JP4588664B2 - Mold clamping force control method and mold clamping device - Google Patents

Description

  The present invention relates to a mold clamping force control method and a mold clamping device, and more specifically to a method of controlling a mold clamping force generated using an electromagnet in the mold clamping device and the mold clamping device.

  2. Description of the Related Art Conventionally, a molding machine, for example, an injection molding machine, includes an injection device, a mold device, and a mold clamping device. By injecting resin from an injection nozzle of the injection device, filling the cavity space of the mold device, and solidifying the resin. A molded product is obtained. The mold apparatus includes a fixed mold and a movable mold, and operates the mold clamping apparatus to move the movable mold forward and backward with respect to the fixed mold, thereby closing the mold, clamping and opening the mold. It can be carried out.

  The mold clamping device includes a fixed platen to which the fixed mold is attached, a movable platen to which the movable mold is attached, an electric motor, a ball screw shaft connected to an output shaft of the motor, and the ball screw. A ball screw composed of a ball nut screwed to a shaft, a cross head connected to the ball nut, a toggle mechanism disposed between the cross head and a movable platen, and the like, by driving the motor The mold can be closed and clamped by advancing the crosshead and extending the toggle mechanism.

  However, in the mold clamping apparatus having the above-described configuration, a toggle mechanism is used to generate a mold clamping force. Therefore, a bending moment acts on the movable platen, and the mold mounting surface of the movable platen is distorted. Will occur.

  Moreover, since the mold clamping is performed by extending the toggle mechanism, it becomes difficult to control the mold clamping force.

  Therefore, there is provided a mold clamping device that includes an electric motor and an electromagnet, and uses the torque of the motor for mold closing and mold opening operations, and uses the attraction force of the electromagnet for mold clamping operations (for example, Patent Document 1). reference).

  In the mold clamping device, a rear platen is disposed at a predetermined distance from the fixed platen, and a movable platen is disposed so as to be able to advance and retreat along a tie bar provided between the fixed platen and the rear platen. An electromagnet is fixed to the rear end surface of the rear platen, and an adsorption plate is disposed behind the rear platen so as to be movable back and forth. A link mechanism is disposed between the adsorption plate and the movable platen. It can be bent and stretched by a motor.

Therefore, after closing the mold by driving the motor and extending the link mechanism, current is supplied to the coil provided around the electromagnet to drive the electromagnet, and according to the magnitude of the current. The mold can be clamped by generating a magnetic force to attract the suction plate. In this case, an electromagnet is used to generate the mold clamping force, so that the bending moment does not act on the movable platen, and the mold mounting surface is not distorted. Can be controlled.
Japanese Patent No. 3190600

  However, even when a current is supplied to the coil provided around the electromagnet when changing the clamping force, such as at the start of clamping, an eddy current is generated in the direction that cancels the magnetic field, and the current is supplied. However, a state in which a desired magnetic field cannot be obtained may occur.

  FIG. 1 shows a graph for explaining such a state. In the graph, the vertical axis indicates the mold clamping force [t · f] generated by the electromagnet, and the horizontal axis indicates the time [second] for supplying the current to the coil.

  Referring to FIG. 1, due to the generation of the eddy current, about several seconds (about 7 seconds in the example shown in FIG. 1) have passed since the rated current, which is a current necessary for operating the electromagnet, is supplied. A steady mold clamping force (clamping force of about 10 [t · f] in the example shown in FIG. 1) necessary for attracting the suction plate to the electromagnet to perform mold clamping is generated.

  Thus, even when a current is supplied to the coil provided around the electromagnet in order to change the clamping force, such as when clamping is started, it takes a certain time to generate the desired clamping force. This is not a steady process in the mold clamping process and is unique to the rise characteristics when the mold clamping force is changed. Not desirable. In particular, when the molding cycle is short, it is necessary to improve the productivity of the molded product by reducing the generation time of the mold clamping force as much as possible.

  Therefore, the present invention has been made in view of the above points, and in a mold clamping device that generates a mold clamping force using an electromagnet, the time until a desired mold clamping force is generated is shortened, It is an object of the present invention to provide a mold clamping force control method and a mold clamping apparatus capable of improving the rising characteristics in the mold clamping process.

  According to one aspect of the present invention, there is provided a method for controlling a mold clamping force generated using an electromagnet in a mold clamping device, which is necessary for generating a steady mold clamping force when changing the mold clamping force. A mold clamping force control method is provided, wherein a current having a value larger than a rated current value is supplied to a mold clamping drive unit having the electromagnet.

  The current may be supplied to the mold clamping drive unit when a command to change the mold clamping force is issued. The current supplied to the mold clamping drive unit may be a maximum current that can be supplied from the current supply unit.

  Furthermore, the current may be changed to the rated current after the current is passed through the mold clamping drive unit and a predetermined period of time elapses, and when the mold clamping force reaches the steady mold clamping force, the current May be changed to the rated current. The mold clamping force can be detected by pressure detection means.

  Moreover, when the magnetic flux of the electromagnet reaches a steady magnetic flux, the current may be changed to the rated current. The magnetic flux of the electromagnet can be detected by magnetic flux density detection means.

  The current having a value larger than the rated current is energized to the mold clamping drive unit for a certain period of time, a change in the mold clamping force over time within the certain period of time is tested in advance, and based on the result of the test The time for energizing the mold clamping drive unit with the current having a value larger than the rated current is determined, and the time having the value larger than the rated current is determined based on the result of the test After energization, the current may be changed to the rated current.

  According to another aspect of the present invention, there is provided a mold clamping device that generates a clamping force using an electromagnet, a current supply unit that supplies a current to a mold clamping drive unit having the electromagnet, and the current supply unit. A control unit that controls the current supply unit with a current having a value larger than a rated current required for generating a steady mold clamping force. A mold clamping device is provided, wherein the mold clamping drive unit is energized when changing.

  According to the present invention, in a mold clamping device that uses an electromagnet to generate a mold clamping force, it is possible to shorten the time until a desired mold clamping force is generated and to improve the rising characteristics in the mold clamping process. A mold clamping force control method and the mold clamping apparatus can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In the following, 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 when performing the injection In the following description, the moving direction of the screw is assumed to be the front, and the moving direction of the screw when measuring is assumed to be the rear.

  In the following description, mold clamping refers to a state in which the movable mold is further in force from the state in which the parting surface of the movable mold is in contact with the parting surface of the fixed mold. It is pressed by a movable mold.

[First Embodiment]
FIG. 2 is a schematic configuration diagram of a mold apparatus and a mold clamping apparatus according to the first embodiment of the present invention.

  In FIG. 2, 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 and guides the mold clamping device 10. These are two guides as one guide member. In the figure, only one of the two guides Gd is shown.

  Reference numeral 11 denotes a fixed platen as a first fixing member that is placed on the guide Gd and fixed to the frame Fr and the guide Gd. A rear platen 13 as a second fixing member is disposed at a predetermined interval from the fixed platen 11 and facing the fixed platen 11. Between the fixed platen 11 and the rear platen 13, four tie bars 14 (only two of the four tie bars are shown in the figure) are installed as 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.

  A movable platen 12 as a first movable member is disposed along the tie bar 14 so as to be capable of moving forward and backward in the mold opening / closing direction (moving in the left-right direction in the drawing). 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 of the movable platen 12.

  A first screw portion (not shown) is formed at a front end portion (right end portion in the figure) 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. Fixed to. In addition, a guide post 21 as a second guide member having a smaller outer diameter than the tie bar 14 is provided at a predetermined portion at the rear (left side in the drawing) of each tie bar 14, and the rear end surface (left end surface in the drawing). ) Projecting rearward and 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 of each guide post 21. The fixed platen 11 and the rear platen 13 screw the second screw portion and the nut n2. Are linked by 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. A resin (not shown) is filled in each cavity space.

  A mold apparatus 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 that penetrate the guide posts 21 at locations corresponding to the guide posts 21.

  The guide hole 23 is opened at the front end surface (right end surface in the drawing), is opened at the rear end surface of the large diameter portion 24 that accommodates the ball nut n2 and the suction plate 22, and is slid with the guide post 21. A small-diameter portion 25 having a sliding surface 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 formed on the frame Fr in parallel with the guide Gd and corresponding to the moving range of the movable platen 12, and the movable platen 12. A movable element 31 as a second driving element is provided at the lower end of the second element so as to face the stator 29 and to be formed over a predetermined range.

  The mover 31 includes a core 34 projecting toward the stator 29 and having a plurality of magnetic pole teeth 33 formed at a predetermined pitch, and a coil 35 wound around each magnetic pole tooth 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 so as to extend on the core. The permanent magnet alternates between the magnetic poles of N pole and S pole, and the magnetic poles. It is formed by magnetizing at the same pitch as the teeth 33.

  Accordingly, when the linear motor 28 is driven by supplying a predetermined current to the coil 35, the movable element 31 moves forward and backward, and accordingly, the movable platen 12 moves forward and backward, and mold closing and mold opening can be performed. .

  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 (moved in the right direction in the figure) and the movable mold 16 comes into contact with the fixed mold 15, the mold closing is completed, and then the mold clamping is performed. In order to perform mold clamping, an electromagnet unit 37 as a second drive unit and as a mold clamping drive unit is disposed between the rear platen 13 and the suction plate 22.

  In order to transmit the mold clamping force generated by the electromagnet unit 37 to the movable platen 12 at the time of mold clamping, the suction plate 22 is moved back and forth in conjunction with the advance and retreat of the movable platen 12 when the mold is closed and opened. A rod 39 as a clamping force transmission member that extends through the rear platen 13 and the suction plate 22 and connects the movable platen 12 and the suction plate 22 is disposed so as to freely advance and retract.

  Between the front end portion of the rod 39 and the movable platen 12, the load cell 3 is provided as pressure detection means (load detector) that detects a clamping force generated by the electromagnet unit 37 and transmitted to the movable platen 12. Is provided.

  The mold clamping device 10 is constituted 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 disposed on the rear platen 13 side, and an attracting portion 51 as a second driving member disposed on the suction plate 22 side.

  The attracting portion is formed at a predetermined portion of the front end surface of the attracting plate 22, in the present embodiment, the portion surrounding the rod 39 in the attracting plate 22 and facing the electromagnet 49. Also, a predetermined portion of the rear end surface of the rear platen 13, in this embodiment, slightly above and below the rod 39, extends in the horizontal direction, and two grooves 45 as coil arrangement portions are parallel to each other. A core 46 having a rectangular shape is formed between the grooves 45, and a yoke 47 is formed in other portions. A coil 48 is wound around the core 46.

  Therefore, in the electromagnet unit 37, when an electric current is supplied to the coil 48 provided in the groove 45, the electromagnet 49 is driven to attract the attracting portion 51 and generate the mold clamping force.

  The rod 39 is connected to the suction plate 22 at the rear end (left end in the figure) and connected to the movable platen 12 at the front end. Accordingly, the rod 39 is moved forward as the movable platen 12 advances when the mold is closed, thereby causing the suction plate 22 to move forward. Then, the suction plate 22 is moved backward.

  Therefore, a hole 41 for passing the rod 39 and a hole 42 for penetrating the rod 39 are formed in the central portion of the rear platen 13, and an opening at the front end of the hole 41. A bearing member Br1 such as a bush for slidably supporting the rod 39 is disposed. 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.

  In the present embodiment, the mold clamping device 10 is further connected to the control unit 4 and the driver 5. More specifically, the load cell 3 provided between the front end of the rod 39 and the movable platen 12 is connected to the control unit 4, and the coil 48 is connected to the driver 5 serving as a current supply unit. Yes. The control unit 4 and the driver 5 are connected, and the control unit 4 controls the operation of the driver 5 based on the detection signal sent from the load cell 3 and controls the current supplied to the coil 48.

  Under this structure, in the present embodiment, when changing the mold clamping force, such as at the start of mold clamping, the control unit 4 sets the target mold clamping force to be obtained by the change, that is, the target in the steady state. Larger than the value of the steady current (hereinafter referred to as “rated current”) required to generate the mold clamping force (hereinafter referred to as “steady mold clamping force”). The operation of the driver 5 is controlled so that a current of a value is supplied to the coil 48.

  This will be described with reference to FIGS. 3 and 4 in addition to FIG.

  Here, FIG. 3 is a graph showing the relationship between the current supplied from the driver 5 to the coil 48 and the clamping force. In the graph shown in FIG. 3, the vertical axis represents the mold clamping force [t · f] generated by the electromagnet unit 37, and the horizontal axis represents the time [second] for supplying current. FIG. 4 is a graph showing control of the current supplied to the coil 48 when the steady mold clamping force is a target value. In the graph shown in FIG. 4, the vertical axis indicates the mold clamping force [t · f] generated by the electromagnet unit 37 and the current value [A] supplied to the coil 48, and the horizontal axis indicates the time for supplying the current [ Second].

Referring to FIG. 3, for example, when the desired steady mold clamping force F ₀ is about 10 [t · f] and the rated current I ₀ is supplied from the driver 5 to the coil 48, the steady mold clamping force F _{0 is} concerned. In order to obtain the above, time t1 (about 5.9 to 6.0 seconds) is required after a command for changing the mold clamping force is issued from the control unit 4.

On the other hand, when the current supplied from the driver 5 to the coil 48 is about twice the rated current I ₀ , a command for changing the mold clamping force is given by the control unit 4 as indicated by I ₀ × 2 in FIG. Can be obtained at time t2 (about 0.5 seconds) after When the rated current I ₀ is about 3 times, the steady mold clamping force F ₀ can be obtained at time t3 (about 0.3 seconds) as shown by I ₀ × 3 in FIG. When the rated current I ₀ is about 5 times, as shown by I ₀ × 5 in FIG. 3, the steady mold clamping force F ₀ can be obtained at time t4 (about 0.2 seconds). When approximately 9 times the I _0, can be in Figure 3, as indicated by _{I 0} × 9, to obtain the constant clamping force _{F 0} at time t5 (about 0.1 seconds).

That is, by supplying a current having a value larger than the value of the rated current I ₀ from the driver 5 to the coil 48, the rise time of the mold clamping force can be shortened, and the time for obtaining the steady mold clamping force F _0. Can be shortened.

In particular, as apparent from FIG. 3, when the current supplied from the driver 5 to the coil 48 is not less than 5 times the rated current I _0, this effect is significant.

  From the viewpoint of shortening the rise time of the mold clamping force to the maximum, it is desirable to supply the coil 48 with the maximum current that can be supplied by the driver 5 as long as the limit value of the thermal characteristics of the coil 48 is not exceeded.

Based on the relationship between the magnitude of the current supplied from the driver 5 to the coil 48 and the magnitude of the mold clamping force shown in FIG. 3, in this embodiment, as shown in FIG. 4, the steady mold clamping force F ₀ is set as the target. The current supplied to the coil 48 is controlled as a value.

Referring to FIG. 4, when changing the mold clamping force, the control unit 4 controls the driver 5 so as to supply a current having a value larger than the value of the rated current I ₀ to the coil 48. Here, when changing the mold clamping force, for example, to start a mold clamping operation, to change the magnitude of the mold clamping force in multiple stages, or to have a shape with a different thickness in one molded product When a molded product is molded, a command to change the mold clamping force F is issued from the control unit 4 for the purpose of changing the mold clamping force in accordance with the cooling state.

In the example shown in FIG. 4, when changing such a mold clamping force, the control unit 4 supplies the coil 48 with a current I ₀ × 9 that is about nine times the rated current I _0. To control. Therefore, the driver 5 has a capacity capable of supplying the coil 48 with a current I ₀ × 9 having a value about nine times the rated current I ₀ while considering the limit value of the thermal characteristics of the coil 48. As long as the limit value of the thermal characteristics of the coil 48 is not exceeded, there is no particular upper limit for the capacity, and there is a capacity capable of supplying the coil 48 with a current that is about five times the rated current I ₀ or more. You may do it.

  By supplying a current to the coil 48, the electromagnet 49 is driven, and the electromagnet 49 attracts the attracting portion 51 to generate a mold clamping force F according to the magnitude of the current. The mold clamping force F is transmitted to the movable platen 12 and is detected by the load cell 3 as pressure detecting means (load detector) provided between the front end portion of the rod 39 and the movable platen 12.

As shown in FIG. 4, when a current I ₀ × 9 (about 200 [A]) that is about nine times the rated current I ₀ (about 22 [A]) is supplied to the coil 48, the mold clamping force F increases. About 0.13 seconds after the command to change the mold clamping force F is issued from the control unit 4, the mold clamping force F becomes substantially the same value as the steady mold clamping force F ₀ (about 10 [t · f]). Reach.

As described above, the clamping force F detected by the load cell 3, at the time it is sent to the control unit 4 as a detection signal, the detected mold clamping force F has reached a steady clamping force F _0, the control unit 4 operates the driver 5 to change the current supplied to the coil 48 from the current I ₀ × 9 to the rated current I ₀ , and thereafter, the rated current is supplied to the coil 48 until the clamping force F needs to be changed again. I ₀ continues to be supplied, and the mold clamping force F is maintained at substantially the same value as the steady mold clamping force F ₀ (about 10 [t · f]).

That is, in the present embodiment, when the mold clamping force F is changed, the control unit 4 has the value of the rated current I ₀ necessary for generating the target steady mold clamping force F ₀ to be obtained by the change. When a larger current I ₀ × 9 is supplied to the coil 48 and the mold clamping force F reaches the steady mold clamping force F ₀ , the current supplied to the coil 48 is changed from the current I ₀ × 9 to the rated current I. _The driver 5 is operated by comparison control between the current value and the detected value of the clamping force so as to be changed to _zero .

Therefore, when changing the clamping force, such as at the start of clamping, even if an eddy current in the direction to cancel the magnetic field is generated, a clamping force having the same value as the steady clamping force F ₀ can be generated in a short time. And eddy current loss can be compensated. Therefore, it is possible to improve the rising characteristics of the clamping process using an electromagnet, and to improve the productivity of the molded product.

Moreover, the actual change in the clamping force F is detected by the load cell 3, whether the detected mold clamping force F has reached a steady clamping force F ₀ are determined, the control unit 4 is accurately The driver 5 can be activated.

  Furthermore, if the detected value of the clamping force detected by the load cell 3 is feedback-controlled to the current command value, the driver 5 can be operated with higher accuracy.

  By the way, in the above-described example, the load cell 3 is provided between the front end portion of the rod 39 and the movable platen 12 as pressure detection means (load detector) for detecting the clamping force generated by the electromagnet unit 37. ing. However, the present invention is not limited to such an example, and can also be applied to the example shown in FIG.

  Here, FIG. 5 is a schematic configuration diagram of a mold clamping device and the like according to a first modification of the example shown in FIG. In FIG. 5, the same portions as those shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted.

  Referring to FIG. 5, a tie bar sensor 7 may be used as pressure detection means (load detector) for detecting the mold clamping force.

  The tie bar sensor 7 is a sensor that is disposed on the tie bar 14 and detects distortion (mainly elongation) of the tie bar 14. The tie bar 14 is applied with a tensile force corresponding to the mold clamping force at the time of mold clamping, and extends slightly in proportion to the mold clamping force.

  Therefore, by detecting the extension amount of the tie bar 14 by the tie bar sensor 7, it is possible to know the actually applied clamping force. That is, when the fixed mold 15 and the movable mold 16 come into contact with each other, the reaction force of the total axial force applied by the electromagnet unit 37 is detected by the tie bar sensor 7 which is a pressure detection means (load detector).

A detection signal output from the tie bar sensor 7 is sent to the control unit 4. As described with reference to FIG. 2 and the like, the control unit 4 controls the operation of the driver 5 based on the detection signal, and controls the current supplied to the coil 48. Also in this example, as in the example described with reference to FIG. 2 and the like, the actual change in the mold clamping force F is detected by the tie bar sensor 7, and the detected mold clamping force F is the steady mold clamping force F _0. Is determined, and the control unit 4 can operate the driver 5 with high accuracy.

In the example shown in FIGS. 2 and 5, and detects the clamping force F which is generated by the electromagnet unit 37, the detected mold clamping force F is determined whether the reached steady clamping force F ₀ The control unit 4 operates the driver 5. However, the present invention is not limited to such an example, and can also be applied to the example shown in FIG.

  Here, FIG. 6 is a schematic configuration diagram of a mold clamping device and the like according to a second modification of the example shown in FIG. In FIG. 6, the same portions as those shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted.

  Referring to FIG. 6, in this example, the Hall element 9 serving as a magnetic flux density detecting means is provided on the surface of the rear platen 13 facing the suction plate 22. The Hall element 9 is a magnetoelectric conversion element using the Hall effect, and detects the magnetic flux density generated in the electromagnet.

  The Hall element 9 is connected to the control unit 4, and the coil 48 is connected to the driver 5 serving as a current supply unit. The control unit 4 and the driver 5 are connected, and the control unit 4 controls the operation of the driver 5 based on the detection signal sent from the Hall element 9 and controls the current supplied to the coil 48.

In the example shown in FIG. 2 or FIG. 5 described above, the steady mold clamping force F ₀ is set as a target value, the change in the mold clamping force F is detected by the load cell 3 or the tie bar sensor 7, and the detected mold clamping force F is steady. it is determined whether reaches the mold clamping force F _0, and by changing the current supplied to the coil 48.

In this example shown in FIG. 6, the stationary mold clamping force F ₀ flux required to generate a (hereinafter, such a magnetic flux "constant flux") and the target value the value of the change in the magnetic flux B of the electromagnet 49 Is detected by the Hall element 9.

The detection signal output from the Hall element 9 is sent to the control unit 4, and as described with reference to FIG. 2 and the like, the control unit 4 determines that the value of the detected magnetic flux B is a steady magnetic flux based on the detection signal. It is determined whether or not B ₀ has been reached, and when the value of the magnetic flux B reaches the steady magnetic flux B ₀ , the operation of the driver 5 is controlled so that the current supplied to the coil 48 is changed to the rated current I ₀ .

In this example, the actual change in the magnetic flux B is detected by the Hall element 9, whether or not the detected magnetic flux B has reached a steady-state magnetic flux B ₀ is determined, the control unit 4 accurately driver 5 operates Can be made.

  Furthermore, if the detected value of the magnetic flux B detected by the Hall element 9 is feedback-controlled to the current command value, the driver 5 can be operated with higher accuracy.

  Next, the operation of the mold clamping apparatus using the pressure detection means (load detector) of the present invention will be described.

  The molded product molded in the previous cycle is taken out at a position where the movable mold 16 is retracted to the mold open limit. When a current is supplied from this position to the linear motor 28, the movable platen 12 is advanced and the movable mold 16 approaches the fixed mold 15. This process is called a mold closing process.

  Since the position of the linear motor 28 is controlled in the mold closing process, the position can be ensured accurately with good reproducibility. Thereafter, when the movable mold 16 approaches the fixed mold 15 to a predetermined distance, the linear motor 28 starts to decelerate.

Thereafter, when the movable platen 12 further moves forward and the distance between the movable mold 16 and the fixed mold 15 becomes equal to or less than a predetermined distance, the movable platen 12 enters the mold clamping force generation section, and the rated current I is supplied to the coil 48. A current of ₀ or more (for example, I ₀ × 9) is supplied, and the adsorption force is rapidly increased. At this time, when the movable mold 16 and the fixed mold 15 are in contact with each other, that is, in the mold touch state, a mold clamping force is generated in the mold in response to an increase in the suction force.

Thereafter, when the detected value of the pressure detection means (load detector) reaches the set mold clamping force, the control unit 4 changes the current value to the rated current value I ₀ and continues to apply the set mold clamping force to the mold.

  Thereafter, when a predetermined time (for example, the cooling time of the resin filled in the mold) elapses, current is supplied again to the linear motor 28, and the movable platen 12 moves backward to the mold opening limit.

[Second Embodiment]
In the above-described first embodiment of the present invention, the mold clamping force F or the magnetic flux density B is detected by the detection means 3, 7, or 9, and the detection signal output from the detection means 3, 7, or 9 is detected. Based on this, it is determined whether or not the value of the detected mold clamping force F or magnetic flux B has reached the steady mold clamping force F ₀ or steady magnetic flux B ₀ , and the detected value of the mold clamping force F or magnetic flux B is steady. The control unit 4 controls the operation of the driver 5 so that the current supplied to the coil 48 is changed to the rated current I ₀ when the mold clamping force F ₀ or the steady magnetic flux B ₀ is reached.

  However, the present invention is not limited to such an embodiment, and the present invention can be applied to the example shown in FIG. Here, FIG. 7 is a graph showing a waiting time table used in the mold clamping apparatus according to the second embodiment of the present invention. In the following description, the description of the same portions as those described in the first embodiment of the present invention is omitted.

In the graph shown in FIG. 7, a change with time of the mold clamping force F when the current I ₀ × 9 (about 200 [A]) is supplied to the coil 48 is shown. In the graph shown in FIG. 7, the vertical axis represents the mold clamping force [t · f] generated by the electromagnet unit 37 and the current value [A] supplied to the coil 48, and the horizontal axis represents the current supply time [ Second].

In the present embodiment, the graph shown in FIG. 7 is called a waiting time table. The waiting time table supplies a predetermined current (current I ₀ × 9 in this example) to the coil 48 for a certain period of time, tests the change of the mold clamping force F over time within the certain period of time, and calculates the result. This is shown in the graph.

  With this waiting time table, when supplying the predetermined current to the coil 48, the desired target mold clamping force should be reached after how many seconds have passed since the command to change the mold clamping force F is issued from the control unit 4 to the driver 5. That is, it is possible to grasp the waiting time.

For example, in the example shown in FIG. 7, when the current I ₀ × 9 is supplied to the coil 48 and the desired mold clamping force is the mold clamping force F ₁ (about 5 [t · f]), the mold clamping force F It is only necessary to wait for a time t ₁ (about 0.085 seconds) after a command to change the value is issued from the control unit 4 to the driver 5, and the current I ₀ × 9 is supplied to the coil 48 to obtain the mold clamping force F to be obtained. _{In the case of 2} (about 10 [t · f]), it suffices to wait for a time t ₂ (about 0.125 seconds) after a command to change the mold clamping force F is issued from the control unit 4 to the driver 5.

After obtaining the clamping force of a desired target, as in the first embodiment of the present invention, the current supplied to the coil 48 is changed to the rated current I _0.

  Thus, in this embodiment, the waiting time for the target mold clamping force can be set based on the test result. Therefore, the mold clamping force control method of the present invention can be executed without actually detecting the mold clamping force or the magnetic flux density by the detecting means as in the first embodiment of the present invention. The configuration can be simplified. Needless to say, the present embodiment can provide the same effects as those achieved by the first embodiment of the present invention.

  Although the embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment, and various modifications and changes are within the scope of the gist of the present invention described in the claims. It can be changed.

It is a graph for demonstrating the problem resulting from generation | occurrence | production of an eddy current. It is a schematic block diagram of the metal mold | die apparatus and the mold clamping apparatus in the 1st Embodiment of this invention. It is a graph which shows the relationship between the electric current supplied to a coil from a driver, and mold clamping force. It is the graph which showed control of the electric current supplied to a coil when a steady mold clamping force is made into a target value. It is a schematic block diagram of the mold clamping apparatus etc. which concern on the 1st modification of the example shown in FIG. It is a schematic block diagram of the mold clamping apparatus etc. which concern on the 2nd modification of the example shown in FIG. It is the graph which showed the waiting time table used in the mold clamping apparatus which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

3 Load cell 4 Control unit 5 Driver 7 Tie bar sensor 9 Hall element 10 Mold clamping device 37 Electromagnet unit 49 Electromagnet B Magnetic flux B ₀ Steady magnetic flux F Mold clamping force F ₀ Steady mold clamping force I ₀ Rated current

Claims (10)

A method of controlling a clamping force generated using an electromagnet in a clamping device,
When the mold clamping force is changed, a current having a value larger than a rated current value necessary for generating a steady mold clamping force is supplied to the mold clamping drive unit having the electromagnet. Mold clamping force control method. The mold clamping force control method according to claim 1,
A mold clamping force control method, wherein when the command to change the mold clamping force is issued, the current is supplied to the mold clamping drive unit. The mold clamping force control method according to claim 1 or 2,
The mold clamping force control method, wherein the current supplied to the mold clamping drive unit is a maximum current that can be supplied from a current supply unit. A mold clamping force control method according to any one of claims 1 to 3,
A mold clamping force control method, wherein the current is changed to the rated current after a predetermined period has elapsed after the current is passed through the mold clamping drive unit. The mold clamping force control method according to claim 4,
A mold clamping force control method, wherein when the mold clamping force reaches the steady mold clamping force, the current is changed to the rated current. The mold clamping force control method according to claim 5,
A mold clamping force control method, wherein the mold clamping force is detected by pressure detection means. The mold clamping force control method according to claim 4,
A mold clamping force control method, wherein when the magnetic flux of the electromagnet reaches a steady magnetic flux, the current is changed to the rated current. The mold clamping force control method according to claim 7,
A mold clamping force control method, wherein the magnetic flux of the electromagnet is detected by a magnetic flux density detector. A mold clamping force control method according to any one of claims 1 to 3,
The current having a value larger than the rated current is energized to the mold clamping drive unit for a certain period of time, and the change of the mold clamping force with respect to the passage of time within the certain period is tested in advance.
Based on the result of the test, a time for energizing the mold clamping drive unit with the current having a value larger than the rated current is determined,
A mold clamping force control method characterized by changing the current to the rated current after energizing the current having a value larger than the rated current for the time determined based on the result of the test. A mold clamping device that generates a clamping force using an electromagnet,
A current supply unit for energizing a mold clamping drive unit having the electromagnet;
A control unit for controlling the current supply unit,
The control unit applies a current having a value larger than a rated current value necessary for generating a steady mold clamping force to the current supply unit when changing the mold clamping force. A mold clamping device characterized by energizing.

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