JP4782642B2 - Mold clamping apparatus and mold clamping force control method - Google Patents

Description

  The present invention relates to a mold clamping device and a mold clamping force control method, and more particularly to a mold clamping device and a mold clamping force control method for generating a mold clamping force with an electromagnet.

  2. Description of the Related Art Conventionally, in an injection molding machine, resin is injected from an injection nozzle of an injection device, filled into a cavity space between a fixed mold and a movable mold, and solidified to obtain a molded product. ing. A mold clamping device is provided for moving the movable mold relative to the fixed mold to perform mold closing, mold clamping, and mold opening.

  The mold clamping device includes a hydraulic mold clamping device that is driven by supplying oil to a hydraulic cylinder, and an electric mold clamping device that is driven by an electric motor. It is widely used because it has high controllability, does not pollute the surroundings, and has high energy efficiency. In this case, by driving the electric motor, the ball screw is rotated to generate a thrust, and the thrust is expanded by a toggle mechanism to generate a large mold clamping force.

  However, since the electric mold clamping device having the above-described configuration uses a toggle mechanism, it is difficult to change the mold clamping force due to the characteristics of the toggle mechanism, and the responsiveness and stability are improved. The mold clamping force cannot be controlled during molding. Therefore, a mold clamping device is provided in which the thrust generated by the ball screw can be directly used as a mold clamping force. In this case, since the torque of the electric motor and the mold clamping force are proportional, the mold clamping force can be controlled during molding.

  However, in the conventional mold clamping device, the load resistance of the ball screw is low and a large mold clamping force cannot be generated, and the mold clamping force fluctuates due to torque ripple generated in the electric motor. In addition, in order to generate the mold clamping force, it is necessary to constantly supply current to the motor, and the power consumption and heat generation amount of the motor increase. Therefore, it is necessary to increase the rated output of the motor by that amount. The cost of the device becomes high.

Therefore, a mold clamping device using a linear motor for the mold opening / closing operation and utilizing the attractive force of an electromagnet for the mold clamping operation is conceivable (for example, Patent Document 1).
WO05 / 090052 pamphlet

  However, when the attracting force of the electromagnet is used for the mold clamping operation, the magnetic force of the electromagnet is greatly influenced by the gap between the two magnetic poles, that is, the gap between the rear platen and the attracting plate. It can change due to unintended causes such as disturbance due to force or deformation of the device during mold clamping. Therefore, there is a problem in that the same mold clamping force may not be obtained even if the same magnitude of current is supplied to the electromagnet.

  Further, there is a problem that a stable mold clamping force cannot be obtained even when the parallelism of the gap is broken for some reason.

  FIG. 1 is a diagram illustrating an example in which the parallelism of the gap between the rear platen and the suction plate is broken.

  In FIG. 1, reference numeral 513 denotes a rear platen, and 522 denotes a suction plate. Reference numeral 548 denotes an electromagnet coil.

  In FIG. 1, the parallelism between the rear platen 513 and the suction plate 522 is broken by the inclination of the suction plate 522, and the gap δ is larger in the lower part. Therefore, in this case, as shown in (A), the magnetic flux density increases as it goes upward. That is, the adsorption force increases in the upper part and decreases in the lower part. Then, as shown in (B), a moment is generated in the suction plate 522, and the suction plate 522 is further tilted.

  FIG. 2 is a diagram for explaining a problem caused by tilting of the suction plate. In FIG. 2, the same parts as those in FIG.

  In FIG. 2, 510 denotes a mold clamping device, and 519 denotes a mold device. In addition to the rear platen 522 and the suction plate 513, the mold clamping device 510 includes a fixed platen 511, a movable platen 512, and a rod 539 as a mold clamping force transmission member that connects the movable platen 512 and the suction plate 22.

  The mold device 519 includes a fixed mold 515 fixed to the fixed platen 511 and a movable mold 516 fixed to the movable platen 512.

  In the mold clamping device 510 of FIG. 2, the attractive force acting on the adsorption plate 522 by the electromagnet including the coil 548 is transmitted to the movable platen 512 by the rod 539 and the mold clamping is performed. In such a configuration, if clamping is performed while the suction plate 522 is tilted, a moment is generated in the rod 539, and the movable platen 512 may be deformed as indicated by a broken line. As a result, the movable mold 16 is also deformed as indicated by the broken line, and it is possible that not only the rated mold clamping force cannot be obtained but also the shape of the molded product may be affected.

  The present invention has been made in view of the above points, and is capable of reducing the influence of a gap between two magnetic poles on a mold clamping force when generating a mold clamping force using an electromagnet. It is another object of the present invention to provide a mold clamping force control method.

  Therefore, in order to solve the above problems, the present invention is a mold clamping device that generates a mold clamping force with an electromagnet, and the electromagnet has an increase rate of a magnetic flux density with respect to an applied current when the magnetic flux density is less than 1T. A rated or maximum mold clamping force of the mold clamping device is generated in a state where the increase rate is approximately 2% or less compared to the increase rate.

  Further, the present invention is characterized in that the iron core of the electromagnet is an electromagnetic steel plate and generates a rated or maximum clamping force of the clamping device in a state where the magnetic flux density of the electromagnet is 2T or more.

  Further, the present invention is characterized in that the iron core of the electromagnet is silicon steel and generates a rated or maximum clamping force of the clamping device in a state where the magnetic flux density of the electromagnet is 1.4 T or more. To do.

  In the present invention, the iron core of the electromagnet is made of electromagnetic stainless steel, and the rated or maximum mold clamping force of the mold clamping device is generated in a state where the magnetic flux density of the electromagnet is 1.2 T or more. To do.

  In order to solve the above problems, the present invention provides a mold clamping device that generates a clamping force with an electromagnet, and the electromagnet generates a rated or maximum clamping force of the clamping device. The magnetic flux density is 80% or more of the saturation magnetic flux density.

  In order to solve the above problems, the present invention provides a method for controlling a mold clamping force in a mold clamping device that generates a mold clamping force with an electromagnet, wherein the rate of increase in magnetic flux density with respect to the current applied to the electromagnet is increased. The rated or maximum clamping force of the clamping device is generated in a state where the magnetic flux density is approximately 2% or less as compared with the increase rate at less than 1T.

  In order to solve the above problems, the present invention is a method for controlling a mold clamping force in a mold clamping device that generates a mold clamping force with an electromagnet, wherein the magnetic flux density of the electromagnet is 80% or more of the saturation magnetic flux density. In such a state, a rated or maximum clamping force of the clamping device is generated.

  According to the present invention, it is possible to provide a mold clamping device and a mold clamping force control method capable of alleviating the influence of a gap between two magnetic poles on a mold clamping force when a mold clamping force is generated using an electromagnet. it can.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this embodiment, for the mold clamping device, the moving direction of the movable platen when closing the mold is the front, the moving direction of the movable platen when opening the mold is the rear, and the injection device is the injection The description will be made assuming that the moving direction of the screw when performing the measurement is the front and the moving direction of the screw when performing the measurement is the rear.

  FIG. 3 is a view showing a state of the mold device and the mold clamping device when the mold is closed in the embodiment of the present invention, and FIG. 4 is a state when the mold device and the mold clamping device of the embodiment of the present invention are opened. FIG.

  In the figure, 10 is a mold clamping device, Fr is a frame of an injection molding machine, Gd is laid on the frame Fr to form a rail, and supports the mold clamping device 10 as a first guide member for guiding it. The two guides (in the figure, only one of the two guides Gd is shown) 11 is placed on the guide Gd and fixed to the frame Fr and the guide Gd. A fixed platen as a first fixing member, and a rear platen 13 as a second fixing member is disposed at a predetermined distance from the fixed platen 11 and opposed to the fixed platen 11, and the fixed platen A tie bar 14 (only two of the four tie bars 14 are shown in the figure) is laid between 11 and the rear platen 13 as four connecting members. The rear platen 13 is placed on the guide Gd so that it can move slightly with respect to the guide Gd as the tie bar 14 expands and contracts.

  In the present embodiment, the fixed platen 11 is fixed to the frame Fr and the guide Gd, and the rear platen 13 can move slightly with respect to the guide Gd. The fixed platen 11 can be moved slightly with respect to the guide Gd by being fixed with respect to the Fr and the guide Gd.

  A movable platen 12 as a first movable member is disposed along the tie bar 14 so as to face the fixed platen 11 so as to be movable back and forth in the mold opening / closing direction. For this purpose, a guide hole (not shown) for penetrating the tie bar 14 is formed at a position corresponding to the tie bar 14 in the movable platen 12.

  A first screw portion (not shown) is formed at the front end portion of the tie bar 14, and the tie bar 14 is fixed to the fixed platen 11 by screwing the first screw portion and the nut n1. Further, a guide post 21 as a second guide member having an outer diameter smaller than that of the tie bar 14 is protruded rearward from the rear end surface of the rear platen 13 at a predetermined portion at the rear of each tie bar 14, and It is formed integrally with the tie bar 14. A second screw portion (not shown) is formed in the vicinity of the rear end surface of the rear platen 13, and the fixed platen 11 and the rear platen 13 are connected by screwing the second screw portion and the nut n2. The In the present embodiment, the guide post 21 is formed integrally with the tie bar 14, but the guide post 21 may be formed separately from the tie bar 14.

  A fixed mold 15 as a first mold is fixed to the fixed platen 11, and a movable mold 16 as a second mold is fixed to the movable platen 12. Accordingly, the fixed mold 15 and the movable mold 16 are brought into contact with and separated from each other, and mold closing, mold clamping, and mold opening are performed. As the mold clamping is performed, a plurality of cavity spaces (not shown) are formed between the fixed mold 15 and the movable mold 16, and the molding material injected from the injection nozzle 18 of the injection apparatus 17 is used as a molding material. Resin (not shown) is filled in each cavity space. A mold device 19 is configured by the fixed mold 15 and the movable mold 16.

  A suction plate 22 as a second movable member disposed in parallel with the movable platen 12 is disposed behind the rear platen 13 so as to be able to advance and retract along the guide posts 21 and is guided by the guide posts 21. Is done. The suction plate 22 is formed with guide holes 23 through the guide posts 21 at locations corresponding to the guide posts 21. The guide hole 23 is opened at the front end surface, and has a large diameter portion 24 that accommodates the ball nut n2 and a sliding surface that is opened at the rear end surface of the suction plate 22 and is slid with the guide post 21. A small diameter portion 25 is provided. In the present embodiment, the suction plate 22 is guided by the guide post 21, but the suction plate 22 can be guided not only by the guide post 21 but also by the guide Gd.

  By the way, in order to move the movable platen 12 forward and backward, a linear motor 28 as a first drive unit and as a mold opening / closing drive unit is disposed between the movable platen 12 and the frame Fr. The linear motor 28 includes a stator 29 as a first drive element and a mover 31 as a second drive element. The stator 29 is parallel to the guide Gd on the frame Fr. In addition, the movable platen 12 is formed corresponding to the moving range of the movable platen 12, and the movable element 31 is formed at a lower end of the movable platen 12 so as to face the stator 29 and over a predetermined range.

When the length of the stator 29 is Lp, the length of the movable element 31 is Lm, and the stroke of the movable platen 12 is Lst, the length Lm corresponds to the maximum propulsive force by the linear motor 28. And the length Lp is
Lp> Lm + Lst
To be.

  The mover 31 includes a core 34 and a coil 35. The core 34 includes a plurality of magnetic pole teeth 33 that are protruded toward the stator 29 and formed at a predetermined pitch, and the coil 35 is wound around the magnetic pole teeth 33. The magnetic pole teeth 33 are formed in parallel to each other in a direction perpendicular to the moving direction of the movable platen 12. The stator 29 includes a core (not shown) and a permanent magnet (not shown) formed to extend on the core. The permanent magnet is formed by magnetizing the N-pole and S-pole magnetic poles alternately and at the same pitch as the magnetic pole teeth 33.

  Accordingly, when the linear motor 28 is driven by supplying a predetermined current to the coil 35, the movable element 31 is advanced and retracted, and accordingly, the movable platen 12 is advanced and retracted to perform mold closing and mold opening. it can.

  In the present embodiment, the permanent magnet is disposed on the stator 29 and the coil 35 is disposed on the mover 31, but the coil is disposed on the stator and the permanent magnet is disposed on the mover. You can also. In this case, since the coil does not move as the linear motor 28 is driven, wiring for supplying power to the coil can be easily performed.

  By the way, when the movable platen 12 is moved forward and the movable mold 16 abuts against the fixed mold 15, the mold is closed and subsequently the mold is clamped. In order to perform mold clamping, an electromagnet unit 37 is disposed between the rear platen 13 and the suction plate 22 as a second driving unit and as a mold clamping driving unit. A rod 39 as a mold clamping force transmission member extending through the rear platen 13 and the suction plate 22 and connecting the movable platen 12 and the suction plate 22 is disposed so as to freely advance and retract. The rod 39 advances and retracts the suction plate 22 in conjunction with the advance and retreat of the movable platen 12 when the mold is closed and opened, and transmits the mold clamping force generated by the electromagnet unit 37 to the movable platen 12 during mold clamping. To do.

  The mold clamping device 10 is configured by 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.

  The electromagnet unit 37 includes an electromagnet 49 as a first driving member formed on the rear platen 13 side, and an attracting portion 51 as a second driving member formed on the attracting plate 22 side. A predetermined portion of the front end surface of the attracting plate 22, in the present embodiment, is formed in a portion that surrounds the rod 39 and faces the electromagnet 49 in the attracting plate 22. In addition, in the present embodiment, two grooves 45 as coil arrangement portions having a rectangular cross-sectional shape are parallel to each other at a predetermined portion of the rear end surface of the rear platen 13, slightly above and below the rod 39. A core 46 having a rectangular shape is formed between the grooves 45, and a yoke 47 is formed in another portion. A coil 48 is wound around the core 46.

  The core 46, the yoke 47, and the suction plate 22 are formed by laminating thin plates made of a ferromagnetic material, and constitute an electromagnetic laminated steel plate.

  In the present embodiment, the electromagnet 49 is formed separately from the rear platen 13, and the attracting portion 51 is formed separately from the attracting plate 22. The electromagnet is formed as a part of the rear platen 13, and the attracting portion is formed as a part of the attracting plate 22. It can also be formed.

  Therefore, in the electromagnet unit 37, when an electric current is supplied to the coil 48, the electromagnet 49 is driven to attract the attracting part 51 and generate the mold clamping force.

  The rod 39 is connected to the suction plate 22 at the rear end and is connected to the movable platen 12 at the front end. Therefore, the rod 39 is moved forward as the movable platen 12 moves forward when the mold is closed to advance the suction plate 22, and is moved backward as the movable platen 12 is moved backward when the mold is opened. Retreat.

  For this purpose, a hole 41 for penetrating the rod 39 and a hole 42 for penetrating the rod 39 are formed in the central portion of the rear platen 13 and the central portion of the suction plate 22. A bearing member Br1 such as a bush that slidably supports the rod 39 is provided facing the opening. Further, a screw 43 is formed at the rear end of the rod 39, and the screw 43 and a nut 44 as a mold thickness adjusting mechanism supported rotatably on the suction plate 22 are screwed together.

  By the way, when the mold closing is completed, the suction plate 22 is brought close to the rear platen 13, and a gap δ is formed between the rear platen 13 and the suction plate 22. However, the gap δ becomes too small or large. If it is too large, the adsorbing part 51 cannot be adsorbed sufficiently, and the mold clamping force becomes small. The optimum gap δ changes as the thickness of the mold apparatus 19 changes.

  Therefore, a large-diameter gear (not shown) is formed on the outer peripheral surface of the nut 44, and a die thickness adjusting motor (not shown) as a die thickness adjusting driving unit is disposed on the suction plate 22. A small-diameter gear attached to the output shaft of the motor is engaged with a gear formed on the outer peripheral surface of the nut 44.

  Then, when the mold thickness adjusting motor is driven according to the thickness of the mold device 19 and the nut 44 is rotated by a predetermined amount with respect to the screw 43, the position of the rod 39 with respect to the suction plate 22 is adjusted, The position of the suction plate 22 with respect to the fixed platen 11 and the movable platen 12 is adjusted, and the gap δ can be set to an optimum value. That is, the mold thickness is adjusted by changing the relative positions of the movable platen 12 and the suction plate 22.

  The mold thickness adjusting device is configured by the mold thickness adjusting motor, the gear, the nut 44, the rod 39, and the like. In addition, a rotation transmitting portion that transmits the rotation of the mold thickness adjusting motor to the nut 44 is constituted by the gear. The nut 44 and the screw 43 constitute a movement direction conversion unit, and the rotation direction of the nut 44 is converted into a straight movement of the rod 39 in the movement direction conversion unit. In this case, the nut 44 constitutes the first conversion element, and the screw 43 constitutes the second conversion element.

  Next, the operation of the mold clamping apparatus 10 having the above configuration will be described.

  When a new mold apparatus 19 is attached along with the replacement of the mold apparatus 19, first, the distance between the suction plate 22 and the movable platen 12 is changed in accordance with the thickness of the mold apparatus 19, and the mold is changed. Thickness adjustment is performed. In the mold thickness adjustment, the fixed mold 15 and the movable mold 16 are attached to the fixed platen 11 and the movable platen 12, respectively, and then the movable mold 16 is retracted to place the mold apparatus 19 in an open state. .

  Subsequently, in the distance adjusting step, the linear motor 28 is driven, and the movable mold 16 is brought into contact with the fixed mold 15 to perform a mold touch. At this time, no mold clamping force is generated. In this state, the mold thickness adjusting motor is driven to rotate the nut 44, and the distance between the rear platen 13 and the suction plate 22, that is, the gap δ is adjusted to a preset value.

  At this time, the coil 48 is embedded in the rear platen 13 so that the coil 48 is not damaged even if the rear platen 13 and the suction plate 22 come into contact with each other, and the coil 48 does not protrude from the surface of the rear platen 13. In this case, the surface of the rear platen 13 functions as a stopper for preventing damage to the coil 48.

  Thereafter, the mold opening / closing processing means (not shown) performs mold opening / closing processing, and supplies current to the coil 35 in the state of FIG. 4 when the mold is closed. Subsequently, the linear motor 28 is driven, the movable platen 12 is advanced, and the movable mold 16 is brought into contact with the fixed mold 15 as shown in FIG. At this time, a gap δ is formed between the rear platen 13 and the suction plate 22, that is, between the electromagnet 49 and the suction portion 51. Note that the force required for mold closing is sufficiently reduced compared to the mold clamping force.

  Subsequently, the mold opening / closing processing means supplies current to the coil 48 during mold clamping, and attracts the attracting portion 51 by the attracting force of the electromagnet 49. Along with this, the clamping force is transmitted to the movable platen 12 via the suction plate 22 and the rod 39, and clamping is performed. Under this structure, in this embodiment, when changing the mold clamping force, such as at the start of mold clamping, the control unit sets the target mold clamping force to be obtained by the change, that is, the target in a steady state. Clamping force The value of a steady current (hereinafter referred to as “rated current”) required to generate a mold clamping force (hereinafter referred to as “steady mold clamping force”). Control is performed so that the coil 48 is supplied.

  The mold clamping force is detected by a load detector (not shown), and the detected mold clamping force is sent to the control unit, and is supplied to the coil 48 so that the mold clamping force becomes a set value. Current is adjusted and feedback control is performed. During this time, the resin melted in the injection device 17 is injected from the injection nozzle 18 and filled in each cavity space of the mold device 19. As the load detector, a load cell disposed on the rod 39, a sensor for detecting the extension amount of the tie bar 14, or the like can be used.

  When the resin in each cavity space is cooled and solidified, the mold opening / closing processing means stops supplying current to the coil 48 in the state shown in FIG. 3 when the mold is opened. Along with this, the linear motor 28 is driven, the movable platen 12 is retracted, and the movable mold 16 is placed at the retract limit position as shown in FIG. 4, and the mold opening is performed.

  In the present embodiment, the core 46, the yoke 47, and the suction plate 22 are all made of an electromagnetic laminated steel plate, but the periphery of the core 46 and the suction portion 51 in the rear platen 13 are electromagnetic laminated. You may make it comprise with a steel plate. In the present embodiment, an electromagnet 49 is formed on the rear end surface of the rear platen 13, and the attracting portion 51 is disposed on the front end surface of the attracting plate 22 so as to be capable of moving forward and backward. However, it is possible to dispose the electromagnet on the front end surface of the suction plate 22 so as to be able to advance and retreat, with the suction portion opposed to the suction portion on the rear end surface of the rear platen 13.

  In the present embodiment, the linear motor 28 is arranged as the first drive unit. However, instead of the linear motor 28, an electric motor, a hydraulic cylinder or the like is arranged. Can do. When the motor is used, the rotational rotational motion generated by driving the motor is converted into a linear motion by a ball screw as a motion direction conversion unit, and the movable platen 12 is advanced and retracted.

  By the way, in the mold clamping apparatus 10 according to the present embodiment, a mold clamping force is generated by an adsorption force by the electromagnet 49 and the adsorption plate 22, and the adsorption force is generated by the electromagnet 49 (or the rear platen 13) and the adsorption plate 22. Is affected by the value of the gap δ. This is because the magnetic flux density of the electromagnet 49 changes according to the value of the cap δ.

  Therefore, the inventors of the present application paid attention to the relationship between the gap δ and the magnetic flux density, and arranged the relationship as shown in FIG.

  FIG. 5 is a diagram for explaining the correlation between the gap and the magnetic flux density. In the graph 200 shown in FIG. 5, the horizontal axis represents the current value applied to the coil 48 of the electromagnet 49, and the vertical axis represents the magnetic flux density of the electromagnet 49. Here, the graph 200 shown in FIG. 5 is a graph under the condition that the number of windings of the coil 48 is equal. In addition, although the horizontal axis represents current for convenience, the magnitude of the magnetic flux density generated between the gap δ is determined by the magnetomotive force (= coil current × number of coil turns) generated by the gap δ and the coil 48. Magnetic force may be used. Further, if the current applied to the coil 48 is constant, the horizontal axis is the number of turns of the coil 48.

Curve 201 by solid line shows the change in magnetic flux density corresponding to the applied current when the value of the gap δ is x _0. A curved line 202 indicated by a broken line shows a change in magnetic flux density according to an applied current when the value of the gap δ is x _o + Δx. Further, a broken line curve 203 indicates a change in magnetic flux density according to the applied current when the value of the gap Δ is x ₀ −Δx.

In the case of the electromagnet in this configuration, under the condition that the number of turns of the coil 48 is equal, the magnetic flux density is in accordance with the change of the applied current, and the rising linear region → break point → saturation region (saturation magnetic flux density or magnetic flux density close to saturation magnetic flux density is In general, when using electromagnets (not limited to mold clamping devices), the rated current value is from the rising linear region to the break point from the viewpoint of good efficiency with respect to the applied current. Value is adopted. Therefore, even in the mold clamping device 10, from the viewpoint of good efficiency with respect to the applied current, for example, when the rated current a current value I ₁ indicated by the dashed line 204 (current for rated clamping force), the gap δ It can be seen from FIG. 5 that the magnetic flux density fluctuates by ΔB ₁ when the value of x ₀ −Δx (curve 203) and when the value of the gap δ is x _o + Δx (curve 202).

  That is, the region from the rising linear region to the break point is a preferable current value from the viewpoint of good efficiency with respect to the applied current, but it can also be said to be a region sensitive to the change in the gap δ. The size of the gap δ can change due to unintentional causes such as disturbance due to injection reaction force and deformation of the device during mold clamping, and the parallelism between the suction plate 22 and the rear platen 13 is broken. Considering that there may be cases where it is not constant, it is considered that the current value in the region sensitive to the change in the gap δ is undesirable from the viewpoint of obtaining a stable clamping force.

  On the other hand, FIG. 6 is a diagram for explaining the correlation between the gap and the magnetic flux density when the rated current value is in the saturation region of the magnetic flux density. In FIG. 6, the same parts as those in FIG. 5 are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

6, the rated current I _2, the value of the saturation region near the magnetic flux density (including saturation region) is employed. In this case, the fluctuation range of the magnetic flux density is ΔB ₂ (ΔB ₂ <ΔB) when the value of the gap δ is x ₀ −Δx (curve 203) and when the value of the gap δ is x _o + Δx (curve 202). ₁ ) It turns out that it can be suppressed. The value of ΔB ₂ becomes smaller when the magnetic flux density is saturated.

  Therefore, the mold clamping device 10 according to the present embodiment is designed so that the rated current value is in the saturation region of the magnetic flux density, in other words, the electromagnet 49 is magnetically saturated when the rated mold clamping force is generated. For example, the influence on the mold clamping force due to the change in the gap δ can be reduced. That is, even if the size of the gap δ changes due to an unintended cause such as a disturbance due to an injection reaction force or deformation of the device during mold clamping, the fluctuation range of the mold clamping force obtained by the same rated current is reduced. be able to. Further, even when the parallelism between the suction plate 22 and the rear platen 13 is lost, the difference in the clamping force between the portion where the gap δ is large and the portion where the gap δ is small can be suppressed, so that the rod 39 The moment generated on the movable platen 12 and the movable mold 16 can be reduced. The rated mold clamping force refers to a mold clamping force that is determined by design for each mold clamping device 10 as a mold clamping force that is generated when mold clamping is performed. This corresponds to the maximum clamping force that can be generated. This is because the mold clamping is generally performed by the maximum mold clamping force that the mold clamping apparatus 10 can generate.

  Such a mold clamping device 10 may be designed in the following procedure, for example.

  First, a rated mold clamping force is determined (for example, 50 t) (step S1). Subsequently, the device configuration of the mold clamping device 10 is determined (step S2). Subsequently, the largest gap δ value estimated from the assembly adjustment error is predicted (for example, 1.2 mm) (step S3). Subsequently, a material used for the iron core of the electromagnet 49 is determined (for example, silicon steel) (step S4). Subsequently, the saturation magnetic flux density of the iron core material is obtained (for example, 1.6 T) (step S5). That is, since the magnetization characteristics differ depending on the material, it is necessary to obtain the saturation magnetic flux density according to the determined material.

  FIG. 7 is a diagram for explaining a difference in magnetization characteristics depending on materials. In the graph 300 shown in FIG. 7, the horizontal axis represents the current value applied to the electromagnet coil, and the vertical axis represents the magnetic flux density of the electromagnet.

  In the graph 300, a curve 401 indicates a change in magnetic flux density according to an applied current in the case where the laminated thin plates are electromagnetic steel plates. A curve 402 shows a change in magnetic flux density according to an applied current when the laminated thin plate is silicon steel. Further, a curve 403 shows a change in magnetic flux density according to an applied current when the laminated thin plates are electromagnetic stainless steel. Thus, depending on the material, the magnetization characteristics are significantly different, and therefore the value of the saturation magnetic flux density is also different.

  Subsequently, the electromagnet 49 is designed so that magnetic flux saturation occurs in the state of the gap δ predicted in step S3 (step S6). Specifically, if the counter area of the electromagnet 49 is reduced, the magnetic flux tends to be saturated. In addition, what is necessary is just to redesign from step S2, when an apparatus structure is changed with the shape of the electromagnet 49. FIG.

  In this way, by selecting the material characteristics, even if the gap δ when the rated current flows is constant, the saturation magnetic flux density can be changed to eliminate the electromagnetic force imbalance that occurs between the gaps δ. it can.

Furthermore, used as the core of the same, by reducing the value of x ₀ of the gap [delta], it may be easily reached saturation magnetic flux density. In this case, after the assembly of the mold clamping device is completed, even if it is desired to change the saturation magnetic flux density when the rated mold clamping force is generated, the mold clamping device can be disassembled by adjusting the gap δ distance. And the saturation magnetic flux density can be adjusted.

  Further, when considering the accuracy of the mold clamping force, the design may be performed in the following procedure.

First, a rated mold clamping force is determined (for example, 50 t) (step S11). Subsequently, the accuracy of the mold clamping force is determined (for example, ± 0.5 t) (step S12). Subsequently, the device configuration of the mold clamping device 10 is determined (step S13). Subsequently, a range (x ₀ ± Δx) of values of the gap value x ₀ and the gap δ that are assumed as references based on the assembly adjustment error is predicted (for example, 1.0 ± 0.1 mm) (step S14). Subsequently, from the results of steps S11 and S13, a change in the gap δ expected from load deformation is predicted (for example, 0.1 mm) (step S15). Subsequently, a material used for the iron core of the electromagnet 49 is determined (for example, silicon steel) (step S16). Subsequently, the magnetic flux density at which the fluctuation of the clamping force falls within the value determined in step S2 is obtained with respect to the fluctuation of the gap δ predicted in steps S15 and S16 (for example, 1.8T) (step S17). Subsequently, the electromagnet 49 is designed so that the mold clamping force determined in step S11 is achieved with the magnetic flux density obtained in step S17 (step S18). Specifically, the magnetic flux density tends to increase if the counter area of the electromagnet 49 is reduced, and the magnetic flux density tends to decrease if the counter area is increased. In addition, what is necessary is just to redesign from step S13, when an apparatus structure is changed with the shape of the electromagnet 49. FIG. If a satisfactory electromagnet 49 cannot be obtained, the allowable range may be reduced by redesigning steps S14 and S17 or steps S13, S15, and S17.

  Thus, by selecting the material characteristics, even if the gap δ when the rated current flows is constant, the saturation magnetic flux density can be changed to eliminate the electromagnetic force imbalance between the gaps. .

Furthermore, used as the core of the same, by reducing the value of x ₀ of the gap [delta], it may be easily reached saturation magnetic flux density. That is, the curve 201 is shifted to the curve 203 side in FIG. In this case, after the assembly of the mold clamping device is completed, even if it is desired to change the saturation magnetic flux density when the rated mold clamping force is generated, the mold clamping device can be disassembled by adjusting the gap δ distance. And the saturation magnetic flux density can be adjusted.

  The designed electromagnet 49 preferably generates magnetic saturation when generating a rated mold clamping force (that is, when performing mold clamping after mold closing), but does not necessarily cause magnetic saturation. It does not have to be. For example, when considered based on a graph as shown in FIG. 7, since the slope changes 50 to 200 times between the rising portion and the saturation region, the electromagnet 49 has a rate of increase in magnetic flux density with respect to the applied current. The rated mold clamping force may be generated in a state where the magnetic flux density is approximately 2% or less compared with the increase rate at less than 1T. Further, the condition described on the left may be satisfied with respect to the expected error range. Such a region is, for example, about 2.0 T or more in the case of a magnetic steel sheet, as shown in FIG. Moreover, if it is silicon steel, it will be about 1.4T or more. Moreover, if it is electromagnetic stainless steel, it will be about 1.2T or more.

  Further, even when the electromagnet 49 is capable of obtaining a magnetic flux density of about 80% of the saturation magnetic flux density when generating the rated mold clamping force, the influence of the gap δ on the mold clamping force can be sufficiently suppressed.

  As described above, according to the mold clamping device 10 in the embodiment of the present invention, when the rated mold clamping force is obtained, the electromagnet 49 is in a magnetic saturation state or a state close to magnetic saturation. The influence (or sensitivity) of 49 on the magnetic force can be reduced. Therefore, even when the gap δ changes somewhat (for example, within an error range), or even when the parallelism between the suction plate 22 and the rear platen 13 slightly collapses (for example, within the error range), it is obtained by the rated current. The mold clamping force can be stabilized.

  Moreover, although the example using the laminated board which consists of a thin board was shown in this invention, you may make it form the core 46 and the yoke 47 with the iron core which consists of the same member. In this case, by changing the material of the iron core to electromagnetic steel plate, silicon steel, or electromagnetic stainless steel, the design should be made so that the rated clamping force can be obtained with the saturation magnetic flux density, similar to the core 46 constituted by the laminated plate. Can do.

  As mentioned above, although the Example of this invention was explained in full detail, this invention is not limited to the specific embodiment which concerns, In the range of the summary of this invention described in the claim, various deformation | transformation * It can be changed.

It is a figure which shows the example in which the parallelism of the gap between a rear platen and an adsorption | suction board collapse | crumbled. It is a figure for demonstrating the problem by an adsorption | suction board inclining. It is a figure which shows the state at the time of the mold closing of the metal mold apparatus and mold clamping apparatus in embodiment of this invention. It is a figure which shows the state at the time of the mold opening of the metal mold | die apparatus and mold clamping apparatus in embodiment of this invention. It is a figure for demonstrating the correlation with a gap and magnetic flux density. It is a figure for demonstrating the correlation with a gap and magnetic flux density when the value of a rated current is made into the saturation region of magnetic flux density. It is a figure for demonstrating the difference in the magnetization characteristic by material.

Explanation of symbols

10, 510 Mold clamping device 11, 511 Fixed platen 12, 512 Movable platen 13 Rear platen 14 Tie bar 15, 515 Fixed mold 16, 516 Movable mold 17 Injection device 18 Injection nozzle 19, 519 Mold device 21 Guide post 22, 522 Adsorption plate 23 Guide hole 24 Large diameter portion 25 Small diameter portion 28 Linear motor 29 Stator 31 Movable element 37 Electromagnet unit 39, 539 Rod 41, 42 Hole 43 Screw 44 Nut 45 Groove 46 Core 47 Yoke 48, 548 Coil 49 Electromagnet 51 Adsorption Part Br1 Bearing member Gd Guide Fr Frame n1, n2 Nut

Claims (7)

A mold clamping device for generating a mold clamping force by an electromagnet,
The electromagnet has a rated or maximum mold of the clamping device in a state where the increasing rate of the magnetic flux density with respect to the applied current is about 2% or less compared to the increasing rate when the magnetic flux density is less than 1T. A mold clamping device that generates a clamping force.   2. The mold clamping according to claim 1, wherein the iron core of the electromagnet is an electromagnetic steel plate, and the rated or maximum mold clamping force of the mold clamping device is generated in a state where the magnetic flux density of the electromagnet is 2T or more. apparatus.   The iron core of the electromagnet is silicon steel, and the rated or maximum mold clamping force of the mold clamping device is generated in a state where the magnetic flux density of the electromagnet is 1.4 T or more. Clamping device.   The iron core of the electromagnet is electromagnetic stainless steel, and the rated or maximum mold clamping force of the mold clamping device is generated in a state where the magnetic flux density of the electromagnet is 1.2 T or more. Clamping device. A mold clamping device for generating a mold clamping force by an electromagnet,
The mold clamping device according to claim 1, wherein the electromagnet has a magnetic flux density of 80% or more of a saturation magnetic flux density when generating the rated or maximum mold clamping force of the mold clamping device. A method of controlling the clamping force in a clamping device that generates clamping force by an electromagnet,
In a state where the increase rate of the magnetic flux density with respect to the current applied to the electromagnet is approximately 2% or less compared to the increase rate when the magnetic flux density is less than 1 T, the rated or maximum mold clamping of the mold clamping device is performed. A mold clamping force control method characterized by generating a force. A method of controlling the clamping force in a clamping device that generates clamping force by an electromagnet,
A mold clamping force control method, wherein the rated or maximum mold clamping force of the clamping device is generated in a state where the magnetic flux density of the electromagnet is 80% or more of the saturation magnetic flux density.

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