JPH09155534A - Hydraulic circuit for metal injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the service life of a die by attaching a braking accumulator to a pipe line, absorbing a surge pressure generated through braking in the final process of injection and thereby reducing impact force and impact noise. SOLUTION: With the oil quantity changed of an electromagnetic flow regulating valve 11 and with an electromagnetic valve 12 shut for the purpose of minimizing the inertia force of an injection ram 2, a pressure is raised inside the pipe line D, braking the speed of the injection ram 2. With the pressure raised exceeding that of the braking accumulator 18, the pressure oil flows in the braking accumulator 18, actuating the injection ram 2 as a braking pressure. With the pressure oil in the pipe line D returning to an oil tank 3, a logic valve 19 is shut, so that the pressure of the braking accumulator 18 escapes to the oil tank 3 until reaching the set pressure of an electromagnetic pressure regulating valve 16. Consequently, the high speed advance of the injection ram 2 is braked by the logic valve 19 in the final injection process, with the surge pressure absorbed by the accumulator 18, enabling the impact force and the impact noise to be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit for a metal injection molding machine, and more particularly to a hydraulic circuit for an injection cylinder of a metal injection molding machine.

[0002]

2. Description of the Related Art Conventionally, in a metal injection molding machine, when a molten metal material (molten metal) is injected into a mold, the molten metal is rapidly cooled during the injection process, resulting in insufficient filling and defective products. There is. Therefore, in injection molding of metallic materials, an accumulator is usually used to control the speed of the injection ram to 1 m.
/ Sec to 5 m / sec, or a method of molding at a higher speed is adopted.

[0003]

However, when the molten metal is injected into the mold at high speed, a surge pressure is generated in the molten metal due to the inertial force of the injection ram in the final step of injection, the mold is slightly opened, and a molded product is formed. There was a problem that burrs were generated and had to be removed in a later process. Further, due to the inertial force, there are problems that a violent impact noise is generated and the life of the mold is shortened. Even if a speed switching command is issued in the final step of injection to suddenly reduce the speed of the injection ram, it cannot be reduced due to inertial force, and the same problem occurs. Thus, the inertial force in the final step of injection has a great influence on the strength of the machine and the quality of the molded product.

The present invention has been made in order to solve the above-mentioned problems of the prior art described above, and minimizes the inertial force of the injection ram to improve the life of the mold and the like. The purpose is to reduce the occurrence of burrs.

[0005]

In the hydraulic circuit of the injection cylinder of the metal injection molding machine according to the present invention, the front chamber of the injection cylinder is connected to one end, and the other end has a communicating position and a shut-off position for communicating with the hydraulic tank. A branch is connected to a solenoid valve connected to a logic valve, the other end of the logic valve is connected to a throttle valve via a conduit, and a brake accumulator is attached to the conduit. It is characterized by being

It is preferable that an electromagnetic pressure adjusting valve is attached to the outlet side of the throttle valve. It is preferable that an electromagnetic valve having a communication position and a cutoff position communicating with the hydraulic pump is connected to the pipeline to which the brake accumulator is attached via the pipeline.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 1, an injection cylinder 1 of a metal injection molding machine is provided with an injection ram 2 for filling a mold with a molten metal material so as to be movable back and forth. A front chamber 1a is formed in the portion and a rear chamber 1b is formed in the rear portion.

First, the construction of the hydraulic circuit of the injection cylinder 1 for operating the injection ram 2 will be described.

The discharge side of a hydraulic pump 4 that sucks the working oil in the oil tank 3 through the suction filter 3a and discharges it as high-pressure oil is connected to a check valve 5 via a pipe line A. An electromagnetic pressure control valve 6 is attached to the pipe line A. The check valve 5 is connected via a pipe B to a solenoid valve 7 having a communication position, i position, a b position, and a cutoff position. A pressure switch 8, an injection accumulator 9, and a safety valve 10 are sequentially attached to the pipe line B from the check valve 5 side. The electromagnetic valve 7 is connected to the rear chamber 1b of the injection cylinder 1 via a conduit C provided with an electromagnetic flow rate adjusting valve 11. When the solenoid valve 7 is set to the a position, the rear chamber 1b of the injection cylinder 1 is communicated with the hydraulic pump 4 and the injection ram 2 advances, and when the injection ram 2 is set to the b position,
The pressure oil in the rear chamber 1b returns to the tank. The injection cylinder 1
The front chamber 1a is connected to a solenoid valve 12 having a communication position a and a cutoff position via a pipe D.
When the solenoid valve 12 is set to the a position, the pressure oil in the front chamber 1a of the injection cylinder 1 returns to the tank.

A pipeline E is branched from a pipeline A on the discharge side of the hydraulic pump 4, and a solenoid valve 13 having a communication position a and a cutoff position is connected to the pipeline E.
The solenoid valve 13 is connected to a check valve 14 via a pipe line F. The check valve 14 is connected to a throttle valve 15 via a pipe line G. An electromagnetic pressure adjusting valve 16 is attached to the outlet side of the throttle valve 15. Further, a pressure switch 17 and a brake accumulator 18 are sequentially attached to the conduit G from the check valve 14 side. When the solenoid valve 13 is set to the a position, the brake accumulator 18 communicates with the hydraulic pump 4 and accumulates pressure.

A pipe line H is branched from the pipe line G, and one end of a logic valve 19 which opens toward the pipe line H is connected to the pipe line H, and the other end of the logic valve 19 is connected to the pipe line D. It is connected. The pressure is applied to the logic valve 19 in the closing direction by the pilot line from the line H.

In FIG. 1, a portion surrounded by a chain line is a brake circuit hydraulic circuit added by the present invention to the hydraulic circuit of the conventional injection cylinder 1, and this brake circuit hydraulic circuit is blocked. When the hydraulic block 20 for the brake circuit is converted into the injection cylinder 1,
Pressure switch 17, brake accumulator 18, F
Without using rubber pipes for connection with pipes, etc., flanges,
Since a metal joint or the like can be used, the pressure of the hydraulic circuit for the brake circuit can be increased. Next, the operation of the hydraulic circuit of the injection cylinder 1 described above will be described.

Prior to the injection process by the injection ram 2, when the solenoid valves 7 and 13 are set to the shutoff positions, the pressure oil from the hydraulic pump 4 is accumulated in the injection accumulator 9 at the pressure set by the pressure switch 8. The safety valve 10 operates when an abnormal pressure is reached. When the solenoid valve 7 is turned off and the solenoid valve 13 is turned on, the brake accumulator 1
The pressure oil from the hydraulic pump 4 is accumulated at 8 at the set pressure of the pressure switch 17.

Next, in the injection process, when the electromagnetic valve 13 is set to the shut-off position and the electromagnetic valve 7 is set to the a-position, the electromagnetic flow control valve 1
The pressure oil having the oil amount set in 1 is sent to the rear chamber 1b of the injection ram 2, and the injection ram 2 advances at a high speed (1 m / sec to 5 m / sec).

In the final step of injection, in order to minimize the inertial force of the injection ram 2, the speed of the injection ram 2 is usually required to be 0.1 m / sec or less. Therefore, the amount of oil of the electromagnetic flow rate adjusting valve 11 is changed, and at the same time, the electromagnetic valve 12 is set to the shutoff position. As a result, the pressure in the pipe D, which is the drain pipe, increases, and the speed of the injection ram 2 is braked. When the pressure rises and exceeds the pressure of the brake accumulator 18, the logic valve 19 opens and the pressure oil flows into the brake accumulator 18 and at the same time, flows through the throttle valve 15 and the electromagnetic pressure adjusting valve 16 to the oil tank 3. However, the throttle valve 15 causes a time delay, and the oil amount and the pressure corresponding to this delay time are further increased by the brake accumulator 16.
Is stored in the injection ram 2 and acts as a brake pressure on the injection ram 2.

This delay time is controlled by a timer equipped in a control device (not shown), and when the timer expires, the solenoid valve 1
2 is in position a, and the pressure oil in the conduit D, which is the drain conduit, returns to the oil tank 3. When the pressure oil in the pipe line D returns to the oil tank 3, the logic valve 19 is closed, and the pressure of the brake accumulator 18 passes through the throttle valve 15 to reach the set pressure of the electromagnetic pressure control valve 16 until it reaches the hydraulic tank 3. Escape and prepare for the next injection step.

[0018]

Since the present invention is configured as described above, the logic valve instantaneously brakes the high speed advance of the injection ram in the final step of injection, and the surge pressure generated is absorbed by the accumulator. Thus, the inertial force of the injection ram can be minimized, the impact force and the impact noise can be reduced, the life of the mold and the like can be improved, and the occurrence of burrs can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a hydraulic circuit of an injection cylinder of a metal injection molding machine.

[Explanation of symbols]

 1 injection cylinder 1a front chamber 1b rear chamber 2 injection ram 3 oil tank 3a suction filter 4 hydraulic pump 5, 14 check valve 6, 16 electromagnetic pressure adjusting valve 7, 12, 13 electromagnetic valve 8, 17 pressure switch 9 injection accumulator 10 Safety valve 11 Electromagnetic flow control valve 15 Throttle valve 18 Accumulator for brake 19 Logic valve 20 Hydraulic block for brake A to H pipeline

Claims (3)

[Claims] 1. A communication position in which a front chamber (1a) of the injection cylinder (1) is connected to one end and a hydraulic tank (3) is connected to the other end in a hydraulic circuit of an injection cylinder (1) of a metal injection molding machine. And a logic valve (19) is branched and connected to a pipe line (D) to which a solenoid valve (12) having a shut-off position is connected, and the other end of the logic valve (19) has a pipe line (H,
A hydraulic circuit of a metal injection molding machine, characterized in that a throttle valve (15) is connected via G), and a brake accumulator (18) is attached to the pipe line (G). 2. The hydraulic circuit of a metal injection molding machine according to claim 1, wherein an electromagnetic pressure regulating valve (16) is attached to the outlet side of the throttle valve (15). 3. The brake accumulator (18)
The hydraulic pump (4) in the pipe (G) where
Solenoid valve (13) having a communicating position and a shut-off position communicating with the
3. The hydraulic circuit of the metal injection molding machine according to claim 1, wherein the hydraulic circuit is connected via a pipe line (F).