JP4286268B2 - Injection molding machine - Google Patents

Description

The present invention relates to a pre-plasticization suitable for injection molding of rubber (Pre-pla = Pre-plasticizing ) type injection molding machine, may be made in particular the temperature distribution of the molding material injected from the tip of the injection nozzle sufficiently uniform structure And the improvement of Japanese Patent Application No. 2005-178670.

  An example of the pre-plastic injection molding machine is shown in FIG. 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. Plunger 7 that slides, a taper portion (hereinafter referred to as an injection pot taper portion) 8A from the lower end of the main body portion of the injection pot 6 to the tip, and a portion (hereinafter referred to as an injection pot tip portion) 8B that becomes an injection passage at the tip thereof The injection nozzle 9 is mounted on the tip of the injection pot tip 8B, and the vicinity of the lower end of the metal 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.

  In the injection molding machine, first, the raw rubber is put into the extruder 3 as indicated by the arrow, and is plasticized while being sent to the left in FIG. 15 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 taper portion 8A, the injection pot tip portion 8B, and the injection nozzle 9, and further sprue 16, runner 17 and the gate 18 are press-fitted into the cavities 19 and 20 in the mold 10 and vulcanized.

  By the way, it is common sense that it is effective to shorten the vulcanization time of the plasticized rubber filled in the cavities 19 and 20 in order to improve the productivity of rubber vulcanized products and reduce the product cost. For this reason, it is required to set the temperature of the filled rubber into the cavities 19 and 20 as high as possible.

  In injection molding, the most effective method for instantaneously increasing the temperature of the filled rubber in the cavities 19 and 20 is to apply an injection pressure to the rubber measured in the injection pot 6 by the injection plunger 7. It is also known that it is ideal to utilize the self-heating of rubber due to injection shear heat generation (hereinafter referred to as injection heat generation) generated during injection filling.

  Further, in order to increase the injection heat generation, it is necessary to lower the injection plunger 7 at a high pressure and high speed, and as a result, it is necessary to increase the injection pressure during injection filling (hereinafter referred to as the actual injection pressure). It is important to set the rubber flow path from the pot 6 to the cavities 19 and 20 in the mold 10 to an appropriate thickness so that the actual injection pressure can be set high.

  However, in the conventional injection molding machine having the structure shown in FIG. 15, when the injection plunger 7 is simply lowered at high pressure and high speed and the actual injection pressure is set to a high condition, the rubber during injection filling is locally abnormally injected. The temperature of the filled rubber injected into the cavities 19 and 20 becomes extremely uneven due to heat generation, and scorch, that is, “an initial stage in which the vulcanization reaction starts and loses plasticity” is likely to occur. Even if the product enters the inside 20 and causes a product failure or does not become a scorch, the vulcanized state inside the product partially varies and becomes non-uniform, thereby reducing the quality performance of the product.

  For this reason, in the conventional injection molding machine having the structure of FIG. 15, in order to reduce local abnormal injection heat generation, the injection pressure and the injection speed must be set low so that the actual injection pressure becomes low. Therefore, this could not be effectively used as an ideal injection heat generation, and as a result, the vulcanization time was prolonged, the productivity could not be improved, and the product cost was increased.

  Regarding the cause of local heat generation at the time of injection in a conventional injection molding machine, the present inventor in Japanese Patent No. 3579196 is shown in FIG. 17 at the boundary portion between the original diameter of the nozzle A portion shown in FIG. In this way, the rubber stays and the flow velocity decreases, and the rubber that stays and decreases in velocity causes friction with the fast-flowing rubber in the center of the flow and causes local self-heating, which causes scorch rubber to be mixed in the molded product. As a countermeasure against this problem, it has been proposed to prevent the occurrence of scorch and mixing by arranging a commutator-like core in the nozzle.

In addition, as for the cause of local heat generation of the conventional injection molding machine, the present inventor in Japanese Patent No. 3579197, the flow velocity distribution of rubber at the tip of the nozzle A section and the heat generation distribution of rubber during the flow (FIGS. 18 and 19). As a result, the temperature difference of the rubber injected from the nozzle becomes larger as the flow velocity becomes higher as shown in FIG. It has been proposed to improve the flow velocity distribution and the temperature distribution as shown in FIG. 20 by installing a rod-like member at the tip portion substantially coaxially with the nozzle portion.

  However, measures to prevent scorch at the nozzle part and uniform injection heat generation temperature distribution by attaching a commutator-like core or rod-like member in the nozzle as described above lacks versatility in the following points. The inventor's recent research has revealed that this is not an ideal means of using the injection heat to make the best use of the ability of the injector.

  That is, a, when the commutator-like core or rod-like member is installed, the flow passage cross-sectional area inside the nozzle is abruptly reduced, and injection molding cannot be performed as planned when using a poorly flowable compound material. There is a need to carefully select usable compounding materials.

  b. During injection, the commutator-like core and rod-shaped member itself become hot due to friction with the rubber. Therefore, the commutator-like core and rod-shaped member in the nozzle are surrounded by the period between the completion of injection molding and the next injection molding. If the rubber is heated and vulcanized, the vulcanized rubber may clog the nozzle during the next injection, making it impossible for injection molding. As a result, the injection heat of the target rubber can be reduced by applying only a small amount of the injection capacity so that the rod-shaped member itself does not overheat, or by lowering the pressure during injection filling or lowering the injection speed. Must be kept low.

Therefore, the main problem to be solved by the present invention is that it is not necessary to select the fluidity of the rubber in the compounding material, the maximum injection pressure of the injection molding machine is utilized to the maximum, and the maximum injection heat generation is generated in the rubber. The purpose is to obtain an injection molding machine that can prevent the occurrence of scorch due to the retention of rubber, thereby improving the quality of the molded product, and realizing versatile injection molding that can maximize the productivity. .

An injection molding machine according to the present invention for solving the above-described problem has a cylindrical main body portion and a tapered portion formed in a tapered shape connected to the tip of the main body portion, and in a plasticized state. a shooting pot which the material is supplied, a cylindrical injection pot tip passage provided by connecting the tip of the tapered portion, an injection nozzle provided by connecting the tip of the injection-pot tip passage, the injection pot as an injection molding machine equipped with a plunger that is formed in a tapered shape is movably accommodated in the longitudinal direction of the injection pot, in which the taper angle of the tapered portion is less 45 degrees 10 degrees.

  The process of obtaining the present invention will be briefly explained. First, the present inventor has continued research afterwards, and as a result, the retention of rubber in the injection nozzle described above and the tendency of scorch generation at the starting point of the nozzle original diameter due to the low flow rate. In addition, it was found that the tendency of the temperature distribution of the injection heat generation of the rubber generated from the flow velocity distribution at the nozzle tip changes with the taper angle between the injection pot main body lower end and the injection pot tip passage as the most important factor (FIG. 3). To FIG. 7).

That is, the angle θ of the taper 8A between the lower end of the injection pot main body portion shown in FIG. 16 and the tip portion 8B is generally 60 ° or more (60 ° in FIG. 3), but this is as shown in FIGS. As shown in FIGS. 6 and 7, since the temperature difference of the heat-generating rubber is reduced as shown in FIGS. 6 and 7, the injection speed can be increased, for example, by changing the taper angle θ from the current 60 ° to 45 °. At high speed of 30 cc / sec, the temperature difference between injection heat generation rubber becomes less than half, and when θ is reduced to 35 ° or less, the temperature difference between injection heat generation rubber becomes approximately 1/10 or less of the temperature difference when θ is 60 °. It has been found.

  However, even if the taper angle is changed, as is apparent from the structure of the injection molding machine in FIG. 15, the nozzle 9 from the lower end of the injection pot main body portion depends on the arrangement state of the upper die plate 11 and the extruder (plasticizer) 3. Since the distance to the tip is determined, in actual design, there is a nozzle original diameter portion 8C as shown in FIGS. 8 to 10, and there is a boundary between the original diameter 8C and the throttle portion downstream thereof. The surprising fact that the retention of rubber and the rubber scorch in this part, which became a problem in the conventional injection molding machine having a taper angle θ of 60 ° or more, does not occur when θ is 45 ° or less, was discovered.

The taper angle θ becomes small because the injection heating rubber temperature distribution towards the sharp uniform, but the nozzle scorch occurring at the beginning of the boundary and aperture nozzles original size is what will not occur, which according to the inventor's study For example, generally, the rubber measured in the injection pot 6 becomes a high injection pressure by the plunger 7 pushing pressure (high pressure drop), and the rubber flows between the lower end 6b of the injection pot main body 6a and the tip of the nozzle 9 (see FIG. 5). The rubber pressure in the injection pot causes a pressure loss due to the frictional resistance in the road, and the pressure loss is caused by the injection shear heat generation to cause self-heating, but the taper angle θ as shown in FIGS. There the tapered portion the pressure loss hardly Namaze in 8A at 60 ° or more, the pressure loss in the nozzle portion 9 ends up concentrated, this results nozzle section exit shear heating In the middle, the influence of friction at the boundary between the nozzle original diameter and the drawing start point becomes extremely large and causes a nozzle scorch. Also, the rubber temperature distribution at the nozzle tip becomes very strong as shown in FIG. A large temperature difference of the injected rubber is generated by the injection speed as shown in FIG.

  However, when the taper angle θ is reduced to 45 ° or less, the pressure loss in the tapered portion 8A increases as shown in FIGS. 21 to 23 and 24, and the taper angle θ is about 10 °. As a result, the tapered portion 8A has a substantially uniform pressure loss in position, and as a result, the heat generated by the rubber injection can be evenly distributed in the tapered portion 8A without concentrating on the nozzle portion. The effect shown in FIG. 19 in the nozzle portion can be made extremely small without causing scorch, and as a result, a uniform injection heat generating rubber temperature can be obtained with the injection rubber temperature difference being 1/10 or less of the conventional one.

  However, when the taper angle θ is set to a small and acute angle, the temperature of the heat generated by the injection from the nozzle is the pressure actually applied to the rubber in the injection pot 6 during injection (actual injection pressure) as shown in FIG. However, according to the findings of the inventor, the injection heat generation coefficient (slope of the graph) varies depending on the taper angle θ. Here, the injection heat generation coefficient is the rubber injection heat generation temperature per actual injection pressure of 10 Mpa.

  The result is shown in FIG. 12. According to this, as the taper angle θ decreases, the injection heat generation coefficient decreases, and particularly when θ is 10 ° or less, there is a significant decrease. This is because not all the actual injection pressure applied to the rubber in the injection pot is converted into the shearing heat generation of the rubber, but the wall surface (machine side metal surface) itself due to the friction between the rubber and the flow path wall surface from the injection pot to the nozzle tip. Is heated due to friction with the rubber, and this causes a heat loss when viewed from the injection heat generation temperature obtained on the rubber side, and the injection heat generation coefficient is reduced. Thus, it has been found that heat loss occurs along the entire length of the flow path. (Conversely, when the taper angle θ is 60 ° or more, since the rubber injection pressure loss is concentrated on the nozzle portion, the heat loss also occurs only at the nozzle portion, and the heat generation coefficient increases.)

  From these, the injection pot taper angle θ depends on the flow characteristics and vulcanization speed (easiness of scorch) determined by the rubber composition used, and the uniformity of the injection heat generation temperature and the injection heat generation coefficient between 10 ° and 45 °. It can be said that it is ideal to select an optimum angle in terms of (heat generation efficiency of rubber). However, when the present inventor conducted further research after that, in order to effectively select the ideal angle, the injection pot tip passage connecting the injection pot and the injection nozzle is necessary due to the structure of the injection molding machine. It turned out that it was unbelievable.

  By the way, as described above, in order to increase injection heat generation, it is necessary to lower the injection plunger at high pressure and high speed in the injection pot, and as a result, it is necessary to increase the injection pressure during injection filling (hereinafter referred to as actual injection pressure). However, as a means for solving a further problem in the conventional injection molding machine having the structure of FIG. 15 in this case, the present inventor disclosed in Japanese Patent No. 3681847, an injection pot main body of part A in FIG. In order to prevent the occurrence of scorch due to stagnation of rubber at the boundary between the lower end of the section and the tapered section, the plunger tip and the inner wall of the injection pot facing the plunger at the position where the plunger moves forward in the injection pot are completed. It is proposed that the distance from the portion is 1.0 millimeter or less.

  However, if the distance between the tip of the plunger at the completion of injection and the inner wall portion of the injection pot facing it is 1.0 mm or less, it is necessary to push the distance between the lower end of the injection pot main body and the taper portion in part A of FIG. The effect that the retained rubber that has undergone scorch or vulcanization reaction due to the continuous heat generated by frictional heat with the flowing rubber at the boundary portion can be easily discharged into the molded product for each injection molding. However, it is not possible to eliminate the rubber retention itself in part A. For this reason, the scorch or the vulcanization reaction has progressed due to continuous heat generated by frictional heat. It cannot be fundamentally prevented.

  On the other hand, when the injection pot taper angle θ is set to 10 ° to 45 ° as in the present invention, the angle Y of the boundary A portion between the lower end of the injection pot main body and the taper portion as shown in FIGS. In the prior art, since the injection pot taper angle θ was 60 ° or more, the result was 150 ° or less. For this reason, the rubber stayed in the A portion even while the plunger was lowered, whereas in the present invention, As a result, the injection pot taper angle θ is set to 10 ° to 45 °, and as a result, the angle Y of the A portion approaches 157.5 ° to 175 °, which is closer to a straight line, and is injected onto the inner wall surface of the A portion. Inventor's recent research has revealed that the occurrence of scorch itself can be fundamentally suppressed without the rubber inside staying, but this is at an angle Y of part A, for example, a radius of curvature of 20 mm or more. Large This is new knowledge including examples of processing curved surfaces.

Further, the present inventor generates a scorch due to a further problem in the conventional injection molding machine shown in FIG. 15, that is, the retention of rubber in the injection pot tip passage connecting the injection pot and the injection nozzle of FIG. 15B in this specification . In order to prevent this, in Japanese Patent No. 3681847, the angle of the inner wall of the tip passage with respect to the axis of the injection pot is set to 0.2 ° to 45 °, thereby gradually reducing the cross-sectional area of the tip passage of the injection bot toward the injection nozzle. However, in rubber injection molding machines, all plasticized rubber (residual rubber that remains even after the plunger descends) remaining in the injection pot tip passage part when the molding machine stops after production is completed is scorched. In this case, it is common to remove the injection nozzle and clean the scorched rubber in the tip passage section by repeated injection. However, in the proposal of the patent, once clogged, it cannot be solved only by repeating the injection, and the injection molding machine must be disassembled and the clogged rubber must be taken out or the parts must be replaced. As far as this problem is concerned, the remaining scorch rubber can be easily cleaned by repeating the injection when the injection pot tip passage is cylindrical and the passage cross-sectional area is not gradually reduced as in the prior art.

  By the way, as described above ([0018]), even if the injection pot taper angle θ is changed, the arrangement of the upper die plate 11 and the extruder (plasticizer) 3 can be clearly understood from the structure of the injection molding machine in FIG. Since the distance from the lower end of the injection pot main body to the tip of the injection nozzle 9 is determined depending on the installed state, there is an injection pot tip passage connecting the injection pot and the injection nozzle in actual design. When the pot taper angle θ is set to 10 ° to 45 °, the passage length H can be set shorter than the conventional injection pot taper angle θ of 60 ° or more as shown in FIGS. As shown in FIG. 7, the temperature difference between the exothermic rubbers can be made extremely smaller and uniform than in the case of θ = 60 °, and as a result, the injection speed can be molded 2 to 3 times faster than the conventional molding conditions. The flow rate of rubber in the injection pot tip passage can also be increased at that rate, and the passage length H is shortened as described above even if the wall surface flow velocity of the passage decreases toward the injection nozzle due to frictional resistance with the wall surface. As a result, since the flow velocity can be increased, the wall surface flow velocity does not stop in the middle of the passage, so it has been found that there is no stagnation of rubber in the injection pot tip passage connecting the injection pot and the injection nozzle, and scorch generation can be prevented. .

As is clear from the above description, the present invention provides a molding material having a cylindrical main body portion and a tapered portion formed in a tapered shape connected to the tip of the main body portion, and in a plasticized state. a shooting pot to be supplied, a cylindrical injection pot tip passage provided by connecting the tip of the tapered portion, an injection nozzle provided by connecting the tip of the injection-pot tip passage, the said injection pot in the injection molding machine equipped with a plunger that is formed in a tapered shape is movably accommodated in the longitudinal direction of the injection pot by having a taper angle of the tapered portion is less 45 degrees 10 degrees, the disadvantages of the prior art By selecting the taper angle from the range of 10 ° to 45 °, which is optimal for the rubber fluidity and vulcanization speed in the rubber compounding material The maximum injection pressure of the injection molding machine is utilized to the maximum even if it is a rubber material, and the maximum injection heat generation with the optimal injection heat generation coefficient for rubber is generated, and the occurrence of scorch due to the retention of rubber is reliably prevented, As a result, an injection molding machine capable of improving the quality of the molded product and realizing versatile injection molding capable of maximizing productivity can be obtained.

Complementing the effects of the present invention, according to the inventors' past inventions, Japanese Patent Application Nos. 2001-237148 and 2004-555026 , the measured rubber temperature is increased by a rubber retention prevention structure that is replaced with a new material for each shot, and By using the present invention in combination with the above-described invention, which can achieve high temperature and uniform injection heat generation with an optimal injection pot structure without abnormal local heat generation in the injection nozzle, the above-described invention can be used. The amazing quality and productivity as shown in FIG. 14 and described below can be realized.

  That is, until now, rubber injection molding has been considered inferior in quality to compression molding that has continued from the past. Symbolically, as shown in FIG. 14, for example, in the case of O-ring packing, the roundness is not perfect due to the elastic effect in the compression direction even in the conventional compression molding, and in the conventional injection molding, the injection heat generation The temperature distribution is large and partial scorching occurs. As a result, the thermal shrinkage of the molded product varies partially, and the dimensional accuracy is extremely poor compared to compression molding. The product can be filled in a short time, has no rubber elastic influence and no scorch, and has uniform heat shrinkage, so that a product with extremely high dimensional accuracy can be obtained which faithfully reproduces the shape of the mold.

  In compression molding, normal temperature rubber is set in a high temperature mold and compression molded. As a result, during heat vulcanization, the rubber in the cavity is heated to the mold temperature while being heated by heat transfer and vulcanized. At this time, the rubber thermally expands in the cavity, and the thermal expansion amount protrudes from the mold parting surface (split surface). At this time, the rubber near the cavity wall in the cavity starts vulcanization faster than the inside, There is a problem that the protruding rubber flows out while breaking the vulcanized rubber on the outer periphery and the appearance and quality of the molded parting line are poor.

  Furthermore, in conventional injection molding, the injection heat generation is set low in order to prevent scorching of the nozzle part, so that the parting is performed by thermal expansion due to the heat transfer temperature rise from the mold after filling the cavity, similar to compression molding. The line protruded and was destroyed by rubber.

  According to the injection molding machine of the present invention, without lowering the actual injection pressure at a uniform injection heat generation rubber temperature without scorching, it is possible to set the rubber temperature filling the cavity to a temperature equivalent to the mold, and as a result, After the thermal expansion of the rubber in the cavity, the cavity is filled, and there is almost no thermal expansion in the cavity, so that the parting line is not broken and a good quality product can be obtained.

  Furthermore, when the present invention is combined with the injection transfer molding apparatus of Japanese Patent Application No. 2003-183634, which is the present invention of the present inventor, the injection molding of a multi-cavity mold with no restrictions on the number of products is performed. Ultra-short vulcanization can be achieved with single-piece quality stability. That is, not only can high-quality and high-productivity injection molding be realized, as is the case with multi-piece production, but also two functions of injection heat generation and filling, namely high-speed high-pressure injection and high-temperature rubber after injection heat generation. By molding by dividing into filling, the fluidity becomes extremely good, and as a result, it can be transferred and filled very gently, and composite molded products with rubber such as inserted fibers and thin metal plate members are also insert members Can be molded without deforming, and the range in which injection molding can be performed can be widened.

1 shows the injection molding machine of the present invention , Table 1 shows the productivity compared with the conventional machine, FIG. 2 shows the injection transfer molding machine of the present invention , and Table 2 shows the productivity of the conventional injection molding machine. Although the comparison was shown, all have a cylindrical injection pot tip passage 8B that leads from the injection pot tip to the injection nozzle, and the distance from the lower end of the injection pot main body to the tip of the injection nozzle is constant. In both Table 1 and Table 2, the optimum injection pot tip taper angle should be selected from 10 ° to 45 ° in accordance with the vulcanization speed (155 ° C. tc (10), tc (90)) in rubber compounding. Thus, a significant productivity improvement effect can be seen regardless of the rubber composition.

In more detail, the values (time) of tc (10) and tc (90) are blended with a faster vulcanization rate, in other words, a rubber that is easily blended with scorch. When tc (10) of the pot is 90 sec, the pot tip angle θ is a small acute angle (Tables 1 and 2) θ = 16 °. Although the injection rubber temperature is the smallest, the vulcanization speed of the rubber itself is fast, so with the conventional machine, the vulcanization time of 8 minutes can be greatly reduced to 3 minutes, and tc (10) is 180 seconds The bot tip angle θ is large (Tables 1 and 2). When θ = 45 °, the pot tip passage is the longest but the rubber itself is difficult to scorch. Can be high Similarly, rubber with a slow vulcanization speed can be significantly shortened to 3 minutes with a conventional machine having a vulcanization time of 8 minutes. The injection heat generation rate of the injection molding machine shown in Table 1 is the same even though the pot tip angle θ is the same. The reason why the injection transfer molding machine in Table 2 is higher than the case is that, in the case of injection transfer molding, the transfer pot 26 is made to generate heat by injection as compared with ordinary injection molding, so there is no need to pass the runner 17 on the rubber side. This is probably because the heat generation loss is small and the injection heat generation rate is high.

  The present invention will be described with reference to FIGS. 1 and 2. The injection molding machine and the injection transfer molding machine of the present invention are connected to a metal case 1 via an injection pot 6 and an injection pot tip passage 8B provided at the tip of the pot 6. The injection nozzle 9 and the injection port 5 for supplying the plasticized molding material from the side into the pot are formed, and the plunger 7 is slidably disposed in the injection pot 6. And an injection transfer molding machine, wherein the taper angle is 10 degrees or more and 45 degrees or less between the injection pot 6 main body lower end and the injection pot tip passage 8B.

As described above, in the rubber injection molding, it is ideal to set the cavity filling rubber temperature to a uniform and high temperature. For this purpose, as shown in FIG. 13, the rubber in the injection pot that is metered into the injection pot 6 is used. The present inventor has already proposed the structure of an injection molding machine for realizing this in Japanese Patent Application Nos. 2001-237148 and 2004-555026 . FIG. 1 shows a first embodiment in which the taper angle θ between the lower end of the injection pot main body and the injection pot tip passage 8B in the structure is 30 °.

  The description of the injection molding machine of FIG. 1 is made assuming that the reference numerals used in the description of FIG. 15 represent the same thing, the metal case 1, the injection pot 6, and the injection pot tip passage 8B provided at the tip of the pot. The injection nozzle 9 connected in this manner and the input port 5 for supplying the plasticized molding material into the pot 6 from the side are formed, and the plunger 7 is slidably disposed in the injection pot 6. The injection molding machine and the injection transfer molding machine are configured such that the taper angle is 10 degrees or more and 45 degrees or less between the lower end of the injection pot main body and the injection pot tip passage 8B.

  The injection transfer molding machine of the present invention is shown in FIG. 2, which is a taper angle between the lower end of the injection pot main body and the injection pot tip passage 8B in Japanese Patent Application No. 2003-183634 previously invented by the present inventor. A case where θ is 30 ° is shown as Example 2.

  The injection transfer molding machine according to the present invention in FIG. 2 will be described. The injection transfer molding machine according to the present invention connects an injection nozzle 9 at the tip of an injection pot 6 having a plunger 7 therein to a sprue 22 formed on a presser foot 21. In addition, an injection pot 26 having a volume change is formed between the upper mold 25 and the presser 21 in the product mold 24 with a mold clamping mechanism in which a large number of arbitrarily arranged cavities 23 are formed, and the transfer injection pot 26 and the cavity In the injection transfer molding machine in which the gates 27 are connected to each other, the angle θ of the injection pot tip tapered portion 8A into which the tip 7 ′ of the plunger 7 is fitted is set to a taper angle of 10 ° to 45 °.

In both the embodiment of the injection molding machine of the present invention shown in FIG. 1 and the embodiment of the injection transfer molding machine of the present invention shown in FIG. 2, the check valve shown in FIG. 15 is not provided. This is because it has a mechanism for preventing the back flow of rubber to the extruder 3 at the time of injection by connecting the screw tip and the inlet 5 by being advanced by an operating cylinder (not shown).
(At the time of measurement, the screw is moved backward to allow the plasticized rubber to pass through the screw tip and the insertion port 5 with a space therebetween.) In FIG. 2, reference numeral 28 indicates the upper die 25 that forms the transfer injection pot. Fig. 2 shows a hydraulic cylinder for enabling directional actuation.

  The fact that the present invention is extremely effective with respect to the second embodiment shown in FIG. 2 will now be further described. The present inventor has disclosed the structure of the injection machine of Japanese Patent Application No. 2001-237148 in Japanese Patent Application No. 2003-183634 previously invented. However, the taper angle θ between the injection pot main body lower end and the injection pot tip passage 8B in the present invention is 10 ° or more and 45 ° or less. By using this, an ideal injection transfer molding machine can be realized in the following points.

  The injection transfer molding machine first injects and heats the rubber into the mold transfer pot, fills the transfer pot, then applies the clamping force by the mold clamping operation, and transfers and fills the rubber in the mold transfer pot into the cavity. By doing so, we have proposed a manufacturing method that can achieve vulcanization in a short time and maintain high quality without causing adverse effects on the runner even in a multi-cavity mold with multiple cavities. The important point is how short it is possible to perform transfer molding from the transfer pot to the cavity by injection filling and mold clamping operation, and if these series of operations take time, the injection ~ If rubber begins to vulcanize during transfer molding, and vulcanization starts before filling into the cavity, molding filling itself becomes impossible, or even if it can be filled, the product is extremely unsatisfactory in terms of quality. Teshi Cormorant.

  However, when the taper angle θ is set to 45 ° or less as shown in FIG. 6, the temperature difference of the injected rubber can be very small even if the injection speed is high, so that the rubber is transferred without scorching during injection. Since the temperature of the rubber injected into the pot and injected into the transfer pot is uniform, the flowability of the rubber between the cavities is uniform, the filling balance between the cavities is good, and transfer molding without variation is possible.

  In the present invention, as shown in FIG. 12, as the taper angle θ decreases, the injection heat generation coefficient decreases (in practice, however, it further decreases because it passes through the sprue, runner, and gate from the nozzle as in the apparatus of FIG. 1). In the case of injection transfer molding, the injection heat loss in the mold side rubber flow path hardly occurs because the runner and gate do not pass through the sprue connected to the nozzle and are directly injected into the mold transfer pot. Even at the same injection filling pressure, the temperature of the heat generated in the transfer pot is higher than that in normal injection molding, which is advantageous in terms of shortening the vulcanization time of the molded product.

  The present invention has been devised for rubber injection molding and injection transfer molding, but can be applied to plastic injection molding and injection transfer molding with further research.

FIG. 1 is a schematic cross-sectional view of an embodiment of an injection molding machine according to the present invention.
FIG. 2 is a schematic cross-sectional view of an embodiment of an injection transfer molding machine according to the present invention.
FIG. 3 is a schematic cross-sectional view showing a combination of an injection pot and a plunger with a taper angle θ = 60 ° , posted for comparison of basic performance.
FIG. 4 is a schematic cross-sectional view showing an example of a combination of an injection pot and a plunger with a taper angle θ = 45 ° , posted for comparison of basic performance.
FIG. 5 is a schematic cross-sectional view showing another example of a combination of an injection pot and a plunger with a taper angle θ = 16 ° , posted for comparison of basic performance.
FIG. 6 is a diagram showing the influence of the taper angle of the injection pot on the injection speed and the injection heat generation temperature difference in the injection molding machine.
FIG. 7 is a diagram showing a relationship between an injection pot taper angle and an injection heat generation rubber temperature difference at an injection speed of 30 cc / sec in an injection molding machine.
FIG. 8 is a schematic cross-sectional view showing a combination of an injection pot having a nozzle base diameter and a plunger of a conventional injection molding machine, which is posted for comparison of basic performance.
FIG. 9 is a schematic cross-sectional view showing an example of a combination of an injection pot having a nozzle base diameter and a plunger of the injection molding machine of the present invention, which is posted for comparison of basic performance.
FIG. 10 is a schematic cross-sectional view showing another example of a combination of an injection pot having a nozzle base diameter and a plunger of the injection molding machine of the present invention, posted for comparison of basic performance.
FIG. 11 is a diagram showing the relationship between injection pressure and injection heat generation.
FIG. 12 is a diagram showing a relationship between an injection pot taper angle and an injection heat generation coefficient.
FIG. 13 is a diagram showing the establishment requirements for the cavity-filled rubber temperature according to the present invention and the effects of the formation factors.
FIG. 14 is a diagram comparing quality effects of the injection molding of the present invention with other molding methods.
FIG. 15 is a schematic sectional view of an embodiment of a conventional injection molding machine.
FIG. 16 is a schematic sectional view of another embodiment of a conventional injection molding machine.
17 is a detailed view of part A in FIG. 18, showing a state in which the nozzle scorch is attached.
18 is a detailed view of part A of FIG. 18, showing a state where the nozzle scorch is not attached.
FIG. 19 is a diagram schematically showing a flow velocity distribution and a temperature distribution at the tip of part A in FIG. 18;
FIG. 20 is a diagram showing the relationship between injection speed and injection rubber temperature difference in nozzle injection of an injection molding machine.
FIG. 21 is a schematic cross-sectional view showing a combination of an injection pot for an injection molding machine having an injection pot taper angle of 60 ° having an injection pot tip passage and a plunger, posted for comparison of basic performance.
FIG. 22 is a schematic cross-sectional view showing a combination of an injection pot for an injection molding machine with an injection pot taper angle of 45 ° having an injection pot tip passage and a plunger, posted for comparison of basic performance.
FIG. 23 is a schematic cross-sectional view showing a combination of an injection pot for an injection molding machine with an injection pot taper angle of 10 ° having an injection pot tip passage and a plunger posted for comparison of basic performance.
FIG. 24 is a comparison diagram of the taper angle and the injection pressure at each position in the combination of three types of injection pots and plungers for injection molding machines with different injection pot taper angles shown in FIGS.
FIG. 25 is a schematic cross-sectional view for explaining a rubber retention state at a boundary portion A between an injection pot main body lower end and a taper portion in a combination of an injection pot for an injection molding machine having an injection pot taper angle of 60 ° and a plunger. It is.
FIG. 26 is a schematic cross-sectional view for explaining a rubber retention state at a boundary portion A between an injection pot main body lower end and a taper portion in a combination of an injection pot for an injection molding machine having an injection pot taper angle of 45 ° and a plunger. It is.
FIG. 27 is a schematic cross-sectional view for explaining a rubber retention state at a boundary portion A between an injection pot main body lower end and a taper portion in a combination of an injection pot for an injection molding machine having an injection pot taper angle of 10 ° and a plunger. It is.
FIG. 28 is a schematic cross-sectional view for explaining the change in the wall surface flow velocity of the injection pot tip passage in the combination of an injection pot for an injection molding machine having an injection pot taper angle of 60 ° and a plunger.
FIG. 29 is a schematic cross-sectional view for explaining a change in wall surface flow velocity of the injection pot tip passage in a combination of an injection pot for an injection molding machine having an injection pot taper angle of 45 ° and a plunger.
FIG. 30 is a schematic cross-sectional view for explaining a change in the wall surface flow velocity of the injection pot tip passage in a combination of an injection pot for an injection molding machine having an injection pot taper angle of 10 ° and a plunger.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Metal case 2 Screw 3 Extruder 4 Check valve 5 Passage 5a Inlet 6 Injection pot
6a Injection bot body
6b Injection bot main body lower end 7 Plunger 7 'Plunger tip portion 8A Taper portion 8B Injection pot tip passage 8C Original diameter portion 9 Injection nozzle 10 Mold 11 Upper die plate 12 Lower die plate 13 Tie bar 14 Heat insulation board 15 Heating board 16, 22 Sprue 17 Runner 18, 27 Gate 19, 20, 23 Cavity 21 Presser 24 Product mold 25 with mold clamping mechanism Upper mold 26 Injection pot.

Claims (1)

A cylindrical main body portion and a tapered portion connected to the tip of the main body portion and formed in a tapered shape; an injection pot to which a molding material in a plasticized state is supplied; and a tip of the taper portion connecting a cylindrical injection pot tip passage provided, the injection and the injection nozzle provided by connecting the tip of the pot tip passage out, tapered shape is movably accommodated in the longitudinal direction of the shooting pot to the injection pot injection molding machine, wherein in an injection molding machine equipped with a formed plunger, that the taper angle of the tapered portion is less 45 degrees 10 degrees.

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