Injection device

Abstract

An injection device 1 according to the present invention injects a molding material, the injection device comprising: a screw 13 which is rotationally driven around a rotary shaft 12 and is driven forward / backward in the axial direction; an injection motor 21 which is the forward / backward drive source of the screw 13; a motion conversion mechanism 41 which includes a screw shaft 42 that rotates together with the rotational motion of the injection motor 21, and a nut 43 inside which the screw shaft 42 is disposed, the motion conversion mechanism converting the rotational motion of the injection motor 21 into linear motion in the axial direction; a metering motor 31, which is the rotational drive source of the screw 13; a driving force transmission member 51 which is connected to the screw 13 and respectively transmits, to the screw 13, a rotational driving force that is based on the rotational motion of the metering motor 31, and a forward / backward driving force that is based on the linear motion of the screw shaft 42 of the motion conversion mechanism 41; and an axial force detection unit 61 which detects an axial-direction force acting on the screw 13 in the axial direction, wherein the axial force detection unit 61 has an annular axial force sensor 62 disposed so as to be capable of rotating relatively between the screw 13 and the driving force transmission member 51 around the rotary shaft 12 of the screw 13, and a rotation suppressing member 63 which suppresses rotation of the axial force sensor 62 which respect to the rotation of the screw 13 and the driving force transmission member 51.

Description

Technical Field

[0001] This invention relates to an injection device that injects a molding material using a screw, and particularly proposes a technique that contributes to improving the detection accuracy of the axial force acting on the screw.

Background Art

[0002] An injection device used in an injection molding machine mainly measures and injects a molding material such as a resin material using a screw that is rotationally driven by a metering motor and axially driven by an injection motor.

[0003] Generally, in metering, the rotation of the screw by the metering motor sends a predetermined amount of the molding material to the tip side of the cylinder while melting it. Also, in injection, the predetermined amount of the molding material sent to the tip side of the cylinder during metering is injected into the mold device by the forward movement of the screw by the injection motor. Thereafter, as a holding pressure, the screw may be further advanced by the injection motor to apply a required pressure to the molding material in the mold device.

[0004] The injection motor of the injection device outputs a rotational motion as a rotary motor. In order to convert this rotational motion into a linear motion in the axial direction of the screw, a motion conversion mechanism is used. For example, Patent Document 1 describes an injection device including a screw shaft that rotates by the rotational motion of an injection motor and a nut in which the screw shaft is disposed inside as such a motion conversion mechanism. Also, between the metering motor and the injection motor and the screw, a driving force transmission member for transmitting the rotational driving force from the metering motor and the axial forward and backward driving force transmitted through the motion conversion mechanism from the injection motor to the screw is disposed.

[0005] By the way, in an injection device, for example, during the above-mentioned holding pressure, an axial force sensor for detecting an axial force acting axially on the screw is provided as a reaction force or the like that the screw receives from the molding material.

[0006] An axial force sensor is desirable because it does not rotate with the screw, and the closer its mounting position is to the screw, the higher the accuracy of detecting axial force. However, as mentioned above, in this type of injection device, where the transmission path of driving force from the injection motor or metering motor to the screw is complex, it is not easy to mount the axial force sensor in a location near the screw that does not rotate.

[0007] In this regard, Patent Document 1 proposes an injection device having "a pressure detector disposed between the rotating shaft and the drive shaft," and having "a rotation limiting mechanism that limits the rotation of the pressure detector." [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2017-47576 [Overview of the project] [Problems that the invention aims to solve]

[0009] Patent Document 1 states that the "pressure detector" is "displaced between the rotating shaft and the drive shaft." This "pressure detector" has room for improvement in terms of further improving the accuracy of detecting axial force.

[0010] This invention aims to address these problems and its objective is to provide an injection device that can detect the axial force acting on the screw with relatively high accuracy. [Means for solving the problem]

[0011] An injection molding apparatus capable of solving the above problems is an injection molding apparatus for injecting a molding material, comprising: a screw that is rotationally driven around a rotating shaft and is driven to move back and forth in the axial direction; an injection motor that is the source of the screw's forward and backward movement; a motion conversion mechanism that includes a screw shaft that rotates together with the rotational motion of the injection motor and a nut on which the screw shaft is positioned to the inside, and converts the rotational motion of the injection motor into linear motion in the axial direction; a metering motor that is the source of the screw's rotational drive; a drive force transmission member connected to the screw that transmits rotational driving force based on the rotational motion of the metering motor and forward and backward movement driving force based on the linear motion of the screw shaft of the motion conversion mechanism to the screw, respectively; and an axial force detection unit that detects the axial force acting on the screw in the axial direction, wherein the axial force detection unit comprises an annular axial force sensor arranged to be rotatable relative to the screw and the drive force transmission member around the rotation shaft of the screw, and a rotation suppression member that suppresses the rotation of the axial force sensor with respect to the rotation of the screw and the drive force transmission member. [Effects of the Invention]

[0012] According to the injection device described above, the axial force acting on the screw can be detected with relatively high accuracy. [Brief explanation of the drawing]

[0013] [Figure 1] This is a cross-sectional view along the axial direction showing an injection device according to one embodiment of the present invention. [Figure 2] This is a cross-sectional view showing an enlarged view of the main part of the injection device in Figure 1. [Figure 3] This is a cross-sectional view showing the screw in the forward position of the injection device shown in Figure 2. [Figure 4] This is a cross-sectional view showing an injection device of another embodiment. [Figure 5] This is an enlarged cross-sectional view showing the connection point between the screw and the drive force transmission member of the injection device in Figure 1. [Figure 6] This is a cross-sectional view showing the connection point between the screw and the drive force transmission member in an injection device of another embodiment. [Figure 7]It is a cross-sectional view showing the procedure for taking out the axial force detection unit with the injection device of FIG. 1. [Figure 8] It is a cross-sectional view showing the procedure following FIG. 7. [Figure 9] It is a cross-sectional view showing the procedure following FIG. 8. [Figure 10] It is a cross-sectional view showing the procedure following FIG. 9.

Mode for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The injection device 1 illustrated in FIG. 1 is an injection molding machine, for example, disposed on a slide base 101 of a moving device that moves the injection device 1 forward and backward, and injects a molding material into a mold device. In this embodiment, the injection device 1 includes a screw 13 that is rotationally driven around a rotation shaft 12 inside a cylinder 11 and is driven to advance and retreat in the axial direction (the left - right direction in FIG. 1), an injection motor 21 as a source for driving the screw 13 to advance and retreat, and a metering motor 31 as a source for driving the screw 13 to rotate. The rotational driving force from the metering motor 31 and the advancing and retreating driving force from the injection motor 21 are respectively transmitted to the screw 13 via a driving force transmission path.

[0015] (Screw) The screw 13 has a rotation shaft 12 that extends into the cylinder 11 from the inside of the metering motor 31, and spiral flights are provided around a screw main body portion 13a that is mainly located inside the cylinder 11. Further, the screw tip portion 13b inside the cylinder 11 is formed to taper toward the front side in the axial direction, and the screw base end portion 13c is located inside the metering motor 31 and connected to the driving force transmission path.

[0016] Here, the direction along the rotation shaft 12 of the screw 13 is referred to as the axial direction, and this axial direction corresponds to the left - right direction in FIG. The screw tip portion 13b side (the left side in FIG. 1) in the axial direction of the screw 13 is defined as the front side, and the screw base end portion 13c side (the right side in FIG. 1) is defined as the rear side.

[0017] (Injection motor and metering motor) The injection motor 21 and the metering motor 31 can be supported and arranged on the rear side in the axial direction of the screw 13 on an injection motor support member 22 and a metering motor support member 32 provided upright on the slide base 101, respectively. The injection motor support member 22 and the metering motor support member 32 are interconnected at a plurality of locations around the metering motor 31 by rods 24, 25, etc., for example.

[0018] Both the injection motor 21 and the metering motor 31 output rotational motion as rotational motors, and each can include a rotor 21a, 31a as a rotor, a stator 21b, 31b as a stator including a coil disposed on the outer peripheral side of the rotors 21a, 31a, and a stator frame 21c, 31c to which the stators 21b, 31b are attached on the inner surface. Note that bearing portions 21d, 31d can be provided between the rotors 21a, 31a and the stator frames 21c, 31c. An encoder 25b that is connected to the rotor 21a by a shaft portion 25a and detects the rotation of the rotor 21a is provided on the rear end surface of the stator frame 21c of the injection motor 21.

[0019] The metering motor 31 is located on the front side of the injection motor 21 in the axial direction of the screw 13 and is provided such that the driving force transmission path passes through its inside.

[0020] (Driving force transmission path) In the injection device 1 of this embodiment, the driving force transmission path mainly includes a motion conversion mechanism 41 that converts the rotational motion of the injection motor 21 into linear motion in the axial direction of the screw 13, and a driving force transmission member 51 that is connected to the screw base end portion 13c of the screw 13 and transmits the rotational driving force based on the rotational motion of the metering motor 31 and the forward and backward driving force based on the linear motion converted by the motion conversion mechanism 41 to the screw 13, respectively.

[0021] Of these, the motion conversion mechanism 41 includes a screw shaft 42 that rotates together with the rotational motion of the injection motor 21, and a nut 43 on which the screw shaft 42 is positioned on the inside. In this example, the nut 43 is fixedly attached to a cylindrical body 22a that connects the stator frame 21c of the injection motor 21 and the injection motor support member 22.

[0022] The screw shaft 42 is spline-coupled, for example, at its base end 42a, to the inner surface of a cylindrical rotating member 23 provided on the inner circumference side of the rotor 21a of the injection motor 21. The rotational motion of the injection motor 21 causes it to rotate within the nut 43, allowing it to advance forward or retract in the axial direction. A key 42b is provided on the outer surface of the base end 42a of the screw shaft, and a corresponding keyway is provided on the inner surface of the cylindrical rotating member 23. This converts the rotational motion of the injection motor 21 into linear motion in the axial direction.

[0023] However, the motion conversion mechanism is not limited to the illustrated configuration in which the screw shaft 42 is spline-coupled to the cylindrical rotating member 23 on the injection motor 21 side, as long as it includes a screw shaft and a nut and can convert the rotational motion of the injection motor 21 into linear motion.

[0024] The driving force transmission member 51 can have a structure such as the one described below. In this embodiment, the driving force transmission member 51, which is located inside the metering motor 31, has, as shown in Figure 2, a cylindrical body portion 52 that surrounds the tip portion 42c of the screw shaft 42 that protrudes axially forward from the nut 43, and a front end wall portion 53 that covers the axially forward opening of the cylindrical body portion 52.

[0025] The tip portion 42c of the screw shaft can be connected to the axial rear side of the front end wall portion 53 of the drive force transmission member 51 via a bearing 54 such as a thrust self-aligning roller bearing or other thrust bearing. This allows the tip portion 42c of the screw shaft to rotate relative to the drive force transmission member 51. In this case, the inner ring of the bearing 54 is attached to the tip portion 42c of the screw shaft, and the outer ring of the bearing 54 is attached to the front end wall portion 53. Furthermore, a key 52a is provided on the outer circumferential surface of the cylindrical body portion 52 of the drive force transmission member 51, and when this is fitted into a key groove on the inner circumferential surface of the rotor 31a of the metering motor 31, the cylindrical body portion 52 and the rotor 31a are spline-coupled.

[0026] On the other hand, the screw 13 is connected at its screw base end 13c to the axially forward side of the front end wall portion 53 of the drive force transmission member 51.

[0027] If the drive force transmission member 51 has the structure described above, the drive force transmission member 51 rotates together with the rotational motion of the metering motor 31, and independently of that rotation, the drive force transmission member 51 can move linearly in accordance with the linear motion of the screw shaft 42 of the motion conversion mechanism 41. As a result, the rotational driving force based on the rotational motion of the metering motor 31 and the forward and backward driving force based on the linear motion of the screw shaft 42 of the motion conversion mechanism 41 are effectively transmitted to the screw 13 connected to the drive force transmission member 51.

[0028] (Axial force detection unit) Incidentally, when performing injection molding with an injection molding machine, the injection device 1 uses a metering motor 31 to rotate the screw 13, melting the molding material and sending it to the tip of the cylinder 11 for metering. Then, the injection motor 21 advances the screw 13, injecting the molding material from the tip of the cylinder 11 into the mold device. After that, the injection motor 21 further advances the screw 13, performing a holding pressure to apply a predetermined pressure to the molding material inside the mold device.

[0029] During such holding pressure operations, it is necessary to detect the axial force acting on the screw 13 in the axial direction. To detect the axial force acting on the screw 13, the injection device 1 is equipped with an axial force sensor.

[0030] The axial force sensor can also be installed at a location on the axial rear side of the drive force transmission path described above, for example, at a location such as the cylindrical body 22a between the injection motor 21 and the injection motor support member 22. However, in this case, the axial force is transmitted from the screw 13 to the axial force sensor via the drive force transmission member 51, which can be spline-coupled to the metering motor 31 side of the drive force transmission path, and is affected by sliding resistance between the metering motor 31 side and the drive force transmission member 51, reducing the accuracy of axial force detection. Alternatively, even if the axial force sensor is installed inside the drive force transmission member 51 between it and the tip of the screw shaft 42c, the axial force detected by the axial force sensor may include similar sliding resistance forces of the drive force transmission member 51, raising concerns that the desired accuracy may not be obtained. Therefore, it is desirable to install the axial force sensor in a position closer to the screw 13.

[0031] On the other hand, in the vicinity of the screw 13, the drive force transmission member 51, which receives rotational driving force from the metering motor 31, and the screw 13 rotate. If the axial force sensor also rotates along with this rotation, the accuracy of the axial force sensor's detection of axial force decreases.

[0032] Under these circumstances, in the illustrated embodiment, the axial force detection unit 61 for detecting an axial force acting axially on the screw 13 includes a load cell such as a washer or other annular axial force sensor 62 that is rotatably arranged relative to the screw 13 and the drive force transmission member 51 around the rotation axis 12 of the screw 13, and a rotation suppression member 63 that suppresses the rotation of the axial force sensor 62 in relation to the rotation of the screw 13 and the drive force transmission member 51.

[0033] In this configuration, the axial force sensor 62 is positioned axially forward of the drive force transmission member 51 and between it and the screw 13. Because it is close to the screw 13, it is virtually unaffected by the sliding resistance of the drive force transmission member 51 in the drive force transmission path when detecting the axial force from the screw 13. Furthermore, the rotation-suppressing member 63 prevents the axial force sensor 62 from rotating in relation to the rotation of the screw 13 and the drive force transmission member 51. As a result, the axial force sensor 62 can detect the axial force with high accuracy.

[0034] Here, the rotation suppression member 63 can be made capable of suppressing the rotation of the axial force sensor 62 by, for example, connecting the axial force sensor 62 to a member that does not rotate together with the screw 13 or the drive force transmission member 51. The rotation suppression member 63 illustrated in Figures 2 and 3 connects the axial force sensor 62 to the metering motor support member 32, thereby suppressing the rotation of the axial force sensor 62 that could be caused by the rotation of the screw 13 and the drive force transmission member 51.

[0035] More specifically, the metering motor support member 32 is provided with a slide hole 33 into which a rotation-restricting member 63 is inserted and positioned. The shape of the slide hole 33 for the rotation-restricting member 63 is appropriately determined in accordance with the shape of the rotation-restricting member 63 so that the rotation-restricting member 63 inserted therein can slide in the axial direction. The rotation-restricting member 63 can be, for example, a cylindrical shape such as a cylinder surrounding the rotation shaft 12 of the screw 13, as shown in the figure. Alternatively, although not shown in the figure, the rotation-restricting member 63 may be one or more rod-shaped or plate-shaped members extending in the axial direction on the outer circumference of the rotation shaft 12 of the screw 13, or multiple rod-shaped or plate-shaped members spaced apart from each other in the circumferential direction.

[0036] Regardless of the shape of the rotation-suppressing member 63 as described above, it is preferable that it be axially slidable within the slide hole 33 of the metering motor support member 32. This allows, for example, when a forward-moving driving force is transmitted from the injection motor 21 to the screw 13 via the driving force transmission member 51, the rotation-suppressing member 63 to slide within the slide hole 33, as shown in Figure 3, and move forward together with the axial force sensor 62 between the driving force transmission member 51 and the screw 13. When a backward-moving driving force is transmitted to the screw 13, the rotation-suppressing member 63 and the axial force sensor 62 move backward together with the driving force transmission member 51 and the screw 13, as shown in Figure 2. During such forward and backward movement, the slide hole 33 restricts the displacement of the rotation-suppressing member 63 inserted therein in the circumferential direction of the rotation shaft 12, thereby suppressing the rotation of the rotation-suppressing member 63 and the axial force sensor.

[0037] In this case, the rotation-retaining member 63 may have its axially forward portion protruding beyond the metering motor support member 32, as shown in Figure 3. However, it is desirable to design the presence and amount of such protrusion in consideration of the arrangement relationship with surrounding members. In addition, although the illustrated slide hole 33 penetrates the metering motor support member 32 in the axial direction, a slide hole that does not penetrate the metering motor support member in the axial direction is also possible.

[0038] The rotation-suppressing member is not limited to the one that connects the axial force sensor 62 to the metering motor support member 32 as described above. For example, in the axial force detection unit 161 of another embodiment shown in Figure 4, a rotation-suppressing member 163 is provided that connects the axial force sensor 162 to the stator frame 31c of the metering motor 31.

[0039] The rotation-suppressing member 163 in Figure 4, as an example, has a shape that includes a cylindrical portion 163a extending axially from the axial force sensor 162 and a flange-like portion 163b extending from the axial front end of the cylindrical portion 163a to the outer circumference and reaching the stator frame 31c. The stator frame 31c is fixedly attached to the axial rear side of the metering motor support member 32, and the rotation-suppressing member 163 can function to suppress the rotation of the axial force sensor 62 by connecting the axial force sensor 62 to this stator frame 31c.

[0040] In this case, for example, by configuring the cylindrical portion 163a of the rotation-restricting member 163 to slide axially relative to the flange-shaped portion 163b, the axial force sensor 162 can move forward or backward together with the drive force transmission member 51 and the screw 13 when forward or backward driving force is transmitted. The embodiment in Figure 4 can be substantially the same as that shown in Figures 2 and 3, except for the configuration of the axial force detection unit 161 other than the rotation-restricting member 163. Instead of the rotation-restricting member 163 including the cylindrical portion 163a and the flange-shaped portion 163b, a rod-shaped or plate-shaped rotation-restricting member that is provided at one or more locations in the circumferential direction of the rotating shaft 12 and bends midway along the axial direction may be used.

[0041] If the axial force sensor 62 transmits and receives signals and / or receives power via a wired connection, the wiring 64 of the axial force sensor 62 included in the axial force detection unit 61 can be extended from the axial force sensor 62, for example, inside the rotation suppression member 63, along the rotation suppression member 63, and through the slide hole 33, as shown by the dashed lines in Figures 2 and 3. This prevents the wiring 64 from being cut or damaged due to the rotation or advancement / reverse displacement of the surrounding drive force transmission member 51 and screw 13. In the case of an axial force sensor using wireless communication and contactless power supply, such wiring may be omitted.

[0042] The driving force transmission member 51 can be connected to the axial force sensor 62 by interposing a bearing 55 between it and the axial force sensor 62 at the front end wall portion 53, as shown in the enlarged view in Figure 5. This bearing 55 effectively supports the axial force sensor 62, which receives axial force from the screw 13, from behind in the axial direction. Therefore, it is preferable to use a thrust bearing, and in particular a self-aligning thrust roller bearing that has self-aligning properties and is not affected by mounting errors.

[0043] The illustrated axial force sensor 62 has an outer annular portion 62a that protrudes to the rear on the outer edge of the rear surface in the axial direction. The front end wall portion 53 of the drive force transmission member 51 is provided with a central raised portion 53a that rises to the front in the axial direction. The bearing 55 has its inner ring attached between the front surface of the front end wall portion 53 of the drive force transmission member 51 and the central raised portion 53a, and its outer ring attached between the rear surface of the axial force sensor 62 and the outer annular portion 62a. When the inner ring of the bearing 55 is attached to the front end wall portion 53 of the drive force transmission member 51 and the outer ring is attached to the axial force sensor 62 in this way, the axial force sensor 62, which is arranged as shown in the illustration, is more reliably supported in the axial direction by the front end wall portion 53 of the drive force transmission member 51, thereby further improving the detection accuracy of the axial direction by the axial force sensor 62.

[0044] In the illustrated example, a connecting cylindrical portion 53b extending in the axial direction is provided on the central raised portion 53a of the front end wall portion 53 of the drive force transmission member 51. On the other hand, the shaft end portion 12a of the screw base end portion 13c of the screw 13 is inserted into the connecting cylindrical portion 53b. These connecting cylindrical portion 53b and shaft end portion 12a constitute a coupling portion that transmits rotational driving force from the drive force transmission member 51 to the screw 13, serving as the connection point between the screw 13 and the drive force transmission member 51.

[0045] Furthermore, in this embodiment, the screw 13 is fixedly mounted to the rotating shaft 12 at the screw base end 13c, as shown in Figure 5, and a joint flange 14 is provided that extends from the rotating shaft 12 outward and holds the connecting cylindrical portion 53b inward. The joint flange 14 functions to reliably connect the screw 13 and the driving force transmission member 51 in the axial direction, so that the screw 13 does not separate significantly from the driving force transmission member 51 even when the screw 13 is retracted (so-called suck-back) after holding pressure or metering.

[0046] The joint flange 14 may include, for example, a flange portion 15 that bites into and connects to the rotating shaft 12 and expands in an annular shape, such as a ring, on its outer circumference, and a ring portion 16 that fits onto the axial rear side of the flange portion 15 and surrounds the outer circumference of the connecting cylinder portion 53b. The flange portion 15 has an outer fitting portion 15a that extends from its outer circumference to the axial rear and bends inward, and the ring portion 16 has an inner fitting portion 16a that extends from its inner circumference to the axial front and bends outward. The flange portion 15 and the ring portion 16 are fitted together by their outer fitting portion 15a and inner fitting portion 16a. In order to facilitate disassembly during maintenance of the axial force detection unit 61, which will be described later, it is preferable that the joint flange 14 be detachably attached to the rotating shaft 12 by composing the flange portion 15 of multiple detachable parts, such as two.

[0047] If the screw 13 has a joint flange 14 as described above, the axial force sensor 62 can be positioned around the shaft end portion 12a and the connecting cylindrical portion 53b, between the joint flange 14 of the screw 13 and the front end wall portion 53 of the drive force transmission member 51.

[0048] In this case, by interposing a bearing 17 between the ring portion 16 of the joint flange 14 and the axial force sensor 62, the screw 13 can be connected to the joint flange 14 so as to be rotatable relative to the axial force sensor 62. For the same reasons as those described earlier for the bearing 55 between the drive force transmission member 51 and the axial force sensor 62, it is preferable that this bearing 17 between the joint flange 14 and the axial force sensor 62 be a thrust bearing, particularly a thrust self-aligning roller bearing.

[0049] To ensure that axial force is transmitted more reliably from the joint flange 14 to the axial force sensor 62, it is preferable to attach the inner ring of the bearing 17 between the joint flange 14 and the axial force sensor 62 to the axial force sensor 62, and to attach the outer ring of the bearing 17 to the ring portion 16 of the joint flange 14. In this example, the inner ring of the bearing 17 is attached between the axial front surface of the axial force sensor 62 and the inner annular portion 62b that is provided on the inner peripheral edge of the front surface and protrudes forward. Furthermore, a cylindrical projection 16b is formed on the outer edge of the ring portion 16 of the joint flange 14, which protrudes axially to the rear, and the outer ring of the bearing 17 is supported by this cylindrical projection 16b.

[0050] In the illustrated embodiment, the axial force sensor 62 supports a bearing 17 between itself and the joint flange 14 with its inner annular portion 62b, and supports a bearing 55 between itself and the front end wall portion 53 of the drive force transmission member 51 with its outer annular portion 62a. As a result, the connection point of the annular axial force sensor between the screw 13 and the joint flange 14 via the bearing 17 is located on the inner circumference side of the connection point between the screw 13 and the joint flange 14 via the bearing 55 than the connection point between the drive force transmission member 51 and the front end wall portion 53 via the bearing 55.

[0051] Furthermore, it is preferable that the shaft end portion 12a of the screw 13 and the joint flange 14 and the connecting cylinder portion 53b be able to displace relative to each other in the axial direction so that the axial force transmitted from the screw 13 to the joint flange 14 via the rotating shaft 12 is reliably transmitted by the axial force sensor 62 between the joint flange 14 and the front end wall portion 53.

[0052] Specifically, for example, a key and a keyway are provided on the outer circumferential surface of the shaft end portion 12a and the inner circumferential surface of the connecting cylinder portion 53b, respectively, and a key and a keyway are provided on the outer circumferential surface of the connecting cylinder portion 53b and the inner circumferential surface of the ring portion 16 of the joint flange 14, respectively, and they can be spline-connected. In this case, small axial clearances C1 and C2 are provided between the end face of the shaft end portion 12a and the bottom face of the connecting cylinder portion 53b, and between the circumferential surface of the opening of the connecting cylinder portion 53b and the joint flange 14, respectively. This allows the screw 13 to undergo a slight relative axial displacement with respect to the drive force transmission member 51, and the axial force acting on the screw 13 is effectively transmitted to the axial force sensor 62 between the joint flange 14 and the drive force transmission member 51, so that the axial force sensor 62 can detect the axial force with higher accuracy.

[0053] If the screw 13 does not have the joint flange 14 described above, an axial force transmission flange 214 can be fixedly attached to the screw base end 13c of the rotating shaft 12 of the screw 13, as shown in the embodiment in Figure 6. The axial force transmission flange 214 is rotatably connected to the axial force sensor 62 via a bearing 17. In Figure 6, the shaft end 12a and the connecting cylinder portion 53b are spline-coupled, and clearances C1 and C2 are provided between the shaft end 12a and the connecting cylinder portion 53b, and between the axial force transmission flange 214 and the connecting cylinder portion 53b, respectively, so that the axial force is effectively transmitted from the screw 13 to the axial force sensor 62 via the axial force transmission flange 214. The embodiment in Figure 6 has a configuration that is substantially the same as described above, except that the joint flange 14 is replaced with an axial force transmission flange 214. It is preferable that the axial force transmission flange 214 be detachably attached to the rotating shaft 12 by being composed of two or more detachable parts.

[0054] Incidentally, as shown in the embodiments in Figures 1-3, 5, and 6, when the rotation-suppressing member 63 of the axial force detection unit 61 connects the axial force sensor 62 to the metering motor support member 32, the sensor connection portion of the metering motor support member 32 to which the axial force sensor 62 is connected by the rotation-suppressing member 63 can also be formed integrally with the motor support portion that supports the metering motor 31. However, in order to facilitate maintenance of the axial force detection unit 61 as described later, it is preferable that the sensor connection portion 32b of the metering motor support member 32 be separate from the motor support portion 32a, such as a frame, and be configured to be detachable from the motor support portion 32a, as shown in the illustrated embodiment. In this case, the sensor connection portion 32b, which may be provided with a slide hole 33 as described above, can be shaped like a cylinder, etc., taking into consideration the rod-shaped, plate-shaped, or cylindrical shape of the rotation-suppressing member 63.

[0055] As shown in Figure 1, the metering motor support member 32 has a cylinder support portion 32c, which has a hole 32d through which a screw 13 passes, detachably attached to the axial front side of a frame-shaped motor support portion 32a. A cooler, such as a water cooler, can be provided on the cylinder support portion 32c near the supply port for the molding material into the cylinder 11, although this is not shown in the figure.

[0056] The injection device 1 described above can be disassembled as follows when performing maintenance on the axial force detection unit 61, such as replacing the axial force sensor 62. First, the cylinder support portion 32c is removed from the motor support portion 32a of the metering motor support member 32 together with the cylinder 11, thereby exposing the screw 13 as shown in Figure 7.

[0057] Next, while sliding the rotation-preventing member 63 within the slide hole 33, the sensor connecting portion 32b is removed from the motor support portion 32a of the metering motor support member 32, as shown in Figure 8. This allows access to the screw base end 13c, so the flange portion 15 of the joint flange 14 at the screw base end 13c is disassembled and removed from the screw 13, the connection between the screw 13 and the drive force transmission member 51 is released, and the shaft end 12a of the rotating shaft 12 of the screw 13 is pulled out from the connecting cylinder portion 53b of the drive force transmission member 51, resulting in the state shown in Figure 9.

[0058] Subsequently, by removing the remaining ring portion 16 and bearing 17 of the joint flange 14, the axial force sensor 62 and rotation suppression member 63 of the axial force detection unit 61 can be removed. This results in the state shown in Figure 10.

[0059] In this type of disassembly, the axial force detection unit 61 can be removed without disassembling the metering motor 31, the drive force transmission member 51, and the injection motor 21 side. Therefore, according to this embodiment, as described above, by arranging the axial force detection unit 61 near the screw 13 inside the injection device 1, the accuracy of axial force detection can be improved while maintenance of the axial force detection unit 61 can be performed relatively quickly and easily. After disassembling the injection device 1 in this way, it can be reassembled by performing the above procedure in reverse.

[0060] (Cylinder) The cylinder 11 has a screw 13 positioned inside, and melts the molding material supplied to the inside from a supply port (not shown) by heating and rotation of the screw 13. A heater 18 is positioned around the cylinder 11 to heat the molding material inside.

[0061] The cylinder 67 has a nozzle 19 on the axially forward side, with its inner and outer diameters decreasing, and a heater 18 is also positioned around the nozzle 19.

[0062] (Operation of the injection device) The injection device 1 described above is mounted on an injection molding machine and operates as described below during injection molding to perform each step.

[0063] With the molding material already measured and placed inside the cylinder 11 in a predetermined amount during the previous injection molding metering process, a mold clamping process is performed by closing a mold device (not shown) to create a clamped state.

[0064] Next, the screw 13 is advanced to inject the molding material into the mold device, and a filling process is performed to fill the cavity in the mold device with the molding material. Then, the screw 13 is further advanced to perform a holding pressure process to maintain the molding material inside the nozzle 19 of the cylinder 11 at a predetermined pressure.

[0065] Next, a cooling process is performed to cool and harden the molding material filled in the mold device to obtain a molded product. During this process, a metering process is performed in which a molding material supplied separately into the cylinder 11 is melted while being fed toward the nozzle 19 of the cylinder 11 by the rotation of the screw 13 under heating by the heater 18, and a predetermined amount of molding material is placed toward the nozzle 19.

[0066] After the cooling process, the mold device is opened to the open state, and the molded product is removed from the mold device using an ejector device or the like in the removal process. [Explanation of Symbols]

[0067] 1 Injection device 11 cylinders 12 Rotation axes 12a Shaft end 13 Screw 13a Screw body 13b Screw tip 13c Screw base 14 Joint flange 214 Axial force transmission flange 15 Flange section 15a Outer fitting part 16 Ring section 16a Inner fitting part 16b Cylindrical protrusion 17 Bearings 18 Heater 19 nozzles 21 Injection motor 31 Measuring motor 21a, 31a rotor 21b, 31b staters 21c, 31c stator frame 21d, 31d bearing part 22 Injection motor support member 22a cylinder 23. Cylindrical rotating member 24, 25 rods 25a Shaft 25b encoder 32 Measuring motor support member 32a Motor support section 32b Sensor connection section 32c Cylinder support section 32d hole 33 slide holes 41 Motion conversion mechanism 42 Screw shaft 42a Screw shaft base 42b key 42c Screw shaft tip 43 nuts 51 Driving force transmission member 52 Cylindrical main body 52a Key 53 Front end wall 53a Central ridge 53b Connecting cylinder part 54, 55 Bearings 61, 161 Axial force detection unit 62, 162 Axial force sensor 62a Outer ring 62b Inner annular portion 63, 163 Rotation restraining member 163a Cylindrical part 163b Flange-shaped portion 64 Wiring 67 Cylinder 101 Slide Base C1, C2 clearance

Claims

1. An injection device for injecting molding material, A screw that is driven to rotate around a rotating shaft and also driven to move back and forth in the axial direction, The injection motor is the drive source for the screw's forward and backward movement, A motion conversion mechanism that includes a screw shaft that rotates together with the rotational motion of the injection motor and a nut positioned inside the screw shaft, which converts the rotational motion of the injection motor into linear motion in the axial direction, The metering motor is the rotational drive source for the screw, A drive force transmission member connected to the screw transmits to the screw the rotational drive force based on the rotational motion of the metering motor and the forward / backward drive force based on the linear motion of the screw shaft of the motion conversion mechanism, An axial force detection unit that detects the axial force acting on the screw in the axial direction, Equipped with, The injection device comprises an annular axial force sensor positioned to be rotatable relative to the screw and a drive force transmission member in a transmission path that transmits forward and backward driving force from the injection motor to the screw via a motion conversion mechanism around the rotation axis of the screw, and a rotation suppression member that prevents the axial force sensor from rotating together with the screw and the drive force transmission member.

2. The injection device includes a metering motor support member that supports the metering motor, The injection device according to claim 1, wherein the rotation-suppressing member prevents the rotation of the axial force sensor from being suppressed and allows it to be displaceable in the axial direction, connected to the metering motor support member.

3. The metering motor support member has a sliding hole for the rotation restraining member, The injection device according to claim 2, wherein the rotation-restricting member is inserted into the slide hole so as to be slidable in the axial direction.

4. The injection device according to claim 3, wherein the rotation-restricting member is one or more rod-shaped or plate-shaped members extending in the axial direction on the outer circumference of the screw's rotation axis, or a cylindrical member surrounding the rotation axis of the screw.

5. The injection device according to claim 3 or 4, wherein the axial force detection unit has wiring extending from the axial force sensor through the slide hole along the rotation suppression member.

6. The aforementioned metering motor support member, A motor support section that supports the metering motor, The axial force sensor is connected by a rotation-suppressing member, and the sensor connection part is detachable from the motor support part. An injection device according to any one of claims 2 to 5, having the following:

7. The aforementioned driving force transmission member, A cylindrical body surrounding the tip of the screw shaft, The front end wall portion provided at the axial front opening of the cylindrical main body portion and An injection device according to any one of claims 1 to 6, having the following:

8. The injection device according to claim 7, wherein the front end wall portion of the driving force transmission member and the axial force sensor are connected via a bearing so as to be rotatable relative to each other.

9. The injection device according to claim 8, wherein the bearing between the front end wall portion of the drive force transmission member and the axial force sensor is a thrust bearing.

10. The injection device according to claim 8 or 9, wherein the inner ring of the bearing between the front end wall of the drive force transmission member and the axial force sensor is attached to the front end wall of the drive force transmission member, and the outer ring of the bearing is attached to the axial force sensor.

11. The coupling portion at the connection point between the screw and the drive force transmission member includes a connecting cylinder portion extending in the axial direction from the front end wall portion of the drive force transmission member, and a shaft end portion provided at the screw base end of the rotating shaft and inserted into the connecting cylinder portion. The screw has a joint flange at its base end that is detachably attached to the rotating shaft and holds the connecting cylindrical portion inward. The injection apparatus according to any one of claims 8 to 10, wherein the axial force sensor is located around the shaft end and the connecting cylinder portion, between the joint flange of the screw and the front end wall portion of the drive force transmission member.

12. The injection device according to claim 11, wherein the shaft end and joint flange and the connecting cylinder portion are displaceable relative to each other in the axial direction, and the axial force acting on the screw is transmitted to an axial force sensor between the joint flange of the screw and the front end wall portion of the drive force transmission member.

13. The injection device according to claim 11 or 12, wherein the screw is connected to the axial force sensor via a bearing at the joint flange so as to be rotatable relative to it.

14. The injection device according to claim 13, wherein the bearing between the joint flange of the screw and the axial force sensor is a thrust bearing.

15. The injection device according to claim 13 or 14, wherein the connection point of the annular axial force sensor to the joint flange of the screw via a bearing is located on the inner circumference side than the connection point to the front end wall portion of the drive force transmission member via a bearing.

16. The injection device according to any one of claims 13 to 15, wherein the inner ring of the bearing between the joint flange of the screw and the axial force sensor is attached to the axial force sensor, and the outer ring of the bearing is attached to the joint flange.

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