JP6970530B2 - Molding machine, hollow molding machine equipped with it, and manufacturing method of hollow molded product - Google Patents

Description

The present invention relates to a mold clamping machine, a hollow molding machine equipped with the mold clamping machine, and a method for manufacturing a hollow molded product.

In a hollow molding machine (blow molding machine), a cylindrical parison extruded from a head connected to an extruder is sandwiched between a pair of molds, and air is blown into the parison inside the mold to manufacture a hollow molded product. do. In such a hollow molding machine, there is known one provided with a mold clamping machine for sandwiching a parison by moving a pair of molds in an open state in a closing direction.

In Patent Document 1, the pair of molds is moved by the electric servomotor until the pair of molds are close to each other at a predetermined distance, and when the pair of molds are close to the predetermined distance, the electric servomotor is stopped to form a hydraulic cylinder. The tie bar is fastened by the lock mechanism, and then the pair of molds are fastened by the hydraulic cylinder via the tie bar.

Japanese Unexamined Patent Publication No. 2014-066417

The inventor has found various problems in developing a mold clamping machine that moves a pair of molds in an open state in a closing direction.
Other issues and novel features will become apparent from the description and accompanying drawings herein.

In the mold clamping machine according to one embodiment, a pair of movable plates to which a pair of molds are attached are moved to one of an electric servomotor that moves the mold in the opening / closing direction via a ball screw, and a pair of movable plates. It is equipped with a hydraulic cylinder that is attached and presses the movable plate in the closing direction of the mold, and operates both the electric servomotor and the hydraulic cylinder when the movement distance from the initial position of the mold exceeds a predetermined distance. ..

According to the above-described embodiment, it is possible to provide a high-quality mold clamping machine that is suitable for, for example, a hollow molding machine.

It is a schematic sectional drawing which shows the outline of the hollow molding machine which concerns on Embodiment 1, and the manufacturing method of the hollow molded article. It is a schematic sectional drawing which shows the outline of the hollow molding machine which concerns on Embodiment 1, and the manufacturing method of the hollow molded article. It is a schematic sectional drawing which shows the outline of the hollow molding machine which concerns on Embodiment 1, and the manufacturing method of the hollow molded article. It is a schematic sectional drawing which shows the outline of the hollow molding machine which concerns on Embodiment 1, and the manufacturing method of the hollow molded article. It is an external photograph of a plastic fuel tank for a vehicle. It is a top view which shows the schematic structure of the mold clamping machine which concerns on Comparative Example 1. FIG. It is a top view which shows typically the mold clamping operation of the mold clamping machine which concerns on Comparative Example 1. It is a top view which shows typically the mold clamping operation of the mold clamping machine which concerns on Comparative Example 1. It is a top view which shows typically the mold clamping operation of the mold clamping machine which concerns on Comparative Example 1. It is a top view which shows typically the mold clamping operation of the mold clamping machine which concerns on Comparative Example 1. It is a top view which shows typically the mold clamping operation of the mold clamping machine which concerns on Comparative Example 1. FIG. 3 is a schematic cross-sectional view showing a hollow molded product manufactured by the mold clamping machine according to Comparative Example 1. It is a top view which shows the schematic structure of the mold clamping machine which concerns on Embodiment 1. FIG. It is a timing chart which shows the movement of a mold, the operation of an electric servomotor, and the operation of the hydraulic pressure of a hydraulic cylinder during the mold clamping operation of the mold clamping machine according to the first embodiment. It is a flowchart which shows the flow of the process in the mold clamping operation of the mold clamping machine which concerns on Embodiment 1. FIG. It is a top view which shows typically the molding state of the parison during the mold clamping operation of the mold clamping machine which concerns on Embodiment 1. FIG. It is a top view which shows typically the molding state of the parison during the mold clamping operation of the mold clamping machine which concerns on Embodiment 1. FIG. It is a top view which shows typically the molding state of the parison during the mold clamping operation of the mold clamping machine which concerns on Embodiment 1. FIG. It is a schematic cross-sectional view which shows the hollow molded article manufactured by the mold clamping machine which concerns on Embodiment 1. FIG. It is a timing chart which shows the movement of the mold, and the operation of the electric pressure of the electric servomotor and the hydraulic cylinder during the mold opening operation of the mold clamping machine according to the first embodiment.

Hereinafter, specific embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. Further, in order to clarify the explanation, the following description and drawings have been simplified as appropriate.

(Embodiment 1)
<Overall configuration of hollow molding machine>
First, with reference to FIG. 1, the overall configuration of the hollow molding machine according to the first embodiment will be described.

The hollow molding machine according to the first embodiment is an extrusion blow molding machine that extrudes a parison. 1 to 4 are schematic cross-sectional views showing an outline of a hollow molding machine and a method for manufacturing a hollow molded product according to the first embodiment. The right-handed xyz coordinates shown in FIG. 1 are for convenience in explaining the positional relationship of the components. Normally, the xy plane is a horizontal plane, and the z-axis plus direction is vertically upward. As shown in FIG. 1, the hollow forming machine 1 according to the first embodiment includes an extruder 10, a head 20, a parison wall thickness adjusting device 30, a mold clamping machine 40, and a lower pinch device 61.

The extruder 10 is a screw type extruder, and a screw 12 extended in the x-axis direction is housed inside a cylinder 11 extended in the x-axis direction. A hopper 13 for charging the resin pellet 51, which is the raw material of the parison 53, is provided on the upper side of the x-axis minus side end of the cylinder 11. The resin pellet 51 supplied from the hopper 13 is extruded from the root portion of the rotating screw 12 toward the tip portion, that is, in the plus direction of the x-axis. The resin pellet 51 is compressed by the screw 12 that rotates inside the cylinder 11 and changes into the molten resin 52. Although not shown, a motor is connected to the screw 12 as a drive source via, for example, a speed reducer.

The head 20 is connected to the extruder 10 via an adapter 14 provided at the x-axis plus side end of the extruder 10. The head main body 21 is a cylindrical housing extending in the vertical direction (z-axis direction), and is connected to the extruder 10 on the side surface of the upper end portion (z-axis plus side end portion). On the upper side of the head main body 21, a discharge amount adjusting device 22 for adjusting the discharge amount of the molten resin 52 by moving the core 32 of the parison wall thickness adjusting device 30 described later up and down is provided. Inside the head body 21, a spindle 23 extended in the vertical direction (z-axis direction) so as to connect the discharge amount adjusting device 22 and the core 32 of the parison wall thickness adjusting device 30 is housed. A parison wall thickness adjusting device 30 is installed at the lower end portion (z-axis minus side end portion) of the head main body 21.

The parison wall thickness adjusting device 30 includes a substantially cylindrical die 31 having a truncated cone-shaped through hole, a substantially truncated cone-shaped core 32 inserted into the through hole of the die 31, and an inner peripheral surface of the tip of the die 31. The flexible ring 33 provided in the above is provided. The gap between the die 31 and the core 32 is the resin flow path. The molten resin 52 that has passed through the resin flow path is formed into a cylindrical shape and is extruded as a parison 53 from the discharge port.

Here, the discharge port is defined by the flexible ring 33 and the core 32. That is, the cross-sectional shape of the parison 53 is defined by the flexible ring 33 and the core 32. When the core 32 is moved up and down by the discharge amount adjusting device 22, the diameter of the core 32 at the discharge port changes. Therefore, the distance between the flexible ring 33 and the core 32, that is, the wall thickness of the cross section of the parison 53 changes. This change in wall thickness is a change in the longitudinal direction of the parison 53.

The mold clamping machine 40 includes a pair of molds 41a and 41b and a pair of movable plates 42a and 42b. The molds 41a and 41b are fixed to the movable plates 42a and 42b, respectively. The molds 41a and 41b open and close as the movable plates 42a and 42b slide in the x-axis direction. 1 and 3 show a state in which the molds 41a and 41b are open, and FIG. 2 shows a state in which the molds 41a and 41b are closed. The details of the mold clamping machine 40 will be described later. The lower pinch device 61 is provided at a position below the molds 41a and 41b in the mold clamping machine 40, and sandwiches the lower portion of the parison 53 extruded from the parison wall thickness adjusting device 30.

Next, with reference to FIGS. 1 to 4, a method for manufacturing a hollow molded product in the hollow molding machine according to the first embodiment will be described.
As shown in FIG. 1, the molten resin 52 extruded from the extruder 10 in the positive direction on the x-axis changes the flow direction downward in the vertical direction (minus direction on the z-axis) in the head 20, and is transmitted from the parison wall thickness adjusting device 30. Extruded as parison 53.

As shown in FIG. 1, in the hollow molding machine 1, the parison 53 is extruded in a predetermined amount in the vertical downward direction (z-axis negative direction) with the dies 41a and 41b open. As shown in FIG. 2, when the parison 53 reaches the specified length, the lower portion of the parison 53 is sandwiched by the lower pinch device 61. Then, the molds 41a and 41b are moved in the closing direction (the mold 41a is moved in the x-axis plus direction and the mold 41b is moved in the x-axis minus direction), and the pre-blow is performed from the flow path formed in the center of the core 32. Send gas (air) to inflate the parison 53 a little.

After that, as soon as the molds 41a and 41b are closed, the air in the preblow is stopped, and as shown in FIG. 3, the blowing needle 43 is pierced into the parison 53 to send air into the parison 53, and the parison 53 is transferred to the mold 41a, Inflate to the inner surface shape of 41b. Then, the parison 53, which is a molten resin in a state of being inflated and pressed against the inside of the molds 41a and 41b, is cooled. As a result, the hollow molded product 54 is manufactured.

If the molds 41a and 41b are moved in the negative direction on the y-axis while the molds 41a and 41b are closed, the extrusion of the parison 53 can be continued. In the state where the molds 41a and 41b are closed, the extrusion of the parison 53 may be stopped without moving in the negative direction on the y-axis. Then, as shown in FIG. 4, after the molds 41a and 41b are opened and the hollow molded product 54 is taken out, the molds 41a and 41b move in the y-axis plus direction and return to their original positions.

The hollow molded product 54 shown in FIG. 4 is simplified. The hollow molded product 54 may have a complicated shape such as, for example, a plastic fuel tank (PFT) for a vehicle. FIG. 5 is an external photograph of a plastic fuel tank for a vehicle. The actual plastic fuel tank has a large number of irregularities and has a complicated shape in which waste meat is likely to occur.

Since the hollow molding machine according to the first embodiment has a mold clamping machine 40 described in detail later, it is possible to reduce variations in the wall thickness of the hollow molded product to be manufactured. As a result, it is possible to reduce the amount of waste in the hollow molded product and reduce the weight. Therefore, the hollow molding machine according to the first embodiment is suitable for the application of manufacturing the above-mentioned plastic fuel tank for a vehicle as a hollow molded product, which is particularly required to be lightweight.

<Molding machine according to Comparative Example 1>
Next, the mold clamping machine according to Comparative Example 1 examined in advance by the inventor will be described.
FIG. 6 is a plan view showing a schematic configuration of the mold clamping machine 440 according to Comparative Example 1. The right-handed xyz coordinates shown in FIG. 6 are the same as those in FIG. Further, in order to facilitate understanding, the molds 41a and 41b are shown in cross section in FIG.

As shown in FIG. 6, in the mold clamping machine 440 according to Comparative Example 1, a pair of molds 41a, 41b, a pair of movable plates 442a, 442b, a hydraulic cylinder 480a, 480b, a left side rod 481a, 481b, a right side rod 482a, It includes a 482b, a ball screw 48, an electric servomotor 47, and a control unit 463.

The pair of movable plates 442a and 442b are arranged on the base 449 so as to face each other perpendicular to the opening / closing direction of the pair of molds 41a and 41b. A pair of molds 41a and 41b are attached to the pair of movable plates 442a and 442b, respectively.

The ball screw 48 is arranged in parallel to the opening / closing direction (x-axis direction) of the pair of molds 41a and 41b in the base 449, and the first screw portion 48a and the second screw portion are threaded in opposite directions. It has 48b. For example, when a right-handed screw is formed on the first screw portion 48a, a left-handed screw is formed on the second screw portion 48b. The movable platen 442a, which is one of the pair of movable plates, is provided with a first nut portion 44a screwed with the first screw portion 48a. The movable platen 442b, which is the other of the pair of movable plates, is provided with a second nut portion 44b screwed with the second screw portion 48b. That is, by rotating the ball screw 48, the movable platen 442a and the movable platen 442b can be moved synchronously in a direction approaching each other or in a direction away from each other. The electric servomotor 47 is a drive source for rotating the ball screw 48. The rotation of the electric servomotor 47 is transmitted to the ball screw 48 via a timing belt or the like.

The left side rods 481a and 481b extend parallel to the opening / closing direction (x-axis direction) of the pair of molds 41a and 41b, and are slidably supported by the movable platen 442a located on the left side. One end (left end) of the left side rods 481a and 481b is fixed to the pistons of the hydraulic cylinders 480a and 480b, respectively. That is, the left side rods 481a and 481b are moved by the hydraulic cylinders 480a and 480b in the opening / closing direction (x-axis direction) of the pair of molds 41a and 41b, respectively. Connecting portions 483a and 483b are provided at the other ends (right ends) of the left rods 481a and 481b, respectively.

The right side rods 482a and 482b are fixed to the movable platen 442b whose one end (right end) is located on the right side. Connecting portions 484a and 484b are provided at the other ends (left ends) of the right rods 482a and 482b, respectively. The connecting portions 484a and 484b of the right rods 482a and 482b can be connected to the connecting portions 483a and 483b of the left rods 481a and 481b, respectively.

The electric servomotor 47 has a function of detecting the moving distance in the opening / closing direction from the initial position of the pair of molds 41a and 41b. That is, the electric servomotor 47 has a rotary encoder 62 that detects the amount of rotation of the electric servomotor 47. The rotary encoder 62 detects the amount of rotation of the electric servomotor 47, and as a result, detects the moving distance from the initial position of the pair of molds 41a and 41b in the opening / closing direction. The control unit 463 controls the drive of the electric servomotor 47 and the hydraulic cylinders 480a and 480b based on the detection result of the movement distance from the initial position to the opening / closing direction of the pair of molds 41a and 41b from the electric servomotor 47. do.

Next, the mold clamping operation of the mold clamping machine 440 according to Comparative Example 1 will be described.
7 to 11 are plan views schematically showing the mold clamping operation of the mold clamping machine 440 according to Comparative Example 1, respectively. The right-handed xyz coordinates shown in FIGS. 7 to 11 are the same as those in FIG. Further, for easy understanding, in FIGS. 7, 8, 10, and 11, the molds 41a and 41b and the parison 53 are shown in cross sections, and in FIG. 9, the connecting portions 484a and 484b are shown in cross sections. ing.

As shown in FIG. 7, the control unit 463 drives the electric servomotor 47 to rotate the ball screw 48, and moves the pair of movable plates 442a and 442b in directions close to each other. As a result, the pair of molds 41a and 41b in the open state move in the closing direction. At this time, the lower portion of the parison 53 is closed by the lower pinch device 61, and the parison 53 is gradually inflated by the pre-blow air.

As shown in FIG. 8, when the moving distance in the opening / closing direction from the initial position of the pair of molds 41a and 41b reaches a predetermined distance (the pair of molds 41a and 41b move from the initial position to the preliminary mold closed position). At that time, the control unit 463 temporarily stops the electric servomotor 47 to make the pair of movable plates 442a and 442b stationary. Then, the control unit 463 performs a locking operation for connecting the left side rods 481a and 481b and the right side rods 482a and 482b. When the electric servomotor 47 is temporarily stopped, the parison 53 inflated by the air of the preblow is in contact with the inner surfaces of the pair of molds 41a and 41b in the region A shown by the broken line.

As shown in FIG. 9, in the locking operation, the left side rods 481a and 481b are rotated about their respective axes. As a result, the connecting portions 483a and 483b are fitted to the connecting portions 484a and 484b, and the left side rods 481a and 481b and the right side rods 482a and 482b are connected to each other. The period required for this locking operation is about 0.5 seconds. During the locking operation, the electric servomotor 47 is stopped.

While the electric servomotor 47 is temporarily stopped for the locking operation, the portions of the parison 53 that are in contact with the inner surfaces of the pair of molds 41a and 41b are cooled and gradually solidified. Therefore, as shown in FIG. 10, when the locking operation is completed, the portion of the parison 53 that is in contact with the pair of molds 41a and 41b (region A indicated by the broken line) is located on the inner surface of the molds 41a and 41b. It is stuck. After the locking operation is completed, the control unit 463 drives the hydraulic cylinders 480a and 480b to pull the left side rods 481a and 481b to the minus side in the X-axis direction, respectively. As a result, the pair of movable plates 442a and 442b are moved in a direction close to each other, and the pair of molds 41a and 41b are moved in a closing direction.

As shown in FIG. 11, with the molds 41a and 41b closed, the parison 53 is inflated to the inner surface shape of the molds 41a and 41b by blowing gas (air) into the parison 53 by the blowing needle 43. .. That is, the parison 53 further expands and becomes thinner due to the blowing of air by the blowing needle 43, and fits on the inner surfaces of the molds 41a and 41b. However, in the parison 53, the portion (region A shown by the broken line) fixed to the inner surface of the pair of molds 41a and 41b at the completion of the locking operation does not become thin even when air is blown by the blowing needle 43.

FIG. 12 is a schematic cross-sectional view showing a hollow molded product 454 manufactured by the mold clamping machine 440. The right-handed xyz coordinates shown in FIG. 12 are the same as those in FIG. As shown in FIG. 12, the wall thickness of the portion 454a fixed to the inner surface of the pair of molds 41a and 41b at the completion of the locking operation is thicker than that of the other portions 454b. That is, in the hollow molded product 454 manufactured by the mold clamping machine 440, the wall thickness distribution occurs. In order to guarantee sufficient strength in the hollow molded product 454, it is necessary to make the thickness of the other portion 454b of the hollow molded product 454 having a thin wall thickness equal to or more than a predetermined thickness. Therefore, in the thick portion 454a of the hollow molded product 454, the wall thickness becomes unnecessarily thick. As described above, in the mold clamping machine 440 according to Comparative Example 1, since the wall thickness is distributed in the manufactured hollow molded product, there is a problem that the effect of reducing the waste of the hollow molded product and reducing the weight is insufficient. was there.

<Molding machine according to the first embodiment>
Next, the details of the mold clamping machine according to the first embodiment will be described. The parts common to Comparative Example 1 are designated by the same reference numerals and the description thereof will be omitted.
FIG. 13 is a plan view showing a schematic configuration of the mold clamping machine 40 according to the first embodiment. The right-handed xyz coordinates shown in FIG. 13 are the same as those in FIG. Further, in order to facilitate understanding, the molds 41a and 41b are shown in cross section in FIG.

As shown in FIG. 13, the mold clamping machine 40 according to the first embodiment includes a pair of molds 41a and 41b, a pair of movable plates 42a and 42b, a hydraulic cylinder 46, an electric servomotor 47, a ball screw 48, and a control unit. It is equipped with 63. The pair of movable plates 42a and 42b are arranged on the base 49 so as to be perpendicular to the opening / closing direction of the pair of molds 41a and 41b and to face each other. A pair of molds 41a and 41b are attached to the pair of movable plates 42a and 42b, respectively.

The ball screw 48 is arranged in parallel to the opening / closing direction (x-axis direction) of the pair of molds 41a and 41b in the base 49, and the first screw portion 48a and the second screw portion are threaded in opposite directions to each other. It has 48b. The movable platen 42a, which is one of the pair of movable plates, is provided with a first nut portion 44a screwed with the first screw portion 48a. The movable platen 42b, which is the other of the pair of movable plates, is provided with a second nut portion 44b screwed with the second screw portion 48b. That is, by rotating the ball screw 48, the movable platen 42a and the movable platen 42b are synchronized in a direction toward each other (direction in which the molds 41a and 41b are closed) or a direction in which they are separated from each other (direction in which the molds 41a and 41b are opened). Can be moved.

The hydraulic cylinder 46 is fixed to a fixing plate 64 which is fixedly arranged on the base 49 so as to be perpendicular to the opening / closing direction of the pair of molds 41a and 41b. The tip of the piston rod 46a of the hydraulic cylinder 46 is attached to the movable plate 42a, which is one of the pair of movable plates. The hydraulic cylinder 46 presses the movable platen 42a in the direction in which the pair of molds close (x-axis plus direction). The control unit 63 controls the drive of the hydraulic cylinder 46 and the electric servomotor 47 based on the moving distance from the initial position of the pair of molds 41a and 41b in the opening / closing direction.

As described above, the moving distance of the pair of molds 41a and 41b from the initial position to the opening / closing direction is detected by the rotary encoder 62 included in the electric servomotor 47. That is, the control unit 63 operates the hydraulic cylinder 46 and the electric servomotor 47 based on the detection result of the movement distance from the initial position in the pair of molds 41a and 41b in the opening / closing direction from the electric servomotor 47. In the mold clamping machine 40, a displacement sensor such as a magnetic sensor, an ultrasonic sensor, an eddy current sensor, a photoelectric sensor, or a laser sensor is separately provided as a position detection unit in the pair of molds 41a and 41b. The movement distance from the initial position to the opening / closing direction may be detected. When the position detection unit is separately provided in the mold clamping machine 40, the control unit 63 is a hydraulic cylinder based on the detection result of the movement distance from the initial position to the opening / closing direction of the pair of molds 41a and 41b from the position detection unit. The 46 and the electric servomotor 47 are operated. The details of the control method for driving the hydraulic cylinder 46 and the electric servomotor 47 by the control unit 63 will be described later.

The mold clamping machine 40 further includes tie bars 45a and 45b extending parallel to the opening / closing direction (x-axis direction) of the pair of molds 41a and 41b and slidably supported by the movable plates 42a and 42b. ing. The tie bar 45a is supported at one end (upper end) of the pair of movable plates 42a and 42b in the direction perpendicular to the opening / closing direction (Z-axis direction) of the pair of molds 41a and 41b. The tie bar 45b is supported at the other end (lower end) of the pair of movable plates 42a, 42b in the direction perpendicular to the opening / closing direction (Z-axis direction) of the pair of molds 41a, 41b. The above-mentioned hydraulic cylinder 46 is attached to the central portion of the pair of movable plates 42a and 42b in the direction perpendicular to the opening / closing direction (Z-axis direction) of the pair of molds 41a and 41b. By arranging the tie bars 45a and 45b and the hydraulic cylinder 46 with respect to the pair of movable plates 42a and 42b as described above, the pair of movable plates 42a and 42b can be stably moved. As a result, the mold clamping force can be applied in a well-balanced manner, and the mold can be evenly molded.

Next, the mold clamping operation of the mold clamping machine 40 will be described. In the following description, FIG. 13 will also be referred to as appropriate.
FIG. 14 is a timing chart showing the movement of the mold 41a, the operation of the electric servomotor 47, and the hydraulic operation of the hydraulic cylinder 46 during the mold clamping operation. In the graph showing the movement of the mold 41a in FIG. 14, the horizontal axis is the movement distance [mm] from the initial position in the opening / closing direction of the mold 41a (hereinafter, simply referred to as “movement distance”), and the vertical axis is the mold 41a. The moving speed [mm / sec]. First, the mold 41a is in the mold closing start position in the mold open state. That is, the moving distance is 0 at the mold closing start position. During the mold clamping operation, the mold 41b moves in the direction opposite to the mold 41a in synchronization with the mold 41a due to the rotation of the ball screw 48.

As shown in FIG. 14, the electric servomotor 47 is driven by position control from the mold closing start position to the preliminary mold closing position (moving distance 200 mm) of the mold 41a. Here, the position control is a control method for controlling the rotation angle (position) and the rotation speed (movement speed) of the electric servomotor 47 by a position command. During the period from the mold closing start position to the preliminary mold closing position, the electric servomotor 47 accelerates the mold 41a until the moving speed reaches a predetermined target speed of 150 mm / sec or less, and the moving speed of the mold 41a. After reaching the target speed, the mold 41a is moved at a constant speed.

After moving the mold 41a at a constant speed for about 3 seconds, the electric servomotor 47 decelerates the mold 41a and stops it at the preliminary mold closed position. While the mold 41a is stopped (about 2 seconds) in the preliminary mold closed position, the drive control method of the electric servomotor 47 is switched from the position control to the speed control. As a result, after the mold 41a reaches the preliminary mold closed position, the electric servomotor 47 is driven by speed control. Here, the speed control is a control method that changes the speed of the electric servomotor 47 steplessly according to the speed command voltage.

After switching the control method of the electric servomotor 47, the mold 41a is moved from the preliminary mold closed position in the closing direction again, and air is started to be sent into the parison 53 by pre-blow. During the period from the preliminary mold closing position to the low speed start position (moving distance 550 mm), the electric servomotor 47 accelerates the mold 41a, and when the moving speed reaches 300 mm / sec, the mold 41a is moved at a constant speed. .. Then, the electric servomotor 47 moves the mold 41a at a constant speed for about 2 seconds.

After the mold 41a reaches the low speed start position, the electric servomotor 47 reduces the moving speed of the mold 41a to 150 mm / sec. Then, after the moving speed of the mold 41a reaches 150 mm / sec, the mold 41a is moved at a constant speed by the electric servomotor 47. Further, after the mold 41a reaches the low speed start position, a torque limit (torque limit) is applied to the electric servomotor 47. Here, the torque limit is a control for preventing the electric servomotor 47 from generating a torque exceeding a predetermined torque limit value. When torque is limited on the electric servomotor 47, in speed control, if the actual torque of the electric servomotor 47 is less than or equal to the torque limit value, acceleration is performed until the set speed is reached, and if it exceeds the torque limit value, acceleration is not performed. Operate at a speed that is commensurate with the torque limit.

While the mold 41a is being moved at a constant speed of 150 mm / sec, the operation of the hydraulic cylinder 46 is started when the position of the mold 41a reaches the hydraulic drive start position (a predetermined moving distance of 550 mm or more). That is, when the position of the mold 41a becomes the hydraulic drive start position (a predetermined moving distance of 550 mm or more), the hydraulic cylinder 46 is operated in addition to the electric servomotor 47. In the operation of the hydraulic cylinder, the flow rate of the oil supplied to the hydraulic cylinder 46 is gradually increased. The hydraulic drive start position is set to the optimum position according to the hollow molded product to be manufactured.

After a while after operating the hydraulic cylinder 46, the force applied to the mold 41a by the hydraulic cylinder 46 exceeds the force applied to the mold 41a by the electric servomotor 47. As a result, the actual mold speed becomes larger than the command value of the mold speed by the electric servomotor 47. The position of the mold 41a at this time is referred to as a "drive switching position".

After the position of the mold 41a reaches the drive switching position, the reaction force received by the electric servomotor 47 from the mold 41a increases. However, since the torque limit is applied to the electric servomotor 47, the electric servomotor 47 increases the command value according to the increase in the load after the position of the mold 41a reaches the drive switching position. There is no such thing. That is, after the position of the mold 41a reaches the drive switching position, the electric servomotor 47 does not prevent the pressing pressure of the hydraulic cylinder 46 from becoming strong, and the mold 41a is subjected to the pressing pressure of the hydraulic cylinder 46. Moving. During the period from the mold closing completion position to the pressure holding position (moving distance 595 mm), the mold 41a is strongly pressed by the hydraulic cylinder 46 in order to cut off the parison 53.

FIG. 15 is a flowchart showing the flow of processing in the mold clamping operation in the control unit 463 of the mold clamping machine 40. As shown in FIG. 15, first, the electric servomotor 47 is driven by position control (step S101). Next, it is determined whether or not the position of the mold 41a has reached the preliminary mold closed position (step S102). When it is determined in step S102 that the position of the mold 41a has reached the preliminary mold closed position, the drive of the electric servomotor 47 is switched from the position control to the speed control (step S103).

Following step S103, it is determined whether or not the position of the mold 41a has reached the low speed start position (step S104). When it is determined in step S104 that the position of the mold 41a has reached the low speed start position, the moving speed of the mold 41a is decelerated and the torque limitation in the electric servomotor 47 is started (step S105).

Following step S105, it is determined whether or not the position of the mold 41a has reached the hydraulic drive start position (step S106). When it is determined in step S106 that the position of the mold 41a has reached the hydraulic drive start position, the operation of the hydraulic cylinder 46 is started (step S107). As a result, when the position of the mold 41a reaches the hydraulic drive start position, that is, when the moving distance from the initial position of the mold 41a becomes a predetermined distance or more, the electric servomotor 47 and the hydraulic cylinder 46 Both will be running.

Following step S107, it is determined whether or not the actual mold speed is larger than the command value of the mold speed by the electric servomotor 47 (step S108). When it is determined in step S108 that the actual mold speed is larger than the command value of the mold speed by the electric servomotor, the torque limit value is lowered (step S109). Next, it is determined whether or not the position of the mold 41a has reached the holding pressure position (step S110). When it is determined in step S108 that the position of the mold 41a has reached the holding pressure position, the torque limit value of the electric servomotor 47 is lowered to 0% (step S111), and the process is terminated.

16 to 18 are plan views schematically showing the molding state of the parison 53 during the mold clamping operation of the mold clamping machine 40, respectively. The right-handed xyz coordinates shown in FIGS. 16 to 18 are the same as those in FIG. 1. Further, in order to facilitate understanding, the molds 41a and 41b and the parison 53 are shown in cross sections in FIGS. 16 to 18.

As shown in FIG. 16, from the state where the mold 41a is in the preliminary mold closed position, the pair of molds 41a and 41b are moved in the closing direction by the electric servomotor 47, and air is introduced inside the parison 53 by pre-blow. Is sent. Since the lower part of the parison 53 is closed by the lower pinch device 61, the parison 53 is gradually inflated by the pre-blow air.

As shown in FIG. 17, while the pair of molds 41a and 41b are being moved in the closing direction, a part of the parison 53 (region B shown by the broken line) inflated by the air of the preblow is the mold 41a. It contacts the inner surface of 41b. Even after a part of the parison 53 (region B shown by the broken line) comes into contact with the inner surfaces of the molds 41a and 41b, the position of the molds 41a reaches the holding position without stopping the molds 41a and 41b. The movement of the molds 41a and 41b is continued until.

As shown in FIG. 18, when the molds 41a and 41b are closed, the molds 41a and 41b are pressed by the hydraulic cylinder 46. In this state, the parison 53 is inflated to the inner surface shapes of the molds 41a and 41b by blowing air into the parison 53 by the blowing needle 43. As described above, after a part of the parison 53 first contacts in the pre-blow, the molds 41a and 41b are not stopped and continue to move in the closing direction. Therefore, it is possible to start blowing air into the inside of the parison 53 by the blowing needle 43 before the cooling of the portions of the parison 53 in contact with the inner surfaces of the molds 41a and 41b proceeds. That is, air is started to be blown into the inside of the parison 53 by the blowing needle 43 before the portions of the parison 53 that come into contact with the inner surfaces of the molds 41a and 41b are cooled and fixed. As a result, all the parts of the parison 53 can be expanded almost uniformly by blowing air into the parison 53 by the blowing needle 43.

FIG. 19 is a schematic cross-sectional view showing a hollow molded product 54 manufactured by the mold clamping machine 40. The right-handed xyz coordinates shown in FIG. 19 are the same as those in FIG. As shown in FIG. 19, the wall thickness distribution does not substantially occur in the hollow molded product 54. That is, the wall thickness of the portion 54a that first contacts the inner surfaces of the molds 41a and 41b by pre-blow is almost the same as the wall thickness of the other portions.

As described above, the mold clamping machine according to the first embodiment can expand the parison more evenly as compared with the mold clamping machine according to Comparative Example 1. As a result, as compared with the mold clamping machine according to Comparative Example 1, the amount of waste meat of the hollow molded product can be reduced more and the weight can be further reduced.

Next, the mold opening operation of the mold clamping machine 40 will be described. In the following description, FIG. 13 will also be referred to as appropriate.
When the mold clamping operation is completed in the mold clamping machine 40, the mold is opened in order to take out the hollow molded product. That is, the movable plates 42a and 42b are moved in the direction in which the molds 41a and 41b are opened, and the molds 41a and 41b are returned to the initial positions.

FIG. 20 is a timing chart showing the movement of the mold 41a and the hydraulic operation of the electric servomotor 47 and the hydraulic cylinder 46 during the mold opening operation. In the graph showing the movement of the mold 41a, the horizontal axis is the movement distance [mm] from the initial position in the opening / closing direction of the mold 41a (hereinafter, simply referred to as “movement distance”), and the vertical axis is the movement speed of the mold 41a [ mm / sec]. At the start of the mold opening operation, the position of the mold 41a is the holding position (moving distance 595 mm). During the mold opening operation, the mold 41b moves in the opposite direction to the mold 41a in synchronization with the mold 41a.

As shown in FIG. 20, during the mold opening operation, the electric servomotor 47 is driven by position control, and the hydraulic cylinder 46 is kept stopped. First, the electric servomotor 47 accelerates the mold 41a in the holding position until the moving speed reaches 150 mm / sec. Then, after the moving speed of the mold 41a reaches 150 mm / sec, the mold 41a is moved at a constant speed for about 2 seconds. The hollow molded product manufactured during this period is taken out.

After moving the mold 41a at a constant speed for about 2 seconds, the electric servomotor 47 accelerates the mold 41a until the moving speed reaches 300 mm / sec. Then, after moving the mold 41a at a constant speed for about 4 seconds, the mold 41a is decelerated, and the mold 41a is stopped when the position of the mold 41a reaches the initial position of the mold opening start position.

In this way, in the mold clamping machine 40, in the mold opening operation, the electric servomotor 47 is driven by position control to move the movable plates 42a and 42b. As a result, the molds 41a and 41b can be opened quickly, and the molding cycle time can be shortened.

Although the invention made by the present inventor has been specifically described above based on the embodiments, the present invention is not limited to the embodiments already described, and various changes can be made without departing from the gist thereof. It goes without saying that it is possible.

1 Hollow molding machine 10 Extruder 11 Cylinder 12 Screw 13 Hopper 14 Adapter 20 Head 21 Head body 22 Discharge amount adjustment device 23 Spindle 30 Parison wall thickness adjustment device 31 Die 32 Core 33 Flexible ring 40 Mold tightening machine 41a, 41b Mold 42a , 42b Movable board 43 Blow-in needle 44a 1st nut part 44b 2nd nut part 45a, 45b Tie bar 46 Hydraulic cylinder 46a Piston rod 47 Electric servo motor 48 Ball screw 48a 1st screw part 48b 2nd screw part 49 Base 51 Resin pellet 52 Molten resin 53 Parison 54 Hollow molded product 61 Lower pinch device 62 Position detection unit 63 Control unit 64 Fixed plate

Claims (17)

A pair of molds and
A pair of movable plates to which the pair of molds are attached, and
A hydraulic cylinder attached to one of the pair of movable plates and pressing the movable plate in a direction in which the pair of molds closes.
In order to move the pair of movable plates in the opening / closing direction of the pair of molds, a linear motion mechanism provided separately from the hydraulic cylinder and
The electric servomotor that drives the linear motion mechanism and
A control unit that controls the drive of the hydraulic cylinder and the electric servomotor is provided.
When the control unit closes the pair of molds,
Until the moving distance of the pair of molds from the initial position in the opening / closing direction reaches a predetermined distance , the pair of molds are moved by driving only the electric servomotor.
When the predetermined distance is reached , both the electric servomotor and the hydraulic cylinder are operated .
After stopping the electric servomotor, the pair of molds are held in a state of being molded only by the hydraulic cylinder.
Molding machine. The electric servomotor has a function of detecting the moving distance, and has a function of detecting the moving distance.
The control unit operates the electric servomotor and the hydraulic cylinder based on the detection result of the movement distance from the electric servomotor.
The mold clamping machine according to claim 1. It further has a position detecting unit for detecting the moving distance, and has a position detecting unit.
The control unit operates the electric servomotor and the hydraulic cylinder based on the detection result of the movement distance from the position detection unit.
The mold clamping machine according to claim 1. The pair of movable plates are arranged so as to face each other vertically with respect to the opening / closing direction.
The linear motion mechanism is
A ball screw having a first screw portion and a second screw portion arranged parallel to the opening / closing direction and threaded in opposite directions to each other.
A first nut portion screwed with the first screw portion and provided on one of the pair of movable plates, and a first nut portion.
Threadedly engaged with the second threaded portion, Bei example and a second nut portion provided in the other of the pair of movable platen,
The electric servomotor rotates the ball screw.
The mold clamping machine according to claim 1. When operating both the electric servomotor and the hydraulic cylinder, the control unit applies a torque limit to the drive of the electric servomotor.
The mold clamping machine according to claim 1. When the control unit moves the pair of molds in the opening direction, the control unit moves the pair of molds by driving the electric servomotor.
The mold clamping machine according to claim 1. The hydraulic cylinder is attached to a central portion of one of the pair of movable plates in a direction perpendicular to the opening / closing direction.
A tie bar slidably attached in the opening / closing direction is further provided at one end and the other end of the pair of movable plates in a direction perpendicular to the opening / closing direction.
The mold clamping machine according to claim 1. An extruder that extrudes molten resin,
A head that is connected to the extruder and forms a parison from the molten resin,
A parison wall thickness adjusting device provided at the tip of the head and adjusting the wall thickness of the parison,
It is provided with a mold clamping machine that sandwiches the parison with a pair of molds and blows gas into the sandwiched parison to inflate the parison to the inner surface shape of the pair of molds.
The mold clamping machine
A pair of movable plates to which the pair of molds are attached, and
A hydraulic cylinder attached to one of the pair of movable plates and pressing the movable plate in a direction in which the pair of molds closes.
In order to move the pair of movable plates in the opening / closing direction of the pair of molds, a linear motion mechanism provided separately from the hydraulic cylinder and
The electric servomotor that drives the linear motion mechanism and
A control unit that controls the drive of the hydraulic cylinder and the electric servomotor is provided.
When the control unit closes the pair of molds,
Until the moving distance of the pair of molds from the initial position in the opening / closing direction reaches a predetermined distance , the pair of molds are moved by driving only the electric servomotor.
When the predetermined distance is reached , both the electric servomotor and the hydraulic cylinder are operated .
After stopping the electric servomotor, the pair of molds are held in a state of being molded only by the hydraulic cylinder.
Hollow molding machine. The electric servomotor has a function of detecting the moving distance, and has a function of detecting the moving distance.
The control unit operates the electric servomotor and the hydraulic cylinder based on the detection result of the movement distance from the electric servomotor.
The hollow molding machine according to claim 8. It further has a position detecting unit for detecting the moving distance, and has a position detecting unit.
The control unit operates the electric servomotor and the hydraulic cylinder based on the detection result of the movement distance from the position detection unit.
The hollow molding machine according to claim 8. The pair of movable plates are arranged so as to face each other vertically with respect to the opening / closing direction.
The linear motion mechanism is
A ball screw having a first screw portion and a second screw portion arranged parallel to the opening / closing direction and threaded in opposite directions to each other.
A first nut portion screwed with the first screw portion and provided on one of the pair of movable plates, and a first nut portion.
Threadedly engaged with the second threaded portion, Bei example and a second nut portion provided in the other of the pair of movable platen,
The electric servomotor rotates the ball screw.
The hollow molding machine according to claim 8. When operating both the electric servomotor and the hydraulic cylinder, the control unit applies a torque limit to the drive of the electric servomotor.
The hollow molding machine according to claim 8. When the control unit moves the pair of molds in the direction in which the pair of molds are opened, the control unit moves the pair of molds by driving the electric servomotor.
The hollow molding machine according to claim 8. The hydraulic cylinder is attached to a central portion of one of the pair of movable plates in a direction perpendicular to the opening / closing direction.
A tie bar slidably attached in the opening / closing direction is further provided at one end and the other end of the pair of movable plates in a direction perpendicular to the opening / closing direction.
The hollow molding machine according to claim 8. Steps to extrude parison from molten resin while adjusting the wall thickness,
The pair of molds are moved in the closing direction by at least one of a linear motion mechanism driven by an electric servomotor and a hydraulic cylinder provided separately from the linear motion mechanism, and the extruded parison is moved to the pair of gold. Steps to be sandwiched by the mold and
A step of blowing gas into the parison sandwiched by the pair of molds is provided.
In the step of sandwiching the parison with the pair of molds,
Until the moving distance in the opening / closing direction from the initial position of the pair of molds reaches a predetermined distance , the pair of molds are moved by driving only the electric servomotor.
When the predetermined distance is reached , both the electric servomotor and the hydraulic cylinder are operated .
After stopping the electric servomotor, the pair of molds are held in a state of being molded only by the hydraulic cylinder.
Manufacturing method for hollow molded products. When moving the pair of molds in the closing direction, the pair of molds are moved by driving the electric servomotor until the predetermined distance is reached.
The method for manufacturing a hollow molded product according to claim 15. When operating both the electric servomotor and the hydraulic cylinder, a torque limit is applied to the drive of the electric servomotor.
The method for manufacturing a hollow molded product according to claim 15.

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