TW201325867A - Injection molding machine - Google Patents

Abstract

The present invention provides an injection molding machine with excellent efficiency in production of the molded product. The injection molding machine (10) having the electromagnet (49) to generate the predetermined die clamping force is characterized that it comprises: an electric current supply unit (70) to supply DC current to the coil (48) of electromagnet (49); and a control unit (60) to control the electric current supply unit (70). When releasing the predetermined die clamping force, the control unit (60) makes the DC current which is opposite to the direction of generating the predetermined die clamping force flow through the coil (48) of electromagnet (49).

Description

Injection molding machine

The present invention relates to an injection molding machine.

The injection molding machine is formed into a molded article by filling the molten resin into the cavity space of the mold device and solidifying it. The mold device is composed of a fixed mold and a movable mold, and forms a cavity space between the fixed mold and the movable mold when the mold is closed. The mold closing, mold clamping, and mold opening of the mold device are performed by a mold clamping device. As a mold clamping device, a mold clamping device using a linear motor in a mold opening and closing operation and using an electromagnet in a mold clamping operation has been proposed (for example, see Patent Document 1).

(previous technical literature) (Patent Literature)

Patent Document 1: International Publication No. 05/090052

Conventionally, when the mold clamping force is released before the mold is opened, the supply of current to the electromagnet is cut off. At this time, the mold clamping force does not immediately drop to 0 (zero) due to the influence of the magnetic field remaining in the electromagnet (for example, the magnetic core of the electromagnet), and the mold opening and closing drive unit such as a linear motor is opened. It takes a certain amount of time. Therefore, there is room for improvement in production efficiency.

The present invention has been made in view of the above problems, and an object thereof is to provide an injection molding machine which is excellent in production efficiency of a molded article.

In order to solve the above problems, an injection molding machine according to an aspect of the present invention includes an electromagnet that generates a predetermined mold clamping force, and the injection molding machine includes a current supply unit that supplies a direct current to a coil of the electromagnet. And a control unit that controls the current supply unit to cause a direct current that is opposite to a direction in which the predetermined mold clamping force is generated to flow to the coil of the electromagnet when the predetermined mold clamping force is released.

According to the present invention, it is possible to provide an injection molding machine which is excellent in production efficiency of a molded article.

In the following, the embodiments for carrying out the invention will be described with reference to the accompanying drawings, wherein the same or corresponding components are attached to the same or corresponding components, and the description is omitted. In addition, the moving direction of the movable platen when the mold is closed is set to the front, and the moving direction of the movable platen when the mold is opened is set to the rear.

Fig. 1 is a view showing a state in which the injection molding machine according to the embodiment of the present invention is closed, and Fig. 2 is a view showing a state in which the injection molding machine according to the embodiment of the present invention is opened.

In the figure, 10 is an injection molding machine, Fr is a frame of the injection molding machine 10, and Gd is a guide formed by two guide rails laid on the frame Fr. Piece, 11 is a fixed platen. The fixed platen 11 can be disposed on the position adjustment base Ba which is movable in the mold opening and closing direction (the horizontal direction in the drawing). In addition, the fixed platen 11 can also be placed on the frame Fr.

A movable platen 12 is disposed facing the fixed platen 11. The movable platen 12 is fixed to the movable base Bb, and the movable base Bb can travel on the guide Gd. Thereby, the movable platen 12 can be moved in the mold opening and closing direction with respect to the fixed platen 11.

The rear platen 13 is disposed at a predetermined interval from the fixed platen 11 in parallel with the fixed platen 11. The rear platen 13 is fixed to the frame Fr via the leg portion 13a.

The four connecting rods 14 (only two of the four connecting rods 14 are shown in the drawing) are bridged between the fixed platen 11 and the rear platen 13 . The fixed platen 11 is fixed to the rear platen 13 via a connecting rod 14. The movable platen 12 is disposed to retreat freely along the connecting rod 14. A guide hole (not shown) through which the connecting rod 14 is inserted is formed in a portion of the movable platen 12 corresponding to the connecting rod 14. In addition, a notch portion may be formed instead of the via hole.

A distal end portion (right end portion in the drawing) of the connecting rod 14 is formed with a screw portion (not shown), and the nut n1 is screwed and fastened to the screw portion, whereby the distal end portion of the connecting rod 14 is fixed to the fixed pressure plate 11. The rear end portion of the connecting rod 14 is fixed to the rear pressure plate 13.

The fixed mold 15 is mounted on the fixed pressing plate 11, and the movable mold 16 is mounted on the movable pressing plate 12, so that the fixed mold 15 and the movable mold 16 are contacted and separated with the advancement and retreat of the movable pressing plate 12, thereby performing mold closing, mold clamping and mold opening. . Further, as the mold clamping is performed, a cavity space (not shown) is formed between the fixed mold 15 and the movable mold 16, And filled with molten resin in the cavity space. The mold unit 19 is constituted by the fixed mold 15 and the movable mold 16.

The adsorption plate 22 is disposed in parallel with the movable platen 12. The suction plate 22 is fixed to the slide base Sb via a mounting plate 27, and the slide base Sb can travel on the guide Gd. Thereby, the suction plate 22 becomes retractable at a position further rearward than the rear platen 13. The adsorption plate 22 may be formed of a magnetic material. Further, the mounting plate 27 may be omitted, and at this time, the suction plate 22 is directly fixed to the sliding base Sb.

The rod 39 is disposed to be coupled to the suction plate 22 at the rear end portion and coupled to the movable platen 12 at the front end portion. Therefore, the rod 39 advances with the advancement of the suction plate 22 at the time of mold closing, and advances the movable platen 12, and retreats with the retraction of the suction plate 22 at the time of mold opening, and the movable platen 12 is retracted. To this end, a rod hole 41 for penetrating the rod 39 is formed in a central portion of the rear platen 13.

The linear motor 28 is a mold opening and closing drive unit for advancing and retracting the movable platen 12, and is disposed, for example, between the suction plate 22 coupled to the movable platen 12 and the frame Fr. Further, the linear motor 28 may be disposed between the movable platen 12 and the frame Fr.

The linear motor 28 includes a stator 29 and a mover 31. The stator 29 is formed to be parallel to the guide Gd on the frame Fr and to correspond to the range of movement of the slide base Sb. The movable member 31 is formed to face the stator 29 at a lower end of the slide base Sb and to extend over a predetermined range.

The mover 31 includes a magnetic core 34 and a coil 35. Further, the magnetic core 34 includes a plurality of magnetic pole teeth 33 that protrude toward the stator 29 and are formed at predetermined intervals, and the coils 35 are wound around the respective magnetic pole teeth 33. In addition, the magnetic pole teeth 33 shape The directions are parallel to each other in a direction perpendicular to the moving direction of the movable platen 12. Further, the stator 29 includes a magnetic core (not shown) and a permanent magnet (not shown) formed by extending the magnetic core. The permanent magnet is formed by alternately magnetizing the magnetic poles of the N pole and the S pole. A position sensor 53 that detects the position of the movable member 31 is disposed.

When the linear motor 28 is driven by supplying a predetermined current to the coil 35 of the linear motor 28, the mover 31 is advanced and retracted. As a result, the suction plate 22 and the movable platen 12 advance and retreat, thereby enabling mold closing and mold opening. The linear motor 28 is feedback-controlled based on the detection result of the position sensor 53 so that the position of the movable member 31 reaches the set value.

Further, in the present embodiment, a permanent magnet is disposed on the stator 29, and the coil 35 is disposed on the movable member 31. However, a coil may be disposed on the stator, and a permanent magnet may be disposed on the movable member. At this time, since the coil does not move with the driving of the linear motor 28, the wiring for supplying electric power to the coil can be easily performed.

Further, instead of the linear motor 28, a rotary motor and a ball screw mechanism that converts the rotational motion of the rotary motor into a linear motion or a fluid pressure cylinder such as a hydraulic cylinder or an air cylinder can be used as the mold opening and closing drive unit.

The electromagnet unit 37 generates an adsorption force between the rear platen 13 and the adsorption plate 22. This suction force is transmitted to the movable platen 12 by the rod 39, and a mold clamping force is generated between the movable platen 12 and the fixed platen 11.

Further, the fixed platen 11, the movable platen 12, the rear platen 13, the suction plate 22, the linear motor 28, the electromagnet unit 37, the rod 39, and the like constitute a mold clamping device.

The electromagnet unit 37 is composed of an electromagnet 49 as a mold clamping drive unit formed on the rear platen 13 side and an adsorption portion 51 formed on the suction plate 22 side. The adsorption portion 51 is formed at a predetermined portion of the adsorption surface (front end surface) of the adsorption plate 22, for example, a portion of the adsorption plate 22 that surrounds the rod 39 and faces the electromagnet 49. Further, a predetermined portion of the suction surface (rear end portion) of the rear platen 13, for example, around the rod 39, forms a groove 45 for accommodating the coil 48 of the electromagnet 49. The magnetic core 46 is formed at a position further inside than the groove 45. The coil 48 is wound around the magnetic core 46. A portion other than the magnetic core 46 in the rear platen 13 is formed with a yoke 47.

Further, in the present embodiment, the electromagnet 49 is formed separately from the rear platen 13, and the adsorption portion 51 is formed separately from the adsorption plate 22, but an electromagnet may be formed as a part of the rear platen 13 as a part of the adsorption plate 22. The part forms an adsorption section. Further, the electromagnet and the adsorption portion may be arranged in reverse. For example, the electromagnet 49 can be provided on the side of the adsorption plate 22, and the adsorption portion 51 can be provided on the side of the rear platen 13. Further, the number of the coils 48 of the electromagnet 49 may be plural.

When the current is supplied to the coil 48 in the electromagnet unit 37, the electromagnet 49 is driven to adsorb the adsorption portion 51, whereby the mold clamping force can be generated.

Fig. 3 is a view showing a control system of an injection molding machine according to an embodiment of the present invention. The control unit 60 includes, for example, a CPU, a memory, and the like, and controls the operation of the linear motor 28 and the electromagnet 49 by the CPU processing the control program recorded in the memory. Further, since the operation of the linear motor 28 is conventional, the description thereof is omitted.

The control unit 60 includes a mold clamping processing unit 62 that controls the current supply unit 70 that supplies a direct current to the coil 48 of the electromagnet 49. The mold clamping processing unit 62 outputs a signal indicating a direct current supplied to the coil 48 of the electromagnet 49 to the current supply unit 70.

The current supply unit 70 is configured by, for example, an inverter including a plurality of power modules, and supplies a direct current corresponding to a signal supplied from the mold clamping processing unit 62 to the coil 48 of the electromagnet 49. The current supply unit 70 has a function of changing the direction and intensity (size) of the direct current flowing to the coil 48 of the electromagnet 49.

A DC power source 80 is connected to the current supply unit 70. The DC power source 80 is composed of a rectifier 82 that converts an alternating current of the alternating current power source 90 into a diode of a direct current, and a capacitor 84 that smoothes a direct current output from the rectifier 82.

The control unit 60 includes a mold clamping force detecting unit 63 that detects a mold clamping force. The mold clamping force detecting portion 63 is connected to, for example, a strain sensor 55 that detects the strain (elongation amount) of the connecting rod 14 that is extended according to the mold clamping force, and detects the mold clamping force based on the detection result of the strain sensor 55. When detecting the mold clamping force, a load sensor such as a load sensor for detecting a load applied to the rod 39, and a magnetic sensor for detecting a magnetic field of the electromagnet 49 may be used instead of the strain sensing for detecting the strain of the connecting rod 14. The sensor 55, the type of sensor used to detect the clamping force, can be varied. For example, the strain sensor can be applied not only to the connecting rod 14 but also to the rod 39. Because the strain (the amount of shrinkage) of the rod 39 is proportional to the mold clamping force.

The control unit 60 may further include a mold clamping force determining unit 66 that determines whether or not the mold clamping force is within a predetermined range when the mold clamping force is released. The mold clamping force determining unit 66 utilizes The mold clamping force detected by the mold clamping force detecting unit 63 is determined.

Next, the operation of the injection molding machine 10 having the above configuration will be described. The various operations of the injection molding machine 10 are performed under the control of the control unit 60.

The control unit 60 controls the mold closing process. In the state (opening state) of Fig. 2, the control unit 60 supplies a current to the coil 35 to drive the linear motor 28. As shown in FIG. 1, the movable mold 16 abuts against the fixed mold 15 as the movable platen 12 advances. At this time, a gap δ0 is formed between the rear platen 13 and the adsorption plate 22, that is, between the electromagnet 49 and the adsorption portion 51. In addition, the force required to close the mold is very small compared to the mold clamping force.

Next, the control unit 60 controls the mold clamping process by the mold clamping processing unit 62. The mold clamping processing unit 62 controls the current supply unit 70 to supply a direct current to the coil 48 of the electromagnet 49, and adsorbs the adsorption unit 51 to the electromagnet 49. This adsorption force is transmitted to the movable platen 12 via the rod 39, and a mold clamping force is generated between the movable platen 12 and the fixed platen 11.

The molten resin is filled in the cavity space of the mold device 19 in the mold clamping state. When the resin is cooled and solidified, the mold clamping processing unit 62 controls the current supply unit 70 to adjust the direct current supplied to the coil 48 of the electromagnet 49 to release the mold clamping force.

Next, the control unit 60 controls the mold opening process. The control unit 60 supplies a current to the coil 35 of the linear motor 28 to move the movable platen 12 backward. As shown in Fig. 2, the movable mold 16 is retracted to perform mold opening.

Next, the mold clamping force releasing process of the mold clamping processing unit 62 will be described based on Fig. 4 . The following processing is to apply a predetermined combination to the mold device 19. After the mold force and before the mold opening.

Fig. 4(a) shows the change of the supply current to the coil of the electromagnet with time, and Fig. 4(b) shows the change of the clamping force of the electromagnet with time. In the fourth drawing, an example of the present embodiment is shown by a solid line, another example of the embodiment is shown by a one-dot chain line, and a conventional example is shown by a broken line. In any example, the mold clamping processing unit 62 supplies a constant direct current I _{0 to} the coil 48 of the electromagnet 49 until the time t ₀ , thereby generating a predetermined clamping force P ₀ . (The change with time from the fourth graph to the time t ₀ is only a conventional example).

When the mold releasing process unit 62 in a predetermined clamping force P _0, as of FIG. 4 (a) to the solid line, at time t ₀ the direction of the DC current is reversed, so that a predetermined mold clamping force is generated with P ₀ DC current I in the opposite direction to the flow direction of _a coil of the electromagnet 49 is 48. Therefore, a magnetic field that cancels the direction of the magnetic field remaining on the electromagnet 49 when the supply current to the coil 48 is cut off at time t ₀ as indicated by a broken line in Fig. 4(a) is formed, as shown in Fig. 4 (b). In the middle of the line, the mold clamping force is reduced as indicated by the solid line. Therefore, the standby time before the mold opening can be shortened.

The greater the intensity (size) of the direct current I ₁ in the opposite direction, the shorter the standby time before the mold is opened. The shorter the standby time, the better the production efficiency, but on the other hand, the deceleration of the mold clamping force is increased, and the load applied to the mold device 19 or the like is drastically changed. Therefore, the intensity of the direct current I ₁ in the reverse direction is considered in consideration of the production efficiency and the variation of the load applied to the mold device 19 or the like, and is determined in advance by a test or the like. Further, the intensity of the direct current I ₁ in the reverse direction can also be determined by the intensity of the direct current I ₀ when the predetermined clamping force P ₀ is generated.

However, if the DC current I _{1 in the} opposite direction becomes longer, the electromagnet 49 and the adsorption portion 51 are re-adsorbed. Therefore, as shown by the alternate long and short dash line in Fig. 4(b), the mold clamping force is again increase. Further, it can be presumed that the increase again before the mold clamping force is restored to zero is because the magnetic field remaining in the electromagnet 49 is uneven, and the timing at which the magnetic field disappears differs depending on the situation.

Therefore, in order to suppress the increase in the mold clamping force, when the mold clamping force is released, the mold clamping force determination unit 66 provided in the control unit 60 can determine whether or not the mold clamping force is within a predetermined range (Pmin to Pmax). This determination can be repeated over every predetermined time.

When the mold clamping force determining unit 66 determines that the mold clamping force is within the predetermined range, the mold clamping processing unit 62 can cut off the supply of current to the coil 48 of the electromagnet 49. The timing of cutting off the supply of current to the coil 48 of the electromagnet 49 may be in the middle of increasing the mold clamping force, but it is preferable in the middle of the mold clamping force to decrease. After the supply of current to the coil 48 of the electromagnet 49 is cut off, no current flows through the coil 48, so the mold clamping force decreases at a speed corresponding to the response delay of the electromagnet 49.

When the mold clamping force determining unit 66 determines that the mold clamping force is within the predetermined range or when the current supply to the coil 48 of the electromagnet 49 is cut off, the control unit 60 allows the mold opening operation of the linear motor 28. Since the mold opening operation is performed in a state where the mold clamping force is low, not only the power consumption for the mold opening operation but also the mold opening operation can be stabilized.

Next, a modification of the mold clamping force releasing process of the mold clamping processing unit 62 will be described based on Fig. 5 . The following process applies a pre-mould to the mold device 19. After the mold clamping force is set and before the mold opening.

Fig. 5(a) shows the change of the supply current to the coil of the electromagnet with time, and Fig. 5(b) shows the change of the clamping force of the electromagnet with time.

In the modification shown in Fig. 5, when the predetermined mold clamping force P ₀ is released, the intensity of the direct current flowing to the coil 48 of the electromagnet 49 is gradually decreased from the time t ₀ , and after the time t ₁₁ becomes zero, Change the direction of the DC current and gradually increase the intensity of the DC current. After such a direction that the predetermined direction and generates a mold clamping force in the opposite direction P ₀ of DC current I ₁₁ flows to the solenoid coil 49 is 48, the DC to the coil 48 of the electromagnet 49 the current is reversed at least one time. For each inversion, the maximum value of the DC current intensity is set small (I ₁₁ >I ₁₂ >I ₁₃ >I ₁₄ >I ₁₅ ). The inversion timing (t ₁₂ <t ₁₃ <t ₁₄ <t ₁₅ ) may be before the electromagnet 49 and the adsorption portion 51 start to resorb, that is, before the mold clamping force is about to increase.

By reversing the direction of the direct current flowing to the coil 48 of the electromagnet 49, the influence of the magnetic field unevenness remaining on the electromagnet 49 can be reduced, and the reduction in the mold clamping force can be further promoted, and the production efficiency can be further improved.

Further, when the current supply time is long and the mold clamping force is increased again, the mold clamping force can be lowered again by reversing the direction of the direct current flowing to the coil 48 of the electromagnet 49. Therefore, the degree of freedom in pattern setting is high and the control is relatively simple.

Although an embodiment of the present invention and the like have been described above, the present invention is not limited to the above embodiment and the like, as long as the present invention is not deviated from the scope of the present invention. In addition, various modifications or substitutions can be made to the above-described embodiments and the like.

For example, in FIG. 4. In the example shown in solid lines in, t ₀ reversing the flow direction of the DC current of the coil 48 of the electromagnet 49 at the time, but can also be a current to the electromagnet 49 is temporarily stopped at t ₀ of time The supply, after a predetermined time elapses, supplies a DC current I _{1 in the} opposite direction to the coil 48 of the electromagnet 49.

10‧‧‧ Injection molding machine

15‧‧ ‧ fixed mode

16‧‧‧moving

48‧‧‧ coil of electromagnet

49‧‧‧Electromagnet

55‧‧‧ strain sensor

60‧‧‧Control Department

62‧‧‧Molding Processing Department

63‧‧‧Molding force detection department

66‧‧‧Molding force judgment department

70‧‧‧ Current Supply Department

Fig. 1 is a view showing a state in which the injection molding machine according to the embodiment of the present invention is closed.

Fig. 2 is a view showing a state at the time of mold opening of the injection molding machine according to the embodiment of the present invention.

Fig. 3 is a view showing an injection molding machine control system according to an embodiment of the present invention.

Fig. 4 is a graph showing changes in the supply current to the coil of the electromagnet with time and the change in the clamping force of the electromagnet with time.

Fig. 5 is a graph showing changes with time in the supply current to the coil of the electromagnet and changes in the clamping force of the electromagnet with time.

48‧‧‧ coil

55‧‧‧ strain sensor

60‧‧‧Control Department

62‧‧‧Molding Processing Department

63‧‧‧Molding force detection department

66‧‧‧Molding force judgment department

70‧‧‧ Current Supply Department

80‧‧‧DC power supply

82‧‧‧Rectifier

84‧‧‧ capacitor

90‧‧‧AC power supply

Claims (4)

An injection molding machine including an electromagnet that generates a predetermined mold clamping force, wherein the injection molding machine includes a current supply unit that supplies a direct current to a coil of the electromagnet, and a control unit that controls the current supply unit. When the predetermined mold clamping force is released, the control unit causes a direct current in a direction opposite to a direction in which the predetermined mold clamping force is generated to flow to the coil of the electromagnet. The injection molding machine according to claim 1, wherein the control unit causes a direct current flowing in a direction opposite to a direction in which the predetermined mold clamping force is generated to flow to the coil of the electromagnet when the predetermined mold clamping force is released. Thereafter, the direction of the direct current flowing to the coil of the electromagnet is reversed once or more. The injection molding machine according to the first or second aspect of the invention, wherein the control unit includes a mold clamping force determining unit that determines whether the mold clamping force is within a predetermined range when the predetermined mold clamping force is released. When the mold clamping force determining unit determines that the mold clamping force is within the predetermined range, the current supply unit supplies the current supply to the electromagnet. The injection molding machine according to the third aspect of the invention, wherein the control unit allows the control unit to allow the mold clamping force determination unit to determine that the mold clamping force is within a predetermined range or to cut off the current supply to the electromagnet. The mold opening and closing drive unit is opened.