JPH0719774Y2 - Hydraulic circuit of injection cylinder in injection molding machine - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit for an injection cylinder, which is mainly applied to a small injection molding machine.

[0002]

2. Description of the Related Art A hydraulic circuit of an injection cylinder in a small injection molding machine is known as shown in FIG. That is, reference numeral 1 in FIG. 2 is an injection cylinder. The injection cylinder 1 moves the injection screw 3 inserted in the heating cylinder 2 forward and backward (left and right in FIG. 2). A hydraulic pump 5 is connected to the retreating cylinder chamber 1a of the injection cylinder 1 via an electromagnetic switching valve 4, and a hydraulic pump 5 is connected to the advancing cylinder chamber 1b via another electromagnetic switching valve 6. . A variable throttle valve 7 is provided between the hydraulic pump 5 and the electromagnetic switching valve 4, and a hydraulic motor 8 is connected to the hydraulic pump 5 via an electromagnetic switching valve 6. The hydraulic motor 8 rotates the injection screw 3 in the circumferential direction. Reference numeral 9 is a nozzle, and 10 is a mold.

In the injection molding machine having the above hydraulic circuit, in the automatic operation, the solenoid a of the electromagnetic switching valve 6 is turned on in the injection process, the injection screw 3 moves leftward in the drawing, and the injection screw 3 advances from the nozzle 9. Resin is injected into the mold 10. In the automatic supply process, the solenoid b of the electromagnetic switching valve 6 is turned on and the hydraulic motor 8 operates to rotate the injection screw 3. Further, when automatically removing the internal pressure of the heating cylinder 2, the solenoid b of the electromagnetic switching valve 4 is turned on, and the injection screw 3
Will retreat.

The injection molding machine is usually operated manually when it is started up or the resin is changed. In the case of manual operation, switching of both electromagnetic switching valves 6 and 4 in the injection process and removal of internal pressure is the same as in the case of automatic operation, but in the supplying process, the solenoid b of the electromagnetic switching valve 6 is turned on and The solenoid of the electromagnetic switching valve 4 is turned on to retract the injection screw 3. The reason for operating in this way is
When starting up or changing the resin, the nozzle 9 of the heating cylinder 2 is placed in the mold 1.
Injection screw 3 that is separated from 0 and has a small diameter
In a small-sized injection molding machine having, the relationship between the plasticizing ability of the injection screw 3 and the nozzle hole diameter, and the mechanical sliding resistance of the injection screw 3 do not fall below a predetermined value, so that the injection screw 3 does not easily move backward, As a result, resin leaks from the nozzle 9.

[0005]

As can be understood from the above description, in the conventional hydraulic circuit, the working oil passes through the same circuit during internal pressure removal during automatic operation and during the supply process during manual operation. Backward cylinder chamber 1 of injection cylinder 1
sent to a. For this reason, the variable throttle valve 7 is adjusted during manual operation to make the retreat speed of the injection cylinder 1 appropriate, but when shifting to automatic operation, the variable throttle valve 7 is readjusted and returned to its original state. It has to be done, which is very annoying and inconvenient.

An object of the present invention is to provide a hydraulic circuit of an injection cylinder in an injection molding machine, which does not require adjustment of the variable throttle valve when switching from automatic operation to manual operation and from manual operation to automatic operation. To do.

[0007]

In order to achieve the above object, according to the present invention, a hydraulic pump is connected via a first electromagnetic switching valve to a retreating cylinder chamber of an injection cylinder that advances and retracts an injection screw. In addition, in the hydraulic circuit of the injection cylinder in which the hydraulic pump is connected to the forward cylinder chamber of the injection cylinder through the second electromagnetic switching valve, the first electromagnetic switching valve is substantially switched to the 3-position 4-port electromagnetic switching. A valve, and the first electromagnetic switching valve is communicated with the oil tank when the first electromagnetic switching valve is neutral, and is communicated with the hydraulic pump when one solenoid of the first electromagnetic switching valve is turned on. Together with the first pipe that is shut off when the other solenoid of the first electromagnetic switching valve is turned on, and the solenoid connected to the oil tank when the first electromagnetic switching valve is neutral and one solenoid valve of the first electromagnetic switching valve is connected. Connected to the retreat side cylinder chamber of the injection cylinder by a second pipe that is cut off when is turned on and is connected to the hydraulic pump when the other solenoid of the first electromagnetic switching valve is turned on, Second above
In the pipe, a check valve that frees the flow of hydraulic oil from the reverse side cylinder chamber to the first electromagnetic switching valve and stops the reverse flow, and a flow rate of hydraulic oil that flows from the first electromagnetic switching valve to the reverse side cylinder chamber are provided. A variable throttle valve for adjustment is provided in parallel.

[0008]

When the internal pressure is removed in the automatic operation, one solenoid of the first electromagnetic switching valve is turned on, and the working oil is sent to the retreating cylinder chamber of the injection cylinder through the first pipe. Also, in the supply process during manual operation, the other solenoid of the first electromagnetic switching valve is turned on, and hydraulic oil is sent to the reverse side cylinder chamber of the injection cylinder through the second pipe. As described above, since different pipes are used in the internal pressure removal in the automatic operation and the supply step in the manual operation, it is not necessary to adjust the variable throttle valve individually.

[0009]

1 shows an embodiment of the present invention. Note that FIG.
2 corresponding to those in FIG. 2 are denoted by the same reference numerals and detailed description thereof will be omitted.

The electromagnetic switching valve 12 provided between the retreating cylinder chamber 1a of the injection cylinder 1 and the hydraulic pump 5 is a three-position four-port electromagnetic switching valve. The A port of the solenoid operated directional control valve 12 is connected to the injection pipe 1 through the first pipe 13.
Is connected to the retreat side cylinder chamber 1a, and the B port is connected to the retreat side cylinder chamber 1a by the second pipe 14.
The second pipe 14 flows from the solenoid valve 1 to the reverse side cylinder chamber 1a, and the check valve 15 that allows the hydraulic oil to freely flow from the reverse side cylinder chamber 1a to the solenoid changeover valve 12 to stop the reverse flow. Variable throttle valve 16 for adjusting the flow rate of hydraulic oil
And are provided in parallel.

The relationship between the electromagnetic switching valve 12 and the pipes 13 and 14 will now be described. When the electromagnetic switching valve 12 is in the neutral position, both the pipes 13 and 14 are connected to the oil tank, and the electromagnetic switching valve 12 is connected. When one solenoid a is excited, the first
When the pipe 13 is connected to the hydraulic pump 5, the second pipe 14 is shut off, and the other solenoid b of the electromagnetic switching valve 12 is excited (needless to say, the solenoid a is demagnetized). 13 is cut off, and the second pipe 14 is connected to the hydraulic pump 5. Reference numeral 17 is a relief valve.

Next, the operation of the hydraulic circuit of the injection cylinder in the injection molding machine configured as described above will be described. The solenoid a of the electromagnetic switching valve 6 is turned on in the injection process of the automatic operation, and the solenoid b of the electromagnetic switching valve 6 is turned on in the supply process of the automatic operation, as in the conventional hydraulic circuit of FIG. . When automatically removing the internal pressure of the heating cylinder 2, the solenoid a of the electromagnetic switching valve 12 is turned on. As a result, the hydraulic oil of the hydraulic pump 5 is sent to the retreat side cylinder chamber 1a of the injection cylinder 1 through the first pipe 13,
The injection screw 3 is retracted.

Further, the switching of both the electromagnetic switching valves 6 and 12 in the injection process of the manual operation and the removal of the internal pressure is the same as in the automatic operation. However, in the manual supply process, the solenoid b of the electromagnetic switching valve 6 is turned on and the solenoids b of the other electromagnetic switching valves 12 are also turned on. By this operation, the injection screw 3 is rotated in the circumferential direction by the hydraulic motor 8 to plasticize the resin, and is retracted by the injection cylinder 1 moved by the hydraulic oil flowing through the variable throttle valve 16 of the second pipe 14.

[0014]

The hydraulic circuit of the injection cylinder in the injection molding machine of the present invention is configured as described above, and the hydraulic oil passes through different pipes during the internal pressure removal during automatic operation and the supply process during manual operation. Since it is fed into the retreating side cylinder chamber of the injection cylinder, it is not necessary to readjust the throttle valve each time the injection molding machine is switched from automatic operation to manual operation or from manual operation to automatic operation. For this reason, it is possible to perform the molding work efficiently without any trouble.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a hydraulic circuit of an injection cylinder in an injection molding machine of the present invention.

FIG. 2 is a diagram of a conventional hydraulic circuit.

[Explanation of symbols]

 1 Injection Cylinder 1a Retraction Side Cylinder Chamber 1b Forward Side Cylinder Chamber 3 Injection Screw 5 Hydraulic Pump 6 Electromagnetic Changeover Valve 12 Electromagnetic Changeover Valve a Solenoid b Solenoid 13 First Pipe 14 Second Pipe 15 Check Valve 16 Variable Throttle Valve

Claims (1)

[Scope of utility model registration request] 1. A hydraulic pump is connected to a retreat side cylinder chamber of an injection cylinder for advancing and retreating an injection screw back and forth through a first electromagnetic switching valve, and the hydraulic pump is provided to a forward side cylinder chamber of the injection cylinder. In the hydraulic circuit of the injection cylinder connected via the two electromagnetic switching valves, the first electromagnetic switching valve is substantially a three-position four-port electromagnetic switching valve, and the first electromagnetic switching valve is the first electromagnetic switching valve. When the oil tank is connected when the valve is neutral, and when one solenoid of the first electromagnetic switching valve is turned on, the hydraulic pump is connected and the other solenoid of the first electromagnetic switching valve is turned on To the oil tank when the first electromagnetic switching valve is in the neutral state, and is shut off when one solenoid of the first electromagnetic switching valve is turned on and the first electromagnetic switching A second pipe connected to the hydraulic pump when the other solenoid of the valve is turned on is connected to the backward cylinder chamber of the injection cylinder, and the second pipe is connected to the first electromagnetic chamber from the backward cylinder chamber. A check valve for freeing the flow of hydraulic oil to the switching valve and stopping the reverse flow thereof and a variable throttle valve for adjusting the flow rate of hydraulic oil flowing from the first electromagnetic switching valve to the reverse side cylinder chamber are provided in parallel. A hydraulic circuit of an injection cylinder in an injection molding machine, which is characterized in that