JPH02252518A - Mold clamping device for injection molding machine - Google Patents

Abstract

PURPOSE:To generate a great mold clamping force while a servo motor, a ball screw, etc., are reduced by disposing a regulating nut rotatably supported to a base plate, and a shutter telescopically provided between the end face of a rod and the end face of a mold thickness regulating shaft. CONSTITUTION:A stationary mold 6 and a movable mold 7 are brought into close contact with each other at the time of mold clamping. When no foreign material is confirmed therebetween, a shutter 49 is moved forward. Hydraulic pressure is supplied from a port (b) of a mold clamping cylinder 35, and the output of the cylinder 25 is transmitted sequentially through a base plate 30, a regulating nut 38, a regulating shaft 39, the shutter 49, a rod 46, and a mov able platen 5 to the mold 7. Hydraulic pressure is discharged from the port (b) of the cylinder 35 at the time of mold clamping, hydraulic pressure is sup plied from a port (a) to press the piston 36 of the cylinder 35 to the plate 30. The shutter 49 is retracted, the rotation of a mold opening or closing servo motor 34 is transmitted through a ball screw 31, a pulley 31, and a timing belt 33 to retract the platen 5, thereby opening the molds.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a mold clamping device for an injection molding machine.

(Prior art) Conventionally, a molding material that has been heated and fluidized in a heating cylinder is injected into a mold under high pressure, cooled and solidified or hardened therein, and then the mold is opened to take out the molded product. In the injection molding machine, a mold clamping device is provided to open and close the mold and to prevent the mold from opening due to the high pressure of the injected molding material.

FIG. 4 is a schematic diagram of the conventional toggle type mold clamping device.

In the figure, a base plate 2 and a fixed platen 3 are erected on a frame 1, and tie bars 4 are disposed between them. The tie bars 4 slidably support a movable platen 5, and the movable platen 5 moves toward and away from the fixed platen 3.

A fixed mold 6 is mounted on the fixed platen 3, and a movable platen 5 is mounted on the fixed mold 6.
A movable mold 7 is disposed in the mold 7, and molding material is filled between the two molds 6 and 7 during the injection process.

The molds 6.7 are brought into contact during filling with molding material, but must be opened when removing the molded product. For this purpose, a mold clamping device 8 is provided.

That is, a servo motor 9 for mold opening/closing and mold clamping is disposed behind the base plate 2, and the servo motor 9
The rotation is transmitted to the ball screw 12 via the timing belt lO and the pulley 11. Therefore, the rotational motion of the servo motor 9 becomes a linear motion and is transmitted to the crosshead 13.

The crosshead 13 is connected to a linear toggle lever 14 and a substantially triangular toggle lever 15. Three fulcrums are provided at the triangular apex portion of the toggle lever 15, one of which is attached to the toggle lever 14, the other fulcrum is attached to the support portion 16 of the base plate 2, and the other fulcrum is attached to the support portion 16 of the base plate 2. is connected to a support portion 19 of the movable platen 5 via an arm 17 and a toggle pin 18. Therefore, by moving the rad 13 back and forth to the cross, the toggle levers 14 and 15 and the arm 17 are rotated, and the movable platen 5 is moved back and forth to perform mold opening and closing operations.

The limit point when moving RAD 13 forward to the above cross (
In the illustrated state, mold clamping force is generated by the force amplification function of the toggle mechanism.

In the case of the toggle type mold clamping device, the force can be increased by more than 20 times, so that the servo motor 9, ball screw 12, timing belt 10, etc. can be made smaller accordingly.

In addition, in the toggle type mold clamping device, the molds 6 and 7 are
The length of the tie bar 4 is adjusted by the mold thickness adjustment motor 20 so that it is shorter by λ than the sum of the thickness of the mold and the length of the mold clamping device 8. During mold clamping, the servo motor 9 and the timing belt 10 are used. , Boo January 1, Ball screw 12, Toggle mechanism (
Cross to Rad 13, Toggle Lever 14.15, Arm 1
7. Mold clamping force is generated by stretching the tie bar 4 via the toggle pin 18).

FIG. 5 is a relationship diagram of the forces generated at this time.

In the figure, λ7 is the tie bar 4 when the toggle mechanism is activated.
The amount of elongation, λ, is the amount of contraction of the molds 6, 7 and the mold clamping device 8, and the mold clamping force (Ctf) is the elongation curve KT of the tie bar 4 with respect to the axial displacement, and the amount of contraction of the molds 6, 7 and the mold clamping device 8. The contraction curve of the tightening device 8 is expressed by .

(Problem to be Solved by the Invention) However, in the above conventional mold clamping device of an injection molding machine, when the environmental temperature of the injection molding machine and the mold temperature become higher than when the mold clamping force was set, the heat conduction When the temperature of the tie bar 4 increases and the length of the tie bar 4 increases due to thermal expansion, the mold clamping force will fluctuate as shown by the broken line in the figure even if the tie bar 4 is extended by the same amount λ7. This variation in mold clamping force will have an impact on ultra-precision molding.

Therefore, if we try to eliminate fluctuations in the mold clamping force by detecting the stress in the tie bars 4, etc. and feeding it back so that the mold clamping force is constant and adjusting the amount of extension of the tie bars 4, the cost will be high. It ends up.

For this reason, a direct-acting mold clamping device as shown in FIG. 6 is provided.

In FIG. 6, a servo motor 21 for mold opening/closing and mold clamping is disposed in front of the base plate 2, and the rotation of the servo motor 21 is controlled by a timing belt 22 and a boot IJ 23.
The signal is transmitted to the ball screw 24 via. Therefore, the rotational motion of the servo motor 21 becomes a linear motion and is directly transmitted to the movable platen 5 via the ball screw 24.

In the direct-acting type mold clamping device having the above configuration, compared to the toggle type mold clamping device described above, the mold clamping force does not fluctuate due to changes in the environmental temperature of the injection molding machine and the mold temperature. When using a servo motor with the same capacity, the mold clamping force generated is only about 1720 mm compared to a toggle type mold clamping device.
In order to make this comparable, it is necessary to increase the capacity of the servo motor 2L ball screw 24, etc.

As the capacity of these servo motors 21, ball screws 24, etc. increases, the cost tends to increase dramatically, and it is not possible to increase the mold clamping force due to cost reasons.
It is difficult to manufacture anything larger than 0ft.

The present invention solves the problems mentioned below, makes it possible to generate a large mold clamping force while keeping the capacity of the servo motor, ball screw, etc. It is an object of the present invention to provide a mold clamping device for an injection molding machine whose mold clamping force does not fluctuate even if mold temperature etc. change.

(Means for Solving the Problems) For this purpose, the present invention provides a fixed platen that supports a fixed mold, and a movable mold that supports a movable mold opposite to the fixed platen and moves along tie bars to move both molds. In a mold clamping device for an injection molding machine that has a movable platen that moves the movable platen toward and away from the movable platen, rotational motion is converted into linear motion through a rod that is placed on the back of the movable platen and moves together with the movable platen, and a ball screw connected to the movable platen. It has a servo motor for opening and closing the mold, a small stroke mold clamping cylinder whose piston rod is connected to a tie bar, and whose cylinder part is connected to the base plate 1, and is rotatably supported by the base plate. A mold thickness adjusting shaft is provided which moves forward and backward relative to the end surface of the rod as the adjusting nut rotates.

In addition, there is a space between the end face of the rod and the end face of the mold thickness adjustment shaft.
The shutter is arranged to move forward and backward, moving forward when the mold is clamped and retracting when the mold is opened and closed.

(Function) According to the present invention, a mold opening/closing servo motor that converts rotational motion into linear motion via a rod that is disposed on the back surface of the movable platen and moves together with the movable platen, and a ball screw connected to the movable platen; It has a medium-diameter, small-stroke clamping cylinder whose piston rod is connected to a tie bar and whose cylinder part is connected to a base plate, and
An adjustment nut rotatably supported on the base plate, and a mold thickness adjustment shaft that moves forward and backward with respect to the end surface of the rod as the adjustment nut rotates, are connected to the end surface of the rod and the end surface of the mold thickness adjustment shaft. Shutters that can move forward and backward are arranged between them, so when hydraulic pressure is supplied to the mold clamping cylinder during mold clamping, the mold clamping force is applied to the base plate, adjustment nut, mold thickness adjustment shaft, shutter, It is transmitted to the movable platen via the rod.

When adjusting the mold thickness, by driving the electric motor or oil motor and rotating the adjustment nut, the mold thickness adjustment shaft moves in the direction of the rod and the movable platen position can be changed. .

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a state diagram when the mold is closed in the mold clamping device of the injection molding machine of the present invention, FIG. 2 is a state diagram when the mold is clamped, and FIG. 3 is a state diagram when the mold is opened.

In the figure, a fixed platen 3 is erected and fixed on a frame 1, a base plate 30 is placed upright so as to face it, and a tie bar 4 is disposed between the two. The tie bars 4 slidably support a movable platen 5, and the movable platen 5 moves toward and away from the fixed platen 3.

A fixed mold 6 is disposed on the fixed platen 3, and a movable mold 7 is disposed on the movable platen 5, so that molding material is filled between the two molds 6 and 7 during the injection process. ing. The molds 6.7 are placed in contact when filling with molding material, but must be opened when taking out the molded product. For this reason, a ball screw 31 is installed on the back of the movable platen 5. The ball screw 31 is connected to a mold opening/closing servo motor 34 via a pulley 32 and a timing belt 33. Therefore, the movable platen 5 is moved to the right or left by rotating the mold opening/closing servo motor 34.

Further, at the rear end of each tie bar 4, a mold clamping cylinder 35 with a medium diameter and small stroke is disposed, and the piston 3
6 is fixed to the end of the tie bar 4.

The cylinder portion 37 of the mold clamping cylinder 35 is fixed to the base plate 30. A port a is formed on the rear end surface of the cylinder portion 37, and a port b is formed on the side wall.

By the way, the thickness of the mold 6.7 varies depending on the shape and dimensions of the molded product. Therefore, a mold thickness adjustment mechanism is provided so that it can correspond to each stack thickness. The cough mold thickness adjustment mechanism includes an adjustment nut 38 rotatably supported by the base plate 30;
It is composed of a mold thickness adjustment shaft 39 that engages with the mold thickness adjustment shaft 39 and moves back and forth. The adjustment nut 38 is connected to a drive means 41 such as an electric motor or a hydraulic motor via a gear, a chain, a timing belt, or the like. A through hole 45 is formed in the center of the mold thickness adjustment shaft 39, and a rod 46 is provided on the back surface of the movable platen 5, and when the mold is opened, the rod 46 is inserted into the through hole. It is designed to be housed within 45.

A shutter 49 is provided between the front end surface 47 of the mold thickness adjusting shaft 39 and the rear end surface 48 of the rod so as to be able to move forward and backward. The shutter 49 is driven by a shutter cylinder 50, and moves backward when the mold is closed and opened, as shown in FIGS. 1 and 3, and advances when the mold is clamped, as shown in FIG.

That is, when the mold is clamped as shown in FIG.
When the movable mold 7 and the movable mold 7 are brought into close contact with each other and it is confirmed that there are no foreign objects between them, the shutter 49 moves forward. Then, hydraulic pressure is supplied from port b of the mold clamping cylinder 35, and the output of the mold clamping cylinder 35 is transmitted to the base plate 30, adjustment nut 38, adjustment shaft 39, shutter 49, rod 46,
It is transmitted to the movable mold 7 in the order of the movable platen 5.

Furthermore, when the mold is opened as shown in FIG. is pressed against the base plate 30. At this time, the shutter 49 is moved back. By transmitting the rotation of the mold opening/closing servo motor 34 via the ball screw 31, pulley 32, and timing belt 33, the movable platen 5 is moved backward and the mold is opened.

Note that the adjustment of the mold thickness is performed when the molds 6 and 7 are attached. If the gap between the rod 46 and the shutter 49 is set to be extremely small (within the opening) during mold clamping, the stroke of the mold clamping cylinder 35 during mold clamping can be made small.

Note that the present invention is not limited to the above embodiments,
Various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

(Effects of the Invention) As described above, according to the present invention, rotational motion is converted into linear motion through a rod that is disposed on the back surface of the movable platen and moves together with the movable platen, and a ball screw connected to the movable platen. It has a servo motor for opening and closing the mold, a small stroke mold clamping cylinder whose piston rod is connected to a tie bar, and whose cylinder part is connected to a base plate, and an adjustment nut rotatably supported on the base plate. A mold thickness adjustment shaft moves forward and backward relative to the end surface of the rod as the adjustment nut rotates, and a shutter that can move forward and backward is provided between the end surface of the rod and the end surface of the mold thickness adjustment shaft. Because of this, when hydraulic pressure is supplied to the mold clamping cylinder during mold clamping, the mold clamping force is transmitted to the movable platen via the base plate, adjustment nut, mold thickness adjustment shaft, shutter, and rod. .

Therefore, the following effects can be achieved.

(1) The mold clamping cylinders are arranged separately at the ends of each tie bar, which reduces the weight of each mold clamping cylinder and increases the work space, making assembly, maintenance, and management easier.

(2) A mold clamping cylinder is installed at the end of each tie bar, so even if a mold with poor parallelism is used, the force generated on the tie bar can be made uniform, and the force applied to a particular tie bar can be evened out. It will no longer break under load.

(3) Since mold clamping is performed by a mold clamping cylinder, the capacity of the servo motor and ball screw for opening and closing the mold can be reduced, and costs can be reduced.

(4) The set mold clamping force does not change even if the environmental temperature of the injection molding machine, mold temperature, etc. change, allowing ultra-precision molding. (5) The mold clamping force is generated and maintained by the tie bars. This is done by supplying and discharging hydraulic pressure to a mold clamping cylinder with a small stroke installed at the end, so only a small amount of oil is required for pressurization, and since the compressed volume during pressurization is small, the pressure rise time is shortened. short,
The device that generates hydraulic pressure can be small.

(6) After the molding material is filled into the mold, the movable mold is further advanced and the mold clamping force is changed in multiple steps before the molding material is completely cooled to prevent sink marks, warpage, cracks, and internal distortion. In contrast to the injection compression molding method, which is designed to obtain molded products without any unevenness, in a toggle-type mold clamping device, the frictional state of the toggle mechanism is unstable and it is difficult to precisely control the mold clamping force.

In contrast, in the mold clamping device of the present invention, the mold clamping force can be precisely varied in multiple stages simply by controlling the hydraulic pressure supplied to the b-boat of the mold clamping cylinder.

[Brief explanation of drawings]

Fig. 1 is a state diagram when the mold is closed in the mold clamping device of the injection molding machine of the present invention, Fig. 2 is a state diagram when the same mold is clamped, Fig. 3 is a state diagram when the mold is opened, and Fig. 4 is a state diagram of the conventional injection molding machine. Schematic diagram of toggle type mold clamping device,
FIG. 5 is a diagram showing the relationship of forces generated in a toggle-type mold clamping device, and FIG. 6 is a schematic diagram of a conventional direct-acting mold clamping device. 1...Frame, 2.30...Base plate, 3
... Fixed platen, 4... Tie bar, 5... Movable platen, 6... Fixed mold, 7... Movable mold, 34.
...Servo motor for mold opening/closing, 35...Mold clamping cylinder,
36... Piston, 37... Cylinder part, 38...
・Adjusting nut, 39...Mold thickness adjustment shaft, 45...
Through hole, 46... Rod, 49... Shutter, 50
...Shutter cylinder. Patent applicant Sumitomo Heavy Industries, Ltd. Sub-agent Patent attorney Makoto Kawagoi (1 other person) Figure 1 34: f! Closing wooden tree - Evening figure 4

Claims (1)

[Claims] An injection system having a fixed platen that supports a fixed mold, and a movable platen that supports a movable mold so as to face the fixed platen and moves along tie bars to move the molds toward and away from each other. In the mold clamping device of a molding machine, the mold opens and closes by converting rotational motion into linear motion via (a) a rod placed on the back of the movable platen and moving together with the movable platen, and (b) a ball screw connected to the movable platen. (c) a small stroke mold clamping cylinder whose piston rod is connected to a tie bar and whose cylinder part is connected to a base plate; (d) an adjustment nut rotatably supported by the base plate; (e) ) a mold thickness adjustment shaft that moves forward and backward relative to the end surface of the rod as the adjustment nut rotates; A mold clamping device for an injection molding machine, comprising a shutter that moves forward when the mold is clamped and retreats when the mold is opened and closed.