JP6779802B2 - Injection molding machine - Google Patents

Description

The present invention relates to an injection molding machine.

The controller of the injection molding machine described in Patent Document 1 controls an injection servomotor so that the forward speed of the screw becomes a predetermined set speed in the injection process, and the position of the screw reaches the V / P switching position. At that point, the injection process is switched to the pressure holding process, and in the pressure holding process, the injection servomotor is controlled so that the resin pressure at the front end of the screw is maintained at the holding pressure set pressure.

Japanese Unexamined Patent Publication No. 2011-183705

As shown in FIG. 3, on the front portion of the screw 330, a check flow prevention ring 331 as a check flow prevention valve for preventing backflow of the molding material from the front side (left side in FIG. 3) to the rear side (right side in FIG. Can be attached freely.

The backflow prevention ring 331 is located at the open position shown by the broken line in FIG. 3 in the weighing step, and is located at the closed position shown by the solid line in FIG. 3 in the filling step and the holding pressure step, and this is repeated for each shot. Here, the shot refers to a series of operations for obtaining a molded product, for example, an operation from the start of weighing to the start of the next weighing.

Therefore, the backflow prevention ring 331 is repeatedly moved back and forth and gradually worn. Therefore, the sealing function of the backflow prevention ring 331 gradually deteriorates, and when the screw 330 is pushed forward in the filling step or the pressure holding step, the backflow of the molding material from the front to the rear of the screw 330 occurs.

As shown in FIG. 4, when there is a backflow of the molding material, the position of the screw 330 advances in the filling step and the pressure holding step as compared with the case where there is no backflow of the molding material. This is because when the backflow of the molding material occurs, the amount of the molding material entering the inside of the mold apparatus 10 decreases by that amount, and the amount of advance of the screw 330 increases in order to fill the inside of the mold apparatus 10 with the molding material. ..

If the amount of backflow molding material is too large, a high-quality molded product cannot be obtained, which may result in an unplanned stop. For example, if the amount of backflow molding material is too large, the amount of molding material in front of the screw 330 remaining in the cylinder 310 in the pressure holding step is insufficient, so that the pressure holding step is interrupted. After that, the backflow prevention ring 331 is replaced or repaired. At this time, the screw 330 may be replaced or repaired.

The present invention has been made in view of the above problems, and a main object of the present invention is to provide an injection molding machine capable of suppressing an unplanned stoppage due to backflow of a molding material.

In order to solve the above problems, according to one aspect of the present invention,
A cylinder that heats the molding material, a nozzle provided at the front end of the cylinder, a screw that is rotatably arranged inside the cylinder, and a backflow of the molding material from the front to the rear of the screw. An injection device that includes a check valve to prevent
And a control unit for controlling the injection device,
The control device determines the presence or absence of an abnormality due to the backflow of the molding material, and if it determines that the abnormality is present, corrects at least one of a set value related to the temperature of the cylinder and a set value related to the temperature of the nozzle. A molding machine is provided.

According to one aspect of the present invention, there is provided an injection molding machine capable of suppressing an unplanned stoppage due to backflow of a molding material.

It is a figure which shows the state at the time of completion of the mold opening of the injection molding machine by one Embodiment. It is a figure which shows the state at the time of mold clamping of the injection molding machine by one Embodiment. It is a figure which shows the operation of the backflow prevention ring by one Embodiment. It is a figure which shows the backflow of a molding material by one Embodiment. It is a flowchart which shows the processing of the control apparatus by one Embodiment. It is a figure which shows the measurement completion position of the front end of a screw in the case where there is an abnormality due to backflow according to one Embodiment, and the case where there is no abnormality due to backflow. It is a figure which shows the screw advance speed in the filling process in the case where there is an abnormality due to the backflow and the case where there is no abnormality due to the backflow according to one embodiment. It is a figure which shows the V / P switching position of the front end of a screw between the case where there is an abnormality due to backflow and the case where there is no abnormality due to backflow according to one embodiment. It is a figure which shows the flow of the molding material after the temperature drop by one Embodiment.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings, but in each drawing, the same or corresponding configurations are designated by the same or corresponding reference numerals and the description thereof will be omitted.

(Injection molding machine)
FIG. 1 is a diagram showing a state at the time of completion of mold opening of the injection molding machine according to one embodiment. FIG. 2 is a diagram showing a state at the time of mold clamping of the injection molding machine according to one embodiment. As shown in FIGS. 1 and 2, the injection molding machine includes a mold clamping device 100, an ejector device 200, an injection device 300, a moving device 400, and a control device 700. Hereinafter, each component of the injection molding machine will be described.

(Molding device)
In the description of the mold clamping device 100, the moving direction of the movable platen 120 when the mold is closed (right direction in FIGS. 1 and 2) is forward, and the moving direction of the movable platen 120 when the mold is opened (left in FIGS. 1 and 2). Direction) will be described as backward.

The mold clamping device 100 closes, molds, and opens the mold of the mold apparatus 10. The mold clamping device 100 is, for example, a horizontal type, and the mold opening / closing direction is the horizontal direction. The mold clamping device 100 includes a fixed platen 110, a movable platen 120, a toggle support 130, a tie bar 140, a toggle mechanism 150, a mold clamping motor 160, a motion conversion mechanism 170, and a mold thickness adjusting mechanism 180.

The fixed platen 110 is fixed to the frame Fr. The fixed mold 11 is attached to the surface of the fixed platen 110 facing the movable platen 120.

The movable platen 120 is movable in the mold opening / closing direction with respect to the frame Fr. A guide 101 for guiding the movable platen 120 is laid on the frame Fr. The movable mold 12 is attached to the surface of the movable platen 120 facing the fixed platen 110.

By advancing and retreating the movable platen 120 with respect to the fixed platen 110, mold closing, mold clamping, and mold opening are performed. The mold device 10 is composed of the fixed mold 11 and the movable mold 12.

The toggle support 130 is connected to the fixed platen 110 at intervals, and is movably placed on the frame Fr in the mold opening / closing direction. The toggle support 130 may be movable along a guide laid on the frame Fr. The guide of the toggle support 130 may be the same as that of the guide 101 of the movable platen 120.

In the present embodiment, the fixed platen 110 is fixed to the frame Fr and the toggle support 130 is movable in the mold opening / closing direction with respect to the frame Fr, but the toggle support 130 is fixed to the frame Fr and the fixed platen. The 110 may be movable in the mold opening / closing direction with respect to the frame Fr.

The tie bar 140 connects the fixed platen 110 and the toggle support 130 at intervals L in the mold opening / closing direction. A plurality of tie bars 140 may be used. Each tie bar 140 is parallel to the mold opening / closing direction and extends according to the mold clamping force. At least one tie bar 140 is provided with a tie bar distortion detector 141 that detects the distortion of the tie bar 140. The tie bar distortion 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 for detecting the mold clamping force and the like.

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

The toggle mechanism 150 is arranged between the movable platen 120 and the toggle support 130, and moves the movable platen 120 with respect to the toggle support 130 in the mold opening / closing direction. The toggle mechanism 150 is composed of a crosshead 151, a pair of links, and the like. Each link group has a first link 152 and a second link 153 that are flexibly connected by a pin or the like. The first link 152 is swingably attached to the movable platen 120 with a pin or the like, and the second link 153 is swingably attached to the toggle support 130 with a pin or the like. The second link 153 is attached to the crosshead 151 via the third link 154. When the crosshead 151 is moved back and forth with respect to the toggle support 130, the first link 152 and the second link 153 bend and stretch, and the movable platen 120 moves back and forth with respect to the toggle support 130.

The configuration of the toggle mechanism 150 is not limited to the configurations shown in FIGS. 1 and 2. For example, in FIGS. 1 and 2, the number of nodes in each link group is 5, but it may be 4, and one end of the third link 154 is connected to the nodes of the first link 152 and the second link 153. May be done.

The mold clamping motor 160 is attached to the toggle support 130 and operates the toggle mechanism 150. The mold clamping motor 160 bends and stretches the first link 152 and the second link 153 by advancing and retracting the crosshead 151 with respect to the toggle support 130, and advances and retracts the movable platen 120 with respect to the toggle support 130. The mold clamping motor 160 is directly connected to the motion conversion mechanism 170, but may be connected to the motion conversion mechanism 170 via a belt, a pulley, or the like.

The motion conversion mechanism 170 converts the rotational motion of the mold clamping motor 160 into a linear motion of the crosshead 151. The motion conversion mechanism 170 includes a screw shaft 171 and a screw nut 172 screwed onto the screw shaft 171. A ball or roller may be interposed between the screw shaft 171 and the screw nut 172.

The mold clamping device 100 performs a mold closing step, a mold clamping step, a mold opening step, and the like under the control of the control device 700.

In the mold closing step, the movable platen 120 is advanced by driving the mold clamping motor 160 to advance the crosshead 151 to the mold closing completion position at a set speed, and the movable mold 12 is touched by the fixed mold 11. The position and speed of the crosshead 151 are detected by using, for example, the encoder 161 of the mold clamping motor 160. The encoder 161 detects the rotation of the mold clamping motor 160 and sends a signal indicating the detection result to the control device 700.

In the mold clamping step, the mold clamping force 160 is further driven to further advance the crosshead 151 from the mold closing completion position to the mold clamping position to generate a mold clamping force. At the time of mold clamping, a cavity space 14 is formed between the movable mold 12 and the fixed mold 11, and the injection device 300 fills the cavity space 14 with a liquid molding material. A molded product is obtained by solidifying the filled molding material. The number of cavity spaces 14 may be plural, in which case a plurality of molded articles can be obtained at the same time.

In the mold opening step, the mold clamping motor 160 is driven to retract the cross head 151 to the mold opening completion position at a set speed, thereby retracting the movable platen 120 and separating the movable mold 12 from the fixed mold 11. After that, the ejector device 200 projects the molded product from the movable mold 12.

By the way, the toggle mechanism 150 amplifies the driving force of the mold clamping motor 160 and transmits it to the movable platen 120. The amplification factor is also called the toggle magnification. The toggle magnification changes according to the angle θ (hereinafter, also referred to as “link angle θ”) formed by the first link 152 and the second link 153. The link angle θ is obtained from the position of the crosshead 151. When the link angle θ is 180 °, the toggle magnification is maximized.

When the thickness of the mold device 10 changes due to replacement of the mold device 10 or a temperature change of the mold device 10, the mold thickness is adjusted so that a predetermined mold clamping force can be obtained at the time of mold clamping. In the mold thickness adjustment, for example, the distance L between the fixed platen 110 and the toggle support 130 is set so that the link angle θ of the toggle mechanism 150 becomes a predetermined angle at the time of the mold touch when the movable mold 12 touches the fixed mold 11. To adjust.

The mold clamping device 100 has a mold thickness adjusting mechanism 180 that adjusts the mold thickness by adjusting the distance L between the fixed platen 110 and the toggle support 130. The mold thickness adjusting mechanism 180 rotates the screw shaft 181 formed at the rear end of the tie bar 140, the screw nut 182 rotatably held by the toggle support 130, and the screw nut 182 screwed to the screw shaft 181. It has a mold thickness adjusting motor 183.

The screw shaft 181 and the screw nut 182 are provided for each tie bar 140. The rotation of the mold thickness adjusting motor 183 may be transmitted to a plurality of screw nuts 182 via a rotation transmission unit 185 composed of a belt, a pulley, or the like. A plurality of screw nuts 182 can be rotated in synchronization. It is also possible to individually rotate the plurality of screw nuts 182 by changing the transmission path of the rotation transmission unit 185.

The rotation transmission unit 185 may be composed of gears or the like instead of the belt or pulley. In this case, a passive gear is formed on the outer circumference of each screw nut 182, a drive gear is attached to the output shaft of the mold thickness adjusting motor 183, and a plurality of passive gears and an intermediate gear that meshes with the drive gear are located at the center of the toggle support 130. It is held rotatably.

The operation of the mold thickness adjusting mechanism 180 is controlled by the control device 700. The control device 700 drives the mold thickness adjusting motor 183 to rotate the screw nut 182, thereby adjusting the position of the toggle support 130 that holds the screw nut 182 rotatably with respect to the fixed platen 110, and the fixed platen 110. Adjust the distance L from the toggle support 130.

In the present embodiment, the screw nut 182 is rotatably held with respect to the toggle support 130, and the tie bar 140 on which the screw shaft 181 is formed is fixed to the fixed platen 110, but the present invention is not limited thereto.

For example, the screw nut 182 may be rotatably held relative to the fixed platen 110 and the tie bar 140 may be fixed to the toggle support 130. In this case, the interval L can be adjusted by rotating the screw nut 182.

Further, the screw nut 182 may be fixed to the toggle support 130, and the tie bar 140 may be rotatably held to the fixed platen 110. In this case, the interval L can be adjusted by rotating the tie bar 140.

Furthermore, the screw nut 182 may be fixed to the fixed platen 110 and the tie bar 140 may be rotatably held relative to the toggle support 130. In this case, the interval L can be adjusted by rotating the tie bar 140.

The interval L is detected by using the encoder 184 of the mold thickness adjusting motor 183. The encoder 184 detects the amount of rotation and the direction of rotation of the mold thickness adjusting motor 183, and sends a signal indicating the detection result to the control device 700. The detection result of the encoder 184 is used for monitoring and controlling the position and interval L of the toggle support 130.

The mold thickness adjusting mechanism 180 adjusts the interval L by rotating one of the screw shaft 181 and the screw nut 182 that are screwed together. A plurality of mold thickness adjusting mechanisms 180 may be used, and a plurality of mold thickness adjusting motors 183 may be used.

The mold thickness adjusting mechanism 180 of the present embodiment has a screw shaft 181 formed on the tie bar 140 and a screw nut 182 screwed onto the screw shaft 181 in order to adjust the interval L. Not limited to.

For example, the mold thickness adjusting mechanism 180 may have a tie bar temperature controller that adjusts the temperature of the tie bar 140. The tie bar temperature controller is attached to each tie bar 140 and adjusts the temperature of a plurality of tie bars 140 in cooperation with each other. The higher the temperature of the tie bar 140, the larger the interval L. The temperatures of the plurality of tie bars 140 can be adjusted independently.

The tie bar temperature controller includes a heater such as a heater, and adjusts the temperature of the tie bar 140 by heating. The tie bar temperature controller includes a cooler such as a water-cooled jacket, and the temperature of the tie bar 140 may be adjusted by cooling. The tie bar temperature controller may include both a heater and a cooler.

The mold clamping device 100 of the present embodiment is a horizontal type in which the mold opening / closing direction is horizontal, but may be a vertical type in which the mold opening / closing direction is vertical. The vertical mold clamping device includes a lower platen, an upper platen, a toggle support, a tie bar, a toggle mechanism, a mold clamping motor, and the like. One of the lower platen and the upper platen is used as a fixed platen, and the other one is used as a movable platen. A lower mold is attached to the lower platen, and an upper mold is attached to the upper platen. A mold device is composed of a lower mold and an upper mold. The lower mold may be attached to the lower platen via a rotary table. The toggle support is located below the lower platen. The toggle mechanism is disposed between the toggle support and the lower platen to raise and lower the movable platen. The mold clamping motor operates the toggle mechanism. The tie bar is parallel in the vertical direction, penetrates the lower platen, and connects the upper platen and the toggle support. When the mold clamping device is vertical, the number of tie bars is usually three. The number of tie bars is not particularly limited.

The mold clamping device 100 of the present embodiment has a mold clamping motor 160 as a drive source, but may have a hydraulic cylinder instead of the mold clamping motor 160. Further, 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 the description of the ejector device 200, as in the description of the mold clamping device 100, the moving direction of the movable platen 120 when the mold is closed (right direction in FIGS. 1 and 2) is set to the front, and the movement of the movable platen 120 when the mold is opened. The direction (left direction in FIGS. 1 and 2) will be described as the rear direction.

The ejector device 200 projects a molded product from the mold device 10. The ejector device 200 includes an ejector motor 210, a motion conversion mechanism 220, an ejector rod 230, and the like.

The ejector motor 210 is attached to the movable platen 120. The ejector motor 210 is directly connected to the motion conversion mechanism 220, but may be connected to the motion conversion mechanism 220 via a belt, a pulley, or the like.

The motion conversion mechanism 220 converts the rotational motion of the ejector motor 210 into a linear motion of the ejector rod 230. The motion conversion mechanism 220 includes a screw shaft and a screw nut screwed onto the screw shaft. A ball or roller may be interposed between the screw shaft and the screw nut.

The ejector rod 230 is free to advance and retreat in the through hole of the movable platen 120. The front end portion of the ejector rod 230 comes into contact with the movable member 15 which is movably arranged inside the movable mold 12. The front end portion of the ejector rod 230 may or may not be connected to the movable member 15.

The ejector device 200 performs the ejection process under the control of the control device 700.

In the ejection step, the ejector motor 210 is driven to advance the ejector rod 230 at a set speed, so that the movable member 15 is advanced and the molded product is ejected. After that, the ejector motor 210 is driven to retract the ejector rod 230 at a set speed, and the movable member 15 is retracted to the original position. The position and speed of the ejector rod 230 are detected by using, for example, the encoder 211 of the ejector motor 210. The encoder 211 detects the rotation of the ejector motor 210 and sends a signal indicating the detection result to the control device 700.

(Injection device)
In the description of the injection device 300, unlike the description of the mold clamping device 100 and the description of the ejector device 200, the moving direction of the screw 330 during filling (left direction in FIGS. 1 and 2) is set to the front, and the screw 330 during weighing is set forward. The moving direction (right direction in FIGS. 1 and 2) will be described as the rear.

The injection device 300 is installed on a slide base 301 that can move forward and backward with respect to the frame Fr, and is adjustable with respect to the mold device 10. The injection device 300 is touched by the mold device 10 to fill the cavity space 14 in the mold device 10 with a molding material. The injection device 300 includes, for example, a cylinder 310, a nozzle 320, a screw 330, a weighing motor 340, an injection motor 350, a pressure detector 360, and the like.

The cylinder 310 heats the molding material supplied internally from the supply port 311. The supply port 311 is formed at the rear of the cylinder 310. A cooler 312 such as a water-cooled cylinder is provided on the outer periphery of the rear portion of the cylinder 310. A heater 313 such as a band heater and a temperature detector 314 are provided on the outer periphery of the cylinder 310 in front of the cooler 312.

The cylinder 310 is divided into a plurality of zones in the axial direction of the cylinder 310 (left-right direction in FIGS. 1 and 2). A heater 313 and a temperature detector 314 are provided in each zone. For each zone, the control device 700 controls the heater 313 so that the detection temperature of the 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 10. A heater 313 and a temperature detector 314 are provided on the outer periphery of the nozzle 320. The control device 700 controls the heater 313 so that the detection temperature of the nozzle 320 reaches the set temperature.

The screw 330 is arranged in the cylinder 310 so as to be rotatable and retractable. When the screw 330 is rotated, the molding material is fed forward along the spiral groove of the screw 330. The molding material is gradually melted by the heat from the cylinder 310 while being fed forward. As the liquid molding material is fed forward of the screw 330 and accumulated in the front of the cylinder 310, the screw 330 is retracted. After that, when the screw 330 is advanced, the liquid molding material accumulated in front of the screw 330 is ejected from the nozzle 320 and filled in the mold apparatus 10.

A backflow prevention ring 331 is freely attached to the front portion of the screw 330 as a backflow prevention valve for preventing backflow of the molding material 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 retracts to a closed position (see FIG. 2) that blocks the flow path of the molding material. As a result, the molding material accumulated in the front of the screw 330 is prevented from flowing backward.

On the other hand, 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 when the screw 330 is rotated, and the opening position opens the flow path of the molding material. Advance to (see Figure 1). As a result, the molding material is sent to the front of the screw 330.

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

The injection device 300 may have a drive source for advancing and retreating the backflow prevention ring 331 between the open position and the closed position.

The metering motor 340 rotates the screw 330. The drive source for rotating 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 or the like for converting 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 screwed onto the screw shaft. A ball, a roller, or the like may be provided between the screw shaft and the screw nut. The drive source for advancing and retreating the screw 330 is not limited to the injection motor 350, and may be, for example, a hydraulic cylinder.

The pressure detector 360 detects the pressure transmitted between the injection motor 350 and the screw 330. The pressure detector 360 is provided in the force transmission path between the injection motor 350 and the screw 330 to detect the pressure acting on the pressure detector 360.

The pressure detector 360 sends a signal indicating the detection result to the control device 700. The detection result of the pressure detector 360 is used for controlling and monitoring the pressure received by the screw 330 from the molding material, the back pressure on the screw 330, the pressure acting on the molding material from the screw 330, and the like.

The injection device 300 performs a filling step, a pressure holding step, a weighing step, and the like under the control of the control device 700.

In the filling step, the injection motor 350 is driven to advance the screw 330 at a set speed, and the liquid molding material accumulated in front of the screw 330 is filled in the cavity space 14 in the mold apparatus 10. The position and speed of the screw 330 are detected by using, for example, the encoder 351 of the injection motor 350. The 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, switching from the filling process to the pressure holding process (so-called V / P switching) is performed. The position where V / P switching is performed is also called the V / P switching position. The set speed of the screw 330 may be changed according to the position and time of the screw 330.

After the position of the screw 330 reaches the set position in the filling step, the screw 330 may be temporarily stopped at the set position, and then 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 the pressure holding step, the injection motor 350 is driven to push the screw 330 forward, and the pressure of the molding material (hereinafter, also referred to as “holding pressure”) at the front end of the screw 330 is maintained at a set pressure in the cylinder 310. The remaining molding material is pushed toward the mold device 10. The shortage of molding material due to cooling shrinkage in the mold apparatus 10 can be replenished. The holding pressure is detected using, for example, a pressure detector 360. The pressure detector 360 sends a signal indicating the detection result to the control device 700. The set value of the holding pressure may be changed according to the elapsed time from the start of the holding pressure step and the like.

In the pressure holding step, the molding material in the cavity space 14 in the mold apparatus 10 is gradually cooled, and when the pressure holding step is completed, the inlet of the cavity space 14 is closed with the solidified molding material. This state is called a gate seal, and backflow of the molding material from the cavity space 14 is prevented. After the pressure holding step, the cooling step is started. In the cooling step, the molding material in the cavity space 14 is solidified. A weighing step may be performed during the cooling step to shorten the molding cycle.

In the weighing step, the weighing motor 340 is driven to rotate the screw 330 at a set rotation speed, and the molding material is fed forward along the spiral groove of the screw 330. Along with this, the molding material is gradually melted. As the liquid molding material is fed forward of the screw 330 and accumulated in the front of the cylinder 310, the screw 330 is retracted. The rotation speed of the screw 330 is detected by using, for example, the encoder 341 of the measuring motor 340. The encoder 341 sends a signal indicating the detection result to the control device 700.

In the weighing step, the injection motor 350 may be driven to apply a set back pressure to the screw 330 in order to limit the sudden retreat of the screw 330. The back pressure on the screw 330 is detected using, for example, a pressure detector 360. The pressure detector 360 sends a signal indicating the detection result to the control device 700. When the screw 330 retracts to the weighing completion position and a predetermined amount of molding material is accumulated in front of the screw 330, the weighing process is completed.

The injection device 300 of the present embodiment is an in-line screw type, but may be a pre-plastic type or the like. The pre-plastic injection device supplies the molded material melted in the plasticized cylinder to the injection cylinder, and injects the molding material from the injection cylinder into the mold device. A screw is rotatably or rotatably arranged in the plasticized cylinder and can be moved forward and backward, and a plunger is rotatably arranged in the injection cylinder.

(Mobile device)
In the description of the moving device 400, similarly to the description of the injection device 300, the moving direction of the screw 330 at the time of filling (left direction in FIGS. 1 and 2) is set to the front, and the moving direction of the screw 330 at the time of weighing (FIGS. 1 and 2). The right direction in FIG. 2) will be described as the rear.

The moving device 400 advances and retreats the injection device 300 with respect to the mold device 10. Further, the moving device 400 presses the nozzle 320 against the mold device 10 to generate a 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, the hydraulic fluid (for example, oil) is sucked from one of the first port 411 and the second port 412 and discharged from the other. To generate hydraulic pressure. The hydraulic pump 410 can also suck the hydraulic fluid from the tank 413 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 in the rotational direction and rotational torque according to the control signal from the control device 700. The motor 420 may be an electric motor or an electric servomotor.

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. Since the piston rod 433 penetrates the front chamber 435, the cross-sectional area of the front chamber 435 is smaller than the cross-sectional area of the rear chamber 436.

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, so that the injection device 300 is pushed forward. The injection device 300 is advanced and the nozzle 320 is pressed against the fixed mold 11. The anterior chamber 435 functions as a pressure chamber that generates a nozzle touch pressure of the nozzle 320 by the pressure of the hydraulic fluid supplied from the hydraulic pump 410.

On the other hand, 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, so that the injection device 300 is pushed backward. The injection device 300 is retracted and the nozzle 320 is separated from the fixed mold 11.

The first relief valve 441 opens when the pressure in the first flow path 401 exceeds a set value, returns excess hydraulic fluid in the first flow path 401 to the tank 413, and returns the excess working fluid in the first flow path 401 to the first flow path 401. Keep the pressure below the set value.

The second relief valve 442 opens when the pressure in the second flow path 402 exceeds a set value, returns excess working fluid in the second flow path 402 to the tank 413, and returns the excess working fluid in the second flow path 402 to the tank 413, and enters the second flow path 402. Keep the pressure below the set value.

The flushing valve 443 is a valve that adjusts the excess or deficiency of the circulating amount of the working fluid due to the difference between the cross-sectional area of the anterior chamber 435 and the cross-sectional area of the rear chamber 436, and is 3 as shown in FIGS. Position It consists of a 4-port spool valve.

The first check valve 451 opens when the pressure in the first flow path 401 is lower than the pressure in the tank 413, and supplies the hydraulic fluid from the tank 413 to the first flow path 401.

The second check valve 452 opens when the pressure in the second flow path 402 is lower than the pressure in the tank 413, and supplies the hydraulic fluid from the tank 413 to the second flow path 402.

The electromagnetic switching valve 453 is a control valve that controls the flow of hydraulic fluid between the front chamber 435 of the hydraulic cylinder 430 and the first port 411 of the hydraulic pump 410. The electromagnetic switching valve 453 is provided in the middle of the first flow path 401, for example, and controls the flow of the working liquid in the first flow path 401.

The electromagnetic switching valve 453 is composed of a spool valve having two positions and two ports, as shown in FIGS. 1 and 2, for example. When the spool valve is in the first position (the position on the left side in FIGS. 1 and 2), flow in both directions between the anterior chamber 435 and the first port 411 is allowed. On the other hand, when the spool valve is in the second position (the position on the right side in FIGS. 1 and 2), the flow from the front chamber 435 to the first port 411 is restricted. In this case, the flow from the first port 411 to the anterior chamber 435 is not restricted, but may be restricted.

The first pressure detector 455 detects the hydraulic pressure in the anterior chamber 435. Since the nozzle touch pressure is generated by the hydraulic pressure of the anterior chamber 435, the nozzle touch pressure can be detected by using the first pressure detector 455. The first pressure detector 455 is provided, for example, in the middle of the first flow path 401, and is provided at a position on the front chamber 435 side with reference to the electromagnetic switching valve 453. The nozzle touch pressure can be detected regardless of the state of the electromagnetic switching valve 453.

The second pressure detector 456 is provided in the middle of the first flow path 401, and is provided at a position on the first port 411 side with reference to the electromagnetic switching valve 453. The second pressure detector 456 detects the hydraulic pressure between the electromagnetic switching valve 453 and the first port 411. When the electromagnetic switching valve 453 allows flow in both directions between the first port 411 and the anterior chamber 435, the hydraulic pressure between the first port 411 and the electromagnetic switching valve 453 and the electromagnetic switching valve 453 and the front It is equal to the hydraulic pressure with the chamber 435. Therefore, in this state, the nozzle touch pressure can be detected by using the second pressure detector 456.

In the present embodiment, the nozzle touch pressure is detected by using a pressure detector provided in the middle of the first flow path 401, but even if the nozzle touch pressure is detected by using a load cell or the like provided in the nozzle 320, for example. Good. That is, the pressure detector that detects the nozzle touch pressure may be provided in either the moving device 400 or the injection device 300.

In the present embodiment, the hydraulic cylinder 430 is used as the moving device 400, but the present invention is not limited to this.

(Control device)
As shown in FIGS. 1 and 2, the control device 700 includes a CPU (Central Processing Unit) 701, a storage medium 702 such as a memory, an input interface 703, and an output interface 704. The control device 700 performs various controls by causing the CPU 701 to execute the program stored in the storage medium 702. Further, the control device 700 receives a signal from the outside through the input interface 703 and transmits the signal to the outside through the output interface 704.

The control device 700 is connected to the operation device 750 and the display device 760. The operation device 750 receives an input operation by the user and outputs a signal corresponding to the input operation to the control device 700. The display device 760 displays an operation screen corresponding to an input operation in the operation device 750 under the control of the control device 700. The operation screen is used for setting the injection molding machine and the like. Multiple operation screens are prepared and can be switched and displayed or displayed in an overlapping manner. The user sets the injection molding machine (including input of the set value) by operating the operation device 750 while looking at the operation screen displayed on the display device 760. The operation device 750 and the display device 760 may be composed of, for example, a touch panel and may be integrated. Although the operation device 750 and the display device 760 of the present embodiment are integrated, they may be provided independently. Further, a plurality of operating devices 750 may be provided.

(Backflow of molding material)
FIG. 3 is a diagram showing the operation of the backflow prevention ring according to the embodiment. In FIG. 3, the broken line indicates the state in which the backflow prevention ring 331 is in the open position, and the solid line indicates the state in which the backflow prevention ring 331 is in the closed position.

The backflow prevention ring 331 is located at the open position in the weighing process, and is located at the closed position in the filling process and the pressure holding process, and is repeated for each shot. Here, the shot refers to a series of operations for obtaining a molded product, for example, an operation from the start of weighing to the start of the next weighing.

Therefore, the backflow prevention ring 331 is repeatedly moved back and forth and gradually worn. Therefore, the sealing function of the backflow prevention ring 331 gradually deteriorates, and when the screw 330 is pushed forward in the filling step or the pressure holding step, the backflow of the molding material from the front to the rear of the screw 330 occurs.

FIG. 4 is a diagram showing the backflow of the molding material according to one embodiment. In FIG. 4, the arrows indicate the backflow flow of the molding material.

As shown in FIG. 4, when there is a backflow of the molding material, the position of the screw 330 advances in the filling step and the pressure holding step as compared with the case where there is no backflow of the molding material. This is because if there is a backflow of the molding material, the amount of the molding material entering the inside of the mold apparatus 10 is reduced by that amount, and the amount of advance of the screw 330 is increased in order to fill the inside of the mold apparatus 10 with the molding material. ..

The control device 700 determines the presence or absence of an abnormality due to the backflow of the molding material (step S101 in FIG. 5). This determination may be made for each shot or may be made periodically.

The control device 700 determines the presence or absence of an abnormality due to backflow of the molding material (hereinafter, also simply referred to as “abnormality due to backflow”), for example, (A) cushion amount, (B) filling pressure of the molding material, (C) holding pressure. (D) Judgment is based on at least one of the weighing times. Further, the control device 700 bases the amount of backflow molding material on, for example, at least one of (A) cushion amount, (B) molding material filling pressure, (C) holding pressure, and (D) weighing time. May be determined.

(A) The cushion amount is the position where the screw 330 is most advanced between the start of the pressure holding process and the completion of the pressure holding process, and the distance D from the mechanical advance limit position of the screw 330 (see FIG. 4). It is represented by. The cushion amount is detected by, for example, the encoder 351 of the injection motor 350.

When there is a backflow of the molding material, the amount of the molding material entering the inside of the mold apparatus 10 is reduced by that amount, so that the amount of advance of the screw 330 is increased to fill the inside of the mold apparatus 10 with the molding material, and as a result, the amount of advance is increased. , The cushion amount becomes smaller. The larger the amount of backflow molding material, the smaller the cushioning amount.

Therefore, the control device 700 determines that there is an abnormality due to backflow when the cushion amount is equal to or less than a predetermined amount. On the other hand, when the cushion amount is larger than the predetermined amount, the control device 700 determines that there is no abnormality due to backflow.

Further, the control device 700 may estimate the amount of backflow molding material based on the cushion amount. The larger the amount of backflow molding material, the smaller the cushioning amount. The amount of backflow molding material can be calculated from the amount of decrease in the cushion amount and the inner diameter of the cylinder 310.

(B) The filling pressure of the molding material is the filling pressure at which the molding material is filled inside the mold apparatus 10 in the filling step. The filling pressure of the molding material is detected by, for example, a pressure detector 360. For example, the peak value of the filling pressure of the molding material (hereinafter, also referred to as “peak filling pressure of the molding material”), the pattern of the filling pressure of the molding material, or the like is used.

When there is a backflow of the molding material, the amount of the molding material in front of the screw 330 is reduced, and the force for pushing the molding material forward is weakened, so that the filling pressure of the molding material is reduced. The larger the amount of backflow molding material, the smaller the filling pressure of the molding material.

Therefore, the control device 700 determines that there is an abnormality due to backflow when the peak filling pressure of the molding material is equal to or less than a predetermined value. On the other hand, the control device 700 determines that there is no abnormality due to backflow when the peak filling pressure of the molding material is larger than a predetermined value.

The control device 700 may also estimate the amount of backflow molding material based on the peak filling pressure of the molding material. The larger the amount of backflow molding material, the smaller the peak filling pressure of the molding material.

(C) As described above, the holding pressure is the pressure of the molding material applied to the front end portion of the screw 330 in the holding pressure step. The holding pressure is detected by, for example, a pressure detector 360.

When there is a backflow of the molding material, the amount of the molding material in front of the screw 330 becomes small, and the force pushing the molding material forward becomes weak, so that the holding pressure may not reach the set value. The larger the amount of backflow molding material, the smaller the holding pressure tends to be than the set value.

Therefore, the control device 700 determines that there is an abnormality due to backflow when the holding pressure is out of the permissible range. On the other hand, when the holding pressure falls within the permissible range, the control device 700 determines that there is no abnormality due to backflow. The permissible range is set based on the set value of the holding pressure. For example, when the holding pressure is smaller than a predetermined amount with respect to the set value, it is determined that there is an abnormality due to backflow.

Further, the control device 700 may estimate the amount of backflow molding material based on the holding pressure. The larger the amount of backflow molding material, the smaller the holding pressure.

(D) The weighing time is the time from the start of the weighing process to the end of the weighing process. The time is detected by, for example, a timer.

When there is a backflow of the molding material, the amount of advance of the screw 330 increases and the amount of cushioning decreases as described above, so that it takes time for the screw 330 to return to the weighing completion position and the weighing time becomes long. The larger the amount of backflow molding material, the longer the weighing time.

Therefore, the control device 700 determines that there is an abnormality due to backflow when the weighing time is a predetermined time or longer. On the other hand, when the weighing time is less than a predetermined time, the control device 700 determines that there is no abnormality due to backflow.

The control device 700 may also estimate the amount of backflow molding material based on the weighing time. The larger the amount of backflow molding material, the longer the weighing time.

When the control device 700 determines that there is no abnormality due to backflow (steps S101 and No. in FIG. 5), the control device 700 ends the current process.

On the other hand, when the control device 700 determines that there is an abnormality due to backflow (step S101, Yes in FIG. 5), the control device 700 corrects the molding conditions of the injection device 300 controlled by the control device 700 (step S102 in FIG. 5). The correction amount may be adjusted according to the amount of backflow molding material.

The molding condition is a controlled amount controlled by the control device 700. The control device 700 calculates the manipulated variable so that the deviation between the detected value of the controlled variable and the set value of the controlled variable becomes zero. For example, PID calculation, PI calculation and the like are used to calculate the operation amount.

The control amount correction includes (1) correction of the control amount set value, (2) correction of the control amount detection value, (3) correction of the deviation between the control amount set value and the control amount detection value, and (4). ) Any correction of the manipulated variable calculated from the deviation may be used.

Examples of the control amount to be corrected include the operation of the screw 330, the temperature of the cylinder 310, the temperature of the nozzle 320, and the like. The operation of the screw 330 includes a measurement completion position of the screw 330, a forward speed of the screw 330 in the filling process, a V / P switching position of the screw 330, and the like. The amount of control to be corrected may be one or a plurality. Further, when there are a plurality of control amounts to be corrected, the combination thereof is not particularly limited.

For example, when the control device 700 determines that there is an abnormality due to backflow, it corrects the measurement completion position of the screw 330 rearward as compared with the case where it determines that there is no abnormality due to backflow. As a result, the amount of molding material stored in front of the screw 330 at the completion of the weighing process can be increased, and it is possible to prevent the molding material in front of the screw 330 from becoming insufficient in the pressure holding step.

The weighing completion position of the screw 330 is corrected so that the position of the screw 330 is not in front of the cushion position in the pressure holding process. The cushion position represents the lower limit of the cushion amount. When the screw position is in front of the cushion position in the pressure holding step, the amount of molding material in front of the screw 330 is insufficient, so that the control device 700 interrupts the pressure holding step.

The weighing completion position of the screw 330 may be corrected backward as the amount of backflow molding material increases. As a result, since the screw 330 does not move forward of the cushion position during the pressure holding process due to the backflow of the molding material, interruption of the pressure holding process can be suppressed and unplanned stoppage can be suppressed.

The weighing completion position of the screw 330 may be corrected so that the variation in the cushion amount between shots is small.

Further, when the control device 700 determines that there is an abnormality due to backflow, the forward speed of the screw 330 in the filling step is greatly corrected as compared with the case where it is determined that there is no abnormality due to backflow. As a result, when there is an abnormality due to backflow, the filling pressure of the molding material can be obtained to be the same as when there is no abnormality due to backflow, and a molded product having the same density as when there is no abnormality due to backflow can be obtained. it can.

When the advancing speed of the screw 330 is changed stepwise in the filling process based on the position of the screw 330, the elapsed time, and the like, the control device 700 may correct the advancing speed of the screw 330 in at least a part of the filling process.

The advancing speed of the screw 330 in the filling step is corrected so that the filling pressure of the molding material becomes the same when there is an abnormality due to backflow and when there is no abnormality due to backflow. If the filling pressure of the molding material is too high, the density of the molded product is too high and the weight of the molded product becomes too heavy. On the other hand, if the filling pressure of the molding material is too small, the density of the molded product is too small and the weight of the molded product becomes too light.

The advancing speed of the screw 330 in the filling step may be corrected more as the amount of backflow molding material increases. As a result, the filling pressure of the molding material can be maintained at the same level and the density of the molded product can be maintained at the same level as compared with the case where there is no abnormality due to backflow.

The advancing speed of the screw 330 in the filling step may be corrected so that the variation in filling pressure between shots is small.

Further, when the control device 700 determines that there is an abnormality due to backflow, the control device 700 corrects the V / P switching position of the screw 330 forward as compared with the case where it determines that there is no abnormality due to backflow. As a result, the amount of molding material filled in the mold apparatus 10 can be maintained at the same level by the time the filling process is completed, depending on whether there is an abnormality due to backflow or no abnormality due to backflow, and the weight of the molded product can be reduced. Can be maintained at the same level.

At the V / P switching position of the screw 330, the amount of molding material filled in the mold apparatus 10 is about the same depending on whether there is an abnormality due to backflow or no abnormality due to backflow. Is corrected as follows. If the amount of the molding material to be filled in the mold apparatus 10 by the time the filling process is completed is too large, the weight of the molded product becomes too heavy. On the other hand, if the amount of the molding material filled in the mold device 10 by the time the filling process is completed is too small, the weight of the molded product becomes too light.

The V / P switching position of the screw 330 may be corrected forward as the amount of backflow molding material increases. As a result, the amount of the molding material to be filled in the mold apparatus 10 can be maintained at the same level and the weight of the molded product can be maintained at the same level as compared with the case where there is no abnormality due to backflow.

Further, when the control device 700 determines that there is an abnormality due to backflow, it corrects at least one of the temperature of the cylinder 310 and the temperature of the nozzle 320 lower than when it determines that there is no abnormality due to backflow. As a result, the temperature of the molding material stored in front of the screw 330 can be lowered, and the viscosity of the molding material can be increased. As a result, as shown in FIG. 9, leakage of the molding material from the gap formed by the wear of the backflow prevention ring 331 can be suppressed, and backflow of the molding material from the front to the rear of the screw 330 can be suppressed.

The temperature of the cylinder 310 and the temperature of the nozzle 320 may be corrected within a predetermined temperature range. The upper limit of the temperature range is set so as to suppress the backflow of the molding material. On the other hand, the lower limit of the temperature range is set so as not to interfere with the filling of the molding material into the mold apparatus 10.

The temperature of the cylinder 310 and the temperature of the nozzle 320 may be corrected lower as the amount of backflow molding material increases. Leakage of the molding material from the gap formed by the wear of the backflow prevention ring 331 can be suppressed, and backflow of the molding material from the front to the rear of the screw 330 can be suppressed.

As described above, the control device 700 corrects the molding conditions of the injection device 300 when it determines that there is an abnormality due to the backflow. As a result, insufficient filling of the molding material can be suppressed, so that a high-quality molded product can be obtained, and unplanned stoppage can be suppressed.

The correction of the molding conditions is a life extension process for delaying the time when the backflow prevention ring 331 is replaced or repaired, and the backflow prevention ring 331 is replaced or repaired at the next planned stop. Good. This can prevent unplanned outages. The screw 330 with the backflow prevention ring 331 may be replaced or repaired.

By the way, as described above, the backflow prevention ring 331 is gradually worn, the sealing function of the backflow prevention ring 331 is gradually deteriorated, and backflow occurs. After that, as the shots are piled up, the amount of backflow molding material gradually increases.

Since the amount of the molding material flowing back gradually increases, there may be a time lag between the determination of the presence or absence of an abnormality due to the backflow and the correction of the molding conditions of the injection device 300. Therefore, the shot for correcting the molding conditions of the injection device 300 may be a shot after the next shot for determining the presence or absence of an abnormality due to backflow.

The shot for correcting the molding conditions of the injection device 300 may be the same shot as for determining the presence or absence of an abnormality due to backflow. For example, when determining the presence or absence of an abnormality due to backflow based on the filling pressure of the molding material, the advancing speed of the screw 330 may be corrected so that the variation in the filling pressure between shots becomes small.

(Transformation, improvement)
Although the embodiments of the injection molding machine have been described above, the present invention is not limited to the above-described embodiments and the like, and various modifications are made within the scope of the gist of the present invention described in the claims. It can be improved.

300 Injection device 310 Cylinder 313 Heater 314 Temperature detector 320 Nozzle 330 Screw 331 Backflow prevention ring 340 Weighing motor 350 Injection motor 360 Pressure detector 700 Control device

Claims (3)

A cylinder that heats the molding material, a nozzle provided at the front end of the cylinder, a screw that is rotatably arranged inside the cylinder, and a backflow of the molding material from the front to the rear of the screw. An injection device that includes a check valve to prevent
And a control unit for controlling the injection device,
The control device determines the presence or absence of an abnormality due to the backflow of the molding material, and if it determines that the abnormality is present, corrects at least one of a set value related to the temperature of the cylinder and a set value related to the temperature of the nozzle. Molding machine. A cylinder that heats the molding material, a nozzle provided at the front end of the cylinder, a screw that is rotatably arranged inside the cylinder, and a backflow of the molding material from the front to the rear of the screw. An injection device that includes a check valve to prevent
And a control unit for controlling the injection device,
The control device is an injection molding machine that determines the presence or absence of an abnormality due to the backflow of the molding material, and if it is determined that the molding material has the abnormality, corrects a set value of the advancing speed of the screw . The injection molding machine according to claim 1 or 2 , wherein the control device corrects a set value related to the operation of the screw when it is determined that the abnormality is present.

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