Injection device

Abstract

A simpler configuration enables switching between screw rotation and forward / backward movement. [Solution] According to the present invention, an injection device is provided comprising a screw housed inside a cylinder, a drive shaft having screw threads on its outer surface, an electric motor having a stator and a rotor, and a one-way clutch having an outer ring and an inner ring, wherein the outer ring of the one-way clutch is movable in the axial direction of the screw and its relative rotation with respect to the stator is restricted, the inner ring of the one-way clutch is fixed to the drive shaft, the drive shaft is connected to the rear end of the screw coaxially with the screw, the drive of the rotor is transmitted to the drive shaft via the screw threads, and the first direction in which the one-way clutch allows the inner ring to rotate is the direction in which the screw threads tighten when the rotor is rotated in the first direction.

Description

Technical Field

[0001] The present invention relates to an injection device. In particular, the present invention relates to a backflow prevention mechanism in an injection device having two independent cylinders.

Background Art

[0002] In the field of injection molding, an injection device is known in which, in addition to a first cylinder having an injection axis, a second cylinder for plasticizing or mixing a molding material, which is independent of the first cylinder, is separately provided (for example, Patent Document 1 below). When the molding material is a thermoplastic resin, the second cylinder is a plasticizing cylinder having a screw (referred to as a "plasticizing screw") for plasticizing the molding material, and when the molding material is a thermosetting resin, it is a mixing cylinder having a screw (referred to as a "mixing screw") for mixing the molding material. Here, the "injection axis" refers to an injection plunger or an injection screw disposed inside the first cylinder as an injection cylinder, and hereinafter, the term "injection axis" is used as a term encompassing these structures.

[0003] Such an injection device includes a type called a screw pre-plunger. In a screw pre-plunger type injection device, a first cylinder as an injection cylinder and a second cylinder as, for example, a plasticizing cylinder are connected by a communication passage, and by rotating the plasticizing screw in the plasticizing cylinder, the molten molding material is sent to the injection cylinder through the communication passage, and the molten material is metered in the injection cylinder. Then, by driving the injection axis, the molten material is injected from the injection cylinder into the mold.

[0004] In screw-pre-plasticization injection molding systems, a "backflow prevention operation" is performed after measuring the molding material and before injection into the mold, in order to prevent backflow of the molding material from the injection cylinder to the plasticizing cylinder or mixing cylinder. This backflow prevention operation involves advancing the plasticizing screw or mixing screw inside the second cylinder axially, thereby blocking the passage with the screw tip. This backflow prevention operation prevents backflow of the molding material into the second cylinder, enabling more accurate injection of the resin into the mold. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2013-220600 [Patent Document 2] Japanese Patent Application Publication No. 05-345337 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, the introduction of a backflow prevention mechanism requires a mechanism to enable the forward and backward movement of the screw in the axial direction, in addition to the rotation of the screw inside the second cylinder. For example, in the injection device described in Patent Document 1 above, the rotation of the screw and its movement along the axial direction are switched according to the rotation direction of the motor rotor by a combination of two one-way clutches that allow rotation in different directions and a cam mechanism. Patent Document 2 describes a mechanism that can switch between the rotation of an inline screw and its movement along the axial direction by a combination of a dog clutch, an electromagnetic powder clutch and an electromagnetic clutch.

[0007] Thus, conventionally, achieving both rotation and forward / backward movement of the screw requires a complex configuration, such as incorporating two or more clutches into the screw drive mechanism, which tends to make injection molding machines larger and more complex overall. For these reasons, there is a demand for a simpler configuration to achieve backflow prevention. [Means for solving the problem]

[0008] The present invention provides the following: [1] An injection device comprising a first cylinder having an injection shaft and a second cylinder connected to the first cylinder via a communication passage, the injection device comprising a screw housed inside the second cylinder, a drive shaft having screw threads on its outer surface, an electric motor having a stator and a rotor, and a one-way clutch having an outer ring and an inner ring, wherein the outer ring of the one-way clutch is movable in the axial direction of the screw and its relative rotation with respect to the stator is restricted, the inner ring of the one-way clutch is fixed to the drive shaft, the drive shaft is connected to the rear end of the screw coaxially with the screw, the drive of the rotor is transmitted to the drive shaft via the screw threads, and the first direction in which the one-way clutch allows the rotation of the inner ring is the direction in which the screw threads tighten when the rotor is rotated in the first direction. An injection device as described in [2][1], wherein the electric motor is controlled to rotate the rotor in the first direction, thereby rotating the screw in the first direction to send the molding material in the second cylinder to the first cylinder via the communication passage, and then to rotate the rotor in the second direction opposite to the first direction, thereby advancing the screw along the axial direction, so that the tip of the screw closes the communication passage. An injection device according to [3][1] or [2], wherein the screw threads provided on the drive shaft are reverse threads. An injection device according to any one of [4] [1] to [3], further comprising a first shaft key and a drive nut having an internal thread, wherein the rotor of the electric motor has a hollow cylindrical shape, the drive nut is coupled to the inside of the cylindrical shape of the rotor so that its relative rotation with respect to the rotor is restricted by the first shaft key, and the threads of the drive shaft engage with the internal threads of the drive nut. An injection device according to [5][4], further comprising a second shaft key and a clutch housing fixed to the outer circumferential surface of the outer ring of the one-way clutch, wherein the electric motor comprises a housing for housing the stator and the rotor and a front bracket having a through hole, the front bracket being located between the housing and the second cylinder, and the clutch housing being coupled to the inside of the through hole so as to be movable in the axial direction of the screw by the second shaft key and so as to restrict relative rotation with respect to the front bracket. An injection device according to [6][5], wherein the diameter of the clutch housing is less than or equal to the diameter of the drive nut. An injection device according to [7][6], wherein the electric motor further comprises an end bell connected to the rear end of the housing, the end bell includes a regulating member having a contact surface, the regulating member is configured to adjust the position of the contact surface of the screw in the axial direction relative to the rear end of the housing, and the drive nut is coupled to the rotor so as to be movable in the axial direction of the screw by the first shaft key. An injection device according to any one of items [8](1) to [7], wherein the first cylinder is an injection cylinder, the injection shaft is an injection plunger, the second cylinder is a plasticizing cylinder, and the screw is a plasticizing screw. An injection device according to any one of paragraphs [9][1] to [7], wherein the first cylinder is an injection cylinder, the injection shaft is an injection plunger, the second cylinder is a mixing cylinder, and the screw is a mixing screw. [Effects of the Invention]

[0009] According to the present invention, by connecting the shaft connected to the screw to the rotor of a hollow shaft motor via a screw thread, it becomes possible to switch between the rotation of the screw and its movement along the axial direction while reducing the number of one-way clutches. In other words, it is possible to achieve backflow prevention operation with a simpler configuration. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows an example of an injection molding machine having an injection device according to one embodiment of the present invention. [Figure 2] Figure 1 is a perspective view showing the part of the injection device 10 shown in Figure 1 that is mainly involved in the injection of the molding material, with the exterior of the injection device 10 removed. [Figure 3] This is a schematic partial cross-sectional view of the injection device 10. [Figure 4] This is a schematic exploded perspective view of the screw drive unit 18. [Figure 5] This is a schematic vertical cross-sectional view of the screw drive unit 18. [Figure 6] This is an exploded perspective view showing the front bracket 80F and its surrounding area. [Figure 7] This is an exploded perspective view showing the front bracket 80F and its surrounding area. [Figure 8] This is a schematic vertical cross-sectional view illustrating the arrangement of the parts of the screw drive unit 18 before the start of the plasticization process. [Figure 9] This is a schematic cross-sectional view illustrating the disassembly of the screw drive unit 18 into three units. [Figure 10] Figure 9 is a schematic diagram showing the end unit 18Z disassembled, illustrating an example in which the cylindrical part 80bc and the plate-shaped part 80bp are connected by bolt Sab when adjusting the stroke of the screw 12S. [Modes for carrying out the invention]

[0011] Hereinafter, embodiments of the present invention will be described while referring to the drawings. Various characteristic matters shown in the embodiments described below can be combined with each other. Also, an invention can be established independently for each characteristic. In the drawings shown below, in order to avoid excessive complexity, illustration of some members may be omitted.

[0012] <1. Overall Configuration of Injection Molding Machine> FIG. 1 shows an example of an injection molding machine having an injection device according to an embodiment of the present invention. The injection molding machine 1 shown in FIG. 1 is generally constituted by combining three devices. More specifically, the injection molding machine 1 includes an injection device 10, a mold clamping device 20, and a control device 30.

[0013] In an embodiment of the present invention, as the injection device 10, a device having two independent cylinders (also called barrels) connected to each other via a communication passage is assumed. FIG. 2 shows, with the exterior of the injection device 10 removed, the part mainly related to the injection of the molding material among the injection devices 10 shown in FIG. 1. In the configuration illustrated in FIG. 2, the injection device 10 has a first cylinder 11 and a second cylinder 12 in which a screw is disposed inside.

[0014] The injection device 10 further includes a nozzle cylinder 14, a junction 14Bb, and an injection nozzle 16. The nozzle cylinder 14 is located between the first cylinder 11 and the injection nozzle 16 in the axial direction of the first cylinder 11. The junction 14Bb connects the tip of the second cylinder 12 to the side portion of the nozzle cylinder 14. In other words, the second cylinder 12 is connected to the first cylinder 11 by the nozzle cylinder 14 and the junction 14Bb.

[0015] The clamping device 20 of the injection molding machine 1 is configured to allow the attachment and detachment of a mold (not shown in Figure 1), and has a mechanism to open and close the attached mold based on the control of the control device 30. The clamping device 20 has a mechanism to apply pressure (commonly called "clamping force") to further tighten the mold when it is closed. Molten or liquid molding material is injected into the mold, which is being clamped by the clamping device 20, from the injection nozzle 16 attached to the tip of the nozzle cylinder 14 of the injection device 10.

[0016] The control device 30 of the injection molding machine 1 has at least one processor and at least one memory, and controls the operation of the injection device 10 and the clamping device 20 according to the instructions described in the operation program stored in the memory. As will be described later, the injection device 10 includes a motor that operates a screw housed inside the second cylinder 12, and the control device 30 has the function of controlling the rotational speed and rotational direction of the rotor of the motor of the injection device 10. In Figure 1, the injection device 10 and the control device 30 are shown as separate devices, but for example, the control device 30 may be incorporated into the injection device 10 so that they are a single integrated device.

[0017] (Injection device 10) The details of the configuration of the injection device 10 are described below. Figure 3 schematically shows a partial cross-section of the injection device 10. First, let's focus on the first cylinder 11. The first cylinder 11 is an injection cylinder having an injection shaft 11A inside, where the injection shaft 11A is an injection plunger configured to reciprocate along the axis of the first cylinder 11.

[0018] An injection drive device 11D is positioned at the rear end of the first cylinder 11, on the side opposite to the injection nozzle 16 in the axial direction. The injection drive device 11D is an arbitrary actuator that drives the injection shaft 11A back and forth inside the first cylinder 11 based on instructions from the control device 30. An electric cylinder or a hydraulic cylinder can be exemplified as the injection drive device 11D. Hereinafter, in this specification, the side of each cylinder of the first cylinder 11 and the second cylinder 12 that is closer to the clamping device 20 in the axial direction (the left side in Figure 3) may be referred to as the "front" or "front side," and the side opposite to the clamping device 20 may be referred to as the "rear" or "rear side."

[0019] As explained with reference to Figure 2, a nozzle cylinder 14 is located between the front end of the first cylinder 11 and the injection nozzle 16. A junction 14Bb is located between the front end of the second cylinder 12 and the nozzle cylinder 14. As shown in Figure 3, the nozzle cylinder 14 has a flow path 141 that communicates from the space inside the first cylinder 11 to the space inside the injection nozzle 16, and a part of a connecting passage 142 that defines a flow path connecting the space inside the first cylinder 11 and the space inside the second cylinder 12. The junction 14Bb has the remaining part of the connecting passage 142 inside. It is not necessary for the junction 14Bb to be a separate component from the nozzle cylinder 14 that can be separated from the nozzle cylinder 14. The structure including the nozzle cylinder 14 and the first cylinder 11 may be a single component formed as an integral structure.

[0020] A heater 14H (e.g., a band heater) for temperature control may be attached to the outer surface of the nozzle cylinder 14. Similarly, the first cylinder 11 and the injection nozzle 16 may also be configured to be heated to a predetermined temperature by winding heaters 11H (e.g., a band heater) and heater 16H (e.g., a coil heater) around their outer surfaces, respectively. Furthermore, the junction 14Bb may also have a heater for temperature control.

[0021] Next, let's focus on the second cylinder 12. As schematically shown in Figure 3, the front end of the second cylinder 12 is connected to the junction 14Bb, and the aforementioned communication passage 142 passes through the junction 14Bb and communicates with the space inside the second cylinder 12.

[0022] The second cylinder 12 has a hopper 12P into which the molding material is fed near its rear end. Similar to the first cylinder 11, a heater 12H (e.g., a band heater) is attached to the outer surface of the second cylinder 12.

[0023] A screw 12S is housed inside the second cylinder 12. The screw 12S is either a plasticizing screw or a mixed screw. In either case, since the second cylinder 12 is equipped with the screw 12S, the injection device 10 is called a screw pre-plasticizing injection device.

[0024] As will be explained later with reference to the drawings, in an embodiment of the present invention, the screw 12S is configured to be rotatable around the axial direction of the second cylinder 12 and to move back and forth along the axial direction with a predetermined stroke by the mechanism of a screw drive device 18 located at the rear end of the second cylinder 12. Hereinafter, unless otherwise specified, "axial direction" refers to "axial direction of the second cylinder 12".

[0025] Screw 12S is a plasticizing screw that plasticizes the molding material, for example, if the molding material fed from hopper 12P is a thermoplastic resin, and the second cylinder 12 functions as a plasticizing cylinder. The plasticizing screw typically has a spirally formed screw groove and can be divided into, for example, three zones from the base to the tip. That is, the plasticizing screw may have a feed section, a compression section, and a metering section in that order from the base to the tip. The screw groove on the side of the plasticizing screw is generally formed to be shallower in the metering section compared to the feed section, and becomes shallower in the compression section as it approaches the metering section. By rotating the plasticizing screw, the molding material is plasticized as it moves within the plasticizing cylinder from the base to the tip of the plasticizing screw.

[0026] Alternatively, screw 12S may be a mixing screw for mixing the molding material. In other words, the second cylinder 12 may be a mixing cylinder for mixing a thermosetting resin as the molding material. The mixing screw has at least a mixing section, the mixing section is provided with a structure called, for example, a dalmage or maddock. For example, the mixing section has a plurality of protrusions on its surface. These plurality of protrusions can be provided, for example, by forming a plurality of intersecting helical grooves on the cylindrical surface.

[0027] The thermosetting resin consists, for example, of a liquid main component and a curing agent, and is introduced into the mixing cylinder under pressure from a supply device. The main component and curing agent are mixed by the rotation of the mixing screw as they move within the mixing cylinder from the base to the tip of the mixing screw due to the pressure when they are discharged from the supply device. A feed section may be provided at the base of the mixing screw to facilitate the movement of the molding material within the mixing cylinder from the base to the tip of the mixing screw. In both cases, where the screw 12S is a plasticizing screw and a mixing screw, the second cylinder 12 is equipped with the screw 12S, and therefore the injection device 10 is called a screw pre-plasticizing injection device.

[0028] (Screw drive device 18) The screw drive unit 18 will now be described in detail, assuming that screw 12S is a plasticizing screw. As can be seen from the following description, the screw drive unit 18 has a structure that enables rotation of screw 12S for plasticizing the molding material and movement of screw 12S along the axial direction for backflow prevention.

[0029] Figure 4 shows a disassembled view of the screw drive unit 18. The screw drive unit 18 includes at least a motor for rotating the screw 12S and a one-way clutch, and is configured to allow switching between rotation and forward / backward movement of the screw 12S by switching the rotation direction of the motor. In the example shown in Figure 4, the screw drive unit 18 includes a motor 80 and a one-way clutch 92.

[0030] The motor 80 includes a stator 80S, a rotor 80R, and a housing 80H that houses the stator 80S and the rotor 80R. In this embodiment, the stator 80S is fixed inside the housing 80H, and the rotor 80R is rotatably positioned inside the stator 80S.

[0031] In the configuration illustrated in Figure 4, the motor 80 further includes a front bracket 80F and an end bell 80E. The front bracket 80F and the end bell 80E are each fixed to the housing 80H by means of screws or other means. The end bell 80E is connected to the rear end 80r of the housing 80H, while the front bracket 80F is located between the housing 80H and the second cylinder 12. Here, the end bell 80E includes two parts. Specifically, the end bell 80E includes an annular first member 80Ea and a second member 80Eb, which are fixed to the housing 80H.

[0032] In embodiments of the present invention, the motor 80 is assumed to be an electric motor, particularly a direct-drive hollow motor. Specifically, the rotor 80R has a hollow cylindrical shape and is housed coaxially with the stator 80S. Direct-drive motors have the advantage of being able to generate high torque and allowing other components to be placed inside the rotor 80R.

[0033] In this embodiment, a drive nut 84 is inserted inside the rotor 80R. The drive nut 84 is coupled to the inside of the cylindrical shape of the rotor 80R in such a way that its relative rotation to the rotor 80R is restricted, for example by a key. Here, a key seat 4s is provided on the outer circumferential surface of the drive nut 84, and a keyway Rw is provided on the inner circumferential surface of the rotor 80R, and a shaft key k1 (first shaft key) is positioned inside these slots. There are no particular restrictions on the shape of the shaft key k1; for example, a square key, flat key, dowel key, tapered key, etc., may be used.

[0034] At the rear end of the drive nut 84 is a rear shaft 89 that extends toward the end bell 80E of the motor 80. The rear shaft 89 is coaxial with the central axis of the drive nut 84 and passes through the drive nut 84 to connect to the drive shaft 86 described later. In this example, the rear shaft 89 is inserted into a sleeve 85 having a flange portion 85f, and the sleeve 85 is inserted into a bearing 95 (e.g., a ball bearing) and a thrust bearing 97 (e.g., a thrust ball bearing) fixed to the end bell 80E, thereby integrally supporting the drive nut 84 and rotor 80R within the stator 80S so that they can rotate freely.

[0035] The drive nut 84 has a bottomed hole 84h at its front end. The hole 84h opens towards the second cylinder 12 and extends along the central axis of the cylindrical shape of the rotor 80R. As will be described later, screw threads are formed on the inner circumferential surface that defines the hole 84h. In other words, in this embodiment, the drive nut 84 is a member with internal threads formed on it.

[0036] Figure 5 schematically shows a vertical cross-section of the screw drive device 18. As shown in Figure 5, the inner circumferential surface of the hole 84h has screw threads 84t. The screw threads 84t may have a trapezoidal screw shape.

[0037] In a typical embodiment of the present invention, the screw thread 84t may be a reverse thread. In other words, in a typical embodiment of the present invention, the drive nut 84 is a left-hand thread nut (also called a reverse thread nut). Of course, it is also possible to use a right-hand thread nut as the drive nut 84. As will be described later, whether the drive nut 84 is a left-hand thread nut or a right-hand thread nut should be determined in relation to the control of switching the rotation direction of the rotor 80R. In the following explanation, we will continue assuming that the screw thread 84t is a left-hand thread.

[0038] As shown in Figure 5, a drive shaft 86 extending axially from the screw 12S is inserted into the hole 84h of the drive nut 84. A screw thread 86t is provided on a portion of the outer surface of the drive shaft 86 near the rear end (opposite side from the second cylinder 12), and the drive shaft 86 is coupled to the drive nut 84 by the engagement (meshing) of the screw thread 86t with the screw thread 84t of the drive nut 84. Here, corresponding to the fact that the drive nut 84 is a left-hand thread nut, the screw thread 86t on the outer surface of the drive shaft 86 is also a left-hand thread (so-called reverse thread). Both the screw thread 86t of the drive shaft 86 and the screw thread 84t of the drive nut 84 can be so-called trapezoidal reverse threads.

[0039] On the other hand, the front end of the drive shaft 86 is connected to the screw 12S. In the example shown in Figure 5, a hole 86h is provided at the front end of the drive shaft 86, and the rear end of the screw 12S is inserted into this hole 86h, thereby connecting the screw 12S to the drive shaft 86. The central axis of the drive shaft 86 coincides with the rotation axis of the screw 12S and the central axis of the drive nut 84.

[0040] Screw 12S is connected to drive shaft 86 by a spline joint. That is, the rotation of drive shaft 86 is transmitted to screw 12S via the spline, and screw 12S rotates together with drive shaft 86 at the same rotational speed.

[0041] As will be explained in detail later with reference to the drawings, one of the roles of the drive shaft 86 is to transmit the rotation of the drive nut 84, which rotates together with the rotor 80R, to the screw 12S in the process of plasticizing and weighing thermoplastic molding material, or the process of mixing and weighing thermosetting molding material. The connection of the screw 12S to the drive shaft 86 can be achieved by means such that no relative rotation occurs between them, and is not limited to a spline connection.

[0042] As can be seen from Figure 5, the drive shaft 86 passes through the front bracket 80F of the motor 80. Figures 6 and 7 show the front bracket 80F and its surroundings in detail. As shown in Figures 6 and 7, the front bracket 80F is a member with a through hole 80t in the center, and here a clutch housing 88, which also has a through hole 88t in the center, is positioned inside the through hole 80t of the front bracket 80F (see also Figure 5).

[0043] A bearing 93 can be fitted into the through-hole 88t of the clutch housing 88 to support the area near the front end of the drive shaft 86. A ball bearing can be used for the bearing 93, similar to the bearing 95 described above.

[0044] As shown in Figure 5, a one-way clutch 92 is installed inside the through-hole 88t of the clutch housing 88 in addition to the bearing 93. As shown in the exploded view in Figure 7, the one-way clutch 92 has an outer ring 92S, a retainer 92M that holds rollers, sprags, etc., and an inner ring 92T. The inner ring 92T of the one-way clutch 92 is fixed to the outer circumferential surface of the drive shaft 86 and rotates together with the drive shaft 86. On the other hand, the outer circumferential surface of the outer ring 92S of the one-way clutch 92 is fixed to the inner circumferential surface that defines the through-hole 88t of the clutch housing 88, thereby restricting its relative rotation with respect to the clutch housing 88.

[0045] In this embodiment, the clutch housing 88 is coupled to the front bracket 80F in such a way that it is movable in the axial direction of the screw 12S and its relative rotation to the front bracket 80F is restricted. In the example shown in Figures 4 to 7, the clutch housing 88 is attached to the front bracket 80F via a shaft key k2 (second shaft key) in such a way that it allows axial movement of the screw 12S. More specifically, the shaft key k2 is positioned between a key seat 8s provided on the clutch housing 88 and a keyway Fw provided on the front bracket 80F (see Figure 6). As the shaft key k2, any shape of key can be applied as long as it allows axial movement of the clutch housing 88 of the screw 12S.

[0046] As described above, since the front bracket 80F is fixed to the housing 80H of the motor 80, and the rotation of the clutch housing 88 relative to the front bracket 80F is restricted, the outer ring 92S of the one-way clutch 92 does not rotate relative to the housing 80H of the motor 80. In other words, in the embodiment of the present invention, the relative rotation of the outer ring 92S of the one-way clutch 92 with respect to the stator 80S of the motor 80 is restricted.

[0047] On the other hand, the inner ring 92T of the one-way clutch 92 is fixed to the drive shaft 86 that passes through the inner ring 92T. As a result, the rotation direction of the drive shaft 86 is basically restricted to one direction by the one-way clutch 92, which has an outer ring 92S fixed to the clutch housing 88. In this embodiment of the present invention, the direction in which the one-way clutch 92 allows the rotation of the inner ring 92T (first direction) is the direction in which the threads 86t of the drive shaft 86 tighten when the rotor 80R and drive nut 84 of the motor 80 are rotated in that direction. That is, when viewed axially from the screw drive device 18 toward the second cylinder 12, counterclockwise rotation of the drive shaft 86 (shown by the solid arrow r1 in Figures 6 and 7) is permitted. In contrast, clockwise rotation of the drive shaft 86 (second direction of rotation opposite to the first direction) when viewed axially from the screw drive device 18 toward the second cylinder 12 is blocked by the one-way clutch 92. In this specification, the direction of rotation around the axial direction is expressed with reference to the view from the screw drive device 18 toward the second cylinder 12 in the axial direction of the screw 12S.

[0048] <2. Operation of the screw drive device 18> Next, the operation of the screw drive unit 18 will be described. As is well known, in injection molding using an injection device that has two independent cylinders, one cylinder having a screw inside and the other cylinder having an injection shaft, the following steps are generally performed during one molding shot. 1. A process of plasticizing and weighing the input molding material (or a process of mixing and weighing the liquid main agent, hardener, etc. that constitute the liquid molding material). 2. The process of closing the connecting passage with the screw tip (backflow prevention process) 3. The process of driving the injection shaft to inject the molding material from the injection cylinder into the mold cavity.

[0049] (Process for plasticizing and weighing the molding material: Rotation of rotor 80R in the first direction) Figure 8 schematically shows the arrangement of the parts of the screw drive device 18 before the start of the process of plasticizing the molding material (e.g., pellets of thermoplastic resin). As schematically shown in Figure 8, before the start of the plasticization process, a gap Gp of a certain size is formed between the bottom surface of the hole 84h of the drive nut 84 and the rear end surface of the drive shaft 86 inserted into the hole 84h. The size of the gap Gp, that is, the distance in the axial direction between the bottom surface of the hole 84h and the rear end surface of the drive shaft 86, is, for example, in the range of 0.5 mm to 5.0 mm, preferably in the range of 1.0 mm to 2.0 mm.

[0050] In the plasticization process, the control device 30 (see Figure 1) sends a drive signal to the screw drive device 18 so that the rotation direction of the screw 12S is the first direction described above. The screw drive device 18 receives the drive signal from the control device 30 and rotates the rotor 80R of the motor 80 in the first direction. At this time, the drive of the rotor 80R is transmitted from the drive nut 84, which is coupled to the rotor 80R by the shaft key k1, to the drive shaft 86 via the screw threads 86t.

[0051] As explained with reference to Figures 5 to 7, the first direction is the direction in which the threads 86t of the drive shaft 86 tighten when the drive nut 84 is rotated in that direction together with the rotor 80R of the motor 80. Therefore, when the drive nut 84 rotates in the first direction as the rotor 80R rotates, since the drive nut 84 is a left-hand thread nut, the engagement of threads 84t and 86t causes a force to act on the drive shaft 86 toward the right in the figure. That is, although the drive nut 84 may spin freely relative to the drive shaft 86 at the beginning of the rotor 80R's rotation, the drive shaft 86 is soon pulled into the hole 84h of the drive nut 84, and the drive shaft 86 moves toward the right in the figure.

[0052] As explained here with reference to Figures 6 and 7, the one-way clutch 92 allows the inner ring 92T, which is fixed near the front end of the drive shaft 86, to rotate in a first direction. Furthermore, the clutch housing 88 that holds the one-way clutch 92 is attached to the front bracket 80F by coupling via a shaft key k2. In other words, the outer ring 92S of the one-way clutch 92 is movable in the axial direction of the screw 12S, as is the clutch housing 88. Therefore, as the drive shaft 86 moves, the one-way clutch 92, along with the clutch housing 88, moves toward the right in the figure.

[0053] When the reverse threads of the drive nut 84 and drive shaft 86 are fully tightened, the movement of the drive shaft 86 to the right in the figure stops, and the arrangement of the drive shaft 86, one-way clutch 92, and clutch housing 88 becomes the same as shown in Figure 5 above. When the reverse threads are fully tightened and the movement of these components in the axial direction stops, the rotation of the rotor 80R and drive nut 84 in the first direction is directly transmitted to the drive shaft 86. That is, the drive shaft 86 rotates in the first direction at a rotational speed that matches that of the rotor 80R and drive nut 84. Note that at this time, the rear end face of the drive shaft 86 does not need to be in contact with the bottom surface of the hole 84h. It is also possible that the size of the gap Gp is ​​not zero.

[0054] As described above, the rotation of the drive shaft 86 in the first direction is free and not restricted by the one-way clutch 92. Since the screw 12S is coaxially spline-connected to the front end of the drive shaft 86, the screw 12S rotates with the drive shaft 86 in the first direction with a predetermined torque. Due to the rotation of the screw 12S in the first direction, the molding material fed from the hopper 12P is plasticized by being heated by the heater 12H (see Figure 3) while receiving a shear force from the screw 12S, and is then sent toward the front end of the second cylinder 12.

[0055] Furthermore, once the screw 12S begins to rotate, the reaction force from the resin causes the screw 12S to experience a force directed to the right in the diagram. Therefore, the movement of the drive shaft 86 from the start of axial movement to its cessation can occur in a relatively short period of time. In addition, during the period until the movement of the drive shaft 86 along the axial direction comes to a complete halt, the movement of the drive shaft 86 may be accompanied by a slower rotation in the first direction.

[0056] As the screw 12S rotates in the first direction, the plasticized molding material is sent from the second cylinder 12 to the first cylinder 11 via the communication passage 142 inside the nozzle cylinder 14 and the junction 14Bb (see Figure 3). The control device 30 detects the completion of metering of the molding material by retracting the injection shaft 11A (in this case, the injection plunger) inside the first cylinder 11 by a predetermined amount, or by time control.

[0057] (Process of closing the communication passage 142 (backflow prevention operation): Switching the rotation direction of the rotor 80R) When the control device 30 detects that the metering of the molding material is complete, it causes the injection device 10 to start a backflow prevention operation. In this embodiment, the control device 30 sends a drive signal to the screw drive device 18, which reverses the rotation direction of the rotor 80R from the first direction to the second direction.

[0058] Refer to Figure 5. When the motor 80 reverses the rotation direction of the rotor 80R, the drive shaft 86 (and the screw 12S connected to the drive shaft 86), which was rotating integrally with the drive nut 84 due to the engagement of the reverse threads, also attempts to rotate in the second direction. However, the rotation of the drive shaft 86 in the second direction is prevented by the one-way clutch 92, to which the inner ring 92T is fixed. In other words, with the rotation of the drive shaft 86 stopped, the rotor 80R and the drive nut 84 rotate integrally in the second direction.

[0059] Here, since the first direction is the direction in which the threads 86t of the drive shaft 86 tighten when the drive nut 84 is rotated in that direction, when the drive nut 84 rotates in the second direction together with the rotor 80R, the threads 86t of the drive shaft 86 begin to loosen. This means that a force acts on the drive nut 84 and the drive shaft 86 in a direction that causes them to move away from each other in the axial direction.

[0060] However, in this case, the sleeve 85 having a flange portion 85f is located at the rear end of the drive nut 84, and the flange portion 85f of the sleeve 85 faces the housing raceway plate 97h of the thrust bearing 97. As shown in Figure 5, the thrust bearing 97 restricts the rearward movement of the screw drive device 18 by contacting the end bell 80E (in particular the second member 80Eb in this case), and together with the end bell 80E, it functions as a restricting member that restricts the rearward movement of the drive nut 84 on which the sleeve 85 is mounted.

[0061] In other words, when the threads 86t of the drive shaft 86 begin to loosen, the drive shaft 86 and the drive nut 84 begin to move away from each other, and the flange portion 85f comes into contact with the surface 97f (contact surface) of the housing raceway plate 97h. That is, the housing raceway plate 97h of the thrust bearing 97 receives the rear end of the drive nut 84 via the flange portion 85f of the sleeve 85, and the movement of the drive nut 84 toward the end bell 80E is prevented by the thrust bearing 97 supported by the end bell 80E.

[0062] As a result, the drive shaft 86 and the screw 12S connected to the drive shaft 86 are subjected to a force directed to the left in the figure and move along the axial direction. As can be understood from the above explanation, the clutch housing 88 that holds the one-way clutch 92 is coupled to the front bracket 80F via the shaft key k2, so that the one-way clutch 92 is axially slidable as the clutch housing 88. That is, the screw 12S, drive shaft 86, one-way clutch 92 and clutch housing 88 are pushed out together from the drive nut 84 toward the front (to the left in this case) by the rotation of the drive nut 84 toward the second direction.

[0063] Thus, as the drive nut 84 begins to rotate in the second direction, the torque applied to the drive nut 84 is converted into an axial force by the threads 84t, causing the drive shaft 86 and screw 12S to move toward the left side of the figure (in other words, toward the front end of the second cylinder 12). Along with the drive shaft 86, the screw 12S, one-way clutch 92, bearing 93, and clutch housing 88 move forward as a single unit, returning the arrangement of these components from the state shown in Figure 5 to the state shown in Figure 8. As the screw 12S moves forward together with the drive shaft 86, the tip of the screw 12S is pressed against the entrance of the communication passage 142, and the communication passage 142 is closed by the tip of the screw 12S.

[0064] (Process of injecting molding material into the cavity: Rotor 80R stops) Once the closure of the communication passage 142 is complete, the control device 30 activates the injection drive unit 11D of the injection device 10 to push the injection plunger, which serves as the injection shaft 11A, forward, thereby injecting the metered molding material into the mold cavity via the flow path 141 (see Figure 3). The completion of the closure of the communication passage 142 can be detected, for example, by monitoring the load on the motor 80 through changes in the current value. By detecting the completion of the closure of the communication passage 142 and reducing the rotation speed of the rotor 80R or stopping the rotation of the rotor 80R, problems such as damage to components caused by excessive pressure from the screw 12S can be avoided. Furthermore, in the configuration illustrated in Figures 5 and 8, since the rear end of the rear shaft 89 is exposed from the second member 80Eb of the end bell 80E, the rotation and forward / backward movement of the screw 12S connected via the drive shaft 86 can be visually grasped by observing the rear end of the rear shaft 89.

[0065] The process of injecting molding material into a cavity is generally called the injection process. The injection process includes at least a filling process. The filling process is the process of moving the injection plunger forward to fill the empty cavity with molding material. In many cases, the injection process further includes a holding pressure process. The holding pressure process is the process of applying a predetermined holding pressure to the molding material in the mold by pushing the injection plunger forward, continuing from the filling process, until the portion of the molding material inside the mold gate solidifies or hardens. The purpose of performing the holding pressure process is to prevent backflow of the molding material filled in the product-related parts of the mold space (parts other than the gate, runner, etc.) to the injection device 10 side, and to replenish the aforementioned parts of the mold space with molding material to compensate for shrinkage in the initial stages of solidification or hardening. The blocking of the communication passage 142 by the tip of the screw 12S is also effective in preventing backflow of the molding material into the second cylinder 12 during the holding pressure process.

[0066] The blockage of the communication passage 142 by the screw 12S continues for at least the duration of the discharge of the molding material from the injection nozzle 16. The duration of the discharge of the molding material from the injection nozzle 16 is, for example, the duration of the injection process described above. During this time, the control device 30 may control the drive of the motor 80 so as to continuously apply a constant torque to the rotor 80R. The motor 80 may also have a brake mechanism to temporarily restrict the rotation of the rotor 80R. The control device 30 may perform control such as activating the brake mechanism during the discharge of the molding material so that the rotor 80R does not rotate. After that, the control device 30 waits for the molding material to cool and then activates the clamping device 20 to discharge the molded product from the mold.

[0067] The process described above completes one shot of molding. Subsequently, by switching the rotation direction of the rotor 80R back to the first direction and operating the motor 80, the screw 12S can be retracted, utilizing the reaction force from the resin generated during plasticization. The retraction of the screw 12S also releases the blockage of the communication passage 142 by the tip of the screw 12S.

[0068] As described above, in the embodiment of the present invention, the rotor 80R of the motor 80 is rotated in the first direction, thereby rotating the screw 12S in the first direction and sending the molding material in the second cylinder 12 to the first cylinder 11 via the communication passage 142. Furthermore, after the transfer of the molding material to the first cylinder 11, the operation of the motor 80 is controlled to rotate the rotor 80R in the second direction opposite to the first direction. By switching to rotation in the second direction, the screw 12S is advanced along the axial direction through the cooperation of the action of the reverse thread formed on the drive nut 84 and the drive shaft 86 and the rotation restricting action of the one-way clutch 92, and the communication passage 142 is closed at the tip of the screw 12S. According to the embodiment of the present invention, even with a simpler configuration, it is possible to switch between rotation and forward / backward movement of the screw 12S with relatively simple control, namely switching the rotation direction of the motor 80.

[0069] According to a typical embodiment of the present invention, the rotation of the rotor 80R is converted into the forward motion of the screw 12S via the meshing of the screw threads, so that the tip of the screw 12S can be pressed against the entrance of the communication passage 142 with sufficient force, and backflow of the plasticized molding material from the first cylinder 11 to the second cylinder 12 can be strongly suppressed. In a typical embodiment, the rotational speed of the screw 12S may be arbitrarily set in the range of 0 to 400 rpm, and the ratio of the rotational speed of the rotor 80R and drive nut 84 when rotating in the second direction to the rotational speed of the rotor 80R and drive nut 84 when rotating in the first direction may be in the range of 0.3 to 15. As an example, the rotational speed of the rotor 80R and drive nut 84 when rotating in the second direction may be set to about 120 rpm if the lead of the screw thread 86t of the drive shaft 86 is 3 mm, and the operation of advancing the screw 12S 1.5 mm along the axial direction to close the communication passage 142 with the tip of the screw 12S is to be performed in 0.25 seconds.

[0070] In this embodiment of the present invention, a high-torque electric direct-drive motor is applied to the motor 80, and by taking advantage of the space created around the rotation axis due to the hollow motor, the configuration for switching the operation of the screw 12S is basically housed within this space. According to this embodiment of the present invention, the operation of the screw 12S does not require a configuration of multiple motors, multiple one-way clutches, or a hydraulic system, which is advantageous for miniaturizing the injection device 10. In particular, with respect to the axial direction of the screw 12S, it is possible to reduce the size of the screw drive device 18 compared to conventional designs.

[0071] In this embodiment of the present invention, the use of an electric direct-drive motor eliminates the need for a hydraulic system to drive the screw 12S of the second cylinder 12. By essentially eliminating the need for a hydraulic system, problems such as deterioration of the packing inside the hydraulic cylinder due to heat transfer from the second cylinder 12 (particularly from the hopper 12P) can be avoided, and for example, there is no concern about oil leakage caused by packing deterioration. Furthermore, it becomes possible to raise the upper limit of the set temperature of the cooling device inside the hopper 12P, and improvements in plasticization efficiency and energy saving effects due to reduced heat transfer loss can be expected.

[0072] Furthermore, since the process transition essentially only requires a change in the rotation direction of the rotor 80R and does not require the incorporation of a reduction gear, the time required for operation changeover is short, and power transmission losses and noise are reduced. By using trapezoidal screws and shaft keys for joining the components, it is also possible to avoid localized stress concentration associated with power transmission.

[0073] <3. Improvement of maintainability of injection device 10> In a typical embodiment of the present invention, a hydraulic system is not required for the operation of the screw 12S, and the mechanical configuration is not complex. Therefore, maintenance of each part, such as access to the inside of the motor 80 housing 80H, is easier compared to conventional designs. This point will be explained below.

[0074] Figure 9 shows the screw drive unit 18 disassembled. As shown in Figure 9, the screw drive unit 18 can be disassembled into three units, for example, an outer unit 18X, an inner unit 18Y, and an end unit 18Z.

[0075] As explained with reference to Figure 4, the end bell 80E of the motor 80 can be fixed to the housing 80H, for example, by screw fastening. Therefore, the end bell 80E can be separated from the rear end 80r of the housing 80H by loosening the screw inserted into the screw hole of the end bell 80E. At this time, the sleeve 85 may also be separated together with the end bell 80E from the rear shaft 89 extending from the rear end of the drive nut 84.

[0076] Next, by pulling out shaft keys k1 and k2, the connection of the drive nut 84 to the rotor 80R and the connection of the clutch housing 88 to the front bracket 80F can be released, respectively. Furthermore, by separating the drive shaft 86 from screw 12S, the set of clutch housing 88, bearing 93, one-way clutch 92, drive shaft 86, drive nut 84, and rear shaft 89 can be pulled out as an integral part of the inner unit 18Y from the rotor 80R of the motor 80. By keeping the diameter of the clutch housing 88 less than or equal to the diameter of the drive nut 84, the inner unit 18Y can be removed as an integral part from inside the motor 80.

[0077] Removing the inner unit 18Y allows access to the inside of the motor 80 from the rear end 80r side of the housing 80H. In this example, since the screw 12S is easily accessible by removing the inner unit 18Y, it is also relatively easy to remove the screw 12S from the second cylinder 12.

[0078] (Adjustment of the stroke width of screw 12S in the backflow prevention operation) As described above, here the drive nut 84 is coupled to the rotor 80R of the motor 80 via the shaft key k1. The drive nut 84 may be made movable along the axial direction of the screw 12S by being coupled to the rotor 80R via the shaft key k1. However, unlike the clutch housing 88, it is not essential for embodiments of the present invention that the drive nut 84 be movable relative to the rotor 80R along the axial direction of the screw 12S during the operation of the injection device 10.

[0079] The position of the drive nut 84 inside the rotor 80R in the axial direction determines the amount of movement of the screw 12S along the axial direction (the stroke of the screw 12S). The magnitude of this stroke is the distance the screw 12S moves between the state in which the drive shaft 86 is most retracted into the hole 84h of the drive nut 84 due to the rotation of the rotor 80R in the first direction, and the state in which the tip of the screw 12S abuts against the entrance of the communication passage 142. Typical examples of the stroke magnitude are in the range of 0.5 mm to 5.0 mm, more preferably in the range of 1.0 mm to 2.0 mm (approximately 1.5 mm in this embodiment).

[0080] During the operation of the injection device 10, a force acts on the drive nut 84, basically toward the end bell 80E, regardless of the rotation direction of the rotor 80R. Therefore, by adjusting the limit of the retractable position of the drive nut 84 in the axial direction, the limit of how far the screw 12S can be retracted can be determined. In other words, the stroke of the screw 12S can be adjusted by adjusting the position of the rear end of the drive nut 84.

[0081] As can be seen, for example, from a comparison of Figure 8 and Figure 5, how close the drive nut 84 can be to the end bell 80E inside the rotor 80R depends on the position of the thrust bearing 97 in the axial direction. Disassembled end unit 18Z as shown in Figure 10, the end bell 80E here includes two parts: an annular first member 80Ea fixed to the housing 80H, and a second member 80Eb having a cylindrical portion 80bc inserted into the center of the first member 80Ea. The thrust bearing 97 is restricted from moving further toward the rear end side (right side in Figure 10) of the injection device 10 by the contact of the axial raceway plate 97s of the thrust bearing 97 with the cylindrical portion 80bc of the second member 80Eb.

[0082] As clearly shown in Figure 10, in the configuration illustrated in Figures 9 and 10, the second member 80Eb is composed of two members: the cylindrical portion 80bc and the plate-shaped portion 80bp that covers the opening of the first member 80Ea. Here, screw threads are formed on the outer circumferential surface of the cylindrical portion 80bc and on the inner circumferential surface that defines the opening of the first member 80Ea, and the cylindrical portion 80bc is attached to the first member 80Ea by connection via these screw threads. Therefore, the depth of insertion of the cylindrical portion 80bc into the opening of the first member 80Ea can be adjusted by rotating the cylindrical portion 80bc around its axial direction. For example, by making the insertion of the cylindrical portion 80bc shallower, the position of the cylindrical portion 80bc relative to the rear end of the housing 80H can be made further rearward.

[0083] On the other hand, the plate-shaped portion 80bp is located behind the cylindrical portion 80bc and may have a larger diameter than the cylindrical portion 80bc. After adjusting the insertion depth of the cylindrical portion 80bc into the opening of the first member 80Ea, the plate-shaped portion 80bp is fixed to the first member 80Ea by bolt Saj, as shown in the example in Figure 9. In this state, the rear end surface of the cylindrical portion 80bc is in contact with the plate-shaped portion 80bp, and therefore, the rotation of the cylindrical portion 80bc into the opening of the first member 80Ea is restricted by the frictional force between the rear end surface of the cylindrical portion 80bc and the surface of the plate-shaped portion 80bp. In other words, the plate-shaped portion 80bp fixed to the first member 80Ea functions to restrict the forward and backward movement of the cylindrical portion 80bc after the insertion depth has been adjusted. Thus, in this embodiment, the axial position of the cylindrical portion 80bc relative to the rear end of the housing 80H is adjustable. As will be described later, the plate-shaped portion 80bp can also be used as a tool to rotate the cylindrical portion 80bc when attaching the cylindrical portion 80bc to the opening of the first member 80Ea.

[0084] By positioning the cylindrical portion 80bc of the second member 80Eb further rearward, for example, the position of the thrust bearing 97 in contact with the cylindrical portion 80bc is also moved further rearward. As the thrust bearing 97 is retracted, the position of the surface 97f of the housing raceway plate 97h in contact with the flange portion 85f of the sleeve 85 is moved further rearward, and as a result, the limit of the retraction of the drive nut 84 is also shifted further rearward. Thus, in this embodiment, the thrust bearing 97, as a regulating member, is designed to allow adjustment of the position of its contact surface in the axial direction relative to the rear end of the housing 80H.

[0085] By making the axial position of the contact surface of the thrust bearing 97 adjustable, the stroke of the screw 12S in the forward and backward movement during one shot cycle can be adjusted retrospectively. The lengths of the shaft key k1, key seat 4s, and keyway Rw (see, for example, Figure 4) can be appropriately determined within a range that ensures the required stroke. The length of the keyway Rw along the axial direction may be in a range of, for example, 1.0 to 2.0 times the length of the shaft key k1, preferably 1.2 to 1.8 times. The drive nut 84 may be movable in the axial direction of the screw 12S with respect to the rotor 80R over a range greater than the stroke of the screw 12S.

[0086] (Attachment of the cylindrical portion 80bc to the opening of the first member 80Ea) When attaching the cylindrical portion 80bc to the opening of the first member 80Ea, and when adjusting the insertion depth of the cylindrical portion 80bc, the bolt Saj for connecting the plate-shaped portion 80bp to the first member 80Ea is removed from these members, as schematically shown in Figure 10. At this time, the plate-shaped portion 80bp can be temporarily fixed to the cylindrical portion 80bc by the bolt Sab, as illustrated in Figure 10. By connecting the cylindrical portion 80bc to the plate-shaped portion 80bp with the bolt Sab, it becomes possible to rotate the cylindrical portion 80bc together with the plate-shaped portion 80bp. This facilitates the rotation of the cylindrical portion 80bc relative to the opening of the first member 80Ea.

[0087] As shown in Figure 4, at least one bolt hole Bh may be formed on the outer circumferential surface of the plate-shaped portion 80bp. By providing a bolt hole Bh on the outer circumferential surface of the plate-shaped portion 80bp, a bolt can be attached to the bolt hole Bh and used as a handle to rotate the plate-shaped portion 80bp when adjusting the insertion depth of the cylindrical portion 80bc, making it easier to rotate the cylindrical portion 80bc using the plate-shaped portion 80bp.

[0088] After adjusting the insertion depth of the cylindrical portion 80bc, the bolt Sab is removed from the cylindrical portion 80bc, and as shown in Figure 9, the plate-shaped portion 80bp is pressed against the cylindrical portion 80bc and fixed to the first member 80Ea with the bolt Saj. This restricts further rotation of the cylindrical portion 80bc relative to the first member 80Ea. Alternatively, the plate-shaped portion 80bp may be fixed to the first member 80Ea with the bolt Saj while the cylindrical portion 80bc and the plate-shaped portion 80bp are connected with the bolt Sab. However, the configuration in which the connection between the cylindrical portion 80bc and the plate-shaped portion 80bp by the bolt Sab is released after adjusting the insertion depth of the cylindrical portion 80bc and then fixed to the first member 80Ea with the bolt Saj has the advantage of easily allowing fine adjustment of the rotation of the cylindrical portion 80bc.

[0089] It is certainly possible to adopt a configuration different from that of this embodiment for adjusting the position of the cylindrical portion 80bc in the axial direction and for fixing the cylindrical portion 80bc in the adjusted position. For example, a suitable spacer may be interposed between the plate-shaped portion 80bp and the first member 80Ea.

[0090] Although various embodiments of the present invention have been described above, these are presented as examples and are not intended to limit the scope of the invention. The novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. For example, in the embodiments described above, threads 84t and 86t are left-hand threads, but they may also be right-hand threads. In that case, the direction in which the one-way clutch 92 allows the rotation of the inner ring 92T should be reversed from the direction in the embodiments described above. [Explanation of Symbols]

[0091] 1: Injection molding machine 4s, 8s: Key sheet 10: Injection device 11: First cylinder 11A: Injection axis 11D: Injection drive unit 11H: Heater 12: Second cylinder 12H: Heater 12P: Hopper 12S: Screw 14: Nozzle Cylinder 14Bb: Junction 14H: Heater 16: Injection nozzle 16H: Heater 18: Screw drive mechanism 18X: Outer Unit 18Y: Inner Unit 18Z: End Unit 20: Mold clamping device 30: Control device 80: Motor 80E: Endbell 80Ea: First member 80Eb: Second member 80F: Front Bracket 80H: Housing 80R: Rotor 80S: Stator 80bc: Cylindrical part 80bp: Plate-like portion 80r: rear end 80t: Through hole 84: Drive Nut 84h: Hole 84t: Screw thread 85: Sleeves 85f: Flange section 86: Drive shaft 86h: Hole 86t: Screw thread 88: Clutch Housing 88t: Through hole 89: Rear shaft 92: One-way clutch 92M: Retainer 92S: Outer ring 92T: Inner wheel 93, 95: Bearings 97: Thrust bearing 97f: Surface 97h: Housing track board 97s: Shaft washer 141: Flow channel 142:Communication path Bh: Bolt hole Fw: Keyway Gp: Gap Rw: Keyway Sab: Bolt Saj: Bolt k1: Shaft key k2: Shaft key

Claims

1. An injection device comprising a first cylinder having an injection shaft and a second cylinder connected to the first cylinder via a communication passage, The screw housed inside the second cylinder, A drive shaft having screw threads on its outer surface, An electric motor having a stator and a rotor, A one-way clutch having an outer ring and an inner ring, Equipped with, The outer ring of the one-way clutch is movable in the axial direction of the screw and its relative rotation with respect to the stator is restricted. The inner ring of the one-way clutch is fixed to the drive shaft. The drive shaft is connected to the rear end of the screw coaxially with the screw, The drive of the rotor is transmitted to the drive shaft via the screw threads, An injection device in which the first direction in which the one-way clutch allows the rotation of the inner ring is the direction in which the screw threads tighten when the rotor is rotated in the first direction.

2. An injection device according to claim 1, An injection device in which the electric motor is controlled to rotate the rotor in the first direction, thereby rotating the screw in the first direction to send the molding material in the second cylinder to the first cylinder via the communication passage, and then to rotate the rotor in the second direction opposite to the first direction, thereby advancing the screw along the axial direction, so that the tip of the screw closes the communication passage.

3. An injection device according to claim 1 or claim 2, An injection device wherein the screw threads provided on the drive shaft are reverse threads.

4. An injection device according to claim 1 or claim 2, First shaft key and A drive nut with an internal thread formed on it, Furthermore, The rotor of the electric motor has a hollow cylindrical shape, The drive nut is coupled to the inside of the cylindrical shape of the rotor, with its relative rotation to the rotor restricted by the first shaft key. An injection device in which the threads of the drive shaft engage with the internal threads of the drive nut.

5. The injection device according to claim 4, The second shaft key, A clutch housing fixed to the outer circumferential surface of the outer ring of the one-way clutch, Furthermore, The aforementioned electric motor is A housing that accommodates the stator and the rotor, A front bracket having a through hole, It has, The front bracket is located between the housing and the second cylinder. The clutch housing is coupled to the inside of the through hole by the second shaft key, allowing the screw to move axially and restricting its relative rotation with respect to the front bracket.

6. The injection device according to claim 5, An injection device in which the diameter of the clutch housing is less than or equal to the diameter of the drive nut.

7. The injection device according to claim 6, The electric motor further has an end bell connected to the rear end of the housing, The end bell includes a regulating member having a contact surface, The regulating member is configured to adjust the position of the contact surface of the screw in the axial direction relative to the rear end of the housing. An injection device in which the drive nut is coupled to the rotor by the first shaft key so as to be movable in the axial direction of the screw.

8. An injection device according to claim 1 or claim 2, The first cylinder is an injection cylinder, The injection shaft is an injection plunger, The second cylinder is a plasticizing cylinder, The screw is a plasticizing screw in the injection device.

9. An injection device according to claim 1 or claim 2, The first cylinder is an injection cylinder, The injection shaft is an injection plunger, The aforementioned two cylinders are mixing cylinders, The aforementioned screw is a mixing screw, and the device is an injection mechanism.

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