JPS627459Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement in the hydraulic circuit of an injection molding machine having at least one pair of injection cylinders that move a screw in the axial direction.

FIG. 1 shows a hydraulic circuit of a conventional general injection molding machine. In the figure, 1 is an injection molding barrel;
Reference numeral 2 denotes a feed screw provided within the barrel 1, which is directly connected to the hydraulic motor 3 and is capable of moving in the axial direction and rotating within the barrel 1. 4 and 5 are a pair of injection cylinders provided on both sides of the barrel 1;
They have portoy, b, and ha and d, respectively.

Next, the operation of the hydraulic circuit of the injection molding machine during high-speed injection will be explained. Now, when solenoid C of electromagnetic directional control valve 6 is energized, solenoid B of electromagnetic valve 7 is de-energized, so pilot pressure oil flows from port a to port b to pilot valve 8.
Ports c and d are communicated with each other, and oil from the pump is sent from port c to port d to ports I and C of injection cylinders 4 and 5. On the other hand, the oil from the pumps passes through ports e and f, joins the oil from the pump, and is sent to ports a and c.

As the pistons of the injection cylinders 4 and 5 move forward,
The return oil from ports 2 and 2 is returned to an oil tank 10 via a pilot check valve 9 and then to an oil tank 11 from a port g of a pilot valve 8.

However, in the injection cylinders 4 and 5 of this mechanism, the retraction side cross-sectional area _S2 is larger than the injection side cross-sectional area _S1 , so the amount of oil returned from the portholes and d increases, resulting in excessive pressure loss. . In order to prevent this, it is necessary to increase the capacity of the pilot check valve 9 and the electromagnetic directional control valve 12 including the pilot circuit 16, or to add an additional valve in parallel to release the return oil to the tank. Ta.

Next, the operation when the pistons of both injection cylinders 4 and 5 retreat will be explained. From the above state, when the solenoid C of the electromagnetic directional control valve 6 is deenergized, the pump and the discharge oil from the pump are cut off, and the solenoid B of the electromagnetic valve 7 and the solenoid A of the electromagnetic valve 13 are energized, the pilot pressure oil is , flows from port a to port h, and pressure oil from the pump is sent from port c to port g to port ro and d.

On the other hand, return oil from ports I and C of the injection cylinders 4 and 5 is returned to the oil tank 11 from port D of the pilot valve 8. At this time, the electromagnetic valve 13
Since the solenoid A is energized, the pilot pressure oil from the solenoid valve 13 to the pilot check valve 9 is cut off, so that the pressure oil from the pump does not escape from the pilot check valve 9. In this case, a special solenoid A of the electromagnetic valve 13 is required, which has the disadvantage that the electric control circuit becomes complicated.

In the figure, reference numeral 14 is a relief valve, which is a safety valve for the porthole and the second line of the injection cylinders 4 and 5.

The present invention was proposed with the aim of eliminating the drawbacks of the hydraulic circuit in the conventional injection molding machine described above. Barrel 1, electromagnetic switching valve 6 and pilot circuit 1
A pressure oil source (pump) that drives the pistons of at least one pair of injection cylinders 4, 5 in the axial direction via an electromagnetic switching valve 12 including an injection cylinder 4, 6;
5, a relief valve 14 interposed in the circuit that returns one of the return oil to the oil tank 18, and the above-mentioned electromagnetic switching valve 1.
In the hydraulic circuit of an injection molding machine equipped with a pilot check valve 9 interposed in the circuit between the pilot valve 8 of the second pilot circuit 16 and the oil tank 10, the vent hole i provided in the relief valve 14 is and the pilot circuit 16, and a second pilot circuit 19 is provided between the pilot circuit 16 and the pilot check valve 9,
The present invention relates to a hydraulic circuit for an injection molding machine characterized in that a pilot type switching valve 20 for opening and closing the pilot check valve 9 is interposed in the second pilot circuit 19.

Hereinafter, the present invention will be explained in detail with reference to an embodiment shown in FIG. In the figure, 1 is an injection molding barrel, 2 is a feed screw provided in the barrel 1, 3 is a hydraulic motor, 4 and 5 are a pair of injection cylinders, 6 is an electromagnetic directional valve, and 7 is an electromagnetic valve. , 8 is a pilot valve, ,, is a pump, 9 is a pilot check valve, 10 and 11 are oil tanks, 12 is an electromagnetic directional control valve including a pilot circuit 16, and 14 is a relief valve. The mutually related structure is almost the same as that of the hydraulic circuit in the conventional injection molding machine shown in FIG. 1 above. 15 is a vent circuit that connects the vent hole i of the relief valve 14 and the pilot circuit 16 of the electromagnetic directional valve 12, and the vent circuit 15 is connected to the port h when the solenoid B of the electromagnetic valve 7 is de-energized. The oil tank 17 is in communication with the oil tank 17, and the relief valve 14 is controlled so that the return oil from the ports 1 and 2 is also returned to the oil tank 18. Reference numeral 19 denotes a second pilot circuit that connects the pilot type switching valve 20 and the pilot circuit 16, and the second pilot circuit 19 performs a pilot check when reversing (when the solenoid B of the electromagnetic valve 7 is energized). Close the valve 9 and open the oil tank 10.
It is designed to operate in a way that prevents oil from leaking.

The hydraulic circuit in the injection molding machine of the present invention is
The conventional hydraulic circuit shown in the figure is characterized in that the vent circuit 15 and the second pilot circuit 19 having the above configuration are arranged as described above.

Next, the difference between the operation of the hydraulic circuit of the present invention and the conventional hydraulic circuit during high-speed injection will be explained. In this case, since the solenoid B of the electromagnetic valve 7 is de-energized, the vent hole i of the relief valve 14 The circuit 15 and the pilot circuit 16 are connected to an oil tank 17 via a port h, and a portion of the return oil from the ports 2 and 2 is returned to the oil tank 18. Therefore, the pressure loss of the return oil is reduced, and the injection cylinder 4,
It is possible to reduce the energy loss on the 5 side, or to make the pilot check valve 9 smaller or eliminate it while leaving the pressure loss of the return oil as is.

On the other hand, when the pistons of the injection cylinders 4 and 5 retreat, the solenoid B of the electromagnetic valve 7 is energized.
Port h and port a communicate with each other, and pilot pressure P acts on vent hole i, closing relief valve 14.
Furthermore, the pilot pressure P is controlled by the pilot switching valve 2.
0 also closes the pilot check valve 9, so that the pressure oil from the pump does not escape from the relief valve 14 and the pilot check valve 9, and the backward movement is performed smoothly.

Therefore, according to the present invention, the electromagnetic valve 13 including the solenoid A, which was required in the conventional hydraulic circuit, is no longer necessary, and the electric control circuit is significantly simplified compared to the conventional one, which is a practical effect. be able to.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a conventional hydraulic circuit, and FIG. 2 is a system diagram of an embodiment of the present invention. In Fig. 2, 1: barrel for injection molding, 2:
Feed screw, 3: hydraulic motor, 4, 5: injection cylinder, 6: electromagnetic directional valve including solenoid C, 7: electromagnetic valve including solenoid B, 8: pilot valve, 9: pilot check valve, 1
0, 11, 17, 18: oil tank, 12: electromagnetic directional control valve including pilot circuit 16, 14: relief valve, 15: vent circuit, 19: second pilot circuit, 20: pilot type directional control valve, P : Pilot pressure.

Claims (1)

[Scope of utility model registration request] An injection molding barrel 1 that is directly connected to a hydraulic motor 3 and has a built-in feed screw 2 that moves in the axial direction;
A pressure oil source (pump) that drives the pistons of at least a pair of injection cylinders 4, 5 in the axial direction via an electromagnetic switching valve 6 and a solenoid switching valve 12 including a pilot circuit 16; one of the injection cylinders 4, 5; a relief valve 14 interposed in the circuit that returns the return oil to the oil tank 18; a pilot valve 8 of the pilot circuit 16 of the electromagnetic switching valve 12 and the oil tank 10;
In a hydraulic circuit of an injection molding machine, which is equipped with a pilot check valve 9 interposed in the circuit between the relief valve 14 and the pilot circuit 16, the vent hole i provided in the relief valve 14 and the pilot circuit 16 are connected. A second pilot circuit 19 is provided between the pilot circuit 16 and the pilot check valve 9, and a pilot type switching valve 20 for opening and closing the pilot check valve 9 is interposed in the second pilot circuit 19. A hydraulic circuit in an injection molding machine characterized by: