JPH0427935B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an injection mechanism in an injection molding machine, and particularly to an accumulator used in the injection mechanism.

Prior Art In conventional injection molding machines, when the screw is advanced to perform injection, a hydraulic cylinder is used to perform the injection. In order to obtain instantaneous injection pressure, an accumulator that stores high-pressure oil is used to instantly release a larger amount of high-pressure oil than the amount of oil supplied by the hydraulic pump, speeding up the operation of the hydraulic cylinder and increasing the injection pressure. This increased the speed of the rise and caused high-pressure, high-speed injection.

However, when the injection operation is performed by a motor, an oil-based accumulator cannot be used. Therefore, as shown in Japanese Patent Application No. 58-241057, a flywheel or gas accumulator is used to achieve high pressure. A method for high-speed injection has also been developed. In this case, since the injection start position of the screw differs depending on the metered amount, a stable accumulator effect could not be obtained.

Problems to be Solved by the Invention The present invention provides an injection mechanism in which a motor is used as a drive source for advancing a screw to perform injection, so that even if the metering set amount changes and the injection start position of the screw changes, the accumulator To provide an injection mechanism with an accumulator that can be controlled so that the effect of the fuel is always constant.

Means for Solving the Problems The present invention provides an injection mechanism for an injection molding machine that moves a pressure plate by driving a motor and moves a screw in the axial direction to perform injection. An accumulator is provided, and an accumulator position correction device is provided for correcting the position of the accumulator by moving it in the axial direction of the screw.

Function The injection start position of the screw fluctuates depending on the metering setting amount, but the amount of variation is corrected by the accumulator position correction device, and the accumulator always accumulates a constant amount of energy at the start of injection even if the metering setting amount changes. and press the pressure plate. Therefore, during injection, a certain amount of energy stored in the accumulator is instantaneously applied to the screw, causing injection at high speed and high pressure.

Embodiment The figure shows an embodiment of the present invention, in which 1 is a screw in an injection molding machine, 2 is a screw shaft, and 3 is a pressure plate. Fixed for free movement. Ball nuts 5a and 5b are fixed to the pressure plate 3 and screwed into ball screws 6a and 6b. 7a and 7b are timing gears fixed to the ball screws 6a and 6b; 8 is a timing gear fixed to the drive shaft of the servo motor M1;
A timing belt 9 is placed between a, 7b, and 8. Further, one end of an accumulator 10 is brought into contact with the pressure plate 3, and the accumulator 10 is constituted by a spring 11 in this embodiment. One end is fixed to a plate 12, and the other end is fixed to a plate 13 fixed to the tip of a ball screw 16 of an accumulator position correction device to be described later. Furthermore, guide rods 14a and 14b are fixed to the actuating plate 12, and the guide rods 14a and 14b are attached to the plate 13.
It passes through guide holes 15a and 15b provided in and is slidable. The above ball screw 16
A ball nut 1 has a gear 17 formed on its circumferential surface.
8 are screwed together, and the gear 17 meshes with a gear 19 fixed to the drive shaft of the servo motor M2. And these servo motor M2, gear 1
7, 19, a ball nut 18, and a ball screw 16 constitute an accumulator position correction device. Note that the rotation mechanism for rotating the screw 1 is omitted and not shown because it is not the gist of the present invention.

Next, the operation of this embodiment will be explained.

When the metering stroke is completed and the screw 1 is returned to the injection start position, the servo motor M2 of the accumulator position correction device is driven to move the ball screw 16 to the left in the figure, and the spring 11 is compressed by the plate 13. The repulsive force generated by this compression is transferred to the pressure plate 3 via the actuating plate 12.
Press. Then, the ball screw 16 is advanced to the forward position determined according to the metering setting amount, and the driving of the servo motor M2 is stopped. That is, the accumulator position correction device is operated so that the spring 11 is always compressed by a constant amount even if the metering setting changes. Then, to perform injection, the servo motor M1 is driven, and the ball screws 6a, 6
b is rotated to advance the pressure plate 3 via the ball nuts 5a and 5b, the repulsive force accumulated in the spring 11 is instantaneously superimposed at the start of injection, and the pressure plate 3 and screw 1 moves in the axial direction at high speed and high pressure and is injected. Next, when weighing, the servo motor M
2 is reversed to move the ball screw 16, spring 11, and actuating plate 12 backward, and at the same time rotate the screw 1. The screw 1 is pushed backward by the melting of the molding material, and the screw 1 is pushed backward by the servo motor M.
1, the pressure plate 3 and screw 1 are retracted to the measuring point while applying a constant back pressure. Then, the operation shifts to the injection stroke described above.

In the above embodiment, a spring was used as the accumulator, but a gas-type accumulator may also be used. In this case, a piston shaft of a gas type accumulator may be fixed to the pressure plate 3, and a gas cylinder may be fixed to the tip of the ball screw 16. Moreover, the reverse is also possible.

Furthermore, the accumulator position correction device may be one that uses a rack instead of a ball screw and drives a pinion with a servo motor to correct the position of the accumulator, which can be moved in the direction of the screw axis and fixed at a set position. It's fine as long as it's possible.

Effects of the Invention As described above, the present invention provides an accumulator position correction device to correct the accumulator position according to the metered set amount so that a constant pressure can always be generated, so that the metered set amount does not change. Even if the injection start position of the screw changes, a constant accumulator effect can always be obtained.

[Brief explanation of drawings]

The figure is an explanatory diagram of an embodiment of the present invention. 1... Screw, 3... Pressure plate, 5
a, 5b, 18...Ball nut, 6a, 6b, 1
6... Ball screw, 9... Timing belt,
10...Accumulator, 11...Spring, M
1, M2...Servo motor.

Claims (1)

[Claims] 1. In an injection mechanism of an injection molding machine that moves a pressure plate driven by a motor and moves a screw in the axial direction to perform injection, an accumulator that presses the pressure plate; An injection mechanism with an accumulator, comprising an accumulator position correction device for correcting the position of the accumulator. 2. The accumulator is constituted by a spring, one end of the spring presses the pressure plate, and the other end is fixed to a member that moves in the screw axis direction of the accumulator position correction device. Injection mechanism with an accumulator as described in section. 3. The accumulator is composed of a gas cylinder, and either the piston rod or the cylinder of the gas cylinder is fixed to the pressure plate, and the other is attached to a member that moves in the direction of the screw axis of the accumulator position correction device. An injection mechanism with an accumulator according to claim 1, wherein the injection mechanism is fixed. 4. The above-mentioned accumulator position correction device comprises a ball nut driven by a servo motor, and a ball screw that is threadedly engaged with the ball nut and moves in the direction of the screw axis, and the member that moves in the direction of the screw axis is the ball screw. An injection mechanism with an accumulator according to claim 1, 2, or 3.