JP5387002B2 - Toggle type electric clamping device - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a toggle type electric mold clamping device that can automatically control an upper limit of a mold opening force even if a set mold clamping force is changed.

In a mold clamping device such as an injection molding machine, an electric type is widely used.
An example of such an electric mold clamping device is a toggle type electric mold clamping device 1 as shown in FIG. This toggle type electric mold clamping device 1 includes a fixed platen 3 fixed on a base plate 2 and a movable platen 4 arranged to face the fixed platen 3 so as to be movable back and forth.
A link housing 5 movably disposed with respect to the base 2 is provided at a position separated from the fixed plate 3 by a predetermined distance. Further, between the fixed platen 3 and the movable platen 4, a die 6 comprising a fixed die 6a and a movable die 6b is attached via a die clamp a and a mounting screw b as shown in FIGS. ing. A toggle mechanism 7 is provided between the movable platen 4 and the link housing 5, and a mold clamping motor 8 for operating the toggle mechanism 7 is disposed at the rear end of the link housing 5 by an unillustrated attachment part. .
The toggle mechanism 7 includes a cross head 11 attached to a screw shaft 9 as a drive shaft via a nut member 10, a first toggle link 12 attached to the cross head 11 so as to be swingable, and swingable to the link housing 5. The second toggle link 13 attached and the third toggle link 14 attached to the movable platen 4 so as to be swingable are provided.
In the configuration as described above, the mold clamping motor 8 is driven to rotate the screw shaft 9, the crosshead 11 is advanced via the nut member 10, the toggle mechanism 7 is operated, and the movable platen 4 is advanced. It is the structure which performs mold clamping. In this case, a mold clamping force larger than the propulsive force of the cross head 11 by the mold clamping motor 8 can be generated, and a large mold clamping force can be applied to the mold 6.

  Further, in order to correspond to the thickness (die height) of each die 6, the movable nut 4b mounted on the rear end surface of the link housing 5 is rotated by a die height device (not shown). Then, the link housing 5 interlocked with the movable nut 4b operates forward and backward (left and right in the figure), the toggle mechanism 7 and the movable platen 4 connected to the link housing 5 are also interlocked, and the difference in thickness for each mold Can respond.

In order to correspond to the set clamping force desired by the operator, further die height adjustment is performed. After the die 6 is mounted on the fixed platen 3 and the movable platen 4, first, the die height device is driven to retract the link housing 5 to fully open the die 6 and then the die clamping motor 8 is driven to turn the toggle mechanism 7. Is operated to extend the second toggle link 13 and the third toggle link 14 in a straight line.
Next, the die height device is driven again to advance the link housing 5, the toggle mechanism 7, and the movable platen 4 to touch the fixed mold 6 a and the movable mold 6 b. Thereafter, the mold clamping motor 8 is driven to bend the toggle mechanism 7.
Finally, the die height device is driven, and the movable nut 4b and the ring housing 5 are advanced by a feeding amount corresponding to the set clamping force. This feed amount is the amount of elongation of the tie bar 4 for generating a desired mold clamping force, and can be calculated from the set mold clamping force, the length of the tie bar 4, the cross-sectional area, and the elastic coefficient.

Thus, after the die height adjustment corresponding to the set mold clamping force is completed, the cross head 11 is operated to move the movable platen 4 forward, the mold 6 is touched as shown in FIG. The mold clamping force is applied by moving forward (at this time, the second toggle link 13 and the third toggle link 14 are in a straight line).
In a state where a mold clamping force is applied to the mold 6, a molten resin or metal is injected and filled into the cavity of the mold 6 at a high pressure from an injection device (not shown). After the resin and metal are cooled and solidified, the crosshead 11 is moved backward to remove the mold clamping force, and the mold is opened to take out the molded product.
The mold opening force is required at the moment of opening the fixed mold 6a and the movable mold 6b after removing the mold clamping force. This is because the cooled and solidified resin or metal is in strong contact with the fixed mold 6a, and is a force required to separate them.
This mold opening force is not a large force in a normal molding state, but becomes a large force when injection filling is performed excessively and burrs are generated in the mold 6.

In this state, if the mold opening is forcibly continued with an excessive force, there is a risk of damage to the mold mechanism such as the mold 6 and the die clamp a and the mounting screw b as the mold mounting means (FIG. 6, 7).
Therefore, in order to prevent damage to the mold mechanism (to protect the mold mechanism), the output torque of the electric servo motor is often limited during the mold opening process. That is, during the mold opening process, a torque limit is applied to the electric servo motor, thereby preventing an excessive force from acting on the mold opening / closing mechanism and preventing the mold mechanism from being damaged.

  As an example, Patent Document 1 aims to provide a molding machine capable of preventing damage to the mold mechanism in the mold opening process and capable of high cycle molding without impairing the acceleration / deceleration performance of the mold opening process. The load detecting means for detecting the load of the mold opening / closing mechanism at least in the mold opening stroke, and the actual load of the mold opening / closing mechanism detected in the mold opening stroke detected by the load detecting means are compared with a preset allowable range. Discloses a means for controlling the operation of the mold opening / closing drive source to stop when it falls outside the allowable range.

JP 2002-59467 A

However, in the above control method, it is possible to control the mold opening force by controlling the torque of the mold clamping motor. However, when the object to be processed changes, it is necessary to replace the mold. The tightening force is also different. Therefore, if the appropriate clamping force (hereinafter referred to as the setting clamping force) corresponding to the mold is changed, the toggle magnification at the mold opening position (the force that drives the crosshead and the link mechanism) Since the magnification of the force that the movable movable plate operates is changed, even if the torque of the mold clamping motor is the same, the mold opening force for opening the mold is different, so that appropriate restriction becomes difficult.
The present invention has been proposed to improve the above inconveniences. In a toggle type electric mold clamping device, even if the set mold clamping force is changed, the toggle magnification is automatically recognized and the mold opening is performed. An object of the present invention is to provide a toggle type electric mold clamping device capable of controlling the upper limit of force.

In order to solve the above problems, in the invention according to claim 1, the link housing (23) and the fixed platen (22) are connected by a tie bar (24), and the link housing ( 23) and a fixed platen (22), a movable platen (25) arranged to be reciprocally movable is operated via a toggle mechanism (27), and the link housing (23) is set to a set clamping force. depending moves adjusted along the tie bars (24) in order to advance the mold thickness adjustment, the mold clamping, a toggle type electric mold clamping device performing mold opening, the toggle mechanism (27), the mold clamping motor (28) The crosshead (32) attached to the ball screw mechanism (31) that is rotationally driven by the power from is operated by moving forward and backward to perform mold clamping and mold opening, and a toggle mechanism ( 27) of the crosshead (32) From the toggle magnification of the toggle mechanism (27) based on the position (x) and the position (y) of the movable platen (25), the toggle magnification at the mold opening position corresponding to the set mold clamping force is obtained. By setting the torque limit of the mold clamping motor corresponding to the upper limit value of the mold opening force from the toggle magnification, when the torque of the mold clamping motor reaches the torque limit in the mold opening operation, the mold opening operation is stopped And a control means for controlling so as not to exceed the upper limit of the mold opening force.

  As a result, even if the workpiece to be molded is changed and the corresponding set clamping force is changed, the mold opening is determined from the toggle magnification at the mold opening position corresponding to the set clamping force and the torque limit of the clamping motor. The force can be controlled to an appropriate magnitude, and the mold and mechanism are not damaged.

In the second aspect of the present invention, the power of the mold clamping motor (28) is transmitted to the ball screw mechanism (31) via the belt (29) and the pulley (30), and the control means is based on the following equation: The torque limit of the mold clamping motor is calculated.
Tm = (1 / 2π) · ε · L · Fo · (1 / fz)
However, Tm is the torque limit of the mold clamping motor [kN · m], the reduction ratio of ε belt pulley, L is the thread of the ball screw mechanism for cross-head lead [mm], Fo is the upper limit value of the mold opening force [ kN] and f z are toggle magnifications at the die touch position (die opening position) when the set clamping force is Z [kN] .

  Thereby, the control means controls the torque limit (Tm) of the mold clamping motor automatically obtained by calculation based on the toggle magnification fz at the mold opening position corresponding to the set mold clamping force. The upper limit (Fo) of the opening force can be controlled.

  In the above description of the present invention, symbols or numbers in parentheses () are attached to show correspondence with the embodiments described below.

  According to the present invention, even if the set mold clamping force is changed, the torque limit of the mold clamping motor is calculated from the corresponding toggle magnification, so that the upper limit of the mold opening force can be controlled, and the mold and mold clamping mechanism can be controlled. Can be avoided.

FIG. 3 is a schematic side view illustrating a retreat limit position of a cross head in an embodiment of a toggle type electric mold clamping device according to the present invention. FIG. 3 is a schematic side explanatory view showing a state where the toggle mechanism is operated to move the movable plate forward in the toggle type mold clamping device shown in FIG. 1. FIG. 2 is a schematic side explanatory view showing a mold touch position (mold opening position) where a toggle mold is operated and a movable mold is brought into contact with a fixed mold in the toggle mold clamping apparatus shown in FIG. 1. It is the graph which showed the toggle magnification calculated | required from the relationship between the position of a crosshead, the position of a movable board, the position of a crosshead, and the position of a movable board. It is typical side surface explanatory drawing which shows an example of the conventional toggle type electric mold clamping apparatus. It is the typical principal part side view which showed an example of the fixing means of a metal mold apparatus. It is the typical principal part side view which showed the other example of the fixing means of a metal mold apparatus.

An example of a toggle type electric clamping device 20 is schematically shown in FIGS.
The toggle type electric mold clamping device 20 is movable with respect to the base plate 21 at a position spaced apart from the fixed plate 22 as a fixed mold support device fixed on the base plate 21 by a predetermined distance. The link housing 23 is provided. A plurality of, for example, four tie bars 24 are disposed between the fixed platen 22 and the link housing 23.

Further, a movable platen 25 as a movable mold support device arranged on the base 21 so as to face the fixed platen 22 and capable of moving back and forth (moving in the horizontal direction in the drawing) along the tie bar 24 is provided. It has.
Further, a mold device 26 is disposed between the fixed platen 22 and the movable platen 25. The mold device 26 includes a fixed mold 26a and a movable mold 26b. The fixed mold 26 a is attached to a mold attachment surface of the fixed platen 3 facing the movable platen 25, while the movable mold 26 b is attached to a mold attachment surface of the movable platen 25 facing the fixed platen 22. A cavity that is a space for filling a molten resin or metal is formed between the fixed mold 26a and the movable mold 26b.

A toggle mechanism 27 is provided between the movable plate 25 and the link housing 23 as described above, and a mold clamping motor 28 as a mold clamping drive source for operating the toggle mechanism 27 is provided at the rear end of the link housing 23. It is arranged.
The mold clamping motor 28 is fixed to the link housing 23 by mounting parts (not shown), and transmits power to a ball screw mechanism 31 that converts rotational motion into reciprocating motion via a belt 29 and a pulley 30 as transmission means. It is like that.
The ball screw mechanism 31 is formed by screwing a nut member 31b to a screw shaft 31a that is a drive shaft. By moving a crosshead (described later) attached to the nut member 31b forward and backward (moves in the left-right direction in the figure), The toggle mechanism 27 is operated. The mold clamping motor 28 is preferably a servo motor.

Here, the toggle mechanism 27 will be described. The toggle mechanism 27 includes a cross head 32 attached to a screw shaft 31a as a drive shaft via a nut member 31b, and a first toggle link attached to the cross head 32 so as to be swingable. 33, a second toggle link 34 swingably attached to the link housing 23, and a third toggle link 35 swingably attached to the movable platen 25.
Then, the second toggle link 34 and the first toggle link 33 and the second toggle link 34 and the third toggle link 35 are linked to each other.

  In the above configuration, the toggle mechanism 27 can be operated by driving the mold clamping motor 28 and moving the cross head 32 as a driven member forward and backward through the nut member 31b. In this case, when the cross head 32 is moved forward (moved in the right direction in the figure), the movable platen 25 moves forward to perform mold clamping. A mold clamping force larger than the driving force of the cross head 32 by the mold clamping motor 28 can be generated, and the mold clamping is performed.

In addition, in order to adjust the position of the link housing 23 with respect to the stationary platen 22, a detailed description and illustration are omitted, but a mold clamping position adjusting means (die height device) is provided at the rear end of the link housing 23 (left end in the figure). It is arranged.
Here, a plurality of, for example, four tie bar insertion holes (not shown) are formed in the link housing 23, and the left end in the figure of the tie bar 24 is inserted into each tie bar insertion hole and connected by a movable nut 24b.
A right end (not shown) of the tie bar 24 is fixed to the fixing plate 22 by a fixing nut 24a.

  A mold thickness adjusting motor (not shown) as a drive source for the mold clamping position adjusting means is disposed at the upper portion of the rear end of the link housing 23. By driving such a mold thickness adjusting motor to operate the movable nut 24b, the link housing 23 can be advanced and retracted by a predetermined distance.

FIG. 1 shows a state in which the cross head 32 and the movable platen 25 are positioned at the retreat limit, and the respective positions are x = 0 and y = 0. FIG. 2 shows a state during the mold closing operation or the mold opening operation. Further, FIG. 3 shows a state at the moment when the fixed mold 26a and the movable mold 26b are touched or when the mold clamping force is removed and the fixed mold 26a and the movable mold 26b are opened.
When the cross head 32 moves forward (to the right) from the state of FIG. 3, the second toggle link 34 and the third toggle link 35 extend in a straight line, and a large mold clamping force is applied to the mold.

By the way, when the upper limit is set for the mold opening force, the torque limit (Tm) of the mold clamping motor can be calculated as follows. The upper limit value {Fo (kN)} of the mold opening force is obtained by dividing the mold opening force at which the mold mechanism is broken by the safety factor.
The set mold clamping force is Z (kN), the toggle magnification at the mold touch position (die opening position) when the set mold clamping force is Z (kN) is fz {= 1 / (dy / dx)}, The lead screw of the crosshead ball screw is L (mm), the reduction ratio of the belt pulley is ε (for example, 1/3), the torque limit of the mold clamping motor is Tm (N · m), and the thrust of the crosshead is Fc (KN) and the rotational torque of the crosshead ball screw is Tc (N · m)
Then,
Fo = Fc × fz (1)
(Fc × 1000) × (L × 1/1000) = 2π × Tc (2)
Tc = (1 / ε) × Tm (3)
From Eqs. (1), (2), and (3), if Fc and Tc are deleted,
Tm = (1 / 2π) · ε · L · Fo · (1 / fz)
Thus, the torque limit (Tm) of the mold clamping motor can be calculated.

Next, in the toggle type electric mold clamping device 20 configured as described above, a series of mold clamping operations and mold opening operations will be described (see FIG. 4).
In order to perform such a series of operations, in the toggle type electric mold clamping device 20, the toggle relationship between the position (x) of the crosshead 32 in the toggle mechanism 27 and the position (y) of the movable platen 25 is determined. The toggle magnification {1 / (dy / dx)} of the mechanism 27 (reciprocal of the value obtained by differentiating y by x) is obtained, and the toggle magnification fz {= 1/1 / at the mold opening position corresponding to the set clamping force (ZkN). (Dy / dx)} and a control means (not shown) for controlling the upper limit value Fo of the mold opening force from the toggle magnification fz and the torque limit Tm (Nm) of the mold clamping motor 28. It has.
In other words, the control means stores software for executing a calculation of Tm = (1 / 2π) · ε · L · Fo · (1 / fz) based on the aforementioned knowledge. The software also stores data for grasping the toggle magnification fz at the mold touch position (die opening position) corresponding to the set mold clamping force.

4 is a graph showing the relationship between the position x of the crosshead 32 and the position y of the movable platen 25, and the toggle magnification fz corresponding to the position of the crosshead 32, that is, 1 / (dy / dx). The graph about is shown.
From this graph, it can be seen that the toggle magnification rapidly increases near the mold clamping completion position and becomes infinite at the mold clamping completion position.
In the mold clamping operation, for example, in order to perform the mold clamping operation with the set mold clamping force 8000 kN, the mold clamping start position (die touch position), that is, the position xa of the cross head 32 is set to start the mold clamping with the set mold clamping force 4000 kN. The position (die touch position), that is, the position close to the mold opening limit position as compared with the position xb of the cross head 32. To set a larger mold clamping force, from the mold clamping start to the mold clamping completion position It can be seen that it is necessary to increase the amount of feed of.

  It can also be seen that there is a difference between the toggle magnification f (8000) at the mold touch position when the set clamping force is 8000 kN and the toggle magnification f (4000) at the mold touch position when 4000 kN. In the present invention, it is possible to control the upper limit of the mold opening force by taking this difference into consideration.

When the mold clamping operation, injection filling, and cooling solidification are completed, removal of mold clamping force and mold opening operation are started. Filling amount of molten resin or molten metal, which is the material to be processed into the mold May be excessive, the mold opening force required for mold opening may increase.
However, since the control unit can grasp the toggle magnification fz at the mold opening position corresponding to the set mold clamping force, the mold can be calculated from the calculation of Tm = (1 / 2π) · ε · L · Fo · (1 / fz). The torque of the mold clamping motor 28 being opened is monitored, and when the torque limit Tm is reached, the mold opening force can be controlled to Fo or less by performing an emergency stop.

As described above, by considering the toggle magnification fz at the mold opening position corresponding to the set mold clamping force (ZkN), even if the set mold clamping force (ZkN) is changed, the mold can be obtained from the corresponding toggle magnification fz. The torque limit Tm of the clamping motor can be obtained, and the upper limit of the mold opening force Fo can be controlled.
Therefore, when a large burr occurs and the mold opening force increases and the torque of the mold clamping motor reaches Tm, the control means immediately stops the mold opening operation, thereby damaging the mold or the mold mechanism. Can be avoided.

  The present invention is not limited to the toggle type electric mold clamping device in the injection molding machine mentioned in the above example. The present invention can be applied to other molding apparatuses such as die casting machines.

20 toggle type electric mold clamping device 21 base 22 fixed plate 23 link housing 24 tie bar 24a fixed nut 24b movable nut 25 movable plate 26 mold device 26a fixed die 26b movable die 27 toggle mechanism 28 mold clamping motor 29 belt 30 pulley 31 Ball screw mechanism 31a Screw shaft 31b Nut member 32 Crosshead 33 First toggle link 34 Second toggle link 35 Third toggle link

Claims (2)

The link housing (23) and the stationary platen (22) are connected by a tie bar (24), and reciprocating between the link housing (23) and the stationary platen (22) with the tie bar (24) as a guide. The movable platen (25) arranged in an operable manner is operated via a toggle mechanism (27), and the link housing (23) is attached to the tie bar (24) to adjust the die thickness in advance according to the set clamping force. along with moving adjustment, clamping, a toggle type electric mold clamping device performing mold opening,
The toggle mechanism (27) is actuated by advancing and retreating a cross head (32) attached to a ball screw mechanism (31) that is rotationally driven by power from a mold clamping motor (28). It is configured to perform mold opening,
Wherein the toggle mechanism (27) the position of the crosshead (32) and (x), wherein based on the position of the movable platen (25) (y), said toggle magnification of the toggle mechanism (27), the set mold clamping The toggle magnification at the mold opening position corresponding to the force is grasped, and from this toggle magnification , the torque limit of the mold clamping motor corresponding to the upper limit value of the mold opening force is set, and in the mold opening operation, the mold clamping motor When the torque reaches the torque limit, the toggle type is provided with control means for controlling the mold opening force so as not to exceed the upper limit value of the mold opening force by emergency stop of the mold opening operation. Electric mold clamping device. The power of the mold clamping motor (28) is transmitted to the ball screw mechanism (31) via the belt (29) and the pulley (30),
The toggle type electric mold clamping apparatus according to claim 1, wherein the control means calculates the torque limit of the mold clamping motor based on the following formula.
Tm = (1 / 2π) · ε · L · Fo · (1 / fz)
However, Tm is the torque limit of the mold clamping motor [kN · m], the reduction ratio of ε belt pulley, L is the thread of the ball screw mechanism for cross-head lead [mm], Fo is the upper limit value of the mold opening force [ kN] and f z are toggle magnifications at the die touch position (die opening position) when the set clamping force is Z [kN] .

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