JPH04320822A - Method for preventing response delay of suck back action of injection molding machine and hydraulic system therefor - Google Patents

Abstract

PURPOSE:To eliminate response delay of suck back action due to lack of oil in a front oil chamber of an injection cylinder relating to an oil system for preventing response delay of suck back action in an injection molding machine. CONSTITUTION:There are provided a screw 1, a motor 6 for rotating the screw 1, an injection cylinder 2 for moving forward and rearward the screw 1, and a changeover valve 8 for feeding oil to a front oil chamber 4 and a rear oil chamber 5 of the cylinder 2 and discharging oil therefrom. Further, a back pressure regulating valve 9 is provided between the chamber 5 and the valve 8. For plasticization, the valve 8 serves, in its neutral state, as a system for interconnecting the chamber 4 and chamber 5.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is directed to an injection molding machine.
The present invention relates to a hydraulic circuit for preventing delay in response to suckback operation.

0002

[Prior Art] In a conventional injection molding machine, the screw 1
As shown in FIG. 2, the hydraulic circuit for operating the forward and backward movement of the It is composed of a chamber 4 and a switching valve 8 for supplying and discharging oil to and from a rear oil chamber 5. In the hydraulic circuit of this device, when the solenoid a of the switching valve 8 is excited, the pressure oil discharged from the pump 10 is supplied to the front oil chamber 4 of the injection cylinder 2, causing the screw 1 to retreat (note that this operation is (referred to as back process). When the screw 1 retreats, oil discharged from the rear oil chamber 5 of the injection cylinder 2 passes through the switching valve 8 and returns to the tank 11. On the other hand, when the solenoid b of the switching valve 8 is excited, pressure oil is supplied to the rear oil chamber 5 of the injection cylinder 2 to advance the screw 1. When the screw 1 moves forward, oil discharged from the front oil chamber 4 of the injection cylinder 2 passes through the switching valve 8 and flows into the tank 1.
It is returned to 1.

In the plasticizing process, the switching valve 8 is in a neutral state, the front oil chamber 4 of the injection cylinder 2 and the tank 11 are in communication, and the motor 6 rotates the screw 1 to plasticize the material 7 (resin). . The screw 1 moves backward while rotating due to the reaction force of the plasticized material 7 sent forward, and the oil discharged from the rear oil chamber 5 of the injection cylinder 2 is sent to the tank 12 via the back pressure regulating valve 9. return. On the other hand, the front oil chamber 4 sucks up negative pressure from the tank 11.

0004

However, in such a conventional hydraulic circuit, when the screw 1 retreats during the plasticizing operation, the front oil chamber 4 of the injection cylinder 2 is affected by the negative pressure generated by the retreat of the piston 3. Oil is being sucked up from tank 11. However, due to piping resistance, the front oil chamber 4 of the injection cylinder 2 is not easily filled with oil, and a portion thereof is occupied by the gas body. Therefore, when the front oil chamber 4 of the injection cylinder 2 contains gas at the time when the plasticizing operation is completed, if the suckback operation is performed, the switching valve 8 is switched and the front oil chamber 4 of the injection cylinder 2 is Even if pressure oil is supplied to the chamber 4, the gas body acts as a buffer and the piston 3
And the screw 1 linked thereto cannot be immediately retracted.

That is, the conventional hydraulic circuit has poor responsiveness during suckback operation, causing a response delay, and the delay is not constant. In addition, screw 1 during plasticization
In order to improve the degree to which the front oil chamber 4 of the injection cylinder 2 is filled with oil when retracting, the pipe resistance between the tank 11 and the injection cylinder 2 can be reduced, but in order to do so, it is necessary to increase the pipe diameter. This meant that the equipment had become larger, including parts such as switching valve piping members. The present invention aims to solve these problems.

[0006]

[Means for Solving the Problems] The present invention provides an injection molding machine characterized in that oil discharged from the rear oil chamber 5 of the injection cylinder 2 during plasticization is supplied to the front oil chamber 4. Further, when the switching valve 8 for switching forward/backward movement of the injection cylinder 2 is in the neutral position, the oil discharged from the rear oil chamber 5 of the injection cylinder 2 can be supplied to the front oil chamber 4 via the switching valve 8. By being characterized by
Solve the above problems.

[0007]

[Operation] During plasticization when the switching valve 8 is neutral, the injection cylinder 2
Since the front oil chamber 4 and the rear oil chamber 5 are connected via the switching valve 8, the oil discharged from the rear oil chamber 5 when the screw 1 retreats is controlled to a low pressure by the back pressure regulating valve 9. while being sent to the front oil chamber 4. Since the oil sent to the front oil chamber 4 is under pressure, the front oil chamber 4 can be easily filled with oil.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for preventing delay in response to suckback operation of an injection molding machine and a hydraulic circuit thereof according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention. The present invention comprises a screw 1, a motor 6 for rotating the screw 1, an injection cylinder 2 for moving the screw 1 forward and backward, and a switching valve for supplying and discharging oil to a front oil chamber 4 and a rear oil chamber 5 of the injection cylinder 2. It consists of 8. Further, a back pressure regulating valve 9 is disposed between the rear oil chamber 2 of the injection cylinder 2 and the switching valve 8. During plasticization,
When the switching valve 8 is in a neutral state, it serves as a circuit that connects the front oil chamber 4 and the rear oil chamber 5 of the injection cylinder 2.

Next, a method for preventing a delay in the suckback operation response of the injection molding machine constructed as described above and the operation of its hydraulic circuit will be explained. When plasticization begins, the screw 1 rotates and retreats due to the reaction force of the force that sends the material 7 forward. The oil discharged from the rear oil chamber 5 due to the retraction of the screw 1 is controlled to a low pressure by the back pressure regulating valve 9, and a portion of the oil is sent to the front oil chamber 4 via the switching valve 8 in a neutral state. In this way, in the present invention, since pressurized oil is supplied to the front oil chamber 4 of the injection cylinder 2 during plasticization, the front oil chamber 4 does not become unfilled during plasticization, and after plasticization In the suckback operation, the screw 1 can immediately retreat.

0010

As is clear from the above description, according to the present invention, part of the oil discharged from the rear oil chamber 5 of the injection cylinder 2 is supplied to the front oil chamber 4 during the plasticizing process. With just a simple hydraulic circuit, the front oil chamber 4 of the injection cylinder 2 can be
It is possible to eliminate the response delay of suckback operation due to unfilled oil inside. Furthermore, even if the injection molding machine becomes larger, it is possible to control with excellent responsiveness without increasing the size of equipment such as switching valves and piping.

[Brief explanation of drawings]

[Fig. 1] Hydraulic circuit diagram showing an embodiment of the present invention

[Figure 2] Conventional hydraulic circuit diagram

[Explanation of symbols]

1...screw 2...Injection cylinder 3...Piston 4...Front oil chamber 5... Rear oil chamber 6...Motor 7...Materials 8...Switching valve 9...Back pressure adjustment valve 10...Pump 11...tank 12...Tank a... Solenoid b... Solenoid

Claims (2)

[Claims] 1. A sack for an injection molding machine, characterized in that oil discharged from a rear oil chamber (5) of an injection cylinder (2) during plasticization is supplied to a front oil chamber (4). How to prevent back movement response delay. [Claim 2] In an injection molding machine, an injection cylinder (
When the switching valve (8) that switches between forward and backward movement (2) is in neutral, the switching valve (8) transfers oil discharged from the rear oil chamber (5) of the injection cylinder (2) to the front oil chamber (4). A hydraulic circuit for preventing delay in response to suckback operation, characterized in that the hydraulic circuit can be supplied through the suckback operation.