. As shown in Figures 1 to 3, this injection molding device 15 is composed of a plasticizing device 20, which is a so-called extrusion device, that has a rotatably mounted screw 23 that plasticizes and transports the rubber material A, which is the molding material introduced into the inside of the heating barrel 22, and extrudes the plasticized rubber material (hereinafter referred to as plasticized rubber material) B toward the tip, and an injection unit 30 that has a communication passage 30a at a connecting portion 40c between the tip side of the plasticizing device 20 and the side surface of the rear end side of the injection unit 30 (injection pot 40), and injects the plasticized rubber material B, which is supplied from the communication passage 30a and filled in the storage space 40a in the injection pot 40, by moving the plunger 32 inside the injection pot 40. In the description of this embodiment, the molding material will be described as a rubber material, but it is not limited to a rubber material and can also be applied to a resin material.

As shown in FIG. 1, the injection molding device 15 is equipped with an injection cylinder 31 constructed with four tie bars 16, and the positional relationship between the plasticizing device 20 and the injection unit 30 is such that the injection unit 30 is in a vertical direction and is fixed by the tie bars 16, the plasticizing device 20 is at a predetermined angle (approximately 90 degrees) with the injection unit 30, and the tip of the plasticizing device 20 is connected to the injection unit 30 at approximately the middle part. As shown in FIG. 2 to FIG. 4A, a communication passage (flow passage) 30a is formed at the connection part 40c between the tip side of the plasticizing device 20 and the side of the rear end side of the injection unit 30 (injection pot 40) to extrude and pour the plasticized rubber material B from the plasticizing device 20 toward the injection unit 30.

[Plasticizing device]
As shown in FIG. 3, the plasticizing device 20 is composed of a heating barrel 22 having a material supply port 24, and a screw 23 that is rotatably provided within the heating barrel 22 and kneads the rubber material A supplied from the material supply port 24 and sends it out to the tip side.
The material supply port 24 is a hole provided on the rear end side of the heating cylinder 22, and the rubber material A is supplied in a ribbon shape (band shape), but it does not have to be in a ribbon shape (band shape), and may be in a shape supplied by, for example, a hopper.

The height of the material supply port 24 in the injection molding device 15 of the present invention (when injection is vertical) is in the following relationship: inline screw type injection molding device > injection molding device of the present invention > preplastication type injection molding device. That is, the height of the material supply port of the inline screw type injection molding device is higher than the height of the material supply port 24 in the injection molding device 15 of the present invention, so a high staircase is required, but the material supply port of the preplastication type injection molding device is only slightly higher than the height of the material supply port 24 in the injection molding device 15 of the present invention, so material can be supplied using only a workbench.

The heating cylinder 22 includes a hollow cylindrical cylinder body and a band heater (not shown) for heating the rubber of the cylinder body. It is acceptable for the heating cylinder to not only simply heat the cylinder but also circulate oil through a pipe that can adjust the temperature. For example, a pipe-shaped jacket is provided on the outer periphery of the cylinder body, and oil at a set temperature is circulated through the pipe of the jacket to heat or cool the rubber material of the cylinder body.
The temperature of the heating barrel 22 is adjusted by heating to plasticize and melt the rubber material A in the barrel body, but it is also possible to adjust the temperature of the heating barrel 22 by cooling it, for example, to keep it at a low temperature in order to suppress heat generation due to the shear force of the screw 23.

The injection molding device 15 of the present invention can share parts with conventional pre-plasticization injection molding devices, and as many parts as possible, such as the screw and heater barrel units, are common, making it economically rational in terms of parts procurement and production.

The screw 23 is provided in the cylinder body, and flights smaller in diameter than the heating cylinder 22 are formed in a spiral shape at a predetermined interval on the outer periphery of the surface over the entire axial length direction. In addition, a hydraulic motor 21 for rotating the screw 23 is connected to the other end side (left side in FIG. 3) of the screw 23 via a rotating shaft. This allows the power of the hydraulic motor 21 to be transmitted, and when the screw 23 is rotated to the right, the rubber material A in the groove between the flights is carried along the groove to the front end side. As a result, the rubber material A supplied from the material supply port 24 becomes plasticized rubber material B that is melted and kneaded by the conductive heat of the heating cylinder 22, and can be extruded from the tip of the heating cylinder 22 to the communication passage (flow passage) 30a of the connecting part 40c between the tip side of the plasticizer 20 and the side of the rear end side of the injection unit 30 (injection pot 40).

[Injection unit]
Next, the injection unit 30 that injects the plasticized and molten plasticized rubber material B sent from the plasticizing device 20 into the clamped mold will be described.
The bottleneck in increasing the general injection pressure is the mechanical strength of the injection block 41. In a general pre-plastication type, the injection block has a side hole (corresponding to the inlet 9 for supplying the rubber material from the side in the conventional art shown in FIG. 8) through which the plasticized rubber material is supplied to the part in contact with the screw, and concentrated stress occurs here, which causes metal fatigue to accumulate and cracks, but the injection unit structure of the injection molding device 15 of the present invention eliminates the need for such a side hole in the injection block 41, eliminating the bottleneck that causes concentrated stress. As a result, the injection molding device 15 of the present invention is capable of increasing the injection pressure (to about 280 MPa) so as to increase the amount of shear heat generation.

In addition, the injection molding device 15 of the present invention is configured with a plasticizer 22 similar to the conventional pre-plasticizer type heating barrel (corresponding to the heating barrel 4 in FIG. 8 of the prior art) and an injection unit 30 corresponding to the injection device, which are separate bodies, but is a first-in, first-out type by not providing a side hole as described above in the injection block 41 of the injection unit 30. That is, the communication passage 30a through which the plasticized rubber material B is supplied from the plasticizer 20 is formed not at the injection block 41 position, but at a position retreated from the plunger nozzle 36 of the injection unit 30 in the present invention. Also, the location of rubber supply in a general in-line screw type injection molding device is different in position at the rear end of the screw. Below, the plasticizer 20 and the injection unit 30 in the injection molding device 15 of the present invention will be described in order.

As shown in Figures 1 and 2, the injection unit 30 of the present invention is held in a vertical position by the tie bars 16 of the injection molding device 15, and as shown in Figure 3, the plunger 32 is pushed vertically downward by the injection cylinder 31 in this state, filling the storage space 40a in the injection pot 40 with plasticized rubber material B in a fluid state from the communication passage 30a on the tip (downstream) side of the plasticizing device 20, and then injecting the plasticized rubber material B into the molding die (corresponding to the reference symbol 10 in Figure 8). By holding the state for a predetermined time, the plasticized rubber material B injected into the molding die is vulcanized to become a rubber product.

In the injection unit 30, an injection pot 40 is formed in a hollow cylindrical shape to store one shot of the plasticized and molten plasticized rubber material B when the plunger 32 is in the retracted position, and the plunger 32 is arranged inside the injection pot 40 so that it can move back and forth in the axial direction. In addition, a plunger nozzle 36 is fixed (inserted and fitted) to the tip side of the plunger 40 on the same axis.

As shown in Figures 2 and 3, in the injection unit 30, an injection cylinder 31 is connected to a plunger 32 via an injection rod 38, and the plunger 32 can be reciprocated by driving the injection rod 31 to extend and retract. This injection cylinder 31 is a hydraulically driven reciprocating piston/cylinder for injecting the plasticized rubber material B, and is not particularly limited here, as any commercially available one can be used, such as pneumatic, electric, or hydraulic.

The injection pot 40 constituting the injection unit 30 is formed with a communication passage (flow path) 30a through which the plasticized rubber material B is supplied from the side of its rear end and the tip end of the plasticizer 20, and the plasticized rubber material B supplied to the injection pot 40 is led to a storage space 40a in the injection pot 40 where it is continuously stored for metering as a specified molding material. When the plunger 32 is moved to the maximum retraction position, metering as the specified molding material is completed and supply from the communication passage 30a is stopped.

Also, a guide member 33 is provided in the vicinity of the communication passage 30a formed in the injection pot 40. This guide member 33 is fixed to the inner peripheral surface of the injection pot 40 near the communication passage 30a, is cylindrical as a whole, and has a guide curved surface that guides the plasticized rubber material B supplied from the communication passage 30a into the injection pot 40 along a curved surface 'R' formed at the tip portion of the guide member 33.
That is, this guide member has the role of guiding the plasticized rubber material B supplied from the communicating passage 30a along a curved surface formed at the tip (downstream) portion thereof to the passages 30b, 30c, and 30d in the injection pot 40. Note that the passages 30b, 30c, and 30d are flow paths for the plasticized rubber material B like the communicating passage 30a, but because they are passages that flow inside the injection pot 40, they are simply referred to as passages for the purpose of explanation.

The guide member 33, which fulfills this role, is cylindrical with a specified overall thickness and is fixed to the inner circumferential surface of the injection pot 40. The cylindrical tip (downstream) portion of the guide member 33 is cut obliquely in the vertical direction by a length 'a' at the position of the upper end of the cylindrical communication passage 30a and at the position on the opposite side of the communication passage 30a (end 33a), forming an elliptical shape in side view.

In other words, if the cylindrical shape of guide member 33 is cut at an angle, the surface will be a straight line when viewed from the side, and the bottom cross section will be approximately elliptical. However, in the present invention, as shown in Figure 4A, the cut surface from the downstream passage side of plunger 32 to the opposite side is slightly concave vertically upward and has a predetermined curved surface 'R' when viewed from the side.
The second role of such guide member 33 is to allow the plasticized rubber material B in a fluid state to flow along the curved surface 'R' to the end portion 33a, thereby preventing the plasticized rubber material B from accumulating near the supply port of the plunger 32 from the communicating passage 30a, and as a result, allowing the material to flow evenly into the passage 30d formed by the groove of the plunger nozzle 36.

As shown in Figure 4A, the plunger nozzle 36 is fixed and integrated with the plunger 32 at the vertically lower tip of the plunger 32. This allows the plunger nozzle 36 to move up and down as the plunger 32 slides. As shown in Figures 4A and 4B, the tip of the plunger nozzle 36 has a roughly conical convex shape in side view, and grooves 36a formed by three vertical protrusions are cut out radially in bottom view to serve as a passage for the plasticized rubber material B.

The injection unit 30 is provided with an injection block 41 that faces and abuts against the plunger nozzle 36 when the plunger 32 descends. The injection block 41 is formed in a symmetrical, approximately inverted circular concave shape and is fitted into the descending end of the injection pot 40. The tip of the injection block 41 has a passage 42a of the injection block extension 42 that serves as a passage for the plasticized rubber material B that communicates with the injection nozzle 43.

As shown in FIG. 4A, the plunger 32 is equipped with a first check ring 34 that moves within the injection pot 40 in response to the pressure exerted by the plasticized rubber material B within the injection pot 40, and a second check ring 35 that is fixed to the rear end side of the plunger 32 relative to the first check ring 34 and moves with it. Below, the first check ring 34 and the second check ring 35 will be described in order.

First, a first check ring 34 is provided to prevent the backflow of the plasticized rubber material B filled in the storage space 40a in the injection pot 40 due to the forward (downward) movement of the plunger 32 to inject into the mold. Generally, the first check ring 34 is used in an in-line screw type injection molding device, and allows the rubber material to flow freely during plasticization, and prevents the material from leaking to the rear side during injection.

The first check ring 34 used in the injection molding device 15 of the present invention is formed in a thick, hollow cylindrical shape as shown in Figures 4A and 4C. The cylindrical outer peripheral surface (outer diameter) 34a and the inner peripheral surface (inner diameter) 40b of the injection pot 40 are in close contact with each other with approximately the same diameter without any gaps to prevent the backflow of the plasticized rubber material B, while allowing the plunger 32 to slide freely in the axial direction of the injection pot 40. In addition, a passage 30c for the plasticized rubber material B is formed in the cylindrical hollow part of the first check ring 34. As a result, the first check ring 34 can fill the storage space 40a in the injection pot 40 with the plasticized rubber material B through the passage 30d formed by the groove of the plunger nozzle 36. The configuration of the first check ring 34 to prevent the backflow of the plasticized rubber material B filled in the storage space 40a in the injection pot 40 will be explained in the second check ring 35.

Next, as shown in Figures 3, 4A and 4C, a second check ring 35 is provided between the rear end of the first check ring 34 and the plunger 32 on the same axis as the plunger nozzle 36 in the injection pot 40. This second check ring 35 is fitted integrally with the plunger 32 and moves in the injection pot 40 with the forward and backward movement of the plunger 32. When the lower end of this second check ring 35 is not in contact with the first check ring 34, a passage 30c for filling the plasticized rubber material B into the storage space 40a in the injection pot is opened, and when the lower end of this second check ring 35 is in contact with the first check ring 34, the passage 30c can be closed. In this way, backflow is prevented by the movements of both the first check ring 34 and the second check ring 35.
Thus, as shown in FIG. 5C, when the plunger 32 is at its most retracted position within the injection pot 40, the first check ring 34 and the second check ring 35 come into tight contact with each other, stopping the supply of plasticized rubber material B from the communicating passage 30a, completing the filling of the plasticized rubber material B into the storage space 40a within the injection pot 40 (metering completed), and stopping the movement of the plunger 32.

[Injection operation of injection unit]
In the injection unit 30 in this embodiment, the plunger 32 is moved downward (forward) to inject the molten plasticized rubber material B stored in the storage space 40a in the injection pot 40 toward the mold through the injection nozzle 43. In this injection operation, the first check ring 34 is pressurized from above during metering, so that it moves downward to form multiple passages that serve as flow paths for the rubber, and is pressurized from below during injection, so that it comes into contact with the second check ring 35 and is checked.
The operation of the injection unit 30 will be described in detail below with reference to FIGS. 5A to 5D.
5A is an operation diagram of a state in which plasticized rubber material B is being metered to a predetermined amount, and a passage 30b through which plasticized rubber material B flows is formed in the gap between the outer periphery of second check ring 35 and injection pot 40. Here, plunger 32 moves backward in the upward direction to secure storage space 40a in injection pot 40, while rubber material A is heated in plasticizer 20 and plasticized by rotation of screw 23, and plasticized rubber material B in a molten state is pushed out through communication passage 30a into passages 30b, 30c, and 30d in injection unit 30, as shown in FIG. Specifically, the plasticized rubber material B supplied to the communication passage 30a passes through a passage 30b in the gap between the inner periphery 40a of the injection pot 40 and the outer periphery 35a of the second check ring 35, and further passes through a passage 30c in the gap between the inner periphery 34b of the first check ring 34 and the plunger 32 facing it, and further flows into a passage 30d of the plunger nozzle 36, and is filled into the storage space 40a in the injection pot 40. Also on the opposite side of the communication passage 30a (the left side in the drawing), the plasticized rubber material B supplied from the communication passage 30a flows along the curved surface R formed in the guide member 33, and further passes through the above-mentioned passages 30b, 30c, and 30d to be filled into the storage space 40a in the same manner.

Figure 5B is an operational diagram showing the state in which a predetermined amount of plasticized rubber material B is being measured, with passages 30b, 30c, and 30d open as in Figure 5A. Furthermore, in Figure 5B, as the storage space 40a in the injection pot 40 is almost completely filled, the upward pressure (pressure) from below by the plasticized rubber material B increases, causing the plunger 32 to move backwards upward compared to Figure 5A (upward arrow C in the drawing).

Figure 5C is an operational diagram of the state when the metering of plasticized rubber material B is completed. Furthermore, as shown in Figure 5B, as the pressure received by the plunger 32 by the plasticized rubber material B gradually increases, the first check ring 34, which remains in contact with the plunger 32, is pushed upward to its maximum extent, and when the plunger 32 reaches its limit position, that is, when the metering is completed, the first check ring 34 and the second check ring 35 abut against each other, and the passage 30b changes from an open state to a closed state.
In other words, the first check ring 34 moves backward in the upward direction in the figure, and the first check ring 34 and the second check ring 35 abut and come into close contact with each other, thereby acting as a backflow prevention ring, and the extrusion of the plasticized rubber material B from the plasticizing device 20 stops and the backward movement of the plunger 32 stops once the metering of the plasticized rubber material B is completed.

The stopping operation when the plunger 32 reaches the limit position is performed by stopping the rotation of the metering screw 23. Specifically, a valve (not shown) connected to the hydraulic motor 21 controls the screw 23. When the rotation of the screw 23 stops, the plasticized rubber material B is no longer fed, and the plunger 32 also stops.
That is, a position sensor (not shown) is attached to the plunger 32, and the plunger 32 is retracted by metering. The position of the plunger 32 is monitored by a control device, and when the position reaches a set value, the valve connected to the hydraulic motor 21 is controlled to stop the hydraulic motor 21.
In order to improve the accuracy of the stopping position, it is also possible to perform control such that the speed is reduced when the target position is approached.

In this way, the backward movement of the plunger 32 opens and closes the passages 30b, 30c, and 30d of the molten plasticized rubber material B in cooperation with the guide member, the first check ring 34, and the second check ring 35, thereby measuring the amount of plasticized rubber material B filled in the storage space 40a in the injection pot 40, and when the measured value reaches a predetermined constant value, the supply of plasticized rubber material B by the plasticizer 20 and the backward movement of the plunger 32 stop. Then, the measurement (injection and filling of a predetermined amount of plasticized rubber material B) into the storage space 40a in the injection pot 40 is completed, and the molten plasticized rubber material B is not sent to the storage space 40a in the injection pot 40.

In FIG. 5D, the first check ring 34 is pressurized from above during metering, so it moves downward to form a flow path for the rubber, but during injection, it is pressurized from below and comes into contact with the second check ring 35 to be checked. In other words, the specified amount of plasticized rubber material B for molding has been measured, so the first check ring 34 and the second check ring 35 come into contact, closing the passages 30a and 30b, and the plunger 32 slides downward (downward arrow D in the figure) to start compression, and the plasticized rubber material B molten in the storage space 40a in the injection pot 40 is injected toward the mold.

Therefore, in the injection molding apparatus 15 of the present invention, the plasticized rubber material B that has flowed in first from the communication passages 30b, 30c, 30d into the storage space 40a in the injection pot 40 is fed in sequence to the plunger nozzle 43 via the above passages, and when the plunger 32 moves forward, the plasticized rubber material B is injected in sequence starting from the front, thereby achieving the desired first-in, first-out. This first-in, first-out system makes it possible to suppress variations in the residence time of the plasticized rubber material B and reduce molding defects.
In addition, since the injection molding apparatus 15 of the present invention does not have a lateral hole in the injection block 43 for supplying the plasticized rubber material B, the bottleneck that would cause the injection block 43 to crack due to accumulation of metal fatigue is eliminated.

In addition, near the rear end of the injection unit 30, a sealing structure 37 is constructed between the inner circumference 40b of the injection pot 40 and the outer circumference 32a of the plunger 32, so that the degree of vacuum in the storage space 40a inside the injection pot 40 can be maintained constant when the plunger 32 is moved up and down inside the injection pot 40. In this case, existing sealing technology can be applied as the sealing structure 37, so there is no particular limitation here, but the drawings show a packing laid around the outer circumference of the rear end side of the injection pot 40 along its circumferential direction as an example of a sealing structure.

[Temperature control nozzle]
6, 7A, and 7B, the injection nozzle of the injection molding device 15 of the present invention is equipped with a temperature control nozzle 43 having a spiral medium passage 43c formed therein through which a medium (running water) for heating and cooling the plasticized rubber material B, which is the molding material, can flow. This is because the plasticized rubber material B needs to be kept at a temperature suitable for molding from the time it is measured in the storage space 40a of the injection pot 40 until the final injection is completed.

Normally, rubber in a typical injection molding machine goes through the following process: (1) The rubber ribbon outside the molding machine is at room temperature with no temperature control (hereafter simply referred to as temperature control); ⇒ (2) It is mixed (shear heat) by the screw of the heating barrel, with temperature control at a temperature of 60-90°C; ⇒ (3) It is stored in the storage space inside the injection pot, with temperature control at a temperature of 60-90°C; ⇒ (4) It passes through the nozzle due to injection pressure (shear heat) at 90-120°C with no temperature control; ⇒ It passes through the runner (shear heat) at 120-140°C with temperature control; (6) In the mold, the temperature rises due to heat transfer from the mold surface, with temperature control at 170-200°C, and is finally molded in the mold.

In the above process, a particular problem is the temperature of the plasticized rubber material B at the tip of the injection nozzle. Immediately after injection, the rubber in this area is hot and there is a risk that it will vulcanize while the rubber in the mold is being vulcanized, so it must be cooled to prevent this. However, at the time of the next injection, this area of rubber will have cooled, and since the friction distance with the nozzle wall is small, no shear heat generation can be expected. For this reason, it is necessary to warm only this area of rubber before injection.

In order to achieve both of these, in the injection molding apparatus 15 of the present invention, as shown in Fig. 6, first, the injection passage 42a for injection, which is the injection block extension 42 connecting the injection block 41 and the injection nozzle 43, is heated by the temperature control cylinder 42b, and in the present invention, as shown in Fig. 3, the injection nozzle 43 is provided with a heating and cooling mechanism 55 which switches between a water heater 50 and a chiller (cooler) 60 as required for circulation. This makes it possible to prevent vulcanization and insufficient heating of the rubber material in this portion by heating or cooling the rubber material remaining in the injection nozzle 43. Also, since scorching occurring in the injection nozzle 43 can be prevented, it is possible to improve the quality and save the rubber material.
The amount of shear heat generated in the injection passage 42 a is smaller than the amount of shear heat generated in the injection nozzle 43 , and it is therefore effective to cool the injection nozzle 43 with a chiller (cooling device) 60 .

The temperature of the temperature control cylinder 42b is controlled by flowing hot oil or hot water into the space between the jacket, which is made of cylindrical steel material, and the injection block 42.

Next, the heating and cooling mechanism 55 is an external device provided separately from the injection unit 30, and is composed of a water heater 50, a chiller (cooler) 60, shutoff valves 51 and 52 for the water heater, and shutoff valves 61 and 62 for the chiller (cooler) 60. The water heater 50 is a known device that, for example, installs a heater in a water storage tank and uses the heat to boil water. The chiller (cooler) 60 is a known device that is a cooling water circulation device that continuously supplies cold water while circulating water through the chiller. The shutoff valves 51, 52, 61, and 62 are known solenoid valves that switch between the hot water of the water heater 50 and the cooling water of the chiller (cooler) 60 as needed. The water heater 50, chiller (cooler) 60, and shutoff valves 51, 52, 61, and 62 are general devices that are already manufactured and sold, so detailed explanations of each are omitted.

The injection nozzle 43 with temperature control function of the present invention will be described using a partial external view of the injection nozzle 43 in Fig. 7A and a partial cross-sectional view of the injection nozzle 43 in Fig. 7B. First, as shown in Figs. 7A and 7B, the injection passage 43a formed in the center of the injection nozzle 43, which has an inlet and an outlet (see "inlet" and "outlet" in the figure) for hot water or cooling water from the heating and cooling mechanism 55 described above, is a passage at the time of injection leading to the mold, and the structure in which the inner diameter of the injection passage 43a is made smaller and thinner than the inner diameter of the injection passage 42a of the injection block extension 42 is intended to control the increase in injection pressure immediately before injection and the heat generation due to the flow friction of the rubber material and temperature control.

7A and 7B, the injection nozzle 43 is formed with a spiral groove 43c that serves as a passage for hot water or cooling water. This spiral groove 43c is a semicircular passage that starts at the hot water or cooling water passage inlet, turns around at the tip of the injection nozzle 43, and leads to an outlet at the other end of the inlet. When hot water or cooling water is supplied to the passage inlet, it travels in a spiral circumnavigation along the spiral groove toward the passage outlet.
In addition, since groove 43c is formed in a semicircular shape, the heat is conducted efficiently, and since it rotates in a spiral shape, the temperature rise speed can be increased. This compensates for the frictional heat caused by the short injection passage 43a during injection, and the temperature can be supplied to the mold at a temperature close to the vulcanization temperature.
In this embodiment, the number of the semicircular grooves 43c is four, but the number is not limited to four. Although it depends on the size of the semicircular grooves 43c, the more spirals there are, the longer the injection passage 43a will be.

As shown in Figures 7A and 7B, the inlet and outlet for the hot water or cooling water are connected to an inverted L-shaped cylindrical pipe 43e. This cylindrical pipe 43e is connected and fixed to the injection nozzle 43, and a cylindrical cover part 43d that seals and covers the spiral groove 43c is attached to the outer periphery of the injection nozzle 43 (the convex ridge part between the groove 43c of the valley part and the groove 43c of the adjacent valley part) 43b.

As shown in FIG. 3, this heating and cooling mechanism 55 is composed of a passage 53 leading to the "inlet" of the injection nozzle 43, hot water heated by a hot water heater 50, shutoff valves 51 and 52 of the hot water heater that control the supply, and shutoff valves 61 and 62 that control the supply of cooling water cooled by a chiller (cooler) 60 to the passage 53 leading to the "inlet" of the injection nozzle. When the rubber material in the passage 43a of the injection nozzle 43 is heated, the shutoff valves 61 and 62 of the chiller (cooler) 60 are closed and the shutoff valves 51 and 52 of the hot water heater 50 are opened to form the hot water passages 53 and 54. Conversely, when the passage 43a of the injection nozzle 43 is cooled, the hot water side shutoff valves 51 and 52 are closed and the shutoff valves 61 and 62 of the chiller (cooler) 60 are opened to form the cooling water passage.

FIG. 7C shows a flow of alternately switching between the hot water from the water heater 50 and the cooling water from the chiller (cooler) 60 in the heating and cooling mechanism 55 configured as above.
In Figure 7C, the horizontal axis indicates the time axis, and the vertical dotted or chain lines indicate the flow chart so that the operating states of the words "injecting" and "injection stopped" in "injection operation,""nozzleheating" and "nozzle cooling" in "nozzle temperature control,""temperature at injection" and "pot temperature" in "rubber temperature after injection," and "temperature at injection" and "pot temperature" in "rubber temperature at nozzle" can be understood.

This flow diagram explains why the rubber temperature of the injection nozzle 43 is reached by heating the injection nozzle 43 (t1-t2), and is lowered to the temperature of the injection pot 40 by cooling the injection nozzle 43 (t3-t4).
Since the plasticized rubber material B is cooled at the time of injection, it is necessary to warm the plasticized rubber material B in advance before injection. Therefore, the shutoff valves 61, 62 of the chiller (cooler) 60 are closed and the shutoff valves 51, 52 of the water heater 50 are opened, and warm water is passed through the spiral passage 43c before the start of injection (t1) to heat the injection nozzle 43.
・Injection begins as soon as the temperature rises (t2).
Immediately after injection, this part is hot and there is a risk that it will vulcanize during the vulcanization of the rubber in the mold. In order to prevent this, it is necessary to cool it. Therefore, immediately after injection (t2), the shutoff valves 51, 52 of the water heater 50 are closed and the shutoff valves 61, 62 of the chiller (cooler) 60 are opened to pass cooling water through the spiral passage to cool the injection nozzle 43.
After the injection is stopped (t3), when the temperature of the rubber in the injection nozzle 43 is lowered by the cooling water, the nozzle cooling is stopped (t4).

As explained above, in the present invention, the timing for switching between the hot water of the water heater 50 and the cooling water of the chiller (cooler) 60 is based on the timing of the injection operation. In this way, the switching between hot water and cooling water using the shutoff valves 51, 52, 61, and 62 is rational because it is an operation that is simply linked to the injection operation of the injection nozzle 43.

In this way, the temperature of the rubber material can be raised close to the vulcanization temperature just before injection, which greatly shortens the vulcanization time in the mold. Also, by heating or cooling the rubber material remaining in the injection passage 43a of the injection nozzle 43, it is possible to prevent insufficient vulcanization and heating of the rubber material in this area.

The above is a detailed description of an embodiment of the present invention, but these are merely examples, and the present invention can be configured in various modified forms without departing from the spirit of the invention.

REFERENCE SIGNS LIST 1 Injection cylinder 2 Injection pot 3 Plunger 4 Heating barrel 5 Screw 6 Plasticizer (extruder)
Reference Signs List 7 Passage at tip of injection pot 8 Injection nozzle 9 Inlet 10 Mold 11 Sprue 12 Runner 13 Gate 14 Cavity 15 Injection molding device 16 Tie bar 20 Plasticizer 21 Hydraulic motor 22 Heater barrel 23 Screw 30 Injection unit 30a Communication path (flow path)
30b, 30c, 30d Passage (flow path)
Reference Signs List 31 Injection cylinder 32 Plunger 33 Guide member 34 First check ring 35 Second check ring 36 Plunger nozzle 36a Plunger nozzle groove 37 Sealing structure 38 Injection rod 40 Injection pot 40a Storage space 40b Inner circumference of injection pot 40c Connection portion 41 Injection block 42 Injection block extension 42a Injection passage of injection block extension 42b Heating barrel (band heater)
42c Inner diameter of injection passage 43 Injection nozzle 43a Injection passage of injection nozzle 43b Outer periphery of injection nozzle 43c Groove of valley of injection nozzle 43d Cover part of injection nozzle 43e Cylindrical piping of injection nozzle 50 Water heater 51 Water heater shutoff valve
52 Water heater shutoff valve 55 Heating and cooling mechanism 60 Chiller (cooler)
61 Chiller shutoff valve 62 Chiller shutoff valve A Rubber material B Plasticized rubber material C Symbol for plunger retraction movement D Symbol for plunger forward movement

Claims (3)

An injection molding apparatus comprising: a plasticizing device having a rotatably mounted screw which transports while plasticizing a rubber material put into a heating barrel, and extruding the plasticized rubber material toward a tip thereof; and an injection unit having a communication passage at a connecting portion with the plasticizing device, and which injects the plasticized rubber material, which is supplied from the communication passage and filled into a storage space in an injection pot by moving a plunger inside the injection pot,
The connecting portion connects the leading end of the plasticizer and the side surface of the rear end of the injection pot,
a first check ring that moves within the injection pot according to the pressure of the plasticized rubber material filled in the injection pot;
a second check ring that is fixed to the rear end side of the plunger relative to the first check ring and moves with the plunger,
an injection molding apparatus characterized in that, when the plunger is at its maximum retraction position within the injection pot, the first check ring and the second check ring come into close contact with each other to stop the supply of the plasticized rubber material from the communicating passage. the communication passage is formed in the injection pot of the injection unit,
2. The injection molding apparatus according to claim 1, further comprising a guide member which is fixed to the inner peripheral surface of the injection pot near the communicating passage, is cylindrical as a whole, and has a guide curved surface formed at the tip portion thereof for guiding the plasticized rubber material supplied from the communicating passage into the injection pot along a curved surface. 3. The injection molding apparatus according to claim 1, wherein the injection nozzle in the injection unit includes a temperature control nozzle having a spiral medium passage through which a medium for heating and cooling the plasticized rubber material can flow.

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