JPH033387Y2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention relates to a mold clamping device for an electric injection molding machine that is configured to perform mold opening/closing and mold clamping operations using an electric type and a toggle mechanism. It is something.

(b) Conventional technology As a mold clamping device for an electric injection molding machine, an electric motor,
There is a combination of a ball screw mechanism and a toggle mechanism. That is, the function of a conventional mold clamping cylinder is performed by an electric motor and a ball screw mechanism. The rotation of the electric motor is converted into linear motion by a ball screw mechanism, which is further amplified by a toggle mechanism and transmitted to the movable platen.

(c) Problems to be solved by the invention However, in the mold clamping device of the conventional electric injection molding machine as described above, it is difficult to control the electric motor just before the movable mold contacts the fixed mold, and There is a problem that the mold may be damaged. That is, the position of the movable platen is detected, for example, by a signal from a pulse generator installed in the electric motor, and when the movable platen reaches a point just before contacting the fixed die, the motor toggles and the rotational speed is reduced. . This prevents the movable mold from contacting the stationary mold with an impact, and also prevents the mold from being damaged due to mold clamping with foreign objects present between the molds. However, the torque of the electric motor is increased 4 to 6 times by the toggle mechanism near the mold closing position, so it is necessary to control the torque of the electric motor to a very small state in order to protect the mold. becomes. but,
It is impossible to control the torque of an electric motor to a very small value with an electric motor, and even if it is possible, it is sensitive to disturbances such as temperature changes, and the control accuracy will be very poor. . For this reason, there was a possibility that the mold would be damaged as described above. The present invention aims to solve these problems.

(d) Means for solving the problems The present invention solves the above problems by providing a fluid pressure cylinder between the movable platen and the stationary part to provide resistance to the movement of the movable platen. That is, the mold clamping device of the electric injection molding machine according to the present invention is provided between the movable platen and the stationary part so that the volume of the pressure chamber between the piston and the cylinder changes according to the movement of the movable platen. A fluid pressure cylinder (pneumatic cylinder 56) and a valve device (an electromagnetic switching valve 70 and a variable throttle valve 72) capable of controlling the pressure of a pressure chamber 68 of the fluid pressure cylinder whose volume decreases when the movable platen moves in the mold closing direction. ), a position detector (pulse generator 54) that outputs a signal corresponding to the position of the movable platen, and a fluid pressure is applied to the pressure chamber from the middle of the mold closing to the mold closing based on the signal from the position detector. and a control device 74 for activating the valve device to generate the signal. Note that the inside brackets indicate corresponding members of the embodiments described later.

(e) Action When the movable plate advances to the specified position when the mold is closed,
The control device reduces the rotational speed of the electric motor and controls the torque to a predetermined value, and at the same time, the control device changes the valve device so that the fluid pressure in the pressure chamber, which had been discharged without resistance, is discharged through the throttle valve. By switching, pressure is generated in the pressure chamber as resistance. This provides resistance to the advancement of the movable platen, and the movable die contacts the fixed die with the force in the forward direction of the movable platen being weakened. Therefore, the torque of the electric motor does not need to be controlled to an extremely low value and can be controlled with sufficient precision, so the movable mold will not come into contact with the fixed mold and there will be no foreign matter between the molds. The mold will not be damaged if the mold is closed while it is sandwiched.

(F) Embodiment FIG. 1 shows an embodiment of the present invention. The fixed platen 10 and the housing 12 are connected by four divers 14, and a movable platen 16 is movably supported by the divers 14. A fixed die 18 is attached to the fixed platen 10, and a movable die 20 is attached to the movable platen 16. The movable platen 16 is connected to a male threaded member 22 provided on the housing 12 via a toggle mechanism 24. The toggle mechanism 24 is a long link 2
6. Connect short link 28 and cross link 30 to pin 32
and a crosshead 36 connected to each other by 34 and integral with the externally threaded member 22, the housing 1
2 and movable platen 16 by pins 38, 40 and 42, respectively. The male threaded member 22 meshes with the female threaded member 44 to constitute a ball screw mechanism. The female threaded member 44 is provided integrally with a gear 46, and this gear 46 is rotatably supported by the housing 12, but is restrained from moving in the axial direction. Gear 46 meshes with another gear 48. The gear 48 is connected to a motor 50 attached to the housing 12 and a coupling 52.
are connected via. The electric motor 50 has a pulse generator 54 (position detector). A main body of a pneumatic cylinder 56 (hydraulic cylinder) is fixed to the stationary part (bed). pneumatic cylinder 5
A piston rod 60 integral with the piston 58 of No. 6 is connected to a bracket 62 fixed to the movable platen 16 via a pin 64. Two pressure chambers 66 and 68 are defined within the pneumatic cylinder 56 by a piston 58 . The pressure chamber 66 is always open to atmospheric pressure. The pressure chamber 68 is connected to an electromagnetic switching valve 70. Solenoid switching valve 70
is configured to open the pressure chamber 68 to atmospheric pressure when it is off, and to open it to atmospheric pressure via the variable throttle valve 72 when it is on. electric motor 50
The operation of the solenoid switching valve 70 and the switching of the solenoid switching valve 70
Controlled by 4. A signal from the pulse generator 54 described above is input to the control device 74 .

Next, the operation of this embodiment will be explained. In the mold opening state, the electromagnetic switching valve 70 is in an OFF state, that is, a state in which the pressure chamber 68 is directly opened to the atmosphere. The electric motor 50 starts operating in response to a signal from the control device 74, and the joint 52, the gear 48, and the gear 46
The female threaded member 44 rotates through the female threaded member 44, and the male threaded member 22 that engages with it moves forward in the right direction in FIG. The movement of the male threaded member 22 is transmitted to the movable platen 16 via the toggle mechanism 24, and the movable platen 16 moves forward to the right in FIG. As the movable platen 16 moves, the piston 58 connected thereto also moves to the right in FIG. 1, and the air pressure in the pressure chamber 68 is released to the atmosphere without resistance. Therefore, in this state, the pneumatic cylinder 56 does not provide resistance to the movement of the movable platen 16. When the count value of the pulse signal from the pulse generator 54 reaches a predetermined value, that is, when the movable platen 16 moves forward to a predetermined position, the control device 74 lowers the rotational speed of the electric motor 50 and also reduces the torque, so that an appropriate control to a certain value. At the same time, the control device 74 outputs a signal that turns on the electromagnetic switching valve 70. As a result, the air pressure from the pressure chamber 68 is discharged through the variable throttle valve 72. Since the variable throttle valve 72 limits the discharge of air pressure from the pressure chamber 68, the air pressure within the pressure chamber 68 provides a resistance force to the movement of the piston 58. Therefore, the force exerted by the electric motor 50 to move the movable platen 16 forward is weakened by the resistance of the pneumatic cylinder 56, and the movable platen 16 moves to the right with a relatively small pushing force. As a result, the movable mold 20 is pressed with a small force and comes into contact with the fixed mold 18. The movable type 20 is the fixed type 18
When it comes into contact with the mold, the electromagnetic switching valve 70 is turned off, and at the same time, the electric motor 50 generates a large torque and applies a mold clamping force between the fixed mold 18 and the movable mold 20.
Injection, molding, and cooling are performed in this state. Next, the mold clamping force is removed and the mold is opened by rotating the electric motor 50 in the opposite direction to that in the above case. At that time, the pneumatic cylinder 56 does not provide resistance to the movement of the movable platen 16.

As mentioned above, when the movable mold 20 contacts the fixed mold 18, the pushing force of the movable platen 16 is small due to the resistance force generated by the pneumatic cylinder 56, so a large impact is generated. The mold closes smoothly without any problems. In this case, electric motor 5
Since the pushing force caused by zero is reduced by the resistance of the pneumatic cylinder 56, the torque of the electric motor 50 does not need to be an extremely small value, and can be set to a value that allows torque control with normal accuracy. This makes it possible to control the mold closing force with high reproducibility and precision, and the mold is reliably protected. Furthermore, since the inertia of the movable parts can be absorbed by the operation of the pneumatic cylinder 56, control of the rotational speed and torque of the electric motor 50 can be quickly switched.
In this embodiment, an electromagnetic switching valve 70 and a variable throttle valve 72 are used as valve devices for controlling the operation of the pneumatic cylinder 56, but it is sufficient if the pressure in the pressure chamber 68 can be controlled, so for example, a pressure control valve may be used. You can also use Furthermore, although a pneumatic cylinder is used in this embodiment, a hydraulic cylinder may be used instead.

(g) Effects of the invention As explained above, according to the invention, resistance is provided by the fluid pressure cylinder when the mold is closed, so the torque of the electric motor immediately before the mold is closed can be reduced to an extremely small value. This eliminates the need to do so, making it possible to control the torque with high precision, allowing the mold to close as specified and reliably protect the mold.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a mold clamping device for an electric injection molding machine according to the present invention. 10...Fixed plate, 12...Housing, 14...
...Tie bar, 16...Movable plate, 18...Fixed type,
20...Movable type, 22...Male thread member, 24...
Toggle mechanism, 44... female thread member, 50... electric motor, 56... pneumatic cylinder, 58... piston, 60... piston rod, 68... pressure chamber,
70...Solenoid switching valve, 72...Variable throttle valve.

Claims (1)

[Scope of Claim for Utility Model Registration] In a mold clamping device for an electric injection molding machine that converts the rotational force of an electric motor into linear motion to operate a toggle mechanism to open and close a mold, between a movable platen and a stationary part. There are two types of hydraulic cylinders: one in which the volume of the pressure chamber between the piston and the cylinder changes according to the movement of the movable platen, and the other in which the volume decreases when the movable platen moves in the mold closing direction. A valve device capable of controlling the pressure in the pressure chamber, a position detector that outputs a signal corresponding to the position of the movable platen, and a position detector that outputs a signal corresponding to the position of the movable platen, and a valve device that controls the pressure in the pressure chamber from the middle of mold closing until the mold closes based on the signal from the position detector. a control device that operates the valve device to generate fluid pressure;
A mold clamping device for an electric injection molding machine, characterized by having the following.