JPH035120A - Regulating method of back pressure of motor-driven injection device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for adjusting back pressure during metering in an electric injection device in which the rotational movement and linear movement of a screw are performed by an electric motor.

(Prior Art) Conventionally, in an injection molding method in which a molded product such as Plus Deck is injected into a molding die to produce a molded product, hydraulic and electric injection devices are mainly used. ing.

First, a conventional hydraulic injection device will be described with reference to FIG. 6.

This hydraulic injection device mainly includes a hopper 71, a screw 73 that mixes and measures the resin input from the hopper in the cylinder tough 2, a motor 51 that allows this screw to rotate, and injects the kneaded resin. The motor 51 and the direct-acting cylinder 52 are generally of a hydraulically operated type that can easily generate a large output.

Next, the electric injection device disclosed in Japanese Patent Publication No. 61-571.68 will be explained using FIG.

In the figure, 53 is a screw housed in a heating cylinder 66, and this screw is fixed to a screw rotation driven gear 54 disposed at the rear. 5
Reference numeral 6 denotes a support body that is slidably guided by the guide bar 57, and this support body rotatably supports the driven gear 54 for screw rotation, and a ball screw 58 whose tip abuts on the axis of the gear 54. This is done by fixing the pole nut 55 that has been fitted. Further, a propulsion driven gear 59 is fixed to the ball screw 58. Each of the screw rotation driven gear 54 and the propulsion driven gear 59 is disposed on the rotating shaft of the motor 62 and connected to a driving gear 63.64 connected by a clutch 60.61. ing.

Further, this device is provided with a back pressure brake unit 65 behind the propulsion driven gear 59, and the screw 5
The backward movement of No. 3 is pressed from the rear of this gear 59. As a result, when the screw 53 retreats due to mixing and metering of the resin charged into the heating cylinder 66 from the hopper 74, the pole nut 55 retreats via the gear 54 and the support 56, causing the ball gear 58 to rotate. Accordingly, the gear 59 is rotated. The back pressure brake unit 65
When the screw 53 is pressed by
This is to provide back pressure against the

(Problems to be Solved by the Invention) However, the conventional injection device described above has the following problems.

That is, in a hydraulic injection device as shown in FIG. 5, (1) peripheral devices such as a hydraulic pump and piping equipment are required, so a large installation space for the injection molding machine is required.

(2) It is difficult to use an injection molding machine in a clean environment due to oil mist etc. emitted from hydraulically operated equipment.

On the other hand, in an electric injection device as shown in Fig. 6,
Although the problems of hydraulic injection devices have been solved, (1) To apply back pressure, it is necessary to use a force to convert the linear motion of a pole nut, etc., into rotational motion of a ball screw, etc. when the screw retreats, and a gear, etc. It is necessary to control this back pressure by adding it to the force generated by the slip torque of the brake that presses against the end face of the brake, so there are many parameters for back pressure (rotational resistance of the ball screw, frictional force of the brake plate, etc.). (brake generation output, etc.), the condition settings become complicated.

(2) Since the gear that is allowed to rotate and the pole nut that is allowed to be propelled are supported by the same support and move at the same time as the screw, a guide to prevent the support from rotating is required and the drive system It requires a large peripheral arrangement space and the configuration becomes complicated.

The present invention was made to solve these problems, and its purpose is to easily configure the back pressure mechanism, which was conventionally composed of a complicated mechanism, and to build a slim device. There is a particular thing.

(Means for Solving the Problems) In order to solve the above problems, the method for adjusting the back pressure of an electric injection device of the present invention is to provide a method for adjusting the back pressure of an electric injection device of the present invention. An injection motor is connected via a linear movement mechanism that converts the injection into a linear movement, and when the linear movement mechanism is allowed to move backward during measurement, the rotational movement of the injection motor transfers the load for back pressure adjustment to the linear movement mechanism. It is characterized by causing it to act on.

(Function) In the present invention, the injection motor is configured to also use a back pressure adjustment means during metering.

That is, at the time of injection, when the injection motor rotates, this rotational motion is converted into a linear motion by the linear mechanism, and the linear mechanism pushes out and propels the screw.

During weighing, the straight-advancing means is allowed to move straight, thereby allowing the screw to retreat during weighing. When the screw moves backward, the linear mechanism applies torque that rotates the output shaft of the motor (but the rotation of the motor in the opposite direction to this rotation applies a load that brakes the backward movement of the screw, causing the back pressure on the screw to be adjusted. It will be done.

Further, according to the present invention, it is possible to construct an injection device in which a screw, a linear movement mechanism, and an injection motor are coaxially connected to the screw.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

Fig. 1 is a schematic cross-sectional view of the electric injection device according to this embodiment, Fig. 2 is a perspective view of the main part of Fig. 1, and Fig. 3 (a) to (
d) is an explanatory diagram of the operation of this embodiment, FIG. 4 is a flowchart of injection molding by the apparatus of this embodiment, and FIG. 5 is a diagram showing changes in current value in each stroke of the injection motor.

As shown in FIGS. 1 and 2, the injection device according to this embodiment includes a screw 2 housed in a superheated cylinder 1.
A rotating shaft 3 fixed to the rear part of the screw 2 with a pin 4, and a driven spur gear 6 fixed with a key 5 to the middle rotating shaft 3a, the middle part of the rotating shaft 3 having a smaller diameter than the lower part. Furthermore, a linear cylinder 13 and an electric injection motor (hereinafter referred to as injection motor) 23 for driving the linear cylinder are provided on the upper part of the rotating shaft 3. placed on the line.

32 is a hopper, which supplies molding material to the inside of the heating cylinder 1 through a pipe 31.

In the above configuration, a metering electric motor (hereinafter referred to as a metering motor) 7 that allows rotation of a driving spur gear 8 that meshes with a driven spur gear 6 is disposed on the side of the rotating shaft 3 on the injection unit base 33. I'm being kicked by someone. Driving side spur gear 8B,
It has a sufficient tooth width so that the rotary shaft 3 does not come off the driven spur gear 6 even if it moves up and down.

With such a configuration, the metering motor 7 is connected to the driven side spur gear 6.
The rotating shaft 3 is allowed to rotate via the driving side spur gear 8, and the screw 2 is rotated within the cylinder 1, thereby kneading the molding material within the cylinder.

Note that the metering motor 7 and the injection motor 23 are controlled by the controller 3.
0 and can control each motor.

The lower part of the linear cylinder 3 is provided with a bearing chamber 13a for fixing the races 12a and 12c on both sides of the thrust bearing 12.The thrust bearing 12 is held at the lower end of the linear cylinder 13 by a cover 13b, and The upper rotating shaft 31 provided at the two ends is fixed to the center race 121 of the thrust bearing 12. A pole nut 22 is fixedly installed on the upper part of the straight cylinder 13, and a coupling 2 is connected to the output shaft 23a of the injection shaft 23 provided at the nigga of the straight cylinder.
5 and 7'.

However, on the side of the straight cylinder 3, there is a protruding piece 2 whose tip is formed into a bifurcated shape and has a through hole parallel to the axial direction of the screw 2.
0 is provided, and a guide shaft 21 fixed to the unit base 33 is inserted into the through hole of this protruding piece 2o. Therefore, the straight cylinder 13 can move forward and backward only in the axial direction of the screw 2 by being guided by the guide shaft 21.

With such a configuration, when the injection motor 23 is allowed to rotate, the linear cylinder 13 moves up and down via the ball screw 24 and ball nut 22, and following this movement, the screw 2 is propelled via the rotating shaft 3. be able to.

During metering, it is necessary to apply back pressure to the screw 2 so that air bubbles and the like do not get mixed into the melt-forming material accumulated in front of the screw 2 rotating inside the heating cylinder 1.

In this embodiment, the back pressure is applied by switching the injection motor 23 to the back pressure motor 1 through the controller 30 and applying a predetermined torque of 1 through to this motor to resist the thrust force that causes the screw 2 to retreat. .

At the time of injection, the controller 30 switches the injection motor 23 to injection mode and applies a predetermined torque to this motor.

26, 27, and 29 are a sensor group for detecting the strokes of the screw 2 or the linear cylinder 13. Reference numeral 26 indicates a backpack completion detection sensor, and 27 indicates a measurement completion detection sensor, which detects the vertical position of the screw 2 by means of a sensor dog 9 fixed to the middle of the rotating shaft 3. Further, 29 is an overrun detection sensor, which uses the side surface of the linear cylinder 13 as a sensor dog to detect the vertical position of the screw 2. Each of the above-mentioned sensors 26, 27, and 29 is connected to a controller (not shown), and a signal from each sensor is sent to a controller 30 to control the injection motor 23 and metering motor 7.

The injection unit case 33 is integrally formed, and the injection motor 23, guide shaft 21, metering motor 7, heating cylinder 1, etc. are attached thereto.

However, for convenience of illustration, the unit case 33 is only partially shown in the drawing.

Although not shown in Fig. 1, when actually performing injection molding, a molding mold is placed near the tip of the heating cylinder 1, and a mold is used to open and close the mold, or to clamp the mold. Equipment, etc. are installed.

Further, in this embodiment, it is assumed that a pressure holding timer and a cooling timer are installed in the controller in order to measure the pressure holding time and cooling time of the molded product in the mold cavity.

Next, the operation of the electric injection device configured as described above will be explained with reference to the operation diagrams shown in FIGS. 3(a) to 3(d) and the flowchart shown in FIG. 4. In the following description, the symbol S in parentheses indicates a step in the flowchart of FIG. 4.

FIG. 3(a) shows a state during metering and crosstalk.

At this time, the injection motor control is switched to the back pressure mode, and the metering motor 7 rotates counterclockwise (CCW; counter clockwise (Sl)), driving side spur gear 8, driven side spur gear 6, and rotating shaft 3. The screw 2 rotates through the hopper 32, and the molding material supplied from the hopper 32 into the heating sill 1 is kneaded and molten. As this molten molding material accumulates in front of the screw 2 within the heating cylinder 1, the screw 2 retreats upward within the heating cylinder 1.

Furthermore, since the injection motor control is switched to the back pressure mode at this time, back pressure is applied to the screw 2 via the ball screw 24, the ball nut 22, the linear cylinder 13, the thrust bearing 12, and the rotating shaft 3.

Next, as shown in FIG. 3(b), when the screw 2 rises and the metering completion detection sensor 27 receives an ON signal (S2), the metering motor 7 stops (S3), and the metering starts. The crosstalk is completed. At this time, the injection motor 23 is switched to injection mode.

After that, turn the injection motor 23 clockwise (CW clock).
A suckback is performed by rotating (S4). This suckback is performed to prevent the molten molding material measured in this step from leaking from the injection port of the cylinder 1 when the mold is opened to take out the molded product in a later step.

When the injection motor 23 is rotated clockwise (CW), the linear cylinder 13 is raised via the ball screw 24 and the ball nut 22. In FIG. 3(C), the path length indicated by a is the suckback stroke.

When the screw 2 moves by this stroke a, the suckback completion detection sensor 26 receives an ON signal (S5
), the injection motor 23 stops (S6), and the suckback ends.

Next, a mold (not shown) provided below the screw 2
, the cooling timer counts up (S7),
When cooling of the molded product is completed, the mold is unclamped (S8), and then the mold is opened (S8).
S9), take out the molded product 5IO), close the mold again and perform mold clamping 5ll) (S12).

Next, as shown in FIG. 3(d), the injection motor 23 is rotated counterclockwise (CCW) (S13), and the linear cylinder 1 is rotated (S13).
When a downward thrust is applied to the screw 3, the screw 2 is pushed downward through the rotating shaft 3, and the molten molding material in front of the screw 2 is injected into the mold. Control of the injection motor 23 is as follows:
The controller 30 first controls the speed of the injection motor 23 (S14). At this time, in order to keep the injection speed constant, the rotation speed of the motor 23 is controlled to be constant. Then, as the molding material is filled into the mold cavity and the pressure inside the mold increases, the current consumed by the injection motor 23 increases, and when the current consumed by the injection motor 23 reaches a set value (S15), injection is completed. In FIG. 3(d), the injection stroke of the screw 2 is indicated by d. Next, the control is switched to current value control in which the output 1 herk is constant (S16), and a low pressure state is established in which a constant pressure is applied to the molding die 4 in the mold cavity. At this time, the pressure holding timer starts counting.

Next, when the pressure holding timer counts up (S17
) Stop the injection motor 23 to complete pressure holding, and start the cooling timer from 1 to 1 (S18).

After passing through the steps as described above, steps 81 to ]8 described above can be repeated again to perform injection molding as described above.

Here, the injection motor and back pressure mode of the injection motor 23 will be explained with reference to FIG. 5.

FIG. 5 shows changes in current value during each stroke of the injection motor 23.

The steps on the horizontal axis correspond to the order of operation shown in Flowchart 1 above. In the figure, Δ is the back pressure motor and the metering stroke 8 above.
1 to S3, a current value p set so that the output torque of the injection motor 23 is constant is given, and a constant back pressure is given to the screw 2 that retreats upward by metering. B corresponds to the injection strokes S13 to S15 and pressure holding strokes S16 to S18 of the injection motor 1. In the injection process, the speed is controlled to be constant, and in the pressure holding process, the output torque of the injection motor 23 is controlled to be constant. A current value q is given so that the pressure is maintained. "I"
The second current values p and q are set by determining in advance the values necessary to obtain the necessary back pressure and holding pressure.

According to the back pressure adjustment method of the electric injection device explained above,
The injection morph 23 can be used as a back pressure adjustment means during metering.

Furthermore, by arranging the screw 2, rotating shaft 3, linear cylinder 13, and injection motor 23 in a tree shape on the propulsion shaft of the screw 2, the width and depth of the installation area are reduced, and the entire device is Although the injection device in the above embodiment is configured as a vertical molding machine, it can also be applied to a horizontal molding machine.

5 (Effects of the Invention) As explained below, according to the method for adjusting back pressure of an electric injection device of the present invention, the injection motor can be used in combination as a back pressure adjusting means during metering. Therefore, there is no need for a brake unit with a complicated structure as in the past, and the entire device can be configured simply.

In addition, since the device can be constructed simply as described above, and the screw, the linear movement mechanism, and the injection motor can be connected on the propulsion shaft of the screw,
An injection device is obtained in which the entire device can be constructed slimly, and the components are arranged in stripes and rows to reduce the footprint of the device.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of an electric injection device according to an embodiment of the present invention, FIG. 2 is a perspective view of the main part of FIG. 1, and FIGS. 3(a) to 3(d) are shown in FIG. 1. An explanatory diagram of the operation of the electric injection device, Fig. 4 is a flowchart of injection molding using the device of this embodiment, Fig. 5 is a diagram showing changes in current value in each stroke of the injection motor, and Fig. 6 is a diagram showing the change in current value in each stroke of the injection motor. FIG. 7 is a sectional view of a conventional hydraulic injection device, and FIG. 7 is a sectional view of a conventional electric injection device. 1... Heating cylinder 2... Screw 3... Rotating shaft 6... Driven side spur gear 7... Metering motor 8... Driving side spur gear 12... Thrust bearing 13... Straight cylinder 22...Pole nut 23...Injection motor 24...Ball screw

Claims (1)

[Claims] (1) An injection motor was connected to the screw that injects the molding material kneaded in the heating cylinder via a linear mechanism that converts the rotary motion of the motor into linear motion, and the linear mechanism was allowed to retreat during metering. A method for adjusting back pressure in an electric injection device, characterized in that a load for adjusting the back pressure is applied to the linear mechanism by rotation of the injection motor in a state in which the injection motor is rotated.