JPH0433618B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an injection side hydraulic circuit of an injection molding machine.

(Prior art) Fig. 1 shows a hydraulic circuit diagram on the injection side of a conventional injection molding machine, and the circuit includes hydraulic pumps A, which supply pressure oil,
B, and an electromagnetic switching valve 1 that switches the pressure oil supply route.
2, and a pressure control valve 3 (combined as a safety relief valve for back-up and a relief valve for injection brake) for controlling pressure.

Now, in FIG. 1, when the solenoid a of the electromagnetic switching valve 1 is energized, the pressure oil supplied from the hydraulic pump A is sent into the E chamber of the injection cylinder 5, and the injection ram 4 moves forward to perform an injection operation. . At this time, the solenoid b of the electromagnetic switching valve 2 is energized, and the oil in the D chamber is returned to the tank 6 through the electromagnetic switching valve 2.
Also, if solenoid b is turned off during high-speed injection operation, D
The oil in the chamber is relieved by being controlled to a predetermined pressure by the pressure control valve 3, and the injection brake is applied because the inertia during high-speed injection is absorbed by the control pressure.

In addition, in the back-back operation (screw retraction operation to prevent resin stringing and dolling), when the solenoid c of the electromagnetic switching valve 2 is energized, the pressure oil supplied from the hydraulic pump B is controlled to a predetermined pressure by the pressure control valve 3. The injection ram 4 is controlled to move back into the D chamber of the injection cylinder, and the screw 7 moves back. Note that 19 is a hydraulic motor, and 29 is a screw cylinder.

However, in the hydraulic circuit shown in FIG. 1, it is necessary to return a large amount of hydraulic oil in the D chamber of the injection cylinder 5 to the tank 6 through the electromagnetic switching valve 2 during injection operation.
In order to minimize the pressure difference when the hydraulic oil passes through the electromagnetic switching valve 2, a large electromagnetic switching valve is required.
Also, during injection braking, when a large volume of hydraulic oil in the D chamber passes through the pressure control valve 3, a large pressure control valve is required to prevent abnormal pressure from occurring that could lead to equipment damage. becomes. Generally, the suction speed is slower than the injection speed, so the amount of oil required is also smaller. Therefore, the pressure control valve 3 may be small. Similarly, if we consider only the back-to-back operation, the electromagnetic switching valve 2 can be a small valve, but the conventional circuit shown in Figure 1 requires a large pressure control valve and electromagnetic switching valve to accommodate the injection operation. .

(Problems to be Solved by the Invention) The present invention improves the shortcomings of the conventional circuit, improves the positional accuracy of speed switching (from high speed to low speed) during injection, reduces the defective rate of molded products, and The purpose of this invention is to provide a circuit configuration that can be used to support the following.

(Means for Solving the Problems) Therefore, the present invention provides a first hydraulic circuit that supplies pressure oil from a first hydraulic pump to chamber D of an injection cylinder;
In the injection side hydraulic circuit, the injection side hydraulic circuit has a second hydraulic circuit that supplies pressure oil from a second hydraulic pump to the E chamber of the injection cylinder, and is provided with first and second electromagnetic switching valves on each of the hydraulic circuits, respectively. A normally open logic valve is provided on the circuit between the first electromagnetic switching valve on the first hydraulic circuit and the D chamber, and a check valve for flowing hydraulic pressure toward the D chamber is provided on a circuit parallel to the circuit including the logic valve. , a circuit connecting the circuit having the logic valve and the circuit having the check valve is provided, and a safety relief valve for a suction circuit is provided on a circuit different from the first hydraulic circuit between the circuit and the first electromagnetic switching valve. It is equipped with a pressure control valve that also serves as a relief valve for the injection brake circuit, and is used as a means to solve the problem.

(Function) Now, in the above configuration, when the solenoid of the first electromagnetic switching valve is energized during the back-back operation,
Pressure oil supplied from the first hydraulic pump is controlled to a predetermined pressure by a pressure control valve, and when the logic valve is closed, it is sent into the D chamber of the injection cylinder through the check valve, and the injection ram is retreated. Also, during injection operation, when the solenoid of the first electromagnetic switching valve is energized, the discharge passage to the logic valve is narrowed and back pressure is created in the D chamber of the injection cylinder.The back pressure absorbs the inertia during injection, and the injection The brakes are applied.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings. Fig. 2 shows an injection side hydraulic circuit of an injection molding machine showing an embodiment of the present invention, and the circuit includes a hydraulic pump A that supplies pressure oil, B, electromagnetic switching valves 1 and 12 that switch the pressure oil supply route, pressure control valve 13 that controls the pressure of the supply oil (combined as a safety relief valve for the back-back circuit and a relief valve for the injection brake circuit), and prevents backflow. It consists of a check valve 14 and a normally open logic valve 15 that sucks and drains a large amount of hydraulic oil.

Here, the operation of the embodiment shown in FIG. 2 will be explained. First, when the solenoid a of the electromagnetic switching valve 1 is energized, the pressure oil supplied from the hydraulic pump A is sent into the E chamber of the injection cylinder 5, and the injection ram 4 moves forward to perform an injection operation. At this time, the oil in the D chamber of the injection cylinder 5 is returned to the tank 16 through the normally open logic valve 15.

During back-back operation, when the solenoid d of the electromagnetic switching valve 12 is energized, the pressure oil supplied from the hydraulic pump B is controlled to a predetermined pressure by the pressure control valve 13, pushing up the poppet 17 of the logic valve 15 and closing the opening 18. At the same time, it is fed into the D chamber of the injection cylinder 5 through the check valve 14, and the injection ram 4 moves back (because the injection ram 4 and the screw 7 are connected, the screw 7 moves back). Become). Furthermore, during the injection operation, the solenoid d of the electromagnetic switching valve 12
When energized, poppet 1 of logic valve 15
7 is pushed up and the passage between chamber D and tank 16 is narrowed, so back pressure is built up in chamber D, which absorbs the inertia during ejection and applies an injection brake.

(Effects of the Invention) As explained in detail above, the present invention provides a pressure control valve consisting of a normally open type logic valve and a balanced piston type relief valve that serves as a safety relief valve for a suction circuit and a relief valve for an injection brake circuit. As a result, even if the solenoid of the electromagnetic switching valve is energized and the injection operation is performed, if the pressure in the D chamber of the injection cylinder rises above a certain level, the poppet of the logic valve will be pushed in the opening direction. Since the oil in room D is returned to the tank,
An injection safety circuit (maximum pressure regulation) is configured.

Furthermore, by using a normally open type logic valve, the pressure control valve and electromagnetic switching valve can be configured with small valves (as long as they can control the amount of oil required for back-up operation). Therefore, logic valve,
By integrating the check valve, the pressure control valve, and the first electromagnetic switching valve (within the two-dot chain line F), the device can be made smaller and simpler.

[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 the main parts of the figure, A...Second hydraulic pump,
B...First hydraulic pump, 1...Second electromagnetic switching valve, 4
... injection ram, 5 ... injection cylinder, 7 ... screw,
12...First electromagnetic switching valve, 13...Pressure control valve, 1
4...Check valve, 15...Logic valve, 16...Tank, 17...Poppet.

Claims (1)

[Claims] 1 A first hydraulic circuit that supplies pressure oil from a first hydraulic pump to chamber D of the injection cylinder, and a second hydraulic circuit that supplies pressure oil from a second hydraulic pump to chamber E of the injection cylinder, and In the injection side hydraulic circuit, which includes first and second electromagnetic switching valves on the hydraulic circuit,
A normally open logic valve is provided on the circuit between the first electromagnetic switching valve on the first hydraulic circuit and the D chamber, and a check valve for flowing hydraulic pressure toward the D chamber is provided on a circuit parallel to the circuit having the logic valve. In addition, a circuit connecting the circuit having the logic valve and the circuit having the check valve is provided, and a safety relief valve for a back-back circuit is provided on a circuit different from the first hydraulic circuit between the circuit and the first electromagnetic switching valve. An injection side hydraulic circuit for an injection molding machine, characterized in that a pressure control valve that also serves as a relief valve for the injection brake circuit is provided.