JP3281305B2 - Control method of screw type injection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a screw-type injection device, and more particularly to a technique for preventing a screw from rotating backward.

[0002]

2. Description of the Related Art FIG. 6 is a sectional view of a typical conventional screw type injection device.
A screw 102 housed in the heating cylinder 101 so as to be able to move forward and backward and rotatable; an injection cylinder 103 for moving the screw 102 back and forth; and a rotating means 105 for rotating the screw 102 via a piston rod 104 of the injection cylinder 103. The plasticizing and measuring step, the standby step, and the injection step described below are performed. Reference numeral 106 denotes a spline. By connecting the spline, torque can be transmitted while allowing the piston rod 104 to move in the axial direction.

Plasticizing and measuring step: The molding material in the hopper 107 is supplied to the heating cylinder 101 while rotating the screw 102, and is transferred by the rotation of the screw 102, during which the molding material is heated by the heating cylinder 101. The molding material is plasticized and kneaded by frictional heat accompanying the transfer and heat transfer from the heating cylinder 101. Then, the screw 102 retreats due to the reaction force of the molten material extruded at the tip of the screw 102, so that the stroke can be measured to measure the stroke. Standby process: Standby from the completion of measurement to the next injection. Injection process: Screw 1
02 is advanced at a stretch, and the molten material metered and accumulated on the front side of the screw 102 is injected from the tip nozzle 108 into a mold (not shown).

[0004] In the injection step, the screw 102 reversely rotates due to the reaction force from the molten material. Therefore, it is desirable to provide a reverse rotation prevention mechanism as disclosed in, for example, Japanese Utility Model Publication No. 1-21783, “Injection Device of Injection Molding Machine”. In other words, in FIG. 1 of the publication, “The injection process is performed next.
At the same time, the electromagnetic clutch 68 is fastened, and the shaft 48 is rotated by the electric motor 70. "
Column 36 to 40).

[0005]

A technique of braking a screw with a brake in an injection step in which the screw must not run idle has been widely adopted. By the way, in the injection step, the injection cylinder 103 is largely stroked. To apply the brake so that the screw 102 does not rotate,
A large force is applied to the spline 106 in the middle. In this state, the spline 106 slides.
06 wears out. As a result, the life of the spline 106 is shortened, and the replacement cost of parts increases.

[0006]

DISCLOSURE OF THE INVENTION The present inventors investigated the process of the screw type injection device in detail, found out that there was a relationship between the operation of the check valve and the reverse rotation, and skillfully used this relationship. The braking time (braking time)
Has been significantly shortened compared to the past. More specifically, a first aspect of the present invention relates to a method for controlling a screw-type injection device including a check valve formed of a ring valve at a tip of a screw and a brake mechanism for preventing reverse rotation of the screw. By setting the mechanism in the braking mode and switching the brake mechanism to the release mode after the ring valve reaches the closed position, the subsequent injection process is performed with the brake mechanism released.

The brake is applied at the start of the injection process, and after the injection is started, the brake is released when the ring valve is closed, and the injection process is continued as it is. The torsional force generated on the screw during braking can be eliminated by releasing the brake. That is, by reducing the time required for abrasion, the life of the spline and the key can be extended, and the life of the screw can be greatly extended.

According to a second aspect of the present invention, the signal for switching the brake mechanism to the release mode is transmitted when the screw has moved a predetermined stroke. The screw advances with the injection. When the advance amount at this time reaches a predetermined value, the brake is released. The stroke of the screw can be easily detected, and a brake release signal is issued based on this information, so that signal detection is simplified and the price of the screw injection device can be prevented from increasing.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The drawings should be viewed in the direction of reference numerals. FIG. 1 is a cross-sectional view of a screw-type injection device according to the present invention.
And the injection cylinder 1 for moving the screw 12 back and forth.
3, an electric motor 15 for rotating the screw 12 via the piston rod 14 of the injection cylinder 13, a brake mechanism 16 provided at the rear of the electric motor 15,
A hopper 17, a stroke sensor 18, a stroke measuring unit 21 that sends distance or position information of the stroke sensor 18 to a master controller 20, a hydraulic control unit 22 that controls a hydraulic pressure applied to the injection cylinder 13,
It comprises a motor control unit 23 for controlling the rotation of the electric motor 15 and a brake control unit 24 for controlling the brake mechanism 16. That is, the master controller 20 is a main control unit that controls the hydraulic control unit 22, the motor control unit 23, and the brake control unit 24 collectively. The motor shaft 26 of the electric motor 15 is connected to the piston rod 14 with a spline 27 or a key.

The brake mechanism 16 includes a rotating disk 32 serving also as a cooling fan 31 attached to the rear end of the motor shaft 26.
And a spring 34 for pressing the brake shoe 33 against the rotating disk 32, and an electromagnet 35 for drawing the brake shoe 33 to the brake release side.
5 to the excited state by turning on the brake shoe 33.
Is separated from the rotating disk 32 to be in a non-braking state, that is, a “brake release mode”, and the electromagnet 35 is stopped to be in a non-excited state. "Brake braking mode". Electromagnet 3
Although the type in which the brake is released when the electric current is supplied to the electromagnet 35 has been described, a brake mechanism in which the electromagnet 35 is brought into a brake state when the electric current is supplied may be used.

FIGS. 2 (a) and 2 (b) are a sectional view and an operation view of a check valve according to the present invention. 3A, a check ring 40 is provided with a ring 42 slidably attached to a screw head 41 and a gap 4 on the inner peripheral surface of the ring 42.
In the state shown in the figure, the molten material flows from the screw 12 through the gaps 43, 4 as shown by arrows.
3 indicates that the head 3 moves forward of the screw head 41.

In FIG. 2B, when the screw 12 is advanced at a high speed along with the start of the injection step, the reaction force of the molten material acts on the ring 42 as shown by an arrow, and is pushed back to retreat the ring 42 to the spacer. It hits 44. As a result,
The gaps 43, 43 are closed by the spacers 44,
The backflow of the molten material can be prevented. A device in which the ring 42 is employed as a main element for preventing backflow as in this embodiment is called a ring valve type backflow prevention valve.

The operation of the above-described screw type injection device will be described below. FIG. 3 is a comprehensive time chart of the screw injection device of the present invention. The horizontal axis indicates time, and the vertical axis indicates screw position. That is, in the plasticizing and measuring step, the brake mechanism 16 is set to the brake release mode in FIG.
The raw material No. 7 is sent to the front of the screw 12, and the screw 12 gradually retreats by the reaction. Screw 12
Is detected by the stroke sensor 18, and when a predetermined stroke is reached, the electric motor 15 is stopped and the brake mechanism 16 is switched to the braking mode. In the standby step, injection is waited while the rotation of the screw is stopped. In the injection process, the piston rod 14 is rapidly advanced by the hydraulic control unit 22. The detailed operation during this time will be described separately, but the molten material is injected from the nozzle into a mold (not shown) by the screw 12 that advances rapidly.

FIG. 4 is a detailed explanatory view of the injection process of the present invention. The horizontal axis represents time, and the vertical axis represents the screw position, the operation of the brake mechanism, and the operation of the electric motor. The curve of the screw is a partially enlarged view of FIG. 3.
The value when moved (value in a range of 5 mm) was defined as "B". For the predetermined stroke, a signal from the stroke sensor 18 and the stroke measuring unit 21 in FIG. 1 is adopted. On the other hand, the brake mechanism switches to the braking mode at least before the start of injection, and switches to the release mode at the point B. The electric motor is stopped in the standby step and the injection step.

FIGS. 5 (a) and 5 (b) are explanatory diagrams comparing the brake mechanism and the spline stress between the prior art and the present invention.
(A) relates to the prior art, and when injection starts at point A, the screw tries to reverse by the reaction force of the molten material, and this is suppressed by the brake mechanism, so that a large stress is generated in the spline. Conventionally, since the braking mode is maintained until the injection process is completed, even if the ring valve closes and the reverse rotation force to the screw decreases or disappears, the reverse rotation energy that was initially applied remains stored in the screw and the spline Does not decrease so much (see (a) lower graph). Therefore, spline wear must take the injection process time into account.

(B) relates to the present invention, and when injection starts at point A, a large stress is generated in the spline. But B
When the brake mechanism is switched to the release mode at this point, the rear end of the screw idles by the torsion angle, and the torsional moment of the screw becomes almost zero. As a result, the force acting on the spline becomes very small, and the wear becomes minimal. That is,
From point A to point B, the amount of wear is large (about the same as before),
After the point, the amount of wear becomes very small. Therefore, according to the present invention, the abrasion of the spline is reduced to a fraction of the conventional one, and there is no need to worry about replacement of the spline. In addition, since the brake mechanism is released, the screw may rotate. However, since the ring valve is closed at the point B, there is no fear that a force for rotating the screw is applied.

In this embodiment, the connection between the motor shaft and the piston rod is spline connection. However, a key connection and a non-circular cross-section shaft connection (for example, a square hole is formed on the piston rod side by using a motor shaft having a square cross-section axis). In other words, the connection form is not particularly limited as long as the torque transmission shaft is slidable.

The determination of "the ring valve has reached the closed position" in claim 1 means that the time, that is, the time from the start of injection, is counted in addition to the stroke detection in the present embodiment, and the ring valve is reached when the predetermined time is reached. May be considered closed and the brake may be put into release mode. Therefore, the switching of the brake mode is not limited to the embodiment as long as it is an index that can be empirically regarded as the ring valve reaching the closed position. Further, the phrase “set the brake mechanism to the braking mode at the start of the injection process” in claim 1 indicates that at least the braking mode is at the start of the injection process. That is, this does not mean that the mode is switched only at the start of the injection process.

Further, the electric motor 15 may be a geared motor having a built-in reduction gear, and the brake mechanism 16 may be a band drum brake.

Further, the present invention is suitable for driving the screw 12 by the electric motor 15. This is because the electric motor 15 needs to have the brake mechanism 16 to run idle with a small torque structurally. However, as long as it has a brake mechanism, other rotating means (for example, a hydraulic motor)
The present invention may be applied to any of them.

[0021]

According to the present invention, the following effects are exhibited by the above configuration. Claim 1 applies a brake at the start of the injection process, releases the brake when the ring valve closes after the start of the injection, and continues the injection process as it is, so that the torsional force generated on the screw during the braking is reduced. This can be solved by releasing the brake and the wear can be reduced, so that the life of the spline and the key can be extended, and the life of the screw can be greatly extended.

According to a second aspect of the present invention, a signal for switching the brake mechanism to the release mode is transmitted when the screw has moved a predetermined stroke. The stroke of the screw can be easily detected, and a brake release signal is output based on this information. Therefore, signal detection is simplified, and an increase in the price of the screw-type injection device can be suppressed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a screw-type injection device according to the present invention.

FIG. 2 is a cross-sectional view and action diagram of a check valve according to the present invention.

FIG. 3 is a comprehensive time chart of the screw injection device of the present invention.

FIG. 4 is a detailed explanatory view of the injection step of the present invention.

FIG. 5 is an explanatory diagram comparing the brake mechanism and the spline stress between the conventional and the present invention.

FIG. 6 is a sectional view of a typical conventional screw-type injection device.

[Explanation of symbols]

10 screw injection device, 12 screw, 15
... Electric motor, 16 ... Brake mechanism, 18 ... Stroke sensor, 21 ... Stroke measuring unit, 23 ... Motor control unit, 24 ... Brake control unit, 32 ... Rotating disk, 33
... brake shoe, 34 ... spring, 35 ... electromagnet, 40 ... check valve (ring valve), 42 ... ring, 44 ... spacer, A ... at the start of injection, B ... when switching to release mode.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-49-74252 (JP, A) JP-A-48-21741 (JP, A) JP-A-5-318546 (JP, A) 132723 (JP, A) Japanese Utility Model 3-1129431 (JP, U) Japanese Utility Model 61-21710 (JP, Y2) Japanese Utility Model 1-271783 (JP, Y2) (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 45/46-45/54 B29C 45/76-45/82

Claims (2)

(57) [Claims] 1. A control method for a screw-type injection device comprising a check valve comprising a ring valve at a tip of a screw and a brake mechanism for preventing reverse rotation of the screw, wherein the brake mechanism is set to a braking mode at the start of an injection step. A method for controlling a screw-type injection device, characterized by switching the brake mechanism to the release mode after the ring valve reaches the closed position, so that the subsequent injection process is executed with the brake mechanism released. 2. The method according to claim 1, wherein the signal for switching the brake mechanism to the release mode is transmitted when the screw has moved a predetermined stroke.