JP2024091103A - Screw head, backflow prevention ring, screw and injection molding machine - Google Patents

Abstract

[Problem] To provide a technology for suppressing deterioration of molding materials. [Solution] The screw has a shaft portion, a screw head, and a backflow prevention ring. The screw head has a base end face facing the backflow prevention ring, located further forward than the backflow prevention ring. The backflow prevention ring has a tip face facing the base end face. The base end face or the tip face has a pressure generating portion that generates pressure between the screw head and the backflow prevention ring as the molding material flows in, and has a portion where the base end face and the tip face face in parallel with each other so that the pressure generated in the pressure generating portion applies a force that causes the base end face to push the tip face toward the base end. [Selected Figure] Figure 5

Description

This disclosure relates to a screw head, a backflow prevention ring, a screw, and an injection molding machine.

Patent Document 1 discloses a structure that includes a screw head, a backflow prevention ring (check ring), and a seal ring (valve seat) at the tip of a screw installed in an injection molding machine. This type of screw is usually configured so that while the screw head and seal ring rotate as the screw rotates, the backflow prevention ring does not rotate.

As a result, when the screw rotates, sliding occurs between the screw head and the backflow prevention ring. The smaller the gap between the screw head and the backflow prevention ring, the greater the amount of heat (shear heat) generated by the molding material due to this sliding.

JP 2000-108178 A

As mentioned above, if a large amount of heat is generated in the molding material, the molding material may deteriorate, resulting in molding defects. In particular, when a highly viscous resin is used as the molding material, the force pressing the backflow prevention ring against the screw head increases, and wear may occur due to contact between the screw head and the backflow prevention ring. In this case, there is a risk that the wear metal powder resulting from wear of the screw head and backflow prevention ring may become mixed into the molded product as foreign matter.

This disclosure provides technology that can suppress deterioration of molding materials.

One aspect of the present disclosure is a screw having a shaft portion, a screw head, and a backflow prevention ring attached to the shaft portion, in which the screw head has a base end face facing the backflow prevention ring on the tip side of the backflow prevention ring, the backflow prevention ring has a tip face facing the base end face, the base end face or the tip face has a pressure generating part that generates pressure between the screw head and the backflow prevention ring as molding material flows in, and the base end face and the tip face have a portion where they face each other in parallel so that the pressure generated by the pressure generating part causes the base end face to apply a force that pushes the tip face toward the base end.

According to one embodiment, deterioration of the molding material can be suppressed.

FIG. 2 is a diagram showing a state when mold opening is completed in the injection molding machine according to the embodiment. FIG. 2 is a diagram showing a state during mold clamping of the injection molding machine according to the embodiment. FIG. 2 is a side cross-sectional view showing the configuration of the tip of the screw. Fig. 4(A) is a cross-sectional view taken along line IVA-IVA in Fig. 3. Fig. 4(B) is a plan view of the protruding portion as viewed from the direction of arrow IVB in Fig. 3. Fig. 4(C) is a plan view of the fin portion according to another configuration example. 11 is a plan view illustrating the relationship between the fin portion and the backflow prevention ring. FIG. FIG. 13 is a diagram showing the force acting on the backflow prevention ring when the screw rotates. FIG. 11 is a side cross-sectional view showing the configuration of the tip of a screw according to a first modified example. FIG. 11 is a plan view illustrating a schematic relationship between a protruding portion of a screw and a backflow prevention ring according to a second modified example.

Below, a description will be given of a mode for carrying out the present disclosure with reference to the drawings. In each drawing, the same components are given the same reference numerals, and duplicate descriptions may be omitted.

(Injection molding machine)
Fig. 1 is a diagram showing a state of an injection molding machine according to an embodiment when mold opening is completed. Fig. 2 is a diagram showing a state of an injection molding machine according to an embodiment when mold clamping is performed. In this specification, the X-axis direction, the Y-axis direction, and the Z-axis direction are perpendicular to each other. The X-axis direction and the Y-axis direction represent the horizontal direction, and the Z-axis direction represents the vertical direction. When the mold clamping device 100 is of a horizontal type, the X-axis direction is the mold opening/closing direction, and the Y-axis direction is the width direction of the injection molding machine 10. The negative Y-axis direction is called the operation side, and the positive Y-axis direction is called the anti-operation side.

As shown in Figures 1 and 2, the injection molding machine 10 has a mold clamping device 100 that opens and closes the mold device 800, an ejector device 200 that ejects a molded product molded by the mold device 800, an injection device 300 that injects molding material into the mold device 800, a moving device 400 that moves the injection device 300 forward and backward relative to the mold device 800, a control device 700 that controls each component of the injection molding machine 10, and a frame 900 that supports each component of the injection molding machine 10. The frame 900 includes a mold clamping device frame 910 that supports the mold clamping device 100, and an injection device frame 920 that supports the injection device 300. The mold clamping device frame 910 and the injection device frame 920 are each installed on the floor 2 via a leveling adjuster 930. The control device 700 is arranged in the internal space of the injection device frame 920. Each component of the injection molding machine 10 will be described below.

(Mold clamping device)
In the description of the mold clamping apparatus 100, the moving direction of the movable platen 120 during mold closing (e.g., the positive X-axis direction) is defined as the front, and the moving direction of the movable platen 120 during mold opening (e.g., the negative X-axis direction) is defined as the rear.

The mold clamping device 100 closes, pressurizes, clamps, releases pressure, and opens the mold of the mold device 800. The mold device 800 includes a fixed mold 810 and a movable mold 820.

The mold clamping device 100 is, for example, a horizontal type, and the mold opening and closing direction is horizontal. The mold clamping device 100 has a fixed platen 110 to which a fixed mold 810 is attached, a movable platen 120 to which a movable mold 820 is attached, and a movement mechanism 102 that moves the movable platen 120 in the mold opening and closing direction relative to the fixed platen 110.

The fixed platen 110 is fixed to the mold clamping unit frame 910. The fixed mold 810 is attached to the surface of the fixed platen 110 facing the movable platen 120.

The movable platen 120 is arranged so as to be movable in the mold opening and closing direction relative to the mold clamping unit frame 910. A guide 101 that guides the movable platen 120 is laid on the mold clamping unit frame 910. A movable mold 820 is attached to the surface of the movable platen 120 that faces the fixed platen 110.

The moving mechanism 102 performs mold closing, pressurization, mold clamping, depressurization, and mold opening of the mold device 800 by moving the movable platen 120 forward and backward relative to the fixed platen 110. The moving mechanism 102 has a toggle support 130 arranged at a distance from the fixed platen 110, a tie bar 140 connecting the fixed platen 110 and the toggle support 130, a toggle mechanism 150 that moves the movable platen 120 in the mold opening and closing direction relative to the toggle support 130, a mold clamping motor 160 that operates the toggle mechanism 150, a motion conversion mechanism 170 that converts the rotational motion of the mold clamping motor 160 into linear motion, and a mold thickness adjustment mechanism 180 that adjusts the distance between the fixed platen 110 and the toggle support 130.

The toggle support 130 is disposed at a distance from the fixed platen 110 and is placed on the mold clamping unit frame 910 so as to be freely movable in the mold opening and closing direction. The toggle support 130 may be disposed so as to be freely movable along a guide laid on the mold clamping unit frame 910. The guide of the toggle support 130 may be the same as the guide 101 of the movable platen 120.

In this embodiment, the fixed platen 110 is fixed to the mold clamping unit frame 910, and the toggle support 130 is arranged to be movable relative to the mold clamping unit frame 910 in the mold opening/closing direction; however, the toggle support 130 may be fixed to the mold clamping unit frame 910, and the fixed platen 110 may be arranged to be movable relative to the mold clamping unit frame 910 in the mold opening/closing direction.

The tie bar 140 connects the fixed platen 110 and the toggle support 130 at a distance L in the mold opening/closing direction. A plurality of tie bars 140 (for example, four) may be used. The plurality of tie bars 140 are arranged parallel to the mold opening/closing direction and extend according to the mold clamping force. At least one tie bar 140 may be provided with a tie bar strain detector 141 that detects the strain of the tie bar 140. The tie bar strain detector 141 sends a signal indicating the detection result to the control device 700. The detection result of the tie bar strain detector 141 is used to detect the mold clamping force, etc.

In this embodiment, a tie bar strain detector 141 is used as the clamping force detector for detecting the clamping force, but the present invention is not limited to this. The clamping force detector is not limited to the strain gauge type, but may be a piezoelectric type, a capacitive type, a hydraulic type, an electromagnetic type, or the like, and the attachment position is not limited to the tie bar 140.

The toggle mechanism 150 is disposed between the movable platen 120 and the toggle support 130, and moves the movable platen 120 in the mold opening/closing direction relative to the toggle support 130. The toggle mechanism 150 has a crosshead 151 that moves in the mold opening/closing direction, and a pair of link groups that bend and stretch with the movement of the crosshead 151. Each of the pair of link groups has a first link 152 and a second link 153 that are connected to bendable and stretchable by a pin or the like. The first link 152 is attached to the movable platen 120 by a pin or the like so that it can swing freely. The second link 153 is attached to the toggle support 130 by a pin or the like so that it can swing freely. The second link 153 is attached to the crosshead 151 via a third link 154. When the crosshead 151 is advanced or retreated relative to the toggle support 130, the first link 152 and the second link 153 bend and stretch, and the movable platen 120 advances or retreats relative to the toggle support 130.

The configuration of the toggle mechanism 150 is not limited to the configuration shown in Figs. 1 and 2. For example, although the number of nodes in each link group is five in Figs. 1 and 2, it may be four, and one end of the third link 154 may be connected to a node between the first link 152 and the second link 153.

The mold clamping motor 160 is attached to the toggle support 130 and operates the toggle mechanism 150. The mold clamping motor 160 moves the crosshead 151 forward and backward relative to the toggle support 130, thereby bending and extending the first link 152 and the second link 153 and moving the movable platen 120 forward and backward relative to the toggle support 130. The mold clamping motor 160 is directly connected to the motion conversion mechanism 170, but may also be connected to the motion conversion mechanism 170 via a belt, pulley, etc.

The motion conversion mechanism 170 converts the rotational motion of the mold clamping motor 160 into the linear motion of the crosshead 151. The motion conversion mechanism 170 includes a screw shaft and a screw nut that screws onto the screw shaft. A ball or roller may be interposed between the screw shaft and the screw nut.

The mold clamping device 100 performs processes such as mold closing, pressure increase, mold clamping, depressurization, and mold opening under the control of the control device 700.

In the mold closing process, the mold clamping motor 160 is driven to move the crosshead 151 forward at a set movement speed to the mold closing completion position, thereby moving the movable platen 120 forward and touching the movable mold 820 to the fixed mold 810. The position and movement speed of the crosshead 151 are detected using, for example, the mold clamping motor encoder 161. The mold clamping motor encoder 161 detects the rotation of the mold clamping motor 160 and sends a signal indicating the detection result to the control device 700.

The crosshead position detector that detects the position of the crosshead 151 and the crosshead movement speed detector that detects the movement speed of the crosshead 151 are not limited to the mold clamping motor encoder 161, and general-purpose detectors can be used. Also, the movable platen position detector that detects the position of the movable platen 120 and the movable platen movement speed detector that detects the movement speed of the movable platen 120 are not limited to the mold clamping motor encoder 161, and general-purpose detectors can be used.

During the pressure increase process, the clamping motor 160 is further driven to move the crosshead 151 further forward from the mold closing completion position to the clamping position, thereby generating a clamping force.

In the mold clamping process, the mold clamping motor 160 is driven to maintain the position of the crosshead 151 at the mold clamping position. In the mold clamping process, the mold clamping force generated in the pressure increase process is maintained. In the mold clamping process, a cavity space 801 (see FIG. 2) is formed between the movable mold 820 and the fixed mold 810, and the injection device 300 fills the cavity space 801 with liquid molding material. The filled molding material is solidified to obtain a molded product.

The number of cavity spaces 801 may be one or more. In the latter case, multiple molded products are obtained at the same time. An insert material may be placed in one part of the cavity space 801, and another part of the cavity space 801 may be filled with molding material. A molded product in which the insert material and molding material are integrated is obtained.

In the depressurization process, the mold clamping motor 160 is driven to move the crosshead 151 back from the mold clamping position to the mold opening start position, thereby moving the movable platen 120 back and reducing the mold clamping force. The mold opening start position and the mold closing completion position may be the same position.

In the mold opening process, the mold clamping motor 160 is driven to move the crosshead 151 backward at a set moving speed from the mold opening start position to the mold opening completion position, thereby moving the movable platen 120 backward and separating the movable mold 820 from the fixed mold 810. After that, the ejector device 200 ejects the molded product from the movable mold 820.

The set conditions for the mold closing process, pressure increase process, and mold clamping process are set together as a series of set conditions. For example, the movement speed and position of the crosshead 151 in the mold closing process and pressure increase process (including the mold closing start position, movement speed switching position, mold closing completion position, and mold clamping position) and the mold clamping force are set together as a series of set conditions. The mold closing start position, movement speed switching position, mold closing completion position, and mold clamping position are arranged in this order from the rear side to the front, and represent the start and end points of the section in which the movement speed is set. The movement speed is set for each section. There may be one or more movement speed switching positions. The movement speed switching position does not have to be set. Only one of the mold clamping position and the mold clamping force may be set.

The setting conditions for the depressurization process and mold opening process are also set in a similar manner. For example, the movement speed and position of the crosshead 151 in the depressurization process and mold opening process (mold opening start position, movement speed switching position, and mold opening completion position) are set together as a series of setting conditions. The mold opening start position, movement speed switching position, and mold opening completion position are arranged in this order from the front to the rear, and represent the start and end points of the section in which the movement speed is set. The movement speed is set for each section. There may be one or more movement speed switching positions. The movement speed switching position does not have to be set. The mold opening start position and mold closing completion position may be the same position. Also, the mold opening completion position and mold closing start position may be the same position.

In addition, instead of the moving speed and position of the crosshead 151, the moving speed and position of the movable platen 120 may be set. Also, instead of the position of the crosshead (e.g., the clamping position) or the position of the movable platen, the clamping force may be set.

The toggle mechanism 150 amplifies the driving force of the mold clamping motor 160 and transmits it to the movable platen 120. The amplification ratio is also called the toggle ratio. The toggle ratio changes according to the angle θ between the first link 152 and the second link 153 (hereinafter also called the "link angle θ"). The link angle θ is determined from the position of the crosshead 151. When the link angle θ is 180°, the toggle ratio is maximum.

When the thickness of the mold device 800 changes due to replacement of the mold device 800 or a temperature change of the mold device 800, the mold thickness is adjusted so that a predetermined clamping force is obtained during mold clamping. In the mold thickness adjustment, for example, the distance L between the fixed platen 110 and the toggle support 130 is adjusted so that the link angle θ of the toggle mechanism 150 becomes a predetermined angle at the time of mold touch when the movable mold 820 touches the fixed mold 810.

The mold clamping device 100 has a mold thickness adjustment mechanism 180. The mold thickness adjustment mechanism 180 adjusts the mold thickness by adjusting the distance L between the fixed platen 110 and the toggle support 130. The mold thickness adjustment is performed, for example, between the end of a molding cycle and the start of the next molding cycle. The mold thickness adjustment mechanism 180 has, for example, a screw shaft 181 formed at the rear end of the tie bar 140, a screw nut 182 held rotatably and immovably on the toggle support 130, and a mold thickness adjustment motor 183 that rotates the screw nut 182 that screws onto the screw shaft 181.

A screw shaft 181 and a screw nut 182 are provided for each tie bar 140. The rotational driving force of the mold thickness adjustment motor 183 may be transmitted to the multiple screw nuts 182 via a rotational driving force transmission unit 185. The multiple screw nuts 182 can be rotated synchronously. Note that by changing the transmission path of the rotational driving force transmission unit 185, it is also possible to rotate the multiple screw nuts 182 individually.

The rotational drive force transmission unit 185 is composed of, for example, gears. In this case, a driven gear is formed on the outer periphery of each screw nut 182, a drive gear is attached to the output shaft of the mold thickness adjustment motor 183, and an intermediate gear that meshes with the multiple driven gears and the drive gear is rotatably held in the center of the toggle support 130. Note that the rotational drive force transmission unit 185 may be composed of a belt, pulleys, etc. instead of gears.

The operation of the mold thickness adjustment mechanism 180 is controlled by the control device 700. The control device 700 drives the mold thickness adjustment motor 183 to rotate the screw nut 182. As a result, the position of the toggle support 130 relative to the tie bar 140 is adjusted, and the distance L between the fixed platen 110 and the toggle support 130 is adjusted. Note that multiple mold thickness adjustment mechanisms may be used in combination.

The distance L is detected using the mold thickness adjustment motor encoder 184. The mold thickness adjustment motor encoder 184 detects the amount and direction of rotation of the mold thickness adjustment motor 183, and sends a signal indicating the detection result to the control device 700. The detection result of the mold thickness adjustment motor encoder 184 is used to monitor and control the position of the toggle support 130 and the distance L. Note that the toggle support position detector that detects the position of the toggle support 130 and the distance detector that detects the distance L are not limited to the mold thickness adjustment motor encoder 184, and general types can be used.

The mold clamping device 100 may have a mold temperature regulator that regulates the temperature of the mold device 800. The mold device 800 has a flow path for a temperature control medium inside. The mold temperature regulator regulates the temperature of the temperature control medium supplied to the flow path of the mold device 800, thereby regulating the temperature of the mold device 800.

In addition, the mold clamping device 100 of this embodiment is a horizontal type in which the mold opening and closing direction is horizontal, but it may also be a vertical type in which the mold opening and closing direction is vertical.

In addition, the mold clamping device 100 of this embodiment has a mold clamping motor 160 as a drive unit, but may have a hydraulic cylinder instead of the mold clamping motor 160. In addition, the mold clamping device 100 may have a linear motor for opening and closing the mold, and an electromagnet for mold clamping.

(Ejector device)
In describing the ejector unit 200, similar to the description of the mold clamping unit 100, the direction of movement of the movable platen 120 when the mold is closed (e.g., the positive direction of the X-axis) is defined as the front, and the direction of movement of the movable platen 120 when the mold is opened (e.g., the negative direction of the X-axis) is defined as the rear.

The ejector unit 200 is attached to the movable platen 120 and moves forward and backward together with the movable platen 120. The ejector unit 200 has an ejector rod 210 that ejects the molded product from the mold device 800, and a drive mechanism 220 that moves the ejector rod 210 in the movement direction (X-axis direction) of the movable platen 120.

The ejector rod 210 is arranged to be movable relative to the movable platen 120. The tip of the ejector rod 210 contacts the advance/retract structure 825 of the movable mold 820.

The drive mechanism 220 has, for example, an ejector motor and a motion conversion mechanism that converts the rotational motion of the ejector motor into the linear motion of the ejector rod 210. The motion conversion mechanism includes a screw shaft and a screw nut that screws onto the screw shaft. Balls or rollers may be interposed between the screw shaft and the screw nut.

The ejector unit 200 performs the ejection process under the control of the control unit 700. In the ejection process, the ejector rod 210 is advanced from the retracted position to the ejection position at a set moving speed, thereby advancing the ejector plate 826 and ejecting the molded product. The ejector motor is then driven to retract the ejector rod 210 at the set moving speed, and the ejector plate 826 is retracted to its original retracted position.

The position and movement speed of the ejector rod 210 are detected, for example, using an ejector motor encoder. The ejector motor encoder detects the rotation of the ejector motor and sends a signal indicating the detection result to the control device 700. Note that the ejector rod position detector that detects the position of the ejector rod 210 and the ejector rod movement speed detector that detects the movement speed of the ejector rod 210 are not limited to the ejector motor encoder, and general types can be used.

(Injection device)
In the explanation of the injection unit 300, unlike the explanations of the mold clamping unit 100 and the ejector unit 200, the movement direction of the screw 330 during filling (e.g., the negative direction of the X-axis) is described as the front, and the movement direction of the screw 330 during metering (e.g., the positive direction of the X-axis) is described as the rear.

The injection device 300 is installed on a slide base 301, and the slide base 301 is arranged so as to be freely movable forward and backward with respect to the injection device frame 920. The injection device 300 is arranged so as to be freely movable forward and backward with respect to the mold device 800. The injection device 300 touches the mold device 800 and fills the cavity space 801 in the mold device 800 with molding material. The injection device 300 has, for example, a cylinder 310 that heats the molding material, a nozzle 320 provided at the front end of the cylinder 310, a screw 330 arranged so as to be freely movable forward and backward and rotatable within the cylinder 310, a metering motor 340 that rotates the screw 330, an injection motor 350 that moves the screw 330 forward and backward, and a load detector 360 that detects the load transmitted between the injection motor 350 and the screw 330.

Cylinder 310 heats the molding material supplied to the inside from supply port 311. The molding material includes, for example, resin. The molding material is formed, for example, in pellet form and supplied to supply port 311 in a solid state. Supply port 311 is formed at the rear of cylinder 310. A cooler 312 such as a water-cooled cylinder is provided on the outer periphery of the rear of cylinder 310. A first heater 313 such as a band heater and a first temperature detector 314 are provided on the outer periphery of cylinder 310, forward of cooler 312.

The cylinder 310 is divided into a plurality of zones in the axial direction of the cylinder 310 (e.g., the X-axis direction). A first heater 313 and a first temperature detector 314 are provided in each of the plurality of zones. A set temperature is set in each of the plurality of zones, and the control device 700 controls the first heater 313 so that the detected temperature of the first temperature detector 314 becomes the set temperature.

The nozzle 320 is provided at the front end of the cylinder 310 and is pressed against the mold device 800. A second heater 323 and a second temperature detector 324 are provided on the outer periphery of the nozzle 320. The control device 700 controls the second heater 323 so that the detected temperature of the nozzle 320 becomes the set temperature.

The screw 330 is arranged in the cylinder 310 so that it can rotate freely and move forward and backward. When the screw 330 is rotated, the molding material is sent forward along the spiral groove of the screw 330. As the molding material is sent forward, it is gradually melted by heat from the cylinder 310. As the liquid molding material is sent forward to the front of the screw 330 and accumulates at the front of the cylinder 310, the screw 330 is moved backward. When the screw 330 is then moved forward, the liquid molding material accumulated in front of the screw 330 is injected from the nozzle 320 and filled into the mold device 800.

A backflow prevention ring 331 is attached to the front of the screw 330 so that it can move back and forth as a backflow prevention valve that prevents the molding material from flowing back from the front to the rear of the screw 330 when the screw 330 is pushed forward.

When the screw 330 is advanced, the backflow prevention ring 331 is pushed backward by the pressure of the molding material in front of the screw 330, and retreats relative to the screw 330 to a blocking position (see FIG. 2) where it blocks the flow path of the molding material. This prevents the molding material accumulated in front of the screw 330 from flowing backward.

Meanwhile, when the screw 330 is rotated, the backflow prevention ring 331 is pushed forward by the pressure of the molding material sent forward along the spiral groove of the screw 330, and advances relative to the screw 330 to an open position (see FIG. 1) where the flow path of the molding material is opened. This causes the molding material to be sent forward of the screw 330.

The backflow prevention ring 331 may be either a co-rotating type that rotates with the screw 330, or a non-co-rotating type that does not rotate with the screw 330.

The injection device 300 may also have a drive source that moves the backflow prevention ring 331 back and forth between the open position and the closed position relative to the screw 330.

The metering motor 340 rotates the screw 330. The driving source that rotates the screw 330 is not limited to the metering motor 340 and may be, for example, a hydraulic pump.

The injection motor 350 advances and retreats the screw 330. Between the injection motor 350 and the screw 330, a motion conversion mechanism that converts the rotational motion of the injection motor 350 into the linear motion of the screw 330 is provided. The motion conversion mechanism has, for example, a screw shaft and a screw nut that screws onto the screw shaft. A ball or roller may be provided between the screw shaft and the screw nut. The drive source that advances and retreats the screw 330 is not limited to the injection motor 350, and may be, for example, a hydraulic cylinder.

The load detector 360 detects the load transmitted between the injection motor 350 and the screw 330. The detected load is converted to pressure by the control device 700. The load detector 360 is provided in the load transmission path between the injection motor 350 and the screw 330, and detects the load acting on the load detector 360.

The load detector 360 sends a signal of the detected load to the control device 700. The load detected by the load detector 360 is converted into pressure acting between the screw 330 and the molding material, and is used to control and monitor the pressure that the screw 330 receives from the molding material, the back pressure on the screw 330, and the pressure that the screw 330 exerts on the molding material.

The pressure detector that detects the pressure of the molding material is not limited to the load detector 360, and a general detector can be used. For example, a nozzle pressure sensor or a mold internal pressure sensor may be used. The nozzle pressure sensor is installed in the nozzle 320. The mold internal pressure sensor is installed inside the mold device 800.

The injection device 300 performs a metering process, a filling process, a pressure holding process, and the like under the control of the control device 700. The filling process and the pressure holding process may be collectively referred to as the injection process.

In the metering process, the metering motor 340 is driven to rotate the screw 330 at a set rotational speed, and the molding material is sent forward along the spiral groove of the screw 330. As a result, the molding material is gradually melted. As the liquid molding material is sent forward of the screw 330 and accumulates at the front of the cylinder 310, the screw 330 is moved backward. The rotational speed of the screw 330 is detected, for example, using the metering motor encoder 341. The metering motor encoder 341 detects the rotation of the metering motor 340 and sends a signal indicating the detection result to the control device 700. Note that the screw rotational speed detector that detects the rotational speed of the screw 330 is not limited to the metering motor encoder 341, and a general one can be used.

In the metering process, in order to limit the sudden retreat of the screw 330, the injection motor 350 may be driven to apply a set back pressure to the screw 330. The back pressure on the screw 330 is detected, for example, using a load detector 360. When the screw 330 retreats to the metering completion position and a predetermined amount of molding material is accumulated in front of the screw 330, the metering process is completed.

The position and rotational speed of the screw 330 in the metering process are set together as a series of setting conditions. For example, a metering start position, a rotational speed switching position, and a metering completion position are set. These positions are arranged in this order from the front to the rear, and represent the start and end points of the section in which the rotational speed is set. The rotational speed is set for each section. There may be one or more rotational speed switching positions. The rotational speed switching position does not have to be set. In addition, a back pressure is set for each section.

In the filling process, the injection motor 350 is driven to advance the screw 330 at a set moving speed, and the liquid molding material accumulated in front of the screw 330 is filled into the cavity space 801 in the mold device 800. The position and moving speed of the screw 330 are detected, for example, by the injection motor encoder 351. The injection motor encoder 351 detects the rotation of the injection motor 350 and sends a signal indicating the detection result to the control device 700. When the position of the screw 330 reaches the set position, a switch from the filling process to the pressure holding process (so-called V/P switch) is performed. The position where the V/P switch is performed is also called the V/P switch position. The set moving speed of the screw 330 may be changed depending on the position of the screw 330, time, etc.

The position and movement speed of the screw 330 in the filling process are set together as a series of setting conditions. For example, a filling start position (also called the "injection start position"), a movement speed switching position, and a V/P switching position are set. These positions are arranged in this order from the rear to the front, and represent the start and end points of the section for which the movement speed is set. The movement speed is set for each section. There may be one or more movement speed switching positions. The movement speed switching positions do not have to be set.

For each section in which the movement speed of the screw 330 is set, an upper limit value for the pressure of the screw 330 is set. The pressure of the screw 330 is detected by the load detector 360. When the pressure of the screw 330 is equal to or lower than the set pressure, the screw 330 is advanced at the set movement speed. On the other hand, when the pressure of the screw 330 exceeds the set pressure, in order to protect the mold, the screw 330 is advanced at a movement speed slower than the set movement speed so that the pressure of the screw 330 is equal to or lower than the set pressure.

In addition, after the position of the screw 330 reaches the V/P switching position during the filling process, the screw 330 may be temporarily stopped at the V/P switching position, and then the V/P switching may be performed. Immediately before the V/P switching, instead of stopping the screw 330, the screw 330 may be moved forward or backward at a slow speed. In addition, the screw position detector that detects the position of the screw 330 and the screw movement speed detector that detects the movement speed of the screw 330 are not limited to the injection motor encoder 351, and general ones can be used.

In the holding pressure process, the injection motor 350 is driven to push the screw 330 forward, and the pressure of the molding material at the front end of the screw 330 (hereinafter also referred to as the "holding pressure") is maintained at a set pressure, and the molding material remaining in the cylinder 310 is pushed toward the mold device 800. The molding material that is insufficient due to cooling contraction in the mold device 800 can be replenished. The holding pressure is detected, for example, using a load detector 360. The set value of the holding pressure may be changed depending on the elapsed time from the start of the holding pressure process. The holding pressure and the holding time for which the holding pressure is maintained in the holding pressure process may each be set multiple times, or may be set together as a series of setting conditions.

During the dwelling process, the molding material in the cavity space 801 in the mold device 800 is gradually cooled, and when the dwelling process is completed, the entrance to the cavity space 801 is blocked by solidified molding material. This state is called a gate seal, and prevents the molding material from flowing back from the cavity space 801. After the dwelling process, the cooling process is started. During the cooling process, the molding material in the cavity space 801 is solidified. A weighing process may be performed during the cooling process in order to shorten the molding cycle time.

The injection device 300 in this embodiment is of the in-line screw type, but may also be of the pre-plastication type. A pre-plastication type injection device supplies molding material molten in a plasticization cylinder to an injection cylinder, and injects the molding material from the injection cylinder into a mold device. A screw is arranged in the plasticization cylinder so that it can rotate freely but cannot move back and forth, or a screw is arranged so that it can rotate freely and move back and forth. Meanwhile, a plunger is arranged in the injection cylinder so that it can move back and forth.

In addition, the injection device 300 of this embodiment is a horizontal type in which the axial direction of the cylinder 310 is horizontal, but it may be a vertical type in which the axial direction of the cylinder 310 is vertical. The mold clamping device combined with the vertical injection device 300 may be either a vertical type or a horizontal type. Similarly, the mold clamping device combined with the horizontal injection device 300 may be either a horizontal type or a vertical type.

(Mobile device)
In describing the moving device 400, similar to the description of the injection device 300, the movement direction of the screw 330 during filling (e.g., the negative X-axis direction) will be described as the forward direction, and the movement direction of the screw 330 during metering (e.g., the positive X-axis direction) will be described as the rearward direction.

The moving device 400 moves the injection device 300 forward and backward relative to the mold device 800. The moving device 400 also presses the nozzle 320 against the mold device 800 to generate nozzle touch pressure. The moving device 400 includes a hydraulic pump 410, a motor 420 as a drive source, a hydraulic cylinder 430 as a hydraulic actuator, and the like.

The hydraulic pump 410 has a first port 411 and a second port 412. The hydraulic pump 410 is a pump that can rotate in both directions, and by switching the rotation direction of the motor 420, it draws in hydraulic fluid (e.g., oil) from either the first port 411 or the second port 412 and discharges it from the other port, generating hydraulic pressure. The hydraulic pump 410 can also draw in hydraulic fluid from a tank and discharge the hydraulic fluid from either the first port 411 or the second port 412.

The motor 420 operates the hydraulic pump 410. The motor 420 drives the hydraulic pump 410 with a rotational direction and rotational torque according to a control signal from the control device 700. The motor 420 may be an electric motor or an electric servo motor.

The hydraulic cylinder 430 has a cylinder body 431, a piston 432, and a piston rod 433. The cylinder body 431 is fixed to the injection device 300. The piston 432 divides the inside of the cylinder body 431 into a front chamber 435 as a first chamber and a rear chamber 436 as a second chamber. The piston rod 433 is fixed to the fixed platen 110.

The front chamber 435 of the hydraulic cylinder 430 is connected to the first port 411 of the hydraulic pump 410 via the first flow path 401. The hydraulic fluid discharged from the first port 411 is supplied to the front chamber 435 via the first flow path 401, thereby pushing the injection device 300 forward. The injection device 300 is moved forward, and the nozzle 320 is pressed against the fixed mold 810. The front chamber 435 functions as a pressure chamber that generates nozzle touch pressure of the nozzle 320 by the pressure of the hydraulic fluid supplied from the hydraulic pump 410.

Meanwhile, the rear chamber 436 of the hydraulic cylinder 430 is connected to the second port 412 of the hydraulic pump 410 via the second flow path 402. The hydraulic fluid discharged from the second port 412 is supplied to the rear chamber 436 of the hydraulic cylinder 430 via the second flow path 402, thereby pushing the injection device 300 backward. The injection device 300 is retracted, and the nozzle 320 is separated from the fixed mold 810.

In this embodiment, the moving device 400 includes a hydraulic cylinder 430, but the present invention is not limited to this. For example, instead of the hydraulic cylinder 430, an electric motor and a motion conversion mechanism that converts the rotational motion of the electric motor into the linear motion of the injection device 300 may be used.

(Control device)
The control device 700 is configured, for example, by a computer, and has a CPU (Central Processing Unit) 701, a storage medium 702 such as a memory, an input interface 703, and an output interface 704 as shown in Figures 1 and 2. The control device 700 performs various controls by causing the CPU 701 to execute a program stored in the storage medium 702. The control device 700 also receives signals from the outside via the input interface 703, and transmits signals to the outside via the output interface 704.

The control device 700 repeatedly manufactures molded products by repeating processes such as the metering process, mold closing process, pressure increase process, mold clamping process, filling process, pressure holding process, cooling process, depressurization process, mold opening process, and ejection process. A series of operations required to obtain a molded product, for example, the operations from the start of a metering process to the start of the next metering process, is also called a "shot" or "molding cycle." The time required for one shot is also called the "molding cycle time" or "cycle time."

One molding cycle includes, for example, a metering process, a mold closing process, a pressurization process, a mold clamping process, a filling process, a pressure holding process, a cooling process, a depressurization process, a mold opening process, and an ejection process, in this order. The order here refers to the order in which each process starts. The filling process, the pressure holding process, and the cooling process are performed during the mold clamping process. The start of the mold clamping process may coincide with the start of the filling process. Completion of the depressurization process coincides with the start of the mold opening process.

Note that, in order to shorten the molding cycle time, multiple processes may be performed simultaneously. For example, the metering process may be performed during the cooling process of the previous molding cycle, or during the mold clamping process. In this case, the mold closing process may be performed at the beginning of the molding cycle. The filling process may be started during the mold closing process. The ejection process may be started during the mold opening process. If an opening/closing valve that opens and closes the flow path of the nozzle 320 is provided, the mold opening process may be started during the metering process. This is because even if the mold opening process is started during the metering process, molding material will not leak from the nozzle 320 as long as the opening/closing valve closes the flow path of the nozzle 320.

Note that one molding cycle may include processes other than the metering process, mold closing process, pressure increase process, mold clamping process, filling process, pressure holding process, cooling process, depressurization process, mold opening process, and ejection process.

For example, after the dwelling process is completed and before the metering process begins, a pre-metering suck-back process may be performed in which the screw 330 is retracted to a preset metering start position. This can reduce the pressure of the molding material accumulated in front of the screw 330 before the metering process begins, and can prevent the screw 330 from retracting suddenly at the start of the metering process.

In addition, after the metering process is completed and before the filling process begins, a post-metering suck-back process may be performed in which the screw 330 is retracted to a preset filling start position (also called the "injection start position"). This can reduce the pressure of the molding material accumulated in front of the screw 330 before the filling process begins, and can prevent the molding material from leaking from the nozzle 320 before the filling process begins.

The control device 700 is connected to an operation device 750 that accepts input operations by the user and a display device 760 that displays a screen. The operation device 750 and the display device 760 may be configured, for example, by a touch panel 770 and may be integrated. The touch panel 770 as the display device 760 displays a screen under the control of the control device 700. The screen of the touch panel 770 may display, for example, information such as the settings of the injection molding machine 10 and the current state of the injection molding machine 10. In addition, the screen of the touch panel 770 may display, for example, an operation unit such as a button that accepts input operations by the user and an input field. The touch panel 770 as the operation device 750 detects an input operation on the screen by the user and outputs a signal corresponding to the input operation to the control device 700. As a result, for example, the user can operate the operation unit provided on the screen while checking the information displayed on the screen to perform settings of the injection molding machine 10 (including input of setting values). In addition, the user can operate the operation unit provided on the screen to perform the operation of the injection molding machine 10 corresponding to the operation unit. The operation of the injection molding machine 10 may be, for example, the operation (including stopping) of the clamping device 100, the ejector device 200, the injection device 300, the moving device 400, etc. The operation of the injection molding machine 10 may also be the switching of a screen displayed on the touch panel 770 serving as the display device 760, etc.

In the present embodiment, the operation device 750 and the display device 760 are described as being integrated as the touch panel 770, but they may be provided independently. Also, multiple operation devices 750 may be provided. The operation device 750 and the display device 760 are disposed on the operation side (negative Y-axis direction) of the mold clamping unit 100 (more specifically, the fixed platen 110).

(Screw details)
Next, the configuration of the tip portion of the screw 330 will be described with reference to Figures 3 and 4. Figure 3 is a vertical cross-sectional view of the tip portion of the screw 330. Figure 4(A) is a cross-sectional view taken along line IVA-IVA in Figure 3. Figure 4(B) is a plan view of the protruding portion 335 as viewed from the direction of arrow IVB in Figure 3. Figure 4(C) is a plan view of a fin portion 336A according to a modified example.

The screw 330 has a backflow prevention ring 331, a seal ring 332, and a screw head 333 at its tip. The backflow prevention ring 331 is arranged in a free state (relatively movable and rotatable) outside the screw head 333. Meanwhile, the seal ring 332 is fixed to the outer circumferential surface of the screw head 333. The screw head 333 is connected to a flight screw (not shown) having a spiral flight in the screw 330.

For this reason, the seal ring 332 and the screw head 333 rotate together with the flight screw and move forward and backward together with the flight screw. On the other hand, the backflow prevention ring 331 is configured as a non-co-rotating type that does not rotate together with the flight screw, the seal ring 332, and the screw head 333.

The backflow prevention ring 331 is formed in an annular shape and has a through hole 331h on the inside through which the screw head 333 is inserted. The through hole 331h is gradually narrowed toward the tip by the inner wall of the backflow prevention ring 331. For example, the inner wall of the backflow prevention ring 331 has a first tapered wall 331a, a second tapered wall 331b, and a parallel wall 331c, in this order, from the base end side toward the tip side. The backflow prevention ring 331 is configured to maintain a predetermined gap between the screw head 333 and the inner wall when the screw 330 rotates. Here, the taper refers to the portion where the wall widens or narrows in the radial direction of the screw along the axial direction of the screw 330.

When assembled to the screw head 333, the backflow prevention ring 331 is disposed between the base end side seal ring 332 and the protruding portion 335 of the screw head 333, which will be described later. The backflow prevention ring 331 is also movable between a closed position in contact with the seal ring 332 and an open position in close proximity to the base end face of the protruding portion 335.

The backflow prevention ring 331 according to this embodiment has a length Lr along the axial direction of the screw head 333 that is set as short as possible. Specifically, the length Lr of the backflow prevention ring 331 should be set to 1/2 or less of the diameter (radial outer diameter) of the backflow prevention ring 331, and more preferably, should be set to 1/5 to 1/2 or less of the diameter of the backflow prevention ring 331, taking strength into consideration.

During the injection process (advancement of the screw 330), the seal ring 332 comes into contact with the backflow prevention ring 331, blocking the tip side of the seal ring 332. The outer shape of the seal ring 332 is appropriately formed to allow the molding material to flow toward the tip side during the metering process (rotation of the screw 330), while providing a seal with the backflow prevention ring 331 when the screw 330 advances.

For example, the tip surface 332a of the seal ring 332 is formed in a tapered shape (cone shape) parallel to the first tapered wall 331a of the backflow prevention ring 331. As a result, when the screw 330 advances, the tip surface 332a of the seal ring 332 comes into surface contact with the first tapered wall 331a of the backflow prevention ring 331, allowing a good seal to be created.

The screw head 333 has a shaft portion 334 that extends along the axial direction of the screw 330, and a protrusion 335 that is provided on the outer peripheral surface of the shaft portion 334 and protrudes in a direction perpendicular to the axial direction.

The shaft portion 334 is connected to the screw flight at the base end by an appropriate connecting means. The outer shape and thickness of the shaft portion 334 may be designed as desired depending on the axial location. For example, the shaft portion 334 has a flange portion 334f on the tip side of the mounting portion 334a on which the seal ring 332 is mounted. The backflow prevention ring 331 is assembled to the outside of the flange portion 334f on the shaft portion 334 and to the outside of the neck portion 334n that is connected to the tip side of the flange portion 334f. The protrusion 335 is provided on the tip side of this neck portion 334n.

Between the flange portion 334f and the neck portion 334n, a tapered portion 334t is provided. The flange portion 334f, the tapered portion 334t, and the neck portion 334n cooperate with the through hole 331h of the backflow prevention ring 331 during the metering process to form a flow path through which the molding material flows. That is, during the metering process, the molding material can be smoothly circulated to the tip side of the screw head 333 by the flow path between the first tapered wall 331a of the backflow prevention ring 331 and the tip surface 332a of the seal ring 332, the flow path between the second tapered surface 332b of the backflow prevention ring 331 and the flange portion 334f and the curved surface of the shaft portion 334, and the flow path between the parallel wall 331c of the backflow prevention ring 331 and the neck portion 334n of the shaft portion 334.

The protruding portion 335 of the screw head 333 according to this embodiment is composed of multiple (three) fin portions 336 that protrude radially from the shaft portion 334. It is needless to say that the number of fin portions 336 is not particularly limited.

Each fin portion 336 stands at a predetermined height relative to the shaft portion 334 and extends with a constant width along the axial direction. The width of each fin portion 336 is smaller than the diameter of the shaft portion 334, but larger than the radius of the shaft portion 334 (see also FIG. 4(A)). For example, the width of each fin portion 336 may be set in the range of about 30% to 95% of the diameter of the shaft portion 334. For example, when there are a large number of fin portions 336 (four to six), the width of each fin portion 336 is smaller than the diameter of the shaft portion 334.

The tip side of each fin portion 336 is inclined toward the tip and toward the center. The outer surface of the tip of the shaft portion 334 is cone-shaped, continuing directly from the inclination of each fin portion 336. In addition, the tip of the screw head 333 is curved in an R shape.

As shown in FIG. 4A, the fins 336 are arranged at equal intervals (120° apart) along the circumferential direction (rotational direction) of the shaft 334. The screw head 333 forms multiple (three) flow spaces 338 between adjacent fins 336 and on the outer circumferential surface of the shaft 334, allowing the molding material to flow.

Each fin portion 336 constituting the protrusion 335 is located further toward the tip side than the backflow prevention ring 331 that is attached to the shaft portion 334, and has a base end surface 337 that faces the backflow prevention ring 331.

The base end surface 337 has a flat surface 337a that faces the backflow prevention ring 331, and an inclined surface 337b that is adjacent to the flat surface 337a and forms a surface that is inclined with respect to the backflow prevention ring 331. In addition, the base portion of the base end surface 337 that connects to the shaft portion 334 is formed into a curved surface 337c that smoothly continues between each fin portion 336 and the neck portion 334n.

The flat surface 337a and the inclined surface 337b are arranged so as to be aligned in a direction (the width direction of the fin portion 336) perpendicular to the protruding direction of the fin portion 336 (the normal direction of the shaft portion 334). In other words, the flat surface 337a and the inclined surface 337b are arranged so as to be adjacent to each other along the rotation direction of the screw head 333. The flat surface 337a and the inclined surface 337b are provided on each of the multiple (three) fin portions 336.

The flat surface 337a is formed on a surface parallel to a direction perpendicular to the axial direction of the shaft portion 334, and constitutes a portion where the base end surface 337 of the protruding portion 335 and the tip surface 331s of the backflow prevention ring 331 face each other in parallel. In other words, the flat surface 337a faces the flat tip surface 331s of the backflow prevention ring 331 in parallel to each other. When the protruding portion 335 is viewed from the base end direction as shown in FIG. 4(A), the flat surface 337a is formed in a substantially rectangular shape with its long side in the protruding direction of the fin portion 336. This flat surface 337a is connected at right angles to each of the protruding end surfaces and adjacent side surfaces of the fin portion 336.

The inclined surface 337b is a wall surface that is inclined with respect to the flat surface 337a, thereby forming a gap space 339 between the backflow prevention ring 331 and the inclined surface 337b. The inclined surface 337b is inclined toward the tip side from the boundary with the flat surface 337a toward the outside in the width direction. When the protruding portion 335 is viewed from the base end direction as shown in FIG. 4(A), the inclined surface 337b is formed in a substantially rectangular shape with a long side in the protruding direction of the fin portion 336, similar to the flat surface 337a. This inclined surface 337b is connected at a right angle to the protruding end surface of the fin portion 336, and is connected at an obtuse angle to the adjacent side surface of the fin portion 336 (see also FIG. 4(B)).

Depending on the inclination of the inclined surface 337b, the gap space 339 opens toward the rotation direction of the screw head 333. The inclined surface 337b functions as a pressure generating part that generates a force that pushes the backflow prevention ring 331 toward the base end as the molding material flows into the gap space 339 when the screw head 333 rotates. The function of this pressure generating part will be described in detail later.

The inclined surface 337b is inclined so as to gradually widen the width of the clearance space 339 from the boundary with the flat surface 337a (the widthwise center of the base end surface 337) toward the side surface of the fin portion 336. That is, in a plan view of the fin portion 336 (see FIG. 4B), the clearance space 339 is formed in a right-angled triangular wedge shape by the tip surface 331s (see also FIG. 5) of the backflow prevention ring 331 and the inclined surface 337b. The clearance space 339 has an opening 339a at the tip in the rotation direction of the screw head 333 that is wider than the width of the gap between the flat surface 337a and the tip surface 331s of the backflow prevention ring 331.

The inclination angle θt of the inclined surface 337b relative to the flat surface 337a is preferably set, for example, within the range of 1.5° to 7°. If the inclination angle θt is greater than 7°, the molding material that has entered the gap space 339 will have difficulty progressing toward the apex angle side of the gap space 339 (toward the flat surface 337a), and sufficient pressing force may not be obtained. Conversely, if the inclination angle θt is smaller than 1.5°, it may be difficult for the molding material to enter the gap space 339 itself.

The positions of the flat surface 337a and the inclined surface 337b are set according to the rotation direction of the screw head 333. For example, when the protruding portion 335 is viewed from the base end direction as shown in FIG. 4(A), if the rotation direction of the screw head 333 is counterclockwise, the flat surface 337a is located on the right side and the inclined surface 337b is located on the left side. Conversely, when the protruding portion 335 is viewed from the base end direction as shown in FIG. 4(A), if the rotation direction of the screw head 333 is clockwise, the flat surface 337a is located on the left side and the inclined surface 337b is located on the right side.

In this embodiment, the boundary between the flat surface 337a and the inclined surface 337b is set at the center line of the fin portion 336 in the width direction. In other words, the ratio of the flat surface 337a to the inclined surface 337b in the width direction of the fin portion 336 is 5:5. However, the ratio of the flat surface 337a to the inclined surface 337b in the width direction of the fin portion 336 is not limited to this, and may be set in the range of 2:8 to 8:2 (the ratio of the inclined surface 337b to the width of the base end surface 337 is in the range of 20% to 80%).

If the ratio of the inclined surface 337b is less than 20%, the amount of molding material that enters the gap space 339 will be small, and there is a risk that sufficient pressing force will not be generated. On the other hand, if the ratio of the inclined surface 337b is greater than 80%, the amount of flat surface 337a will be small, and if the fin portion 336 wears, there is a high possibility that it will no longer be effective as a pressure generating portion.

The screw 330 (screw head 333) of the injection molding machine 10 according to this embodiment is basically configured as described above, and its effects will be explained below.

Figure 5 is a plan view showing the relationship between the fin portion 336 and the backflow prevention ring 331. In the metering process, the fin portion 336 of the screw head 333 rotates around the axis of the shaft portion 334 (see Figure 4), and moves, for example, downward in Figure 5. Meanwhile, the backflow prevention ring 331 is stationary and does not rotate with the screw head 333. However, since the backflow prevention ring 331 is free relative to the screw head 333, it can rotate slightly due to the influence of the flow of the molding material, etc.

When the screw head 333 rotates, the molding material enters the base end surface 337 of the fin portion 336 from the inclined surface 337b side. The inclined surface 337b is inclined toward the base end from the side surface of the fin portion 336 toward the radially inner side (flat surface 337a side), and as the fin portion 336 moves, a large amount of molding material can be introduced into the gap space 339 from the opening 339a of the gap space 339.

The molding material that flows into the gap space 339 moves toward the center of the fin section 336 in the width direction according to the inclination of the inclined surface 337b. As the gap between the inclined surface 337b and the backflow prevention ring 331 narrows toward the center of the fin section 336 in the width direction, the pressure in the gap space 339 increases due to the molding material. The molding material then flows from the apex of the gap space 339 into the gap between the flat surface 337a and the tip surface 331s of the backflow prevention ring 331. Due to the increased molding pressure that increases as the gap space 339 narrows, the base end surface 337 can apply a force that pushes the backflow prevention ring 331 in the base end direction. This force that pushes the backflow prevention ring 331 in the base end direction can be calculated using Reynolds' lubrication theory.

The force generated by the flow of the molding material at the base end surface 337 acts as a repulsive force P opposing the pressing force F that presses the backflow prevention ring 331 toward the tip, as shown in FIG. 6. That is, when the screw 330 is rotated in the metering process, the molding material moves around the screw 330 toward the tip. This molding material moves around the outside of the seal ring 332 and flows into the through hole 331h of the backflow prevention ring 331 while contacting the base end surface of the backflow prevention ring 331. As a result, a pressing force F is applied to the backflow prevention ring 331 in the tip direction.

The molding material that flows into the through hole 331h passes through the backflow prevention ring 331 and flows out into the flow space 338 between the fins 336 on the tip side of the backflow prevention ring 331. Then, as the screw head 333 rotates, this molding material flows into the gap space 339 (see FIG. 5) formed in the base end surface 337 of the fins 336, generating a repulsive force P that pushes the backflow prevention ring 331 in the base end direction.

At a first distance where the tip surface 331s of the backflow prevention ring 331 and the base end surface 337 of the protrusion 335 are close to each other, the repulsive force P is sufficiently greater than the pressing force F. Conversely, at a second distance where the tip surface 331s of the backflow prevention ring 331 and the base end surface 337 of the protrusion 335 are farther apart than the first distance, the repulsive force P is smaller than the pressing force F. This second distance is a position where the base end surface of the backflow prevention ring 331 does not contact the tip surface 332a of the seal ring 332.

That is, when the screw 330 rotates, the base end surface 337 having the inclined surface 337b increases the gap with the backflow prevention ring 331 due to the repulsive force P. The backflow prevention ring 331 is held in a position where the pressing force F and the repulsive force P are in balance. Therefore, the screw 330 can continue to rotate in the metering process without the backflow prevention ring 331 contacting either the protruding portion 335 (each fin portion 336) or the seal ring 332.

As described above, the screw 330 has a flat surface 337a and an inclined surface 337b on the base end surface 337 of the protruding portion 335, which makes it possible to increase the gap with the backflow prevention ring 331. By increasing the amount of the gap, the amount of heat (shear heat) generated by the resin material at the tip of the screw 330 decreases. As a result, deterioration of the molding material can be suppressed, and the inclusion of worn metal powder due to wear can be reduced, making it possible to significantly suppress molding defects.

In addition, the screw head 333 has a flat surface 337a as well as an inclined surface 337b at the base end surface 337, so that even if the backflow prevention ring 331 comes into contact with each fin portion 336 under circumstances such as when there is little molding material in the flow space 338, damage to the fin portion 336 can be suppressed. This makes it possible to suppress inconveniences such as early wear of the inclined surface 337b formed on the base end surface 337, and the durability of the screw head 333 can be increased even with a configuration having the inclined surface 337b.

The injection molding machine 10, screw 330, and screw head 333 of the present disclosure are not limited to the above embodiment, and may take various modified forms. For example, the base end surface 337 is not limited to a configuration in which the pressure generating portion is formed by the inclined surface 337b. As an example, the pressure generating portion may be formed by a stepped surface that has a low step with respect to the flat surface of the tip surface 331s of the backflow prevention ring 331 or the flat surface of the base end surface 337 of the protruding portion 335. Even if the molding material flows into the gap space 339 formed by this stepped surface, the pressure can be increased, and a repulsive force P that presses the backflow prevention ring 331 can be obtained.

Also, as in the fin portion 336A according to another configuration example shown in FIG. 4(C), the base end surface 337 may have a rounded corner 337r at one corner, and this rounded corner 337r may form a gap space 339. For example, the rounded corner 337r may be formed to have a larger radius of curvature than the other corner (rounded corner) of the base end surface 337. Even in this case, the rounded corner 337r can increase the pressure of the molding material that flows in.

For example, the protrusion 335 is not limited to having multiple fins 336. As an example, the protrusion 335 may have a conical shape tapering toward the tip and a spiral groove on the surface. Even in this case, the same effect as above can be obtained by applying a flat surface 337a and an inclined surface 337b to the base end surface 337 of the conical protrusion 335.

Figure 7 is a side cross-sectional view showing the screw 330A according to the first modified example. In the cross-sectional view shown in Figure 7, the screw 330A has an inclined base end surface 337i in each fin portion 336 of the protruding portion 335A, while the backflow prevention ring 331A has an inclined tip surface 331i at the tip surface 331s. For example, the inclined base end surface 337i and the inclined tip surface 331i are formed so as to be parallel to each other when the molding material is injected. That is, in the above-mentioned screw 330, the flat surface 337a perpendicular to the base end surface 337 and the shaft portion may come into contact with the backflow prevention ring 331. In contrast, the screw 330A has an inclined base end surface 337i and an inclined tip surface 331i that are not perpendicular to the axial direction, which greatly reduces the chance of contact between the protruding portion 335 and the backflow prevention ring 331. Even if the screw 330A has an inclined base end surface 337i, it can adopt the flat surface 337a and the inclined surface 337b, as in the above embodiment. Therefore, the screw 330A can also obtain the same effect as the above screw 330.

Figure 8 is a plan view that shows a schematic relationship between the protrusion 335B of the screw 330B and the backflow prevention ring 331B according to the second modified example. As shown in Figure 7, the screw 330B has a flat surface 371 and a recess 372 on the tip surface 370 of the backflow prevention ring 331B. In contrast, the base end surface 337 of each fin portion 336 of the protrusion 335B in the screw 330A is formed flat (flat surface).

The recess 372 of the backflow prevention ring 331B is formed in a right-angled triangular wedge shape in a plan view of the outer circumferential surface of the backflow prevention ring 331B from a radial direction. The recess 372 has an inclined surface (pressure generating portion) 373 that is connected to the flat surface 371 and inclined from the flat surface 371 by an inclination angle θt, and an orthogonal surface 374 that is perpendicular to the flat surface 371. The recess 372 formed in this manner can achieve the same effect as the gap space 339 in the above embodiment.

The backflow prevention ring 331B also has multiple recesses 372 arranged at equal intervals around the circumferential direction of the tip surface 370. In other words, the tip surface 370 of the backflow prevention ring 331B has a shape in which flat surfaces 371 and inclined surfaces 373 are alternately repeated. In other words, the flat surfaces 371 form a portion that faces the base end surface 337 in parallel. This allows the backflow prevention ring 331B to receive the repulsive force P evenly across the entire tip surface 370 as the screw head 333 rotates.

That is, when each fin portion 336 of the screw 330B rotates, the molding material that has moved toward the tip side of the backflow prevention ring 331B enters the recess 372. Inside the recess 372, the molding material moves toward the apex angle of the recess 372 according to the inclination of the inclined surface 373. As the gap between the base end surface 337 of the fin portion 336 and the inclined surface 373 of the backflow prevention ring 331B narrows, the molding material increases the pressure inside the recess 372. Then, the molding material with increased pressure exerts a repulsive force P on the backflow prevention ring 331B, pushing it toward the base end.

As a result, when the screw head 333B rotates, the gap between the backflow prevention ring 331B and the protrusion 335B increases, suppressing the amount of heat generated in the molding material. This allows the injection molding machine 10 to suppress deterioration of the molding material and molding defects caused by deterioration.

The injection molding machine 10, screw 330, and screw head 333 according to the embodiments disclosed herein are illustrative in all respects and are not restrictive. The embodiments can be modified and improved in various ways without departing from the spirit and scope of the appended claims. The matters described in the above embodiments can be configured in other ways as long as they are not inconsistent, and can be combined as long as they are not inconsistent.

10 Injection molding machine 330, 330A Screw 331, 331A Backflow prevention ring 333, 333A Screw head 334 Shaft portion 335, 335A Protruding portion 337 Base end surface 337a Flat surface (flat portion)
337b Inclined surface (pressure generating part)

Claims (12)

A screw having a shaft portion, a screw head, and a backflow prevention ring assembled to the shaft portion,
the screw head has a base end surface facing the backflow prevention ring on the tip side of the backflow prevention ring,
The backflow prevention ring has a tip surface facing the base end surface,
The base end surface or the tip end surface is
a pressure generating section that generates pressure between the screw head and the backflow prevention ring in association with the inflow of molding material;
and a portion where the base end surface and the tip end surface face each other in parallel so that the base end surface applies a force pressing the tip end surface toward the base end side by the pressure generated by the pressure generating unit.
Screw. A screw head having a shaft portion and a protruding portion protruding in a direction perpendicular to the axial direction of the shaft portion,
the protruding portion is located distally of a backflow prevention ring attached to the shaft portion and has a base end surface facing a distal end surface of the backflow prevention ring,
The base end surface is
a pressure generating section that generates pressure between the backflow prevention ring and the pressure generating section as the molding material flows in;
a portion facing the distal end surface in parallel such that the proximal end surface applies a force pressing the distal end surface toward the proximal end side by the pressure generated by the pressure generating unit;
Screw head. the pressure generating portion is a wall surface that forms a gap space between the backflow prevention ring and the pressure generating portion,
The gap space is open toward the rotation direction of the screw head.
A screw head according to claim 2. The wall surfaces are inclined in a direction gradually increasing the width of the gap space from the parallel opposing portions toward the opening.
A screw head according to claim 3. The inclination angle of the wall surface with respect to the parallel opposing portion is set within a range of 1.5° to 7°.
A screw head according to claim 4. The protrusion has a plurality of fins protruding radially from the shaft,
The pressure generating portion and the parallel opposing portion are provided on each of the plurality of fin portions.
A screw head according to claim 2. A screw having a screw head according to any one of claims 2 to 6. An injection molding machine equipped with the screw according to claim 7. A backflow prevention ring is attached to a shaft portion of a screw head and is located on the base end side of a protruding portion protruding in a direction perpendicular to the axial direction of the shaft portion of the screw head,
a tip end surface facing the base end surface of the protrusion,
The tip surface is
a pressure generating section that generates pressure between the base end surface and the pressure generating section as the molding material flows in;
a portion facing the base end surface in parallel such that the base end surface applies a force pressing the tip end surface toward the base end side by the pressure generated by the pressure generating unit;
Backflow prevention ring. the tip surface has portions that face the pressure generating portions in parallel alternately along a circumferential direction of the backflow prevention ring,
The backflow prevention ring of claim 9. A screw having a backflow prevention ring according to claim 9 or 10. An injection molding machine equipped with the screw according to claim 11.

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