JPH0435144Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to an injection molding machine equipped with an injection mechanism driven by a servo motor.

(Prior Art) In an injection molding machine equipped with an injection mechanism driven by a servo motor, the position and speed of the reciprocating screw movement are controlled by feedback signals from a rotation amount detector directly connected to the servo motor. was.

(Problem that the invention attempts to solve) However, when the position and speed of the screw reciprocating motion is detected by a rotation amount detector directly connected to the servo motor and feedback control is performed, the screw is placed between the servo motor and the screw shaft. In a power transmission mechanism, for example, when gears are used, there may be bumps and wear, and when timing belts and pulleys are used, belt loosening or stretching may cause variations and errors, making it difficult for the output of the servo motor to be correctly transmitted to the screw. Otherwise, variations and errors will occur between the settings in the main controller and the actual movement of the screw.

(Means for Solving the Problems) The present invention, as a means for solving the problems of the prior art described above, is a method for solving the problems of the prior art described above, by eliminating the need to directly connect the rotation amount detector for detecting the screw position and speed to the servo motor. By directly connecting to a male threaded shaft located on the same axis as the screw, the movement of the screw itself can be detected and feedback control can be performed to prevent cracks or loosening of the power transmission mechanism installed between the servo motor and the screw. Errors and variations in the movement of the screw caused by the effects of this were removed.

(Example) Examples will be described according to the drawings.

1 is a bed of an injection molding machine, and 2 is a fixed plate of a mold clamping device mounted on the bed 1, and the fixed plate 2 is moved along a stay 4 by advancing or retracting the mold clamping ram 3 to an opposing position. A movable platen 5 is provided which can be moved close to or away from the. A fixed mold 6 is attached to the fixed platen 2, and a movable mold 7 is attached to the movable plate 5. 8 is a product cavity formed by the fixed side mold 6 and the movable side mold 7.

On the other hand, a frame 9 is fixed on the bed on the back injection side of the stationary platen 2, and a worm gear mechanism 11 is attached to the end of the frame 9, and a shift rod 12 is connected to a drive motor 13 via the worm gear mechanism 11. ing. 14 is a housing which connects the shift rod 12 via a mounting flange 15.
The guide rod 16 can be moved forward or backward by moving the shift rod 12 forward or backward. The rear end of a heating tube 17 is fixed to the side wall 14A of the housing 14 facing the stationary plate 2, keeping its axis in the horizontal direction. It is arranged so that it can be moved.

Reference numeral 19 denotes a tip space formed by the inside of the heating cylinder 17 and the tip of the screw 18.

20 is a nozzle provided at the tip of the heating cylinder, and 21 is a sprue provided in the stationary mold 6 and serving as a passage for the molten material.

22 is a hopper for supplying material to the screw 18. On the other hand, the rear end of the screw 18 is connected to a connector 23 with a pulley 22.
The connector 23 is supported by a bearing box 26 via bearings 24 and 25.

27 is a bearing holder for fixing the inner ring of the bearing 24 to the connector 23, and 28 is a flange holding the outer ring of the bearing 24.

The bearing box 26 is guided by the guide rod 16 so as to be slidable in the horizontal direction and without any play in the vertical direction.

A servo motor 29 is fixed to the lower part of the bearing box 26, and together with the pulley 22 via a pulley 30 and a timing belt 31, constitutes a power transmission mechanism for rotationally driving the screw 18.

Reference numeral 32 denotes a cylindrical male screw member with a flange, which is fitted and fixed into the bearing box 26.

Reference numeral 33 is a male threaded shaft disposed on the same axis as the screw 18, and a ball screw portion 34 with a length sufficient for the injection stroke is provided from the end of the shaft near the screw, and a female screw thread is inserted through a ball 35. Member 32
At the same time, a stepped portion 36 is provided at an appropriate position from the other end, and the inner ring of the bearing 37 is fixed to the stepped portion with a pressing force by a bearing retainer 38, and is attached to the housing 14. By fixing the outer ring of the bearing 37 inserted into the bearing case 39 with a pressing force to the flange 42 of the bearing case 39 via the spacer 40 with the bracket 41, the male threaded shaft can freely rotate. Bearing case 3 becomes impossible to move horizontally
Supported by 9.

Reference numeral 43 denotes a rotation amount detector attached to the rear end of the bracket 41, and is directly connected to the male screw shaft 33 by a coupling 44.

Reference numeral 45 denotes a servo motor fixed to the upper part of the housing 14, which transmits power to rotate the male threaded shaft 33 with a pulley 48 provided on the male threaded shaft 33 via a pulley 46 and a timing belt 47. It constitutes a mechanism.

On the other hand, although not shown, the above-mentioned device sets the screw position, speed, etc., and outputs a voltage commensurate with the set values with a main controller and a feedback signal from the rotation amount detector 43 and an output signal from the main controller. Compare and calculate servo motor 4
5 includes a position control section, a speed control section, and a current control section for outputting a predetermined drive current.

Next, the operation will be explained.

FIG. 1 shows a state in which injection is started after the plasticization of the material has been completed and a certain amount of molten material has been stored in the space 19 at the tip of the heating cylinder.

The movable mold 7 and the fixed mold 6 are clamped between the movable platen 5 and the fixed platen 2, which are moved along the stay 4 by the operation of the clamping ram 3, thereby forming a product cavity 8.

On the other hand, due to the operation of the drive motor 13, the housing 1
4 is a worm gear mechanism 11, a shift rod 12,
The housing 1 is attracted toward the side wall of the fixed platen of the frame 9 through the mounting flange 15 .
The tip surface of the nozzle 20 provided at the tip of the heating cylinder 17 fixedly attached to the sprue 21 of the fixed mold 6
is pressed tightly against the inlet of the molten material to form a passageway for the molten material.

When the servo motor 45 is rotated in the forward direction in the above state, its rotational driving force is transmitted to the male threaded shaft 33 through the power transmission mechanism of the pulley 46, timing belt 47, and pulley 48, causing the male threaded shaft to rotate in the normal direction.

The male threaded shaft 33 has an inner ring of a bearing 37 fixed at its stepped portion 36 with a pressing force by a bearing retainer 38, and an outer ring of the bearing 37 inserted into a bearing case 39 attached to the housing 14. is fixed to the flange 42 of the bearing case 39 with a pressing force by the bracket 41 via the spacer 40, and is supported by the bearing case 39 so as to be rotatable and immovable in the horizontal direction. Although the shaft rotates normally, it is not allowed to move in the horizontal direction, so the female threaded member 32 is rotated by the ball screw mechanism formed between the ball screw portion 34 of the male threaded shaft and the female threaded member 32 via the ball 35. receives thrust in the direction of moving forward.

However, the female threaded member 32 is fitted and fixed in the bearing box 26, and the bearing box is slidably guided in the horizontal direction by the guide rod 16, so that the bearing 25, the bearing 24, the bearing retainer 27, and the retainer flange 28 The screw 18 is advanced through the connector 23 supported by the bearing box 26 in the left direction of the drawing, that is, in the injection direction, at a speed approximately proportional to the output rotation speed of the servo motor 45.

On the other hand, the other end of the male screw member 33 disposed on the same axis as the screw 18 is directly connected to the rotation amount detector 43 via the coupling ring 44. The screw position control unit (not shown) of the servo motor 45 captures the rotational speed of the screw 18 as it is, that is, the forward movement of the screw 18.
and is output as a feedback signal to a screw speed control section (not shown). The screw position control section and the screw speed control section that receive the feedback signal perform comparison calculations with the output signals from the main controller (not shown) that output voltages corresponding to the settings of the screw position and speed and the respective set values. After that, a predetermined current is output to the servo motor 45 through a current control section (not shown). The molten material thus stored in the space 19 at the tip end of the heating cylinder is injected into the product cavity 8 at an arbitrary set position while being controlled at a desired speed.

When the above-mentioned injection is completed and the plasticizing process begins, the servo motor 29 for rotating the screw is driven, and the rotational driving force is transmitted to the connector 23, through the power transmission mechanism of the pulley 30, timing belt 31, and pulley 22
Rotate the screw 18. The material supplied from the hopper 22 is stored at the tip of the heating cylinder by the rotating screw 18 while being plasticized.
At this time, the servo motor 45 is outputting a specified torque as back pressure, and the reaction force of the molten material stored at the tip of the heating cylinder counteracts the force that causes the screw 18 to retreat. When the retreating force overcomes the torque of the servo motor 45, the screw 18 begins to retreat and the servo motor 45 is reversed. The rotation amount detector 43 counts the amount of reversal of the male screw shaft itself, which is disposed on the same axis as the screw 18, and outputs it as a feedback signal to the position control unit as in the case of the injection process described above, making it extremely accurate. Then, the screw 18 is stopped at the weighing position. If a back-up step is required, the amount and therefore the stop positioning is equally accurate.

(Operations and Effects) According to the method of the present invention, the setting output signal of the main controller and the feedback signal that is compared and calculated in the position control section and the speed control section are arranged on the same axis as the screw whose position and speed are to be controlled. Since the rotation amount is received from a rotation amount detector that is directly connected to the male threaded member provided, the rotation speed of the screw is completely eliminated from the effects of bumps and loosening of the power transmission mechanism, compared to methods that feedback control the rotation speed of the servo motor that is the drive source. This makes it possible to control the position and speed to a desired state while avoiding variations, which greatly contributes to precision and stable molding.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional front view of a device showing an embodiment of the present invention. 6... Fixed side mold, 7... Movable side mold, 8...
Product cavity, 17...Heating tube, 18...Screw, 23...Connector, 26...Bearing box, 32...Female screw member, 33...Male thread shaft, 34...Ball screw part, 35...Ball, 4
3... Rotation amount detector, 45... Servo motor, 4
6...Pulley, 47...Timing belt, 48
...Pulley.

Claims (1)

[Scope of utility model registration request] In an injection molding machine that obtains a molded product by injecting a plasticized and molten material into a product cavity of a mold that is clamped, a screw that rotates and reciprocates is provided in a heating cylinder of an injection device. A servo motor as a drive source, a main controller for setting its output, a rotation amount detector that detects the output of the servo motor and sends a feedback signal, and a servo motor that compares and calculates the feedback signal with the output signal from the main controller. A position control section, a speed control section, and a current control section are provided for outputting a predetermined drive current to the motor, while the rotational output of the servo motor is controlled by a male motor with a ball screw section disposed on the same axis as the screw. A power transmission mechanism for transmitting power to the screw shaft and a ball screw mechanism for converting the rotational motion transmitted to the male screw shaft into reciprocating motion of the screw are provided, and the rotation amount detector is directly connected to the male screw shaft. An injection molding machine characterized by being equipped with.