JP4191395B2 - Injection molding machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an injection molding machine, and more particularly to a pre-plastic injection molding machine suitable for rubber injection molding.
[0002]
[Prior art]
As the pre-plasticization type injection molding machine is, for example, as shown in FIG. 16. This includes an extruder 3 having a screw 2 and a plasticizing and metering function, an injection pot 6 connected to the extruder 3 by a passage 5 having a check valve 4, and the injection pot 6. And a sliding plunger 9, a portion (hereinafter referred to as an injection pot tip portion) 8 serving as an injection passage at the tip of the pot 6, and an injection nozzle 9 attached to the tip of the injection pot tip portion 8. The vicinity of the lower end of the case 1 is supported by the upper die plate 11 of the mold 10. Reference numeral 12 denotes a lower die plate connected by the upper die plate 11 and the tie bar 13, 14 denotes a heat insulation board, and 15 denotes a heat board.
[0003]
In the injection molding machine, first, the raw material rubber is put into the extruder 3 as indicated by the arrow, and plasticized while being sent to the left in FIG. 16 by the screw 2. After passing through the stop valve 4, it is fed into the injection pot 6 by the passage 5, and the plunger 7 is raised by the injection pressure of the plasticized rubber. Next, the plunger 7 is lowered, and the plasticized rubber in the injection pot 6 is fed into the mold 10 through the injection pot tip 8 and the injection nozzle 9, and through the sprue 16, runner 17 and gate 18. It is press-fitted into the cavity 19 in the mold 10 and vulcanized.
[0008]
By the way , in order to improve the productivity of rubber vulcanized products and reduce the product cost, it is common knowledge that it is effective to shorten the vulcanization time of the plasticized rubber filled in the cavity 19. It is required to set the temperature in the injection pot 6 as high as possible.
[0009]
However, when the temperature of the plasticized rubber in the injection pot 6 is excessively high, a scorch, that is, “an initial stage in which the vulcanization reaction starts and the plasticity is lost” easily occurs, and the scorched rubber enters the cavity 19. This may cause product defects or clog the injection pot tip 8 and the injection nozzle 9.
[0010]
The formation of the scorched rubber is more likely to occur when the rubber adhering to the inner wall surface of the injection pot 6 or the like remains in the place for a long time. It is preferable to reduce the number of injections necessary to completely switch the plasticized rubber existing in the pot 6 to the newly added plasticized rubber as much as possible, and to shorten the remaining time of the rubber adhered to the inner wall surface.
[0011]
That is, it is desirable that the rubber at the remaining portion is completely injected with the smallest possible number of injections and switched to a new plasticized rubber. However, if the changeability is poor, the number of injections increases, and in particular, the temperature in the injection pot 6 is increased. If it is raised, scorch is likely to occur, and conversely, if the switchability is good, the number of injections can be reduced, and the time during which the plasticized rubber is overheated on the inner wall surface is shortened, resulting in the occurrence of scorch. It can be suppressed.
[0012]
However, in the general injection molding machine shown in FIG. 16, the tip 8 of the injection pot has the same diameter over its entire length, and the flow rate of the plasticized rubber at the time of injection is extreme on the inner wall surface compared to its center. When the injection is completed, the plasticized rubber tends to remain in the form of cholesterol. In order to remove the residual rubber from the injection pot tip 8 in preparation for switching to a new plasticized rubber, a considerable number of times ( It is necessary to repeat the injection at least 6 times.
[0013]
When the residual rubber accumulates with time in the injection pot tip 8 and the inner diameter (flow diameter) of the passage 8 becomes smaller, the residual rubber can no longer be removed by repeating the injection. Therefore, in general, for example, the metal case 1 is removed from the upper die plate 11 at every predetermined number of injections determined empirically, and the injection pot tip 8 and the injection nozzle 9 are cleaned to remove the remaining rubber. However, this naturally required a great deal of time and effort, leading to an increase in cost.
[0014]
Therefore, as in the injection molding machine described in Japanese Patent Laid-Open No. 10-166403, only the tip of the injection pot is gradually reduced toward the nozzle, and the inner wall surface of the tip of the injection pot in a cross section including the axis of the injection pot. By changing the inclination angle with respect to the axis to 0.2 ° to improve the flow velocity of the inner wall of the injection pot tip by changing the flow velocity distribution of the plasticized rubber at the time of injection, There is also an idea to eliminate the residue.
[0015]
However, in rubber injection molding machines, all plasticized rubber that remains in the tip of the injection pot is scorched when the molding machine is stopped after production is completed. It is common to remove the nozzle and clean the scorched rubber in the tip of the injection pot by repeated injections. First, the injection molding machine must be disassembled to remove the clogged rubber, or the parts must be replaced, and the time and cost are much greater than in the above case.
[0016]
In short, in conventional injection molding machines, plasticized rubber tends to remain on the inner wall surface of the injection pot tip, etc. due to the structure, so that the number of injections for switching is increased more than necessary, and by injection for switching. However, when the residual rubber cannot be removed, it is necessary to remove the metal case and clean it, and the time and cost for this are enormous. Further, in the one in which the tip of the injection pot described in the above-mentioned Japanese Patent Laid-Open Publication is gradually reduced toward the nozzle, once the passage is clogged, it is necessary to disassemble the injection molding machine, replace parts, etc. There has been a problem that the rubber temperature in the pot is set to a high temperature within a range that does not cause scorch, thereby improving productivity and reducing product cost.
[0017]
[Problems to be solved by the invention]
RESOLUTION try to that challenges the present invention is to a provide child an injection molding machine that obtained by accurately measuring the temperature of the molding material in the injection pot (plasticized rubber).
[0018]
[Means for Solving the Problems]
The injection molding machine according to the present invention for solving the previous SL challenges, formed in a tubular shape, an injection pot molding material is supplied, and an injection nozzle attached to the tip of the injection pot, said shooting pot In an injection molding machine provided with a plunger that is movably accommodated in the longitudinal direction of the injection pot in the injection pot in order to inject the molding material from the injection nozzle , and the tip portion is formed in a tapered shape , said plunger, said not more than angle 45 ° tip, the tip portion of the plunger, in which a built-in temperature sensor for measuring the temperature of the molding material in said shooting pot.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
A preferred embodiment of the present invention will be described with reference to FIGS. 1 to 6 in which the reference numerals used in the description of FIG. 16 represent the same thing. The injection molding machine of the present invention includes a metal case 21 and an injection nozzle. distribution and the injection pot 24 having a 23, a molding material in the plasticized state into the pot 24 to form a charging port 25 for supplying from the side, the slidably plunger 26 before Symbol injection pot 24 as well as setting the injection pot 24 tip and allowed forming a tapered cross section portion to the injection nozzle 23 and the plunger 26 tip, and the tip of the plunger 26, the injection of the molding material, a substantially pre Symbol injection pot 24 tip The shape is such that it satisfies.
[0020]
The embodiment shown in FIGS. 1 to 6 will be described in more detail. First, in the embodiment shown in FIGS. 1 and 2, the injection pot tip portion 22 is connected through a connecting portion 24a with the injection pot 24 body. The portion 22 is formed to have a tapered cross section, and the plunger 26 is connected to the tip of the conventional plunger 7 as shown in FIG. 16 via a connecting portion 26a contacting the connecting portion 24a. A protrusion (tip) 27 having a tapered cross section that can be closely fitted into the portion 22 is formed. The protrusion 27 a of the tip 27 is conical with the inner wall 23 a of the injection nozzle 23.
[0021]
With the above configuration, the plasticized rubber introduced into the injection pot 24 from the insertion port 25 through the passage 5 by the extruder 3 is sequentially pushed into the injection pot tip portion 22 by the lowering of the plunger 26, and passes through the injection nozzle 23. It is press-fitted into the cavity 19 in the mold 10 and vulcanized, but after a predetermined lowering of the plunger 26, its tip 27 enters the injection pot tip portion 22 and continuously extrudes rubber from the injection nozzle 23. Descend. At this time, the flow velocity of the inner wall surface is large due to the shape of the tip portion 22 of the injection pot, and the rubber on the wall surface also flows down without any stagnation. Further, since the injection pot tip portion 22 forms a tapered portion, the connecting point K between the injection pot tip portion 22 and the connecting portion 24a is a slanted protrusion , so that the rubber flows smoothly, and the scorch Is less likely to occur.
[0022]
Then, when the lower end of the main body of the plunger 26 reaches the lower end of the injection pot 24 as shown in FIG. Abutting, and the connecting portion 24a and 26a also abut. Therefore, in this example, there is almost no rubber remaining in the injection pot tip portion 22 and the injection nozzle 23, and in preparation for switching to a new plasticized rubber, the injection is repeated to remove the residual rubber from the injection pot tip portion 22 and the like. There is no need.
[0023]
In the example shown in FIGS. 3 and 4, the injection pot tip portion 22 ′ is formed in a tapered shape directly from the lower end of the injection pot 24 ′ body, and the inner surface of the injection nozzle 23 ′ is also the cylindrical portion 23 ′ at the tip. Except for b, the inner wall 23'a has a tapered cross section continuous with the injection pot tip 22 ', and the tip 27' of the plunger 26 'is used as the injection pot tip 22' and the inner wall 23 of the injection nozzle 23 '. It is formed according to the shape of 'a. The taper angle θ is determined by the diameter of the injection pot 24 ′ determined by the size of the injection molding machine, the thickness of the upper die plate 11, and the position of the extruder 3 attached to the metal case 21, but in the example shown in FIG. θ was 30 degrees.
[0024]
The examples shown in FIGS. 5 and 6 are different from those shown in FIGS. 3 and 4 only in the injection nozzle 23 ″, and a cross section in which the inner surface of the injection nozzle 23 ″ is continuous with the injection pot tip portion 22 ′. This is a tapered inner wall 23 ″ a.
[0025]
Here, it will be described in detail that the inner surfaces of the injection nozzles 23 ′ and 23 ″ are inner walls 23′a and 23 ″ a having a tapered cross section continuous with the injection pot tip portion 22 ″.
As shown in FIG. 7, when injection molding is performed by the injection molding machine, the highest temperature rise of the injection rubber itself due to shear heat generation during injection is due to an injection pressure loss during injection. The site with the highest shear heat generation is the injection nozzle, specifically, the most narrowed portion of the nozzle, that is, the nozzle diameter.
[0026]
In the conventional injection nozzle 9, as shown in FIG. 8, the inner diameter of the nozzle diameter portion 9a is constant over the entire length. Therefore, when the flow velocity distribution of the rubber passing therethrough is viewed, the nozzle diameter portion 9a is shown in FIG. Then, the speed is large near the center and extremely slow on the inner wall surface. Contrary to the flow velocity distribution, the temperature distribution is low near the center and high near the inner wall surface. Therefore, the scorch is likely to occur and the scorch is difficult to remove.
[0027]
Therefore, as shown in FIG. 10, for example, the inner surface of the injection nozzle 23 '' is formed as an inner wall 23''a having a tapered cross section continuous with the injection pot tip portion 22 '' including the nozzle diameter portion. Thus, when the rubber flows down the inner surface of the injection nozzle 23 ″, the flow state is as shown in FIG. 11, and the flow velocity distribution is different from the case where the inner diameter is constant, and the flow velocity of the inner wall portion of the tip portion of the injection pot is improved. To do. Therefore, the residual plasticized rubber at the completion of injection can be eliminated. This is almost the same when the injection nozzle 23 ′ shown in FIGS. 3 and 4 is used, but there is a possibility that the flow velocity at the time of rubber flow is slightly reduced by the cylindrical portion 23′b at the tip. However, when a scorch is generated in the injection nozzle 23 ', there is an advantage that it can be easily removed.
[0028]
3 to 6, the plasticized rubber charged into the injection pot 24 'from the charging port 25 through the passage 5 by the extruder 3 is sequentially injected by the lowering of the plunger 26' in the same manner as described above. It is pushed into the pot tip portion 22 'and is injected into the cavity 19 in the mold 10 through the injection nozzles 23', 23 '' and vulcanized. Enters the injection pot tip 22 'and descends while continuously extruding rubber from the injection nozzles 23', 23 ''. At this time, due to the shape of the tip portion 22 'of the injection pot, the flow velocity of the inner wall surface is large, and the rubber on the wall surface also flows down without stagnation. Further, since the injection pot tip portion 22 ′ forms a tapered portion directly connected to the injection pot 24 ′, the coupling point K ′ between the injection pot tip portion 22 ′ and the injection pot 24 ′ body is shown in FIGS. It is closer to a straight line than the coupling point K in the example shown. Therefore, the rubber flows down more smoothly and the risk of scorching is reduced.
[0029]
12 and 13, for example, as described above, the tip 27 'of the plunger 26' is formed to have a tapered cross section in accordance with the shapes of the injection pot tip 22 'and the inner wall 23'a of the injection nozzle 23'. It shows the mounting state of a suitable temperature sensor. That is, the temperature sensor is necessary for accurate measurement of rubber temperature, which is important for ensuring the quality of rubber injection-molded vulcanized products. Conventionally, for example, from the extruder 3 shown in FIG. It was installed in passage 5. However, due to the influence of frictional heat between the raw rubber and the inner wall of the passage and the temperature of the wall surface of the metal case 1, the accurate rubber temperature cannot be measured.
[0030]
Therefore, like the molten polymer temperature measuring device described in the specification of Japanese Patent No. 2960472, an insertion portion is provided which is protruded from the tip of the injection plunger and inserted into the substantially central portion of the molten polymer, and a temperature sensor is provided at the tip. Although the temperature of the molten polymer is measured by a temperature sensor immediately before the injection plunger is operated, the influence of heat radiation from the plunger is reduced to some extent, but there is a tendency to lack structural durability.
[0031]
The temperature sensor 28 according to the present invention is such that the tip 27 'of the plunger 26' as described above is formed to have a tapered cross section in accordance with the shape of the injection pot tip portion 22 'and the inner wall 24'a of the injection nozzle 24'. Built in without protruding at the tip. In this case, according to the research of the present inventor, there is a relationship shown in FIG. 14 between the angle α of the tip of the plunger 26 ′ and the measurement error of the rubber temperature. Therefore, the angle α is 45 degrees with little measurement error. Select from the following considering durability.
[0032]
In the injection molding vulcanization of rubber, in order to ensure the quality of the molded vulcanized product, the degree of vulcanization (the degree of heat curing reaction of the rubber) of the rubber molded and vulcanized in the mold cavity is controlled to be constant. However, in order to obtain the degree of vulcanization for each injection molding, at least the vulcanization characteristics of the rubber used for each rubber material production unit, for example, measurement data by a curast meter, injection, The rubber temperature measurement data in the injection pot for each molding and the average injection pressure measurement data for each injection molding are required. Conventionally, there has not been a durable and low-error measurement method for measuring the rubber temperature in the injection pot, but this can be solved by the present invention, and a highly accurate prediction calculation of the degree of vulcanization becomes possible.
[0033]
Furthermore, the present inventor has devised means for keeping the temperature of the rubber injected into the mold cavity by injection at a high temperature. As outlined above, in rubber injection molding vulcanization, as described above, the injection pressure of plasticized rubber in the injection pot is increased and the injection heat is increased as much as possible by the shear heat generation of the rubber. It is desirable that the temperature of the is high. This is because the vulcanization time in the mold can be shortened and the productivity can be improved.
[0034]
In particular, in the case where the tip 27 'of the plunger 26' as described above is formed to have a tapered cross section in accordance with the shapes of the injection pot tip 22 'and the inner wall 23'a of the injection nozzle 23', etc. Since the frictional force between the rubber in the fluid state and the injection pot tip 22 'and the inner wall 23'a of the injection nozzle 23' becomes extremely large and the amount of heat generated thereby is large, It is advantageous.
However, in reality, most of the heat generated escapes from a metal case made of iron-based metal, and the rubber itself does not sufficiently heat.
[0035]
As a result of repeated research, the inventor has formed the tip 27 ′ of the plunger 26 ′ as described above in a tapered shape in accordance with the shape of the injection pot tip portion 22 ′ and the inner wall 23′a of the injection nozzle 23 ′. It was devised to apply a ceramic spray coating on the injection pot tip 22 'and the inner wall 23'a of the injection nozzle 23'. As the ceramic sprayed coating in this case, for example, a material whose surface is polished with a total thickness of 80 microns (undercoat, topcoat) with 50/50 alumina / titania is suitable, but the ceramic material is not particularly limited. In both cases, by selecting an appropriate particle size, an air heat insulating layer between the sprayed ceramic particles is formed, and the heat insulating effect can be improved. FIG. 15 is a diagram showing the relationship between the injection pressure with and without ceramic spraying and the temperature of the exothermic rubber, but it can be seen that even with the same injection pressure, the ceramic sprayed one has a maximum rubber temperature of 15 degrees.
[0036]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention , there exists an effect which can provide the injection molding machine which can measure the temperature of the molding material (plasticized rubber) in an injection pot correctly .
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an essential part of a first embodiment of an injection molding machine according to the present invention, and shows a state before a plunger is actuated. FIG. FIG. 3 is a cross-sectional view of the main part of the second embodiment of the injection molding machine according to the present invention, and shows the state before the plunger is actuated. FIG. 4 shows a second embodiment of the injection molding machine according to the present invention. FIG. 5 is a cross-sectional view of the main part of the third embodiment of the injection molding machine according to the present invention, and shows the state before the plunger is operated. FIG. 6 is an injection mold according to the present invention. FIG. 7 is a cross-sectional view of the main part of the third embodiment of the machine, and shows the state after the plunger is actuated. FIG. 7 is a diagram showing the relationship between each flow path position and injection pressure in the injection molding machine. Fig. 9 is an enlarged cross-sectional view of the nozzle. 10 is an enlarged cross-sectional view of an injection nozzle in the injection molding machine according to the present invention. FIG. 11 is a diagram showing a flow state of rubber in the injection nozzle shown in FIG. 10. FIG. 12 is an injection molding machine according to the present invention incorporating a temperature sensor. FIG. 13 is a diagram showing a state of arrangement of the temperature sensor in FIG. 12. FIG. 14 is a graph showing a difference between a tip angle of a plunger of an injection molding machine according to the present invention and a measurement error of a rubber temperature in an injection pot. Fig. 15 is a diagram showing the effect of injection of ceramic on the tip of an injection pot, etc., on the temperature of the heat generated by the injection. Fig. 16 is a cross section of a conventional injection molding machine and mold. Figure.
[Explanation of symbols]
1, 21 Metal case 2 Screw 3 Extruder 4 Check valve 5 Passage 6, 24, 24 'Injection pot 7, 26, 26' Plunger 8, 22, 22 'Injection pot tip portion 9, 23, 23', 23 ''Injection nozzle 23a, 23'a, 23''a Inner wall of injection nozzle 10 Mold 11 Upper die plate 12 Lower die plate 13 Diver 14 Heat insulation panel 15 Heating panel 16 Sprue 17 Runner 18 Gate 19 Cavity 25 Input port 27, 27 'Plunger tip 28 Temperature sensor.

Claims (1)

Is formed in a cylindrical shape, an injection pot molding material is supplied, and an injection nozzle attached to the tip of the injection pot, the molding material in said injection pot to the injection pot to eject from the injection nozzle In an injection molding machine including a plunger that is movably accommodated in the longitudinal direction of the injection pot and has a tip formed in a tapered shape ,
The plunger has an angle of the tip portion of 45 degrees or less,
An injection molding machine characterized in that a temperature sensor for measuring the temperature of the molding material in the injection pot is built in the tip of the plunger .

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