JP2001138374A - Controlling method for mold clamping of injection molding machine and mold clamping device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the mold clamping device of an injection molding machine, in which response delay resulting from the dead zone of a sprue in a servo valve is improved and responsiveness is excellent. SOLUTION: The mold clamping device performs mold opening and mold clamping by taking into/out hydraulic fluid supplied from a hydraulic pressure feeding source 22 through a servo valve 20 having a changeover function of mold opening and mold clamping for a hydraulic pressure chamber 19 for mold opening and a hydraulic pressure chamber 18 for mold clamping, in which both chambers 18, 19 are formed by placing a piston 17 existing in a mold clamping cylinder 16 between both chambers. Also, the mold clamping device has a function performing injection in such a state that a mold is slightly opened. A sprue in the serbo valve exists in the position adding pressure to a hydraulic pressure chamber for mold clamping by equipping a hydraulic pressure generating circuit 10 which adds prescribed pressure to the hydraulic pressure chamber side for mold opening in a state changed over to mold clamping and in a state slightly opening the mold.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold clamping control method and a mold clamping apparatus for an injection molding machine, and more particularly, to a mold clamping control method and a mold clamping function for an injection molding machine having a function of performing injection with a mold slightly opened. It relates to a mold clamping device.

[0002]

2. Description of the Related Art A mold clamping control method of this kind is disclosed, for example, in Japanese Patent No. 2789295. Referring to FIG. 3, a conventional mold clamping apparatus for realizing the mold clamping control method disclosed in the above patent includes a fixed platen 12 fixed to a frame (not shown) and a fixed mold 11 attached thereto, and a movable mold. A movable platen 14 to which the movable platen 13 is attached, a plurality of tie bars 15 for guiding the movement of the movable platen 14, a mold clamping cylinder 16, a piston 17, and a mold formed on the mold clamping cylinder 16 with the piston 17 interposed therebetween. A hydraulic chamber for closing 18 and a hydraulic chamber for opening the mold 19, a servo valve 20 having a function of switching between opening and closing of the mold, a tank 21 for collecting hydraulic oil returned from the clamping cylinder 16, and a hydraulic supply source 22. The fixed platen 12 and the movable platen 1
And a distance sensor (not shown) for detecting an inter-platen distance between the first and second plates. 23 is an accumulator and 24 is a check valve.

The piston 17 is disposed in a mold clamping cylinder 16 fixed to a rear platen 25, and the movable platen 14 is connected to the piston 17. The movable platen 14 is configured to be slidable on the tie bar 15 with the movement of the piston 17. The movable platen 14 injects hydraulic oil into the mold closing hydraulic chamber 18 and switches the mold opening hydraulic chamber 1 by the switching operation of the servo valve 20.
9 to close the mold (Fig. 3).
(Middle, right). On the other hand, the hydraulic oil is injected into the mold opening hydraulic chamber 19 and discharged from the mold closing hydraulic chamber 18 to move in the mold opening direction (left direction in FIG. 3).

That is, in the mold closing operation, the servo valve 20 supplies the working oil from the hydraulic pressure supply source 22 to the mold closing hydraulic chamber 18 and returns the working oil from the mold opening hydraulic chamber 19 to the tank 21. A circuit is formed (P1 in FIG. 3 moves to the right). On the other hand, in the mold opening operation, the servo valve 20 supplies the hydraulic oil from the hydraulic pressure supply source 22 with the mold opening hydraulic chamber 19.
And the hydraulic oil from the mold closing hydraulic chamber 18 is supplied to the tank 21.
(P2 part in FIG. 3 is moved to the left).

[0005] This mold clamping device operates the servo valve 20 so as to maintain the mold opening at a predetermined target value based on various measured values in injection molding such as injection pressure in addition to the value detected by the distance sensor. Performs feedback control. The function of performing injection with the mold slightly opened is disclosed in the above-mentioned patent gazette, and the description is omitted.

[0006]

In this type of conventional mold clamping apparatus including the example shown in FIG. 3, a servo valve 20 is used, and the flow rate of hydraulic oil to the hydraulic chamber 18 for closing the mold and the opening of the mold are controlled. The mold clamping force is generated by controlling the flow rate of the working oil to the hydraulic chamber 19 for use. Here, when the movable platen 14 is at a desired position, the hydraulic pressure in the mold closing hydraulic chamber 18 and the hydraulic pressure in the mold opening hydraulic chamber 19 are in a balanced state. The spool is in the dead zone.

FIG. 4 shows the general characteristics of the servo valve 20, in which the mold opening direction (the left area in FIG. 4) and the mold closing direction (the right area in FIG. 4) are separated by a dead zone. Divided into Under such characteristics, if there is a disturbance, for example, a change in the injection pressure when the spool is in the dead zone, the servo valve 20 attempts to operate to correct this.
For example, the disturbance increases the mold opening, and the servo valve 20 attempts to move the piston 17 in the mold closing direction in order to correct this. However, as is apparent from FIG. 4, the spool is actually controlled from the dead zone. It takes some time to change to a region in the possible mold closing direction. This means that a response delay occurs in the servo valve 20. And
Such a response delay is a response delay of the movable platen position control. In particular, when injection is performed with the mold slightly opened, that is, when the distance between the platens is maintained at a certain value, the molded product becomes overpacked. There is a problem.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a mold clamping control method and a mold clamping device for an injection molding machine having excellent responsiveness capable of improving a response delay caused by a dead zone of a spool in a servo valve. is there.

[0009]

According to the present invention, there is provided a mold closing control method, wherein a mold opening hydraulic chamber and a mold closing hydraulic chamber formed with a piston in a mold clamping cylinder interposed therebetween, respectively. In a mold clamping control method for an injection molding machine, which opens and closes a mold by taking in and out hydraulic oil through a servo valve having a switching function, and performs injection with the mold slightly opened, the mold is switched to the mold closed state. By applying a predetermined pressure to the mold-opening hydraulic chamber while the mold is slightly opened in a state where the mold is slightly open, the spool in the servo valve is brought to a position where the spool raises pressure in the mold-closing hydraulic chamber. It is characterized by having it.

In the mold clamping apparatus according to the present invention, a servo having a function of switching between mold opening and mold closing is provided in a mold opening hydraulic chamber and a mold closing hydraulic chamber formed with a piston in a mold clamping cylinder therebetween. In a mold clamping device of an injection molding machine having a function of opening and closing a mold by taking in and out hydraulic oil from a hydraulic supply source through a valve and performing injection with a mold slightly opened, the mold is switched to the mold closed state. A hydraulic pressure generating means for applying a predetermined pressure to the mold-opening hydraulic chamber side in a state where the mold is slightly opened when the mold is slightly opened, so that the spool in the servo valve is It is characterized in that it is located at a position where pressure is applied.

The hydraulic pressure generating means is connected between a port of the servo valve to be connected to the hydraulic pressure chamber for opening the mold and the hydraulic pressure chamber for opening the mold. A circuit is formed to return the hydraulic oil from the opening hydraulic chamber to the tank via the servo valve. In the case of the mold opening, the hydraulic oil from the hydraulic supply source is opened via the servo valve to open the mold. A first valve for forming a circuit to be supplied to the hydraulic chamber for use, and a first valve connected between the hydraulic chamber for opening the mold and the output side of the hydraulic supply source, and the hydraulic pressure is switched when the mold is closed. A second valve that is switched to supply hydraulic oil from a supply source to the mold opening hydraulic chamber, and a second valve connected between the mold opening hydraulic chamber and the second valve; And a third valve for controlling the hydraulic pressure from the cylinder to a predetermined pressure. The features.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIG. 1, a mold clamping device for an injection molding machine according to an embodiment of the present invention will be described. 1, the same parts as those in FIG. 3 are denoted by the same reference numerals, and the detailed description will be omitted. The mold clamping device according to the present embodiment includes the hydraulic pressure generation circuit 10 that applies a predetermined pressure to the mold opening hydraulic chamber 19 when the servo valve 20 is switched in the mold closing direction, so that the spool in the servo valve 20 is shaped. It is characterized in that it is located at a position where pressure is applied to the closing hydraulic chamber 18.

The hydraulic pressure generating circuit 10 includes first to third valves 1 to 3. The first valve 1 is a logic valve, and is provided between a port (two ports P1 and P2) to be connected to the mold opening hydraulic chamber 19 of the servo valve 20 and the mold opening hydraulic chamber 19. It is connected to the. First
The valve 1 is opened when the pressure on the mold opening hydraulic chamber 19 side exceeds a certain value when the mold is closed, and the hydraulic oil from the mold opening hydraulic chamber 19 passes through the P1 portion of the servo valve 20. To form a circuit for returning to the tank 21. The first valve 1 is also
In the case of opening the mold, a circuit for supplying the hydraulic oil from the hydraulic pressure supply source 22 to the mold opening hydraulic chamber 19 via the P2 portion of the servo valve 20 is formed. Such switching is performed by the first switch shown in FIG.
Automatically performed by the action of the pilot portion shown by the broken line in the valve 1 of FIG. That is, when the hydraulic pressure from the mold-opening hydraulic chamber 19 side increases, the first valve 1 causes the hydraulic oil to flow from the mold-opening hydraulic chamber 19 side to the servo valve 20 side, and the hydraulic pressure from the servo valve 20 side increases. Then, the operation is performed so that the hydraulic oil flows from the servo valve 20 side to the mold opening hydraulic chamber 19 side.

The second valve 2 is an electromagnetic switching valve, which is connected between the mold-opening hydraulic chamber 19 and the output side of the hydraulic supply source 22, and receives a signal from the hydraulic supply source 22 when the mold is switched to the closed state. Switching is performed so that the hydraulic oil is supplied to the mold opening hydraulic chamber 19. Hereinafter, this is called an ON state.

The third valve 3 is a pressure reducing valve, which is connected between the mold opening hydraulic chamber 19 and the second valve 2 and is for adjusting the hydraulic pressure from the second valve 2 to a predetermined pressure. is there. In a state where the mold is closed by the second and third valves 2 and 3, a predetermined pressure is applied to the mold opening hydraulic chamber 19 by the action of the second valve 2 in the ON state. In this state, the hydraulic oil is discharged from the mold-opening hydraulic chamber 19 when the pressure on the mold-opening hydraulic chamber 19 side exceeds a predetermined value, the first valve 1 is opened, and the hydraulic oil is discharged from the tank 21. Return to the side.

In this mold clamping device, the servo valve 2
Using 0, the mold clamping force is generated by controlling the flow rate of hydraulic oil to the hydraulic chamber 18 for closing the mold and the flow rate of hydraulic oil to the hydraulic chamber 19 for opening the mold. Here, in the present embodiment, when the movable platen 14 is in a desired position by generating a mold clamping force in the mold closing direction, the second valve 2 is turned on, and the mold opening hydraulic chamber 19 is previously opened. As shown in FIG. 2, the spool in the servo valve 20 is located not at the dead zone but at a position S1 where pressure is applied to the hydraulic chamber 18 for closing the mold.

In this way, a fixed pressure is applied to the mold opening hydraulic chamber 19, and the mold clamping force is controlled only by the hydraulic pressure for the mold closing hydraulic chamber 18. In this case, if the mold opening amount becomes large due to, for example, a disturbance (mainly injection pressure), the servo valve 20 attempts to move the piston 17 in the mold closing direction to correct this. In this case, as is apparent from FIG. 2, the time required for the spool to change from the position S1 to the position S2 is much shorter than the time described in FIG. This means that the response of the servo valve 20 has been improved. This feature is particularly effective when the mold is slightly opened, that is, when the injection is performed with the distance between the platens maintained at a certain value, and the problem that the molded product is overpacked due to disturbance can be solved. .

It should be noted that the above-described improvement in responsiveness is achieved by the method shown in FIG.
This is important in a state where the movable platen 14 is controlled to a desired position by generating a mold clamping force by the feedback control described in the above section, and the mold opening direction is not necessary.

[0019]

According to the present invention, the response of the position control of the movable platen is improved, especially in the case of performing the injection with the mold slightly opened, and the problem of overpacking of the molded product due to disturbance. The point can be eliminated.

[Brief description of the drawings]

FIG. 1 is a diagram showing a main part of a mold clamping device of an injection molding machine according to an embodiment of the present invention.

FIG. 2 is a view for explaining characteristics of a servo valve in the mold clamping device shown in FIG. 1;

FIG. 3 is a view showing a main part of a mold clamping device of an injection molding machine according to a conventional example.

FIG. 4 is a diagram for explaining characteristics of a servo valve in the mold clamping device shown in FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st valve (logic valve) 2 2nd valve (electromagnetic switching valve) 3 3rd valve (pressure reducing valve) 10 Hydraulic pressure generation circuit 11 Fixed mold 12 Fixed platen 13 Movable mold 14 Movable platen 15 Tie bar 16 type Tightening cylinder 17 Piston 18 Mold closing hydraulic chamber 19 Mold opening hydraulic chamber 20 Servo valve 21 Tank 22 Hydraulic supply source 23 Accumulator 24 Check valve 25 Rear platen

Claims (3)

[Claims] 1. Hydraulic oil is fed into and out of a mold opening hydraulic chamber and a mold closing hydraulic chamber formed with a piston in a mold clamping cylinder therebetween through a servo valve having a function of switching between mold opening and mold closing. In the mold clamping control method of an injection molding machine, which performs opening and closing of the mold by performing injection while the mold is slightly opened, the mold is slightly opened while the mold is switched to the closed state. By applying a predetermined pressure to the mold-opening hydraulic chamber side in a state where the mold is opened, the spool of the servo valve is located at a position where pressure is applied to the mold-closing hydraulic chamber. Mold clamping control method. 2. A hydraulic valve for opening and closing a mold formed between a piston in a mold closing cylinder and a hydraulic chamber for closing a mold, respectively, through a servo valve having a function of switching between opening and closing of the mold. In a mold clamping device of an injection molding machine having a function of opening and closing a mold by taking in and out hydraulic oil and performing injection while a mold is slightly opened, a state in which the mold is closed and the mold is closed. By providing a hydraulic pressure generating means for applying a predetermined pressure to the mold-opening hydraulic chamber side when the mold is slightly opened, the spool in the servo valve is at a position where pressure is applied to the mold-closing hydraulic chamber. A mold clamping device for an injection molding machine, characterized in that: 3. The mold clamping device for an injection molding machine according to claim 2, wherein the hydraulic pressure generating means is provided between a port of the servo valve to be connected to the mold opening hydraulic chamber and the mold opening hydraulic chamber. A circuit that returns the hydraulic oil from the mold-opening hydraulic chamber to the tank via the servo valve when the mold is closed, and from the hydraulic supply source when the mold is opened. A first valve for forming a circuit for supplying the hydraulic fluid of the present invention to the mold opening hydraulic chamber via the servo valve, and between the mold opening hydraulic chamber and the output side of the hydraulic supply source. A second valve that is connected and is switched to supply hydraulic oil from the hydraulic supply source to the mold-opening hydraulic chamber when the mold-closing is switched to the mold-closed hydraulic chamber; And the hydraulic pressure from the second valve Mold clamping apparatus of an injection molding machine, characterized in that it comprises a third valve to a predetermined pressure.