Drive mechanism, injection device, and injection molding machine

Abstract

To achieve reduction in sizes of an injection device and an injection molding machine.SOLUTION: An injection device 3 in one embodiment comprises a cylinder 20, a screw 21 provided in the cylinder 20, and a drive mechanism 22 which rotates, and advances and retreats the screw 21. The drive mechanism 22 has a piston 40 including a hollow piston rod 42, a connection rod 70 whose one end side is inserted to the piston rod 42, and which is rotatable with respect to the piston 40 and is movable in a center axis direction of the piston rod 42 integrally with the piston 40, and a rotor 50 which is arranged around the connection rod 70, and is rotationally driven with a center axis of the connection rod 70 as a rotation axis. The connection rod 70 comprises a plurality of external teeth 75 extending in a center axis direction of the connection rod 70, and the rotor 50 comprises a plurality of internal teeth 51 meshed with the external teeth 75. The screw 21 is non-rotatably connected to the other end side of the connection rod 70 projecting from the piston rod 42.SELECTED DRAWING: Figure 2

Description

【Technical Field】 【0001】 The present invention relates to an injection molding machine. 【Background Art】 【0002】 An injection molding machine for manufacturing resin members or metal members of a desired shape is known. A general injection molding machine is composed of a mold clamping device and an injection device. The mold clamping device holds a mold and opens and closes the held mold. The injection device melts a resin material or a metal material and supplies the melted material to the mold clamping device. 【Prior Art Documents】 【Patent Documents】 【0003】 【Patent Document 1】 Japanese Patent Application Laid-Open No. 2019-171784 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0004】 The injection device includes a cylinder, a screw, a drive mechanism, etc. The drive mechanism rotates, advances, and retracts the screw within the cylinder. In order to miniaturize the injection device and the injection molding machine, miniaturization of the drive mechanism provided in the injection device is required. 【0005】 Other problems and novel features will become apparent from the description of this specification and the accompanying drawings. 【Means for Solving the Problems】 【0006】 An injection device according to one embodiment comprises a cylinder, a screw provided within the cylinder, and a drive mechanism for rotating, advancing, and reversing the screw. The drive mechanism includes a piston including a hollow piston rod, a connecting rod with one end inserted into the piston rod, rotatable relative to the piston, and moving integrally with the piston in the direction of the central axis of the piston rod, and a rotating body arranged around the connecting rod and rotated with the central axis of the connecting rod as its axis of rotation. The connecting rod is provided with a plurality of external teeth extending in the direction of the central axis of the connecting rod, and the rotating body is provided with a plurality of internal teeth that mesh with the external teeth. The screw is non-rotatably connected to the other end of the connecting rod that protrudes from the piston rod. [Effects of the Invention] 【0007】 According to one embodiment, miniaturization of injection devices and injection molding machines can be achieved. [Brief explanation of the drawing] 【0008】 [Figure 1] This is an explanatory diagram schematically showing an injection molding machine according to one embodiment. [Figure 2] This is an explanatory diagram schematically showing an injection device according to one embodiment. [Modes for carrying out the invention] 【0009】 Hereinafter, one embodiment will be described in detail with reference to the drawings. In all the drawings used to describe the embodiment, the same reference numerals will be used for components and devices that have the same or substantially the same function. Furthermore, as a general rule, components and devices that have already been described will not be described again. 【0010】 <Injection molding machine> Figure 1 is a schematic diagram illustrating the injection molding machine 1 according to this embodiment. The injection molding machine 1 consists of a clamping device 2 and an injection device 3. Molds 11 and 12 are attached to the clamping device 2. The clamping device 2 opens and closes the attached molds 11 and 12. The injection device 3 heats the material (for example, a metallic material such as magnesium or a magnesium alloy) to a molten or semi-molten state. Furthermore, the injection device 3 supplies the molten or semi-molten metallic material (molten metal) to the clamping device 2. More specifically, the injection device 3 injects the molten metal into the cavities of the molds 11 and 12. In other words, the injection molding machine 1 according to this embodiment is a metal injection molding machine. 【0011】 <Mold clamping device> The clamping device 2 comprises a fixed platen 13, a clamping housing 14, and a movable platen 15, all mounted on a bed 4. The fixed platen 13 is fixed to the bed 4. Meanwhile, the clamping housing 14 and the movable platen 15 are slidable on the bed 4. 【0012】 The fixed platen 13 and the clamping housing 14 are connected to each other by a number of tie bars 16 that pass through the movable platen 15. More specifically, the fixed platen 13 and the clamping housing 14 are connected by four tie bars 16. The movable platen 15 is slidable between the fixed platen 13 and the clamping housing 14 in their opposing directions. 【0013】 A clamping mechanism 17 is provided between the clamping housing 14 and the movable platen 15. More specifically, a link-type clamping mechanism 17 is provided between the clamping housing 14 and the movable platen 15. Alternatively, a toggle mechanism is provided between the clamping housing 14 and the movable platen 15. Note that the clamping mechanism 17 can be replaced with a direct-pressure type. 【0014】 The clamping mechanism 17 moves the mold 11, which is attached to the movable platen 15, forward and backward relative to the mold 12, which is attached to the fixed platen 13. When mold 11 comes into contact with mold 12, molds 11 and 12 are closed. Conversely, when mold 11 moves away from mold 12, molds 11 and 12 are opened. The clamping mechanism 17 can press mold 11 against mold 12 to prevent molds 11 and 12 from opening while they are closed. 【0015】 <Injection device> The injection device 3 consists of a cylinder 20, a screw 21, a drive mechanism 22, a hopper 23, etc. The hopper 23 is a supply port for supplying metal material to the cylinder 20 and is located at the rear of the cylinder 20. The screw 21 is located inside the cylinder 20 and rotates and moves relative to the cylinder 20. More specifically, the screw 21 is rotationally driven with the central axis of the cylinder 20 as its axis of rotation. The screw 21 is also linearly driven in the direction of the central axis of the cylinder 20. Another way to look at it is that the screw 21 is linearly driven within the cylinder 20 in the direction approaching the clamping device 2 (forward) and in the direction away from the clamping device 2 (rear). 【0016】 The above-described movements of the screw 21 (rotation, forward movement, and reverse movement) are achieved by the drive mechanism 22. Details of the drive mechanism 22 will be explained later. 【0017】 The metal material supplied to the cylinder 20 via the hopper 23 is heated and melted. Heaters are provided around the cylinder 20 to heat it. In this embodiment, a plurality of heaters 24 are wrapped around the outer surface of the cylinder 20. The metal material supplied to the cylinder 20 is heated and melted by the heat emitted from the heaters 24 and by the shear heat generated by the rotation of the screw 21. 【0018】 <Method for manufacturing molded products> The process of manufacturing a molded product such as a metal member using the injection molding machine 1 shown in FIG. 1 is the same as or substantially the same as a known process. Therefore, although a detailed description of the manufacturing process will be omitted, the manufacturing process includes, for example, one or more of the following processes. (Process 1) A process of heating the metal material (for example, magnesium or magnesium alloy processed into powder or pellet form) supplied to the cylinder 20 to a molten state or a semi-molten state (Process 2) A process of rotating the screw 21 to send the molten or semi-molten metal material to the tip side of the cylinder 20 (Process 3) A process of advancing the screw 21 and injecting (injecting) the metal material from the injection nozzle into the cavities of the molds 11, 12 (Process 4) A process of retracting the screw 21 to relieve the pressure of the metal material in the injection nozzle 【0019】 By repeating the process including one or more of the above processes, metal members (molded products) of the same shape are continuously manufactured. That is, metal members (molded products) of a desired shape are mass-produced. 【0020】 <Drive mechanism> FIG. 2 is an explanatory diagram schematically showing the injection device 3. As described above, the injection device 3 includes a drive mechanism 22 that rotates, advances, and retracts the screw 21. The drive mechanism 22 has a piston 40, a rotating body 50, and a connecting rod 70. 【0021】 <Piston> The piston 40 includes an integral piston head 41 and a piston rod 42, and is moved in the central axis direction of the piston rod 42 by hydraulic pressure. That is, the piston 40 is a hydraulic piston. Note that the X-X line in FIG. 2 is a virtual line indicating the central axes of the piston rod 42 and the connecting rod 70. 【0022】 Alternatively, the piston 40 moves in a direction toward the clamping device 2 shown in Figure 1 (forward) and in a direction toward away from the clamping device 2 (rearward). The screw 21 is connected to the piston 40 via a connecting rod 70. Therefore, when the piston 40 moves back and forth, the screw 21 also moves back and forth. More specifically, when the piston 40 moves forward, the screw 21 moves forward. Conversely, when the piston 40 moves backward, the screw 21 moves backward. 【0023】 The piston 40 is moved forward, for example, when performing step 3 described above. In other words, in step 3, the screw 21 is advanced by moving the piston 40 forward, and the metal material is injected from the injection nozzle. 【0024】 The piston 40 is moved backward, for example, when performing step 4 described above. In other words, in step 4, moving the piston 40 backward causes the screw 21 to retract, relieving the pressure of the metal material inside the injection nozzle. By relieving the pressure of the metal material inside the injection nozzle, leakage of the metal material is prevented. Step 4, in which the screw 21 is retracted to prevent leakage of the metal material, is sometimes called "suck-back". 【0025】 <Piston head> The piston head 41 is housed in a hydraulic chamber 60 enclosed by a front wall 60a, a rear wall 60b, and side walls 60c. The piston head 41 is movable back and forth and rotatable within the hydraulic chamber 60. 【0026】 The hydraulic chamber 60 is divided into an upper chamber 61 and a lower chamber 62 by the piston head 41. Alternatively, the space behind (to the right of) the piston head 41 is the upper chamber 61, and the space in front (to the left of) the piston head 41 is the lower chamber 62. The volumes of the upper chamber 61 and the lower chamber 62 increase or decrease as the piston head 41 moves. 【0027】 The hydraulic chamber 60 is connected to the hydraulic system via two ports 63 and 64. When hydraulic fluid is supplied to the upper chamber 61 from port 63, pressure is applied to the upper surface 41a of the piston head 41, causing the piston 40 to move forward (the piston 40 is pushed out). At this time, the hydraulic fluid in the lower chamber 62 is discharged from the lower chamber 62 through port 64. 【0028】 On the other hand, when hydraulic fluid is supplied from port 64 to the lower chamber 62, pressure is applied to the lower surface 41b of the piston head 41, causing the piston 40 to move backward (the piston 40 is pushed back). At this time, the hydraulic fluid in the upper chamber 61 is discharged from the upper chamber 61 through port 63. 【0029】 <Piston rod> The piston rod 42 is hollow. More specifically, the piston rod 42 has a cylindrical shape with one end (the base end) closed by the piston head 41. Alternatively, the piston rod 42 extends forward from the lower surface 41b of the piston head 41. Inside the piston rod 42, there is an insertion hole 45 extending in the direction of the central axis, and the bottom of the insertion hole 45 is closed by the piston head 41. 【0030】 In other words, the piston head 41 is located on the base end side of the piston rod 42. That is, the side on which the piston head 41 is located is the base end side of the piston rod 42. Conversely, the side opposite to the side on which the piston head 41 is located is the tip end side of the piston rod 42. The piston head 41 and the piston rod 42 are coaxial. 【0031】 The piston rod 42 penetrates the front wall 60a and protrudes forward of the front wall 60a. A sealing member 65 is positioned between the front wall 60a and the piston rod 42 to prevent leakage of hydraulic fluid. 【0032】 <Connecting Rod> The connecting rod 70 is cylindrical. One end (base end) of the connecting rod 70 is inserted into the insertion hole 45 of the piston rod 42, and the other end (tip end) of the connecting rod 70 protrudes from the piston rod 42. In the following description, the base end of the connecting rod 70 inserted into the piston rod 42 may be referred to as the "insertion portion 71," and the tip end of the connecting rod 70 protruding from the piston rod 42 may be referred to as the "protruding portion 72" to distinguish them. 【0033】 The outer diameter of the insertion portion 71 of the connecting rod 70 is larger than that of the protruding portion 72. As a result, there is a step between the insertion portion 71 and the protruding portion 72. In other words, the connecting rod 70 is a stepped rod. Alternatively, the tip surface of the insertion portion 71 widens radially outward from the protruding portion 72, forming a flange portion 73. 【0034】 The connecting rod 70 is rotatable relative to the piston rod 42. More specifically, the insertion portion 71 of the connecting rod 70 is rotatably inserted into the insertion hole 45 of the piston rod 42. A bearing 46 is positioned between the inner circumferential surface of the insertion hole 45 and the outer circumferential surface of the insertion portion 71. The bearing 46 rotatably supports the connecting rod 70 and aligns the central axes of the piston rod 42 and the connecting rod 70. In other words, the bearing 46 centers the connecting rod 70. The bearing 46 may be a sliding bearing or a rolling bearing, but a sliding bearing is preferable from the viewpoint of centering accuracy. 【0035】 On the other hand, the connecting rod 70 cannot move forward or backward relative to the piston rod 42. More specifically, a retaining ring 74 that straddles the tip surface of the piston rod 42 and the flange portion 73 of the connecting rod 70 is bolted to the piston rod 42. Also, the rear end surface of the connecting rod 70 abuts against the bottom of the insertion hole 45. 【0036】 In other words, the piston 40 and the connecting rod 70 can rotate relative to each other, but they move together in the front-to-back direction (along the central axis). 【0037】 Multiple external teeth 75 are provided on the outer circumferential surface of the connecting rod 70. More specifically, multiple external teeth 75 are provided on the outer circumferential surface of the protruding portion 72 of the connecting rod 70 that protrudes from the piston rod 42. 【0038】 Each external tooth 75 extends in the direction of the central axis of the connecting rod 70. Furthermore, multiple external teeth 75 are adjacent to each other in the circumferential direction of the connecting rod 70 and are parallel to one another. 【0039】 <Rotating body> The rotating body 50 is positioned around the connecting rod 70 and surrounds it. More specifically, the rotating body 50 is positioned around the projection 72 and surrounds it. In other words, the rotating body 50 is an annular or cylindrical member having an inner diameter through which the projection 72 of the connecting rod 70 can be inserted. 【0040】 The rotating body 50 is positioned in front of the injection device 3. More specifically, the rotating body 50 is positioned between the base and tip of the connecting rod 70 in the central axis direction of the connecting rod 70. Alternatively, the rotating body 50 is positioned in front of the piston 40 and behind the screw 21. 【0041】 Multiple internal teeth 51 are provided on the inner circumferential surface of the rotating body 50, which faces the outer circumferential surface of the connecting rod 70. Each internal tooth 51 extends in the same direction as the external teeth 75. Furthermore, the multiple internal teeth 51 are adjacent to each other in the circumferential direction (direction of rotation) of the rotating body 50 and are parallel to each other. 【0042】 The internal teeth 51 on the rotating body 50 mesh with the external teeth 75 on the connecting rod 70. In other words, the rotating body 50 and the connecting rod 70 are spline-fitted. Alternatively, the connecting rod 70 is a spline shaft with a key formed on its outer surface, and the rotating body 50 is a spline boss or sleeve with a keyway formed on its inner surface. 【0043】 The external teeth 75 on the connecting rod 70 and the internal teeth 51 on the rotating body 50 extend in the direction of the central axis of the connecting rod 70 and mesh with each other. Therefore, the connecting rod 70 and the rotating body 50 cannot rotate relative to each other, while the connecting rod 70 can move in the direction of its central axis relative to the rotating body 50. In other words, the connecting rod 70 can rotate integrally with the rotating body 50, while also being able to move forward and backward independently of the rotating body 50. 【0044】 Furthermore, as previously described, the piston 40 and the connecting rod 70 are rotatable relative to each other, while the connecting rod 70 is movable integrally with the piston 40 in the central axis direction. As a result, the rotating body 50 and the connecting rod 70 are rotatable integrally and independently of the piston 40. On the other hand, the piston 40 and the connecting rod 70 are rotatable integrally and independently of the rotating body 50. 【0045】 The rotating body 50 is rotatably mounted via a bearing 53 to a support portion 52 protruding from the front surface of the front wall 60a. The rotating body 50 is rotationally driven by a motor, with the central axis of the connecting rod 70 as the axis of rotation. For example, torque output from an electric motor is input to the rotating body 50 via a transmission means or reduction means consisting of a belt, pulley, gear, etc. The torque input to the rotating body 50 is transmitted to the connecting rod 70, causing the connecting rod 70 to rotate. At this time, the piston 40 does not rotate. Note that the motor is not limited to an electric motor; for example, a hydraulic motor may also be used. 【0046】 As previously described, the screw 21 is connected to the piston 40 via the connecting rod 70. More specifically, the screw 21 is non-rotatably connected to the tip of the projection 72 of the connecting rod 70. Therefore, when the connecting rod 70 rotates, the screw 21 also rotates. More specifically, when the connecting rod 70 rotates clockwise, the screw 21 also rotates clockwise. On the other hand, when the connecting rod 70 rotates counterclockwise, the screw 21 also rotates counterclockwise. Switching the direction of rotation of the connecting rod 70 is achieved by switching the direction of rotation of the rotating body 50, and switching the direction of rotation of the rotating body 50 is achieved by switching the direction of rotation of the motor. 【0047】 The connecting rod 70 is rotated, for example, when performing steps 1 and 2 described above. In other words, in step 1, the screw 21 is rotated by rotating the connecting rod 70, thereby applying shear stress to the metal material. Also, in step 2, the screw 21 is rotated by rotating the connecting rod 70, thereby feeding the metal material towards the tip of the cylinder 20. 【0048】 As described above, in the injection device 3 of this embodiment, the rotating body 50 for rotating the connecting rod 70 is located at the front of the device, and the external teeth 75 that mesh with the internal teeth 51 of the rotating body 50 are provided on the tip side of the connecting rod 70. On the other hand, if the rotating body 50 is located at the rear of the device, the connecting rod 70 and piston 40 must be extended to the rear, and the external teeth 75 must be provided on the base end side of the connecting rod 70 or behind the piston head 41. In this case, the overall length of the injection device 3 increases, and the injection device 3 becomes larger. Furthermore, the increase in size of the injection device 3 leads to an increase in the size of the injection molding machine 1, which includes the injection device 3. In other words, in this embodiment, miniaturization of both the injection device 3 and the injection molding machine 1 is achieved. 【0049】 Furthermore, in the injection device 3 of this embodiment, the only components that move when the screw 21 moves back and forth are the screw 21, the piston 40, and the connecting rod 70. In other words, the rotating body 50 does not move when the screw 21 moves back and forth. Therefore, the weight that moves back and forth is reduced, and the braking performance of the screw 21 is improved. That is, the braking distance of the screw 21 is shortened, and the screw 21 can be stopped precisely at the desired position. 【0050】 Furthermore, the piston 40 moves back and forth but does not rotate. Therefore, the sealing member provided on the piston 40 slides only in the back and forth direction. As a result, damage or deterioration of the sealing member provided on the piston 40 is prevented or suppressed compared to when the piston 40 rotates. For example, damage or deterioration of the sealing member 65 located between the piston rod 42 and the front wall 60a is prevented or suppressed. 【0051】 The present invention has been described in detail above based on embodiments, but it goes without saying that the present invention is not limited to the above embodiments and can be modified in various ways without departing from its essence. For example, the injection device 3 can be replaced with an injection device (resin injection device) that injects molten resin into molds 11 and 12 attached to the clamping device 2. [Explanation of Symbols] 【0052】 1 injection molding machine 2 Mold clamping device 3 Injection device 4 beds 11,12 molds 13 Fixed plate 14-type clamping housing 15 Movable plate 16 Tie Bar 17 Mold clamping mechanism 20 cylinders 21 Screw 22 Drive mechanism 23 Hoppa 24 Heater 40 pistons 41 Piston Head 41a Top side 41b Bottom side 42 Piston Rod 45 Insertion holes 46 bearings 50 Rotating Bodies 51 Inner teeth 52 Support part 53 Bearings 60 Hydraulic chamber 60a front wall 60b back wall 60c side wall 61 Upper Room 62 Lower chamber Ports 63 and 64 65 sealing member 70 connecting rods 71 Insertion part 72 Protrusion 73 Flange section 74 Retaining ring 75 External teeth XX virtual line

Claims

[Claim 1] A drive mechanism for driving the screw of an injection device, A piston comprising a piston head and a hollow piston rod extending from the piston head in a first direction, the piston being moved by hydraulic pressure in the central axis direction of the piston rod, A connecting rod that is rotatable relative to the piston and moves integrally with the piston in the direction of the central axis of the piston rod, It comprises a rotating body that is rotationally driven with the central axis of the connecting rod as the axis of rotation, The connecting rod comprises an insertion portion that is rotatably inserted into an insertion hole provided in the piston rod, and a projection portion that protrudes from the insertion hole in the first direction. The rotating body is arranged around the protruding portion of the connecting rod, The protruding portion of the connecting rod is provided with a plurality of external teeth extending in the direction of the central axis of the connecting rod. The rotating body is provided with a plurality of internal teeth that mesh with the external teeth, A drive mechanism in which the screw is non-rotatably connected to the end of the protruding portion of the connecting rod. [Claim 2] In the drive mechanism described in claim 1, The aforementioned connecting rod is cylindrical in shape. The rotating body is annular or cylindrical in shape and surrounds the connecting rod. The external teeth are provided on the outer circumferential surface of the connecting rod, The internal teeth are provided on the inner circumferential surface of the rotating body facing the outer circumferential surface of the connecting rod, in a drive mechanism. [Claim 3] In the drive mechanism described in claim 2, The multiple external teeth are adjacent to each other in the circumferential direction of the connecting rod and are parallel to each other. A drive mechanism in which the multiple internal teeth are adjacent to each other in the circumferential direction of the rotating body and are parallel to each other. [Claim 4] In the drive mechanism described in claim 1, The rotating body is a drive mechanism positioned between one end and the other end of the protruding portion in the central axis direction of the connecting rod. [Claim 5] An injection device that melts and injects a material, Cylinder and A screw provided inside the cylinder, The screw is driven by a drive mechanism that rotates, moves forward, and moves backward. The aforementioned drive mechanism is A piston comprising a piston head and a hollow piston rod extending from the piston head in a first direction, the piston being moved by hydraulic pressure in the central axis direction of the piston rod, A connecting rod that is rotatable relative to the piston and moves integrally with the piston in the direction of the central axis of the piston rod, It comprises a rotating body that is rotationally driven with the central axis of the connecting rod as the axis of rotation, The connecting rod comprises an insertion portion that is rotatably inserted into an insertion hole provided in the piston rod, and a projection portion that protrudes from the insertion hole in the first direction. The rotating body is arranged around the protruding portion of the connecting rod, The protruding portion of the connecting rod is provided with a plurality of external teeth extending in the direction of the central axis of the connecting rod. The rotating body is provided with a plurality of internal teeth that mesh with the external teeth, An injection device in which the screw is non-rotatably connected to the end of the protruding portion of the connecting rod. [Claim 6] An injection molding machine comprising a clamping device to which a mold is attached, and an injection device for injecting molten metal or molten resin into the mold, The injection device is, Cylinder and A screw provided inside the cylinder, The screw is driven by a drive mechanism that rotates, moves forward, and moves backward. The aforementioned drive mechanism is A piston comprising a piston head and a hollow piston rod extending from the piston head in a first direction, the piston being moved by hydraulic pressure in the central axis direction of the piston rod, A connecting rod that is rotatable relative to the piston and moves integrally with the piston in the direction of the central axis of the piston rod, It comprises a rotating body that is rotationally driven with the central axis of the connecting rod as the axis of rotation, The connecting rod comprises an insertion portion that is rotatably inserted into an insertion hole provided in the piston rod, and a projection portion that protrudes from the insertion hole in the first direction. The rotating body is arranged around the protruding portion of the connecting rod, The protruding portion of the connecting rod is provided with a plurality of external teeth extending in the direction of the central axis of the connecting rod. The rotating body is provided with a plurality of internal teeth that mesh with the external teeth, An injection molding machine in which the screw is non-rotatably connected to the end of the protruding portion of the connecting rod.

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