Injection molding machine for rubber molding and method for injection molding of rubber molded products

Abstract

Injection molding machines for rubbers use hydraulic cylinders at least for the injection mechanism, which poses problems in terms of molding stability and reduction of power consumption. [Solution] The rubber molding injection molding machine 11 comprises an injection device 13 having an injection servo motor 19 that moves the screw 18 axially, a metering servo motor 20 that rotates the screw 18, a front block 22 to which a heating cylinder 16 is attached directly or via a material supply block 21, a pusher block 26 that is provided behind the front block 22, holds the screw 18 rotatably, and has the metering servo motor 20 attached, and the heating cylinder 16 whose temperature is controlled by a heat medium, and a mold clamping device 14 having a mold clamping servo motor 71 that drives a toggle link mechanism 67.

Description

[Technical Field]

[0001] The present invention relates to an injection molding machine for molding a rubber molded article, and a method for injection molding a rubber molded article. [Background technology]

[0002] A known example of a rubber injection molding machine for molding rubber molded products is described in Patent Document 1. In the rubber injection molding device described in Patent Document 1, the base of the screw shaft is connected to a fluid-pressure-operated piston, and the reciprocating motion of the screw shaft itself injects the material into a pre-closed mold. The rotation of the prime mover is appropriately slowed down by gears to rotate the screw shaft 1. That is, Patent Document 1 only describes the use of a hydraulic cylinder or other hydraulic cylinder as the injection mechanism of the injection device. The metering mechanism of the injection device is also described only as a prime mover, with no mention of whether it uses an electric motor or a hydraulic motor. Furthermore, the specific structure and actuator of the mold clamping device of the injection molding device are not described. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 42-1194 Summary of the Invention [Problem to be solved by the invention]

[0004] The conventional injection molding device for rubbers disclosed in Patent Document 1 uses a hydraulic cylinder at least for the injection mechanism, which causes problems in terms of molding stability and reduction of power consumption.

[0005] The present disclosure aims to solve the above problems and provide an injection molding machine for molding a rubber molded product, which can achieve molding stability or reduce power consumption, and a method for injection molding a rubber molded product. Other objects and novel features will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0006] In one embodiment, an injection molding machine for rubber molding that molds rubber molded products comprises an injection device that includes an injection servomotor that moves the screw axially, a metering servomotor that rotates the screw, a front block to which a heating cylinder is attached directly or via a material supply block, a pusher block that is provided behind the front block, in which the screw is rotatably held and to which the metering servomotor is attached, and the heating cylinder whose temperature is controlled by a heat medium, and a clamping device that includes a clamping servomotor that drives a toggle link mechanism. [Effects of the Invention]

[0007] The rubber injection molding machine for molding the rubber molded products of the present disclosure comprises an injection unit including an injection servomotor that moves the screw axially, a metering servomotor that rotates the screw, a front block to which a heating cylinder is attached directly or via a material supply block, a pusher block that is provided behind the front block and in which the screw is rotatably held and to which the metering servomotor is attached, and the heating cylinder whose temperature is controlled by a heat medium, and a clamping unit that includes a clamping servomotor that drives a toggle link mechanism, thereby achieving molding stability and reducing power consumption. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a side view of a rubber injection molding machine according to a first embodiment. FIG. [Figure 2] 1 is a cross-sectional view of a heating cylinder portion of the injection molding machine for rubber molding of the first embodiment. FIG. [Figure 3] 1 is a table showing the rated output of a metering servo motor and the rated output of an injection servo motor. [Figure 4] FIG. 2 is a side view of a rubber injection molding machine according to a second embodiment. [Figure 5] 1 is a table showing screw diameters and rated outputs of metering servo motors. DETAILED DESCRIPTION OF THE INVENTION

[0009] Specific embodiments will be described in detail below with reference to the drawings. However, the present invention is not limited to the following embodiments. In addition, the following description and drawings have been simplified as appropriate for clarity of explanation. In addition, hatching has been omitted in some parts to avoid cluttering the drawings.

[0010] <Injection molding machine> A rubber injection molding machine 11 for molding a molded rubber product according to a first embodiment of the present invention will be described with reference to Figures 1 and 2. Figure 1 is a side view of the rubber injection molding machine. The screw-in line type rubber injection molding machine 11 is equipped with an injection unit 13 and a mold clamping unit 14 mounted on a base 12. A mold 15 is also attached to the rubber injection molding machine 11, and a heat medium supply unit 17 for controlling the temperature of a heating cylinder 16 with a heat medium, a material supply unit (not shown), a rubber molded product remover, and other devices may be provided as needed.

[0011] <Injection device> The injection device 13 provided on one side of the base 12 includes an injection servomotor 19 that moves the screw 18 in the heating cylinder 16 in the axial direction (forward and backward), a metering servomotor 20 that rotates the screw 18, a front block 22 to which the heating cylinder 16 is attached directly or via a material supply block 21, a pusher block 26 that is provided behind the front block 22 and to which the screw 18 is rotatably held and to which the metering servomotor 20 is attached, and the heating cylinder 16 whose temperature is controlled by a heat medium. Note that the rear of the injection device 13 refers to the right side, which is one side in Figure 1, and the front refers to the side of the nozzle on the left side, which is the other side in Figure 1.

[0012] The injection unit 13 has a slide base 24 on a base 12 that can move forward and backward, and a swivel base 25, which is an injection unit mounting portion, that is swivelably mounted on the slide base 24. A front block 22 is fixedly mounted on the swivel base 25. Furthermore, a rear block 23 is fixedly mounted on the swivel base 25 behind the front block 22.

[0013] A pusher block 26 is provided behind the front block 22 and between the front block 22 and the rear block 23. Two or four guide rods 27 are provided horizontally connecting the front block 22 and the rear block 23. Guide holes are provided in the pusher block 26 at positions corresponding to the guide rods 27, and the pusher block 26 is guided by the guide rods 27 so that it can move back and forth between the front block 22 and the rear block 23 in the same direction as the axial direction of the screw 18. The pusher block 26 may be moved while being guided in part or in whole by a guide member such as a linear guide provided on a base such as the swivel base 25.

[0014] The heating cylinder 16 is fixed facing forward at the axial center of the injection unit 13 and approximately the center of the front block 22 in the operating side and anti-operating side directions. A material supply block 21 is also provided in front of the front block 22. In the embodiment shown in FIG. 1 , the material supply block 21 has a cubic shape with each side ratio within 2:1, and the heating cylinder 16 is inserted approximately at the center. However, the heating cylinder 16 may be attached only to the material supply block 21. Furthermore, the material supply block 21 does not have to be a perfect cube, and may have no corners or be approximately cylindrical. The material supply block 21 is provided with a material supply hole 28 for supplying molding material for rubber molding. In FIG. 1 , the material supply hole 28 is provided eccentrically from the center of the top of the material supply block 21. However, the material supply hole 28 may be provided at the center of the top of the material supply block 21, or on a side or bottom portion. By providing the material supply block 21 independently from the front block 22 in this way, it becomes easier to freely set the orientation (angle with respect to the screw axis) of the material supply hole 28, which is important for the rubber material to bite into the screw 18 inside the heating cylinder 16. It also suppresses the transfer of heat from the heating cylinder 16 to the front block 22. A rubber material supply device (not shown) is provided adjacent to the material supply hole 28.

[0015] The material supply block 21 and / or the rear portion of the heating cylinder 16 are independently temperature-controlled. Specifically, a cooling medium flow path (not shown) is formed inside the material supply block 21 and inside the rear portion of the heating cylinder 16. The cooling medium flow path is provided with a cooling medium supply hose 52 and a discharge hose 53. The cooling medium supplied to the cooling medium flow path is temperature-controlled water or tap water. The cooling medium may be supplied from the heating medium supply device 17 or from a separate supply device. The cooling medium flow path may also be provided only in the material supply block 21. By cooling the material supply block 21 in this manner, the effect of the heat of the heating cylinder 16 on the supply of rubber material from the material supply hole 28 can be greatly reduced.

[0016] The rubber material supplied by the rubber material supply device is often in the form of a long, thin tape (also called a ribbon). Therefore, the rubber material supply device is equipped with a mechanism for feeding out the tape-like rubber material. Meanwhile, a rubber material supply mechanism may also be provided on the side of the material supply hole 28 of the material supply block 21 of the injection device 13, such as one or more pairs of drive rollers that sandwich and supply the rubber material, in order to stably feed the tape-like rubber material into the heating cylinder 16.

[0017] As shown in FIG. 2 , the screw 18 is rotatably and axially movable (forward and backward movement) in the inner bore 161 of the heating cylinder 16. The screw 18 has a relatively low compression ratio. The compression ratio of the screw 18 is preferably in the range of 1.0 to 2.0, more preferably in the range of 1.0 to 1.5, and even more preferably in the range of 1.0 to 1.3. The pitch of the flights 18a of the screw 18 is preferably constant in the feed zone, compression zone, and metering zone. The L / D, obtained by dividing the length L of the screw 18 by the diameter D, is preferably 12 to 20, and even more preferably 13 to 16.

[0018] In addition, a check valve 29 that prevents backflow of molding material during injection is provided on the tip side of the screw 18. There are no restrictions on the type of check valve 29, but in the embodiment shown in Figure 1, a ball check type check valve 29 is attached, in which a ball 31 is inserted in a flow path 30 inside the screw 18 so that it can move in the axial direction of the screw 18. In addition, a screw head 32 is provided on the tip side of the check valve 29.

[0019] The temperature of the heating cylinder 16 is controlled by a heat medium. The heating cylinder 16 is divided into a plurality of zones, and a heat medium flow path 34 is provided in a jacket 33 wrapped around the outer periphery of the heating cylinder 16. In the first embodiment, the heating cylinder is divided into three zones 16a, 16b, and 16c, and a heat medium supply hose 35 and a heat medium discharge hose 36 are provided for each of the zones 16a, 16b, and 16c. The heat medium supply hose 35 and the heat medium discharge hose 36 are each connected to a heat medium supply device 17. In the first embodiment, the heat medium supplied from the heat medium supply device 17 is temperature-controlled water, but heat medium oil may also be used.

[0020] A nozzle 37 is provided at the tip of the heating cylinder 16. A flow path within the nozzle 37 is connected to the inner hole of the heating cylinder 16, and a nozzle hole is provided at the tip of the nozzle 37 through which the rubber material is injected into the mold 15. In the first embodiment, the temperature of the nozzle 37 is not controlled by a heat medium, but the nozzle 37 may also be divided into one or more zones and temperature controlled by a heat medium. Temperature detection means (not shown) are attached to the heating cylinder 16 and the nozzle 37 in correspondence with the temperature-controlled zones.

[0021] A bracket provided on the front block 22 is attached to an injection unit forward / backward movement operating servomotor 38 for moving the entire injection unit 13 forward and backward. Ball screw nuts 39 are fixed to two locations on both sides of the front block 22, sandwiching the heating cylinder 16. A driven pulley 40 is fixed to the ball screw nut 39, and a belt 42, such as a toothed timing belt, is wound around a drive pulley 41 provided on the drive shaft of the injection unit forward / backward movement operating servomotor 38 and the two driven pulleys 40, thereby transmitting driving force. The other end of a ball screw 54 is fixed to a member fixed around the injection unit introduction hole 61b, also known as the "mortar" of the fixed platen 61. One end of the ball screw 54 is inserted into the ball screw nut 39 through an insertion hole formed in the front block 22. The injection unit forward / backward mechanism (nozzle touch mechanism) may be one that uses spring force or a hydraulic cylinder in addition to the electric mechanism, and the number of injection unit forward / backward mechanisms may be one.

[0022] A heating cylinder 16 is fixed to the front block 22, and the rear end surface of the heating cylinder 16 is located inside or at the back of the front block 22, or is located at a position slightly protruding from the rear surface. The rear portion of a screw 18 protrudes from an inner hole 161 in the rear end surface of the heating cylinder 16. A screw connection member 43, such as a screw connector, is coaxially fixed to the screw 18 by spline connection or the like. The screw connection member 43 is rotatably held by bearings (not shown) located at the axial center of the injection unit 13, in the central portions of the pusher block 26 on the operating side and counter-operating side. The screw 18 is indirectly rotatably held by the pusher block 26 via the screw connection member 43. In the present invention, the term "screw" is defined to include not only the screw 18 with flights 18a provided in the heating cylinder 16 but also the screw connection member 43. Therefore, it goes without saying that the "metering servo motor that rotates the screw" in this invention does not only act directly on the screw 18 in the narrow sense inside the heating cylinder, but also includes those that indirectly exert a rotating effect on the screw 18, including the screw connecting member 43.

[0023] A metering servomotor 20 is fixedly attached to a bracket provided on the top of the pusher block 26 (intermediate block), with its drive shaft, to which a drive pulley 44 is fixed, facing forward. In the first embodiment, a metering servomotor 20 with a high rated output (kW) is used to plasticize high-viscosity rubber materials. However, the rated output (kW) of the metering servomotor 20 naturally varies depending on the size of the rubber injection molding machine (such as clamping force and maximum injection capacity). In the first embodiment, the rated output (kW) of the metering servomotor 20 is 45 kW, and the rated output of the injection servomotor 19 is 60 kW. The ratio obtained by dividing the rated output (kW) of the metering servomotor 20 by the rated output of the injection servomotor 19 is 75%. However, in the injection unit 13, multiple servomotors may be used for both the metering servomotor 20 and the injection servomotor 19. Therefore, the total rated output is defined as the sum of the rated outputs (kW) of multiple servo motors, including when multiple servo motors are installed. Also, it goes without saying that when there is one servo motor, the rated output (kW) of one motor is the total rated output (kW).

[0024] 3 shows an example of the use of metering servo motors 20 and injection servo motors 19 in the injection device 13 of a rubber injection molding machine 11. As such, it is preferable that the total rated output (kW) of the metering servo motors 20 is 60% to 100% of the total rated output (kW) of the injection servo motors. In a typical electric injection molding machine for resin molding, the total rated output (kW) of the metering servo motors is about 40% to 60% of the total rated output (kW) of the injection servo motors, and the rubber injection molding machine 11 uses metering servo motors 20 with a particularly high rated output (kW). Furthermore, the injection servo motor 19 used is one with a higher rated output (kW) than that of a typical electric injection molding machine for resin molding with the same mold clamping force.

[0025] In the first embodiment, one metering servomotor 20 is mounted on the top of the pusher block 26. However, to easily install two metering servomotors depending on the type of rubber material and customer requests, multiple bracket mounting portions for mounting the metering servomotor 20 may be provided on both the operating side and the non-operating side of the pusher block 26. In this case, if only one metering servomotor 20 is to be installed, the bracket and metering servomotor 20 are mounted on one of the bracket mounting portions, and no bracket is mounted on the other bracket mounting portion. Alternatively, if the bracket for mounting the metering servomotor 20 on the pusher block 26 is integrally manufactured by casting, two brackets may be provided from the beginning. Furthermore, two driven pulleys 45, 45 are fixed to the screw connecting member 43, and are mounted axially one behind the other, corresponding to the number of brackets and bracket mounting portions. Alternatively, a driven pulley 45 having a width sufficient to accommodate two belts 46, 46 is mounted. Furthermore, one belt 46 may be stretched around one driven pulley 45 and each of the drive pulleys 44 of the two metering servomotors 20 .

[0026] Furthermore, when considering the shaft torque of the screw 18, it is necessary to consider the reduction ratio between the drive shaft of the metering servo motor 20 and the screw 18 (including the screw connecting member 43). The metering servo motor 20 of the first embodiment is not equipped with a reducer, and a toothed drive pulley 44, which serves as a driving member, is fixed to the drive shaft. Meanwhile, a toothed driven pulley 45, which serves as a driven member, is fixed to the screw connecting member 43. A toothed belt 46, such as a timing belt, is wound around both the drive pulley 44 and the driven pulley 45. In the first embodiment, the pulley ratio (ratio of diameters) between the drive pulley 44 and the driven pulley 45 is 1:4.0 to 1:8.0. The diameter ratio is more preferably 1:4.5 to 1:6. In a typical electric injection molding machine for resin molding, the pulley ratio between the drive shaft and the driven shaft of the metering servo motor is approximately 1:6 to 1:3.

[0027] Furthermore, even when the driving member fixed to the drive shaft of the metering servo motor 20 is a driving gear and the driven member fixed to the driven shaft on the screw side is a driven gear, and the gears are engaged without a belt, it is desirable that the ratio of the diameter of the driving gear to the diameter of the driven gear is also 1:4.0 to 1:8.0. Also, when a reducer is used instead of a belt or gear to transmit the driving force from the metering servo motor to the screw shaft, a reduction ratio similar to the pulley ratio, etc., is used. As a result of the above, the maximum rotational speed of the screw 18 of the injection unit 13 is 100 min -1 or 250 min -1 It is preferable that the temperature is 120 min. -1 or 200 min -1 It is more desirable that:

[0028] In the present disclosure, as shown in FIG. 5 , the value obtained by dividing the rated output (kW) of the metering servo motor 20 (or the total rated output (kW) obtained by adding the rated outputs of the respective servo motors when two metering motors are used) by the diameter (mm) of the screw 18 provided in the heating cylinder 16 is preferably 0.60 (kW / mm) to 1.00 (kW / mm). In the first embodiment, the rated output of the metering servo motor 20 is 45 kW, and the diameter (mm) of the screw 18 is 70 mm. Therefore, the value obtained by dividing the total rated output (kW) of the metering servo motors by the screw diameter (mm) is 45 / 70 = 0.643 (rounded up or down). Note that this value is preferably 0.60 (kW / mm) to 1.00 (kW / mm), and more preferably 0.60 (kW / mm) to 0.80 (kW / mm).

[0029] A ball screw nut 48, through which a ball screw 47 for injection (described later) is inserted, is fixed to the rear center of the pusher block 26. The pusher block 26 and other components are also provided with a load cell for detecting the axial force of the screw 18, the ball screw nut 48, and a greasing mechanism, as appropriate.

[0030] An injection servo motor 19 is fixedly attached to a bracket provided on the upper part of the rear block 23, with its drive shaft, to which a toothed drive pulley 49 is fixed, facing rearward. In this embodiment, an injection servo motor 19 with a high rated output (kW) is used for injecting and maintaining pressure of high-viscosity rubber material. A ball screw 47 is rotatably held by bearings (not shown) in the center of the operating side and anti-operating side of the rear block 23. A toothed driven pulley 50 is fixed to the non-threaded portion on the rear end of the ball screw 47. A toothed belt 51, such as a timing belt, is stretched between the drive pulley 49 and the driven pulley 50.

[0031] The number of injection servo motors 19 may be two. In this case, separate belts 51 are stretched between the drive pulleys 49, 49 of the two injection servo motors 19, 19 and two driven pulleys 50 provided on a single ball screw 47 with the drive pulleys 49, 49 offset in the axial direction, or one belt 51 is stretched between the drive pulleys 49, 49 of the two injection servo motors 19 and one driven pulley 50 provided on a single ball screw 47 by using an idler pulley or the like.

[0032] The front side of the ball screw 47 is a threaded portion, which is inserted into the ball screw nut 48 provided on the pusher block 26 as described above. Therefore, when the ball screw 47 rotates, the pusher block 26 moves forward and backward in the same direction as the axial direction of the screw 18.

[0033] <Mold clamping device> The mold clamping unit 14 provided on the other side of the base 12 has a fixed platen 61 fixed to the base and a mold clamping housing 62, with tie bars 63 disposed between them, and a movable platen 64 guided by the tie bars 63 so as to be movable in the mold opening and closing direction. A fixed mold 65 of the mold 15 is provided on a mold mounting surface 61a of the fixed platen 61 so as to be fixable by a mold mounting mechanism (not shown). An insulating plate may be provided on the mold mounting surface of the fixed platen 61. An injection unit introduction hole 61b, also called a "mortar," into which the heating cylinder 16 and the nozzle 37 are inserted is formed on the side of the fixed platen 61 facing the injection unit 13.

[0034] A movable mold 66 of the mold 15 is attached to the mold attachment surface 64a of the movable platen 64 by a mold attachment mechanism (not shown). A heat insulating plate may be provided on the mold attachment surface of the movable platen 64. A pivot support for attaching a link of a toggle link mechanism 67 is provided on the rear side of the movable platen 64. An ejector mechanism 68 is attached to the rear side of the movable platen 64. The ejector mechanism 68 drives protruding members such as an ejector rod and an ejector pin forward and backward using an ejector servo motor 69 and a ball screw mechanism 70 fixed to the movable platen 64. The ball screw mechanism 70 of the ejector mechanism 68 may be of various types, such as one in which a ball screw rotates or one in which a ball screw nut rotates. The movable platen 64 is not limited to being guided only by the tie bars 63, but may also be guided by a guide member on the base 12.

[0035] A mold clamping servo motor 71 is fixed to a bracket on the top or side of the mold clamping housing 62, which is connected to the movable platen 64 via a toggle link mechanism 67, with its drive shaft facing rearward (the other side). A drive pulley 72 is fixed to the drive shaft. Meanwhile, a ball screw 73 is rotatably held by a bearing (not shown) in the center of the mold clamping housing 62 in the directions of the operating side and anti-operating side. A driven pulley 74 is fixed to the non-threaded portion on the rear end side of the ball screw 73. A belt 75 is stretched between the drive pulley 72 and the driven pulley 74.

[0036] A movable platen side portion (one side) of the ball screw 73 is inserted into a ball screw nut 76, and the ball screw nut 76 is fixed to a crosshead 77 that constitutes a part of the toggle link mechanism 67. A journal portion for attaching a link of the toggle link mechanism 67 is provided on the movable platen side portion of the clamping housing 62. The crosshead 77 is also connected to a link 78 connected to the movable platen 64 and a link 79 connected to the clamping housing 62 via another link 80. There are various known types of toggle link mechanism 67 of the clamping unit 14, and any type may be used.

[0037] Furthermore, a mold thickness adjustment motor 81 is fixed to the side surface or the like of the mold clamping housing 62. The driving force of the mold thickness adjustment motor 81 is transmitted to a driven gear fixed to a tie bar nut 82 via a large gear, a chain or the like. A thread is formed on the other end of the tie bar 63, and the tie bar nut 82 is screwed onto the thread. When the tie bar nut 82 is rotated, the position of the mold clamping housing 62 in the mold opening / closing direction (the distance between the fixed platen 61 and the mold clamping housing 62) is adjusted.

[0038] <Control device> The metering servo motor 20 and the injection servo motor 19 are each connected to a control device (not shown) via a servo amplifier (not shown). The control device is connected to the metering servo motor 20 and the injection servo motor 19 as well as the various sensors, actuators, and setting display devices of the rubber molding injection molding machine 11, and is responsible for controlling the rubber molding injection molding machine 11. The control device is also connected to the heat medium supply device 17, a material supply device (not shown), the illustrated internal unloader, a computer that controls the entire factory, and the like.

[0039] <Mold> The rubber molding mold 15 is prepared according to the type of rubber molded product, and is replaced during molding. The rubber molding mold is temperature-controllable to vulcanize the rubber material within the cavity to form the molded product. In the first embodiment, an electric heater such as a cartridge heater (not shown) is installed within the mold 15 to heat it. The mold 15 may also be heated using thermal oil. In the first embodiment, an example is described in which a fixed mold 65 and a movable mold 66 are provided and a cavity C is formed between the two molds 65, 66. However, either the fixed mold 65 or the movable mold 66 may be provided with an independently movable intermediate mold. A deburring device may also be attached to the mold 15. A vacuum suction device that draws a vacuum inside the cavity C may also be attached to the mold 15.

[0040] <Injection molding method for rubber molded products> The rubber of the rubber molded product of the present invention is not limited to a specific type, and may be natural rubber, nitrile rubber, acrylic rubber, ethylene propylene rubber, silicone rubber, fluororubber, etc. The concept of rubber in the present invention also includes various elastomers that require vulcanization, and may be polymers of the above materials.

[0041] The temperature of the heating cylinder 16 of the rubber injection molding machine 11 is controlled by a heat medium supplied from a heat medium supply device 17. The temperature of the heating cylinder 16 depends on the type of rubber material, but is preferably controlled to 50°C to 120°C, more preferably 90°C to 110°C, at least in a zone 16a at the front of the heating cylinder, or in the entire heating cylinder 16. The temperature of the mold 15 attached to the mold clamping device 14 is controlled by an electric heater to 150°C to 200°C, more preferably 160°C to 180°C.

[0042] <Measuring process> The rubber material in tape form is supplied into the heating cylinder 16 from the material supply hole 28 as the screw rotates during metering. At this time, the supply of the rubber material may be assisted by a drive roller or the like. Because the rubber material has a high viscosity when plasticizing, the screw 18 is rotated at a relatively slow speed using the metering servo motor 20 with a large rated output (kW) as described above. Specifically, the rotation speed of the screw 18 during metering is 40 min -1 or 150 min -1 , more preferably 50 min -1 or 150 min -1 It is desirable to set the screw back pressure to approximately 1 MPa. The screw back pressure during the metering process is not limited to this, but is preferably about 1 MPa to 10 MPa. As a result of the above, the metering time required will be relatively long, depending on the volume of the rubber molded product, but this is not a problem as long as it is shorter than the long vulcanization time described below. At the end of the metering process, the fact that the screw 18 has reached a predetermined retreat position is accurately detected by a rotary encoder or the like of the injection servo motor 19, and the rotation of the metering servo motor 20 is accurately stopped, so that the injection volume is accurate and stable.

[0043] <Injection process / holding process> Around the time of the completion of the metering process, the molded rubber product molded in the mold clamping unit 14 is ejected by the ejector mechanism 68 and removed by the remover, and the mold 15 is closed and clamped by the mold clamping unit 14 using the toggle link mechanism 67. After mold clamping is complete, the injection process begins. In the injection process, the screw 18 advances at a relatively slow injection speed of 30 mm / sec to 120 mm / sec to inject and fill the material. After the injection process is completed, the process switches to the dwell process, primarily based on the position of the screw 18. The position of the screw 18 is accurately detected by a rotary encoder or other device on the injection servo motor 19, enabling accurate dwell switching. The dwell time in rubber injection molding varies depending on the size and thickness of the rubber molded product, but is preferably relatively long, ranging from 5 to 60 seconds. Therefore, as mentioned above, the injection servo motor 19 requires a high rated output (kW).

[0044] <Vulcanization process> The rubber molded product injected into cavity C of mold 15 is vulcanized at the above temperature. The vulcanization time, including the pressure dwell time from the start of injection to mold opening, varies depending on the size and thickness of the rubber molded product, but is preferably 60 to 240 seconds. Therefore, using a mold clamping device 14 equipped with a mold clamping servo motor 71 that drives a toggle link mechanism 67, which can significantly reduce power consumption after mold clamping is complete, is optimal for reducing the power consumption of the rubber injection molding machine 11. Furthermore, during injection molding of rubber molded products, the mold temperature is high and the vulcanization time is long, as described above, so flash is likely to occur on the parting surface around cavity C of mold 15. In the case of hydraulic rubber injection molding machines, variations in the injection filling amount, injection speed, and pressure during dwelling can result in large flash, insufficient filling, and unstable molding. However, in the rubber injection molding machine 11 of the present invention equipped with the injection servo motor 19 and the metering servo motor 20, the injection filling amount can be stabilized with high precision by using the metering servo motor 20, and the injection speed and pressure during holding pressure can be stabilized with high precision by using the injection servo motor 19, making it possible to mold injection molded products with even greater suppression of flash and sink marks due to insufficient filling.

[0045] <Injection molding machine of second embodiment> Next, a rubber molding injection molding machine 101 according to a second embodiment will be described, as shown in Fig. 4. In the rubber molding injection molding machine 101 according to the second embodiment, the mold clamping device 14 is substantially the same as that of the first embodiment, so the description of the mold clamping device 14 will be omitted by citing the description of the first embodiment, and only the injection device 112 will be described.

[0046] In an injection device 112 of the second embodiment, a slide base 114, which is an injection device mounting portion, is provided rotatably on a base 113. A front block 115 is provided on a guide plate so as to be movable forward and backward relative to the slide base 114. A pusher block 131 is provided behind the front block 115, and the pusher block 131 rotatably holds a screw 116 and has a metering servomotor 117 attached to it. However, in the second embodiment, no block equivalent to the rear block 23 in the first embodiment is provided.

[0047] The front block 115 has a material supply hole 118 on its top surface, at the axial center of the injection unit 112 or at a position off-center. Alternatively, a material supply block shaped like that of the first embodiment may be directly attached to the front of the front block 115 to form the material supply hole 118. In this case, rubber material can be supplied from all directions in addition to the top. A heating cylinder 119 is attached to the center of the operating side and semi-operating side of the front block 115. Each zone of the heating cylinder 119 is heated by an electric heater 138. The heating cylinder 119 is also equipped with a cooling fan 120 for cooling each zone as needed. The heating cylinder 119 is equipped with a temperature detection means (not shown). A nozzle 121 is provided in front of the heating cylinder 119, but the nozzle 121 may also be heated by an electric heater. For this reason, a heat medium supply device for controlling the temperature of the heating cylinder 119 is not provided in the second embodiment.

[0048] An injection servo motor 122 is attached with its drive shaft and drive pulley 123 facing forward at the upper portion of the front block 115 closer to the operation side and at the upper portion closer to the opposite side, with the axial center of the front block 115 as the boundary. Bearings (not shown) for rotatably supporting a ball screw 124 are provided at the upper portion closer to the operation side and at an intermediate position in the height direction of the front block 115 closer to the opposite side, with the axial center of the front block 115 as the boundary. The ball screw mechanisms 125 including the ball screws 124 on the operation side and the opposite side have the same structure. Therefore, only one of them will be described. A driven pulley 126 is fixed to the front non-threaded portion of the ball screw 124. A belt 127 is stretched between the drive pulley 123 and the driven pulley 126 at the front portion of the front block 115. The drive pulley 123, the driven pulley 126, and the belt 127 may also be provided at the rear portion of the front block 115. Furthermore, the injection servomotor 122 may be of a direct drive type in which the drive shaft is directly connected to a ball screw, and the servomotors of the other described portions may also be of the direct drive type.

[0049] Cylinder portions 129a of hydraulic cylinders 129 of an injection unit forward / backward movement mechanism 128 are attached to positions nearer to the operating side and anti-operating side with respect to the axial center of the front surface of the front block 115, different from the position where the driven pulley 126 is provided. Meanwhile, the ends of rod portions 129b of the hydraulic cylinders 129 are attached to both sides of the injection unit introduction hole 61b of the fixed platen 61. Hydraulic oil is supplied to the hydraulic cylinders 129 from a pump (not shown) and the hydraulic cylinders 129 are operated by valves (not shown).

[0050] A rear end 119a of a heating cylinder 119 faces the center of the rear side surface of the front block 115, and a flightless portion of a screw 116 protrudes from an inner hole of the heating cylinder 119. A screw connection member 130 such as a screw connector is coaxially coupled to the screw 116. The screw connection member 130 is rotatably supported by bearings (not shown) provided in the center of the operating side and anti-operating side of a pusher block 131 provided behind the front block 115, with the axial center as the boundary, and an extended portion on one end protrudes to the rear of the pusher block 131. In the second embodiment as well, the screw of the present invention includes within its concept not only the screw 116, most of which is provided inside the heating cylinder 119, but also the screw connection member 130.

[0051] In the second embodiment, only a pusher block 131 is provided behind the front block 115, and is not divided into a pusher block 26 (intermediate block) and a rear block 23 as in the first embodiment. The pusher block 131 is movable forward and backward while being guided by a guide member 132, such as a linear guide, which is provided on the slide base 114 and is separate from the guide plate for forward and backward movement of the front block 115. A metering servo motor 117 is fixed to the upper part of the pusher block 131 so that its drive shaft and drive pulley 133 face backward. A driven pulley 134 is fixed to an extension portion on one end of the screw connection member 130. A belt 135 is stretched between the drive pulley 133 and the driven pulley 134. Here, the rated output (kW) and pulley ratio of the metering servo motor 117 are the same as those described in the first embodiment. Also, as in the first embodiment, the pusher block 131 may be provided with only two brackets for mounting the metering servo motor 117, and the metering servo motor 117 may be mounted on either one of them, or two or more metering servo motors may actually be provided.

[0052] Ball screw nuts 136 are provided at an upper portion of the pusher block 131 closer to the operation side and at an intermediate position in the height direction of the pusher block 131 closer to the anti-operation side. Ball screws 124 are inserted into the ball screw nuts 136. The injection device 112 is also provided with a greasing mechanism and a detection means for detecting the force applied to the screw 116.

[0053] <Operation of injection molding machine and molding method of second embodiment> In the rubber molding injection molding machine 101 of the second embodiment, the pusher block 131 and the screw 116 (including the screw connecting member 130) are moved forward and backward by driving an injection servo motor 122 provided in the front block 115 via a power transmission mechanism such as a belt 127, a driven pulley 126, and a ball screw mechanism 125 (back pressure control is also included in this because it is the same). Also, the screw 116 (including the screw connecting member 130) is rotated by driving a metering servo motor 117 provided in the pusher block 131 via a power transmission mechanism such as a belt 135 and a driven pulley 134. The molding conditions for rubber molding using the rubber molding injection molding machine 101 are substantially the same as those in the first embodiment, so the explanation of the first embodiment will be used and a detailed explanation will be omitted.

[0054] <Modification of rubber injection molding machine> In addition to the first and second embodiments, the rubber injection molding machine may also use a vertical clamping device in which the movable platen and movable mold are moved vertically to open and close the mold. When a vertical clamping device is used, ejection and removal of the rubber molded product may be performed at a position where the movable mold, etc. is pulled out from the clamping position. Furthermore, when a vertical clamping device is used in the rubber injection molding machine, the injection device may be one in which the heating cylinder is installed vertically, horizontally, or obliquely. Furthermore, when the heating cylinder is installed vertically, the rubber material supply mechanism may be installed obliquely.

[0055] The injection device may be one in which a driven pulley is fixed to a ball screw to rotate the ball screw, or one in which a driven pulley is fixed to a ball screw nut to move the ball screw back and forth. Also, it may be one in which an injection servo motor is attached to a pusher block.

[0056] Although not listed individually, the present invention is not limited to the above examples, and it goes without saying that the present invention can be applied to those modified by a person skilled in the art based on the spirit of the present invention. The multiple examples described above can also be implemented in appropriate combinations. [Explanation of symbols]

[0057] 11, 101... Rubber injection molding machine 13, 112... Injection device 14...Mold clamping device 16, 119... Heating cylinder 18,116···screw 19, 122 Injection servo motor 20, 117···Metering servo motor 21. Material supply block 22, 115... Front block 26, 131···Pusher block 67···Toggle link mechanism 71···Mold clamping servo motor

Claims

1. A rubber injection molding machine for molding a rubber molded product, an injection servo motor that moves the screw in the axial direction; a metering servo motor that rotates the screw; a front block to which the heating cylinder is attached directly or via a material feed block; a pusher block provided behind the front block, in which the screw is rotatably held and to which the metering servomotor is attached; an injection device including the heating cylinder whose temperature is controlled by a heat medium; a mold clamping device including a mold clamping servo motor that drives a toggle link mechanism; An injection molding machine for rubber molding comprising:

2. A rubber injection molding machine for molding a rubber molded product, an injection servo motor that moves the screw in the axial direction; a metering servo motor that rotates the screw; a front block to which the heating cylinder is attached directly or via a material feed block; a pusher block provided behind the front block, in which the screw is rotatably held and to which the metering servomotor is attached; a rear block provided behind the pusher block and to which the injection servomotor is attached; a material supply block provided in front of the front block; a mold clamping device including a mold clamping servo motor that drives a toggle link mechanism; An injection molding machine for rubber molding comprising:

3. The temperature of the material supply block and / or the rear part of the heating cylinder is independently controlled.

3. The rubber injection molding machine according to claim 1 or 2.

4. A rubber injection molding machine for molding a rubber molded product, an injection servo motor that moves the screw in the axial direction; a metering servo motor that rotates the screw; a front block to which the heating cylinder is attached directly or via a material feed block; a pusher block provided behind the front block, in which the screw is rotatably held and to which the metering servomotor is attached; an injection device in which the total rated output (kW) of the metering servo motors is set to 60% to 100% of the total rated output (kW) of the injection servo motors; a mold clamping device including a mold clamping servo motor that drives a toggle link mechanism; An injection molding machine for rubber molding comprising:

5. A rubber injection molding machine for molding a rubber molded product, an injection servo motor that moves the screw in the axial direction; a metering servo motor that rotates the screw; a front block to which the heating cylinder is attached directly or via a material feed block; a pusher block provided behind the front block, in which the screw is rotatably held and to which the metering servomotor is attached; an injection device in which a value obtained by dividing the total rated output (kW) of the metering servo motors by a screw diameter (mm) is set to 0.60 (kW / mm) to 1.00 (kW / mm); an injection device in which a diameter ratio between a drive member fixed to a drive shaft of the metering servomotor and a driven member fixed to a screw to which a driving force is transmitted from the drive member is 1:4.0 to 1:8.0; a mold clamping device including a mold clamping servo motor that drives a toggle link mechanism; An injection molding machine for rubber molding comprising:

6. A rubber injection molding machine for molding a rubber molded product, an injection servo motor that moves the screw in the axial direction; a metering servo motor that rotates the screw; a front block to which the heating cylinder is attached directly or via a material feed block; a pusher block provided behind the front block, in which the screw is rotatably held and to which the metering servomotor is attached; a driven pulley is attached to the screw or a shaft connected to the screw; an injection device provided with a plurality of metering servomotors that transmit driving force to the driven pulley via a belt; a mold clamping device including a mold clamping servo motor that drives a toggle link mechanism; An injection molding machine for rubber molding comprising:

7. The screw provided in the heating cylinder has a compression ratio in the range of 1.0 to 2.0, and the screw is provided with a check valve.

7. The rubber injection molding machine according to claim 4.

8. The maximum rotation speed of the screw is 100 min -１ or 250 min -１ That is, 7. The rubber injection molding machine according to claim 4.

9. A method for injection molding a rubber molded product using a rubber injection molding machine, comprising: an injection servo motor that moves the screw in the axial direction; a metering servo motor that rotates the screw; a front block to which the heating cylinder is attached directly or via a material feed block; an injection device including a pusher block provided behind the front block, the pusher block rotatably holding the screw and having the metering servomotor attached thereto; a mold clamping device having a mold clamping servo motor that drives a toggle link mechanism; The temperature of the heating cylinder is 50 to 120°C, and the rotation speed of the screw is 40 min -１ or 150 min -１ As a result, we carry out injection molding of rubber molded products. Injection molding method for rubber molded products.

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