JPH0445865Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a mold clamping device in an injection molding machine.

Conventional technology In the mold clamping mechanism of an injection molding machine, conventionally, a hydraulic mechanism is used as the drive source, and the hydraulic mechanism drives a toggle mechanism to open/close the mold and clamp the mold, and the hydraulic mechanism directly operates the movable platen. It was common to drive the mold to open and close the mold and clamp the mold. Also, using a crank mechanism,
A mold clamping mechanism that opens and closes the mold, closes the mold using a crank mechanism, and then clamps the mold using a hydraulic mechanism that is different from the hydraulic mechanism that drives the link mechanism is also disclosed in Japanese Patent Publication No. 1511/1971 and Japanese Patent Publication No. 1511/1973. This method is known in Japanese Patent Publication No. 53-32381, Japanese Patent Publication No. 53-32381, etc.

In addition, a servo motor is used to drive a movable platen to which one of the molds is attached via a ball screw-nut, etc., to open, close, and clamp the mold. This method is known from Japanese Patent No. 58-17963.

Problems to be Solved by the Invention When the mold clamping mechanism is driven by a hydraulic mechanism, a hydraulic pump, valves, etc. are required, resulting in a complicated configuration. Also,
Since the mold clamping process is controlled by hydraulic pressure, it is complicated and difficult to control the mold opening/closing speed.

On the other hand, in the case where the mold is opened and closed using the above-mentioned crank mechanism, the speed of opening and closing the mold is suitable for the mold opening and closing operation of the injection molding machine due to the motion characteristics of the crank mechanism. The linear motion by the piston is converted into rotational motion to drive the crank mechanism, which opens and closes the mold. Because this hydraulic cylinder-piston linear motion must be converted into rotational motion, the hydraulic cylinder that drives the crank mechanism cannot perform mold clamping operations that require large mold clamping force, and mold clamping is difficult. However, an additional drive source is required, which complicates the configuration.

On the other hand, in the case of the aforementioned servo motor that drives the movable mold to open, close, and clamp the mold, the servo motor needs to output a large output torque, and it is also necessary to maintain the mold clamping force during the mold clamping period. Therefore, it is necessary to use a brake device to maintain the position of the movable platen, which is expensive.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a crank type mold clamping mechanism that has a simple structure, is easy to control the mold clamping process, and can generate a large mold clamp even with a small servo motor.

Means for Solving the Problems The present invention provides a mold clamping mechanism for an injection molding machine that includes a servo motor and a crank that is rotated by the output of the servo motor via a deceleration mechanism. The other end of the movably connected connecting rod is rotatably connected to a movable platen to which a mold is fixed, and a crank is reciprocated by a servo motor to open and close the mold and clamp the mold. The above problem was solved.

Operation When the servo motor is driven, the movable plate moves forward via the crank, and the mold closes before the crank reaches its dead center. Near the dead center of the crank, the moving speed of the movable platen is smaller than the rotational speed of the crank, so the mold does not come into sudden contact with the movable platen. Then, the servo motor is rotated to the dead center of the crank, where the movable plate is at its most advanced position, and when positioned at that position, the mold comes into contact with the mold, and then the movable plate moves until the crank reaches the dead center, thereby clamping the mold. Force is applied to the mold, and this mold clamping force is maintained. At this time, since the mold clamping force is maintained by the crankshaft, no special load is applied to the servo motor, and the rotational position need only be maintained at the position by a minute current.

Embodiment The figure shows an embodiment of the present invention, in which 1 is a servo motor fixed to a base, 2 is a shaft of the servo motor, 3 is a timing gear fixed to the shaft 2 of the servo motor, A crank 4 is composed of a timing gear 6 that rotates on a crankshaft 7 fixed on a base, and a timing belt 5 is stretched between the timing gears 3 and 6. A connecting rod 8 is rotatably connected to the timing gear 6, and the other end of the connecting rod 8 is rotatably attached to a movable platen 9 to which a mold 10 is fixed. In addition,
11 and 12 are tie bars that guide the movable plate 9, and 13 is a stopper.

In the above configuration, when the servo motor 1 is rotated in the direction of arrow a in the figure, the timing gear 6, that is, the crank 4 is driven via the timing gear 3 and the timing belt 5, and as the crank 4 rotates, the The rod 8 pushes the movable platen 9 upward in the figure, presses the mold 10 against the other mold fixed to a stationary platen (not shown), and tightens the mold at the dead center of the crank 4. Since the mold is clamped by stopping the movable platen at the dead center of the crank 4, the mold clamping force is held by the crankshaft 7, and the servo motor 1
The load applied to the servo motor 1 may be a minute current for maintaining the rotational position of the servo motor 1 at the position, and energy loss can be reduced. In addition, the servo motor is stopped at a point slightly past the dead center, and a stopper 13 is provided at this point, and one side of the connecting rod 8 is brought into contact with this to stop the rotation of the crank 4. Then, the crank 4 is mechanically locked by the stopper 13 at a point slightly past the dead center, so it functions as a self-locking mechanism during mold clamping, and there is no need to pass current through the servo motor 1, resulting in unnecessary waste. It is possible to prevent energy consumption and heat generation of the servo motor. Also, since the mold is clamped at the dead center of crank 4,
Sufficient mold clamping force and ideal speed curve during mold clamping can be obtained. In other words, the mold clamping speed needs to be slow from just before the mold closes, but if a crank is used, the movement of the movable platen 9 in the upward clamping direction in the figure is small near the dead center, which is ideal. It is possible to obtain a mold clamping curve.

In the above embodiments, a timing belt or the like is used as the speed reduction mechanism for operating the crank, but it goes without saying that other transmission devices such as gear mechanisms may also be used.

Effects of the Invention The present invention has the following effects because it drives the crank with a servo motor, clamps the mold at the dead center of the crank, and then stops the servo motor to clamp the mold.

Since the mold is clamped using a crank, a small servo motor is sufficient and sufficient mold clamping force can be obtained. Moreover, an ideal mold clamping speed curve can be obtained.

When clamping the mold, there is no need to use a brake device to hold the rotational position of the crank, and only a servo motor is required, and only a small amount of current needs to be passed through the servo motor. This reduces energy loss and creates a simple and inexpensive mold clamping mechanism. can be obtained.

Opening and closing of the mold, generation of mold clamping force, and holding can be controlled only by controlling the servo motor, and the mold clamping speed can be set to an arbitrary value, making speed control easy.

Since mold closing, mold clamping, and mold opening processes can be performed under continuous control of one servo motor, cycle time can be shortened.

(Instead of rotating the crank in one direction,
Since reciprocating motion is adopted, the initially set crank starting point position data (locked-up mold clamping position) and end point position data (mold opening position) related to reciprocating motion can be used repeatedly without conditions. .

In other words, when the crank is rotated in one direction, the rotational position of the crank ascertained by the NC device of the injection molding machine is continuous, so it is difficult to stop the crank at the start and end points or to know the current position of the crank. requires processing to determine the starting and ending positions from continuously changing data. However, in the case of reciprocating motion, this is not necessary and the control program becomes simpler.

Because it is a reciprocating motion, the positions (intervals) of the above starting and ending points can be determined arbitrarily, and only a convenient section of the clamping curve of the crank mechanism (crank and connecting rod) can be used, or the specifications of the mold can be adjusted. The mold opening interval (distance) can be adjusted to an appropriate value accordingly. As a result, the requirements for molding include molding that emphasizes molding speed by using a section where the output end moves at a high speed, and conversely, molding that emphasizes pressure by using a section where the movement speed is low but the output is large. The molding method can be selected to suit the conditions, and the time required to open and close the mold can be minimized, further shortening the cycle time.

[Brief explanation of the drawing]

The figure shows an embodiment of the present invention. 11... Servo motor, 4... Crank, 10
...Mold, 13...Stoppa.

Claims (1)

[Claims for Utility Model Registration] 1. A mold clamping mechanism for an injection molding machine is provided with a servo motor and a crank that is rotated by the output of the servo motor via a reduction mechanism, and one end of the crank is rotatably mounted. In an injection molding machine in which the other end of the connected connecting rod is rotatably connected to a movable platen on which a mold is fixed, and a crank is reciprocated by a servo motor to open and close the mold and clamp the mold. Crank type clamping mechanism. 2. The injection molding machine according to claim 1 of the utility model registration claim, characterized in that a stopper is provided for the reciprocating movement of the crank, and when one side of the connecting rod comes into contact with the stopper, the rotation of the crank is stopped. Crank type clamping mechanism.