JPH0438572B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an injection side hydraulic circuit for an injection molding machine that is effective when applied to an Egan type (a type in which two cylinders are arranged vertically or horizontally in parallel) injection molding machines.

FIG. 1 shows an example of an injection-side hydraulic circuit in a conventional injection molding machine, in which 1 is a hydraulic motor for rotating the screw 2, 3 is a first hydraulic pump that supplies pressure oil to the hydraulic motor 1, and 4 is a hydraulic circuit for injection-side injection molding. This is a second hydraulic pump that supplies pressure oil to an Egan type injection cylinder 5 via an electromagnetic switching valve 6.

During plasticization, pressurized oil is supplied from the first hydraulic pump 3 to the hydraulic motor 1 to rotate the screw 2 and feed the molten resin into the chamber 8 of the screw cylinder 7 at the tip of the screw. The screw 2 is retracted by the resin pressure of this resin.

Since the screw 2 and the ram 9 of the injection cylinder 5 are connected, when the screw 2 moves back, the ram 9 also moves back in sync with this movement. When the ram 9 retreats, it is necessary to suck hydraulic oil to fill the space created in the chamber 10 of the injection cylinder 5, and this hydraulic oil is pumped from the tank 11 through the electromagnetic switching valve 6 with solenoid a de-energized as shown in the figure. is sucked into chamber 10.
Further, during injection, the hydraulic oil in the chamber 10 is returned to the tank 11 via the electromagnetic switching valve 6.

On the other hand, the back-back operation (screw retraction operation to prevent stringing of the resin and prevention of doodling) is performed by energizing the solenoid a of the electromagnetic switching valve 6 using the pressure oil supplied from the second hydraulic pump 4, as shown in FIG. The state is changed, the injection cylinder 5 is fed into the chamber 10, and the screw 2 is moved back.

However, in the circuit shown in FIG. 1, it is necessary to return a large amount of hydraulic oil in the chamber 10 of the injection cylinder 5 to the tank 11 via the electromagnetic switching valve 6 during injection, and at this time, the pressure difference when passing through the electromagnetic switching valve 6 Therefore, it was necessary to make the electromagnetic switching valve 6 a large electromagnetic switching valve.

Furthermore, when drawing hydraulic oil from the tank 11 into the chamber 10 of the injection cylinder 5 during plasticization, a large volume of hydraulic oil must be passed through the electromagnetic switching valve 6 with a pressure difference of less than 1 kg/cm ² . Also, a large electromagnetic switching valve 6 was required. Therefore, the circuit shown in Fig. 1 requires a large electromagnetic switching valve as described above, making it difficult to downsize and simplify the device, and it is difficult to increase the specs (plasticizing ability, injection rate) of the injection molding machine. It was also difficult to respond.

The present invention was proposed in order to solve the above-mentioned conventional drawbacks, and by installing a logic valve that can flow a large amount in a small space, the present invention can be made smaller, simpler, plasticizing ability, and injection rate. The object of the present invention is to provide an injection side hydraulic circuit for an injection molding machine that can easily correspond to the specifications of the injection molding machine.

In order to achieve this object, the present invention provides an injection molding machine having an injection cylinder that advances the screw by supplying pressure oil to a first chamber on the side that advances the ram. A passage for the hydraulic oil is provided in the second chamber to suck the hydraulic oil from the tank during plasticization and return it to the same tank during injection, and a normally open logic valve is disposed on the passage. When the solenoid of the switching valve is energized, it connects to the passage of pressure oil supplied from the hydraulic pump, and when pressure oil is supplied from the passage to the opening, it moves against the biasing force and enters the tank. It has a poppet that closes a communicating passage, branches from the passage connected to the opening of the logic valve and communicates with the second chamber, and oil flows from the hydraulic pump to the second chamber, but oil does not flow from the two chambers. It is an object of the present invention to provide an injection side hydraulic circuit for an injection molding machine, which is configured to include a circuit having a check valve that does not allow oil to flow.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows an embodiment of the present invention.
is rotated by a hydraulic motor 1 driven by a first hydraulic pump 3, and during plasticization, the molten resin is sent into the chamber 8 of the screw cylinder 7 at the tip of the screw, and the screw 2 is retracted by the resin pressure of this resin.

The ram 9 of the injection cylinder 5 is connected to the screw 2, and moves forward and backward in synchronization with the forward and backward movement of the screw 2. During injection, the first ram 9 on the side that advances the ram 9
The screw 2 is advanced by pressure oil supplied to the chamber 12. Also, when the screw 2 is retracted during plasticization, the tank 1 is placed in the second chamber 13 on the side where the ram is retracted.
4 through the first opening 16 of the logic valve 15, the chamber 17, and the passage 18. In addition, as mentioned above, when the ram 9 moves forward during injection, a large amount of hydraulic oil in the second chamber 13 flows into the passage 1.
8, chamber 17, and return to tank 14 via first opening 16. Said logic valve 15 is normally open and is arranged to normally communicate passage 18 with tank 14.

Further, the second opening 19 of the logic valve 15 is connected to a passage 20, and the passage 20 is connected to the tank 22 when the solenoid a of the electromagnetic switching valve 21 is de-energized.
However, when the solenoid a is energized, it is communicated with the second hydraulic pump 23, and when the pressure oil from the second hydraulic pump 23 is supplied to the opening 19, the spring is normally activated. 24, the poppet 25, which is in the position shown in the drawing, is pushed up against the force and closes the first opening 16.

26 is a circuit branched from the passage 20 and connected to the passage 18, and an orifice 27 is installed on the circuit 26.
A check valve 28 is provided that allows oil from the hydraulic pump 23 to flow into the second chamber 13, but does not allow oil to flow from the second chamber 13.

Next, to explain the operation, during plasticization, pressure oil from the first hydraulic pump 3 is supplied to the hydraulic motor 1 to rotate the screw 2, and the molten resin is sent into the chamber 8 at the tip of the screw, and the screw 2 is moved by the resin pressure. fall back. At this time, a space is created in the second chamber 13, so
To fill the space, a large amount of hydraulic fluid is drawn from the tank 14 through the first opening 16 of the logic valve 15, the chamber 17, and the passage 18.

Next, during injection, pressure oil is supplied to the first chamber 12 of the injection cylinder 5 to advance the ram 9, and a large amount of hydraulic oil in the second chamber 13 is supplied to the passage 18 and the logic valve 15.
is returned to the tank 14 through the chamber 17 and the first opening 16.

Next, during back-to-back operation, the solenoid switching valve 21
When solenoid a is energized, pressure oil flows from the hydraulic pump 23 into the passage 20 and is supplied to the second opening 19 of the logic valve 15, pushing up the poppet 25 against the spring 24 and closing the first opening 16. At the same time, the pressure oil in the passage 20 passes through the orifice 27 of the circuit 26 and the check valve 28 to the passage 18.
At this point, since the first opening 16 is closed, all of the pressure oil is directly fed into the second chamber 13 of the injection cylinder 5, and a suction operation is performed.

As explained in detail above, the present invention provides a hydraulic oil passage in the second chamber on the side where the ram of the injection cylinder is retracted, which sucks hydraulic oil from the tank during plasticization and returns it to the tank during injection. Since a normally open logic valve is installed in the tank, a large volume of hydraulic oil can be sucked from the tank and returned to the tank without passing through the solenoid directional valve as in the past, so the solenoid directional valve can be made larger. There's no need. Furthermore, since the logic valve used in the present invention allows a large volume of hydraulic oil to flow in a small space, it is possible to downsize and simplify the device, and it is also possible to easily respond to spec-up of an injection molding machine. The invention is also particularly advantageous for Egan type injection units.

[Brief explanation of drawings]

FIG. 1 is an injection side hydraulic circuit diagram of a conventional injection molding machine, and FIG. 2 is an injection side hydraulic circuit diagram of an injection molding machine showing an embodiment of the present invention. Explanation of main parts of the diagram 1...Hydraulic motor, 2...
...Screw, 5...Injection cylinder, 12...1st
Room, 13... Second room, 14... Tank, 15...
Logic valve, 16...first opening, 18...
Passage, 19... Second opening (other opening), 20...
...Passage (pressure oil passage), 21...Solenoid switching valve, 2
3...Second hydraulic pump (hydraulic pump), 24...
Spring, 25...Poppet, 26...Circuit,
28...Check valve, a...Solenoid.

Claims (1)

[Claims] 1. In an injection molding machine that has an injection cylinder that advances the screw by supplying pressure oil to the first chamber on the side that advances the ram, pressure oil is supplied from the tank during plasticization to the second chamber of the same injection cylinder on the side that retracts the ram. A hydraulic oil passage is provided to suck oil and return it to the same tank during injection, and a logic valve that is normally open is installed on the passage. a poppet connected to a passage for pressure oil supplied from a pump, and closing the passage communicating with the tank by moving against an urging force when pressure oil is supplied from the passage to the opening; A circuit including a check valve that branches from a passage connected to the opening of the logic valve and communicates with the second chamber, and allows oil to flow from the hydraulic pump to the second chamber, but does not flow oil from the second chamber. An injection side hydraulic circuit for an injection molding machine, characterized in that it is provided with: