JP2529641B2 - Hydraulic circuit of injection molding machine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit of an injection molding machine in which a hydraulic cylinder and a hydraulic source are connected to each other via a four-port valve.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional hydraulic circuit 50 in an injection molding machine. In the figure, reference numeral 60 denotes an injection device in an injection molding machine, which has an injection nozzle 62 at the front end and a heating cylinder 61 having a hopper 63 at the rear part. Heating cylinder 61
Insert the screw 64 into the inside of the
A screw drive unit 65 is coupled to the rear end of the screw 1. The screw drive unit 65 includes an injection cylinder (hydraulic cylinder) 66 having a double-rod type piston 67 built therein.
The front rod 67f of No. 7 is coupled to the rear end of the screw 64, and the rear rod 67r is spline coupled to the shaft of the oil motor 68 arranged at the rear end of the injection cylinder 66.

On the other hand, the hydraulic circuit main body 51 is connected to the injection cylinder 66, and the hydraulic circuit 50 is constituted by this.
The hydraulic circuit main body 51 includes a four-port servo valve 52 and a four-port switching valve 53 connected to the front oil chamber 66f and the rear oil chamber 66r of the injection cylinder 66, and also has a pilot operated check valve 54, a switching valve 55, and a hydraulic pressure source 56. And an oil tank 57, which are connected as shown in FIG. Therefore, in the injection process, the four-port servo valve 52 is changed to the symbol b.
Then, by switching the four-port switching valve 53 to the symbol b, the pressure oil of the hydraulic power source 56 is transferred to the rear oil chamber 6 of the injection cylinder 66.
6r, the piston 67 (screw 64) moves forward, and the oil discharged from the front oil chamber 66f is returned to the oil tank 57. At this time, the four-port servo valve 52
The pressure control (speed control) is performed by. On the other hand, in the metering process, the four-port switching valve 53 is left unchanged and the four-port servo valve 52 is switched to the symbol a. As a result, the screw 64 is rotated by the oil motor 68 to perform measurement, and the screw 64 retracts as the measurement progresses, so that the piston 67 also retracts and the oil discharged from the rear oil chamber 66r of the injection cylinder 66 is discharged from the oil tank 57. The oil in the oil tank 57 flows into the front oil chamber 66f due to the negative pressure. At this time, back pressure control is performed by the four-port servo valve 52.

[0004]

However, since such a conventional hydraulic circuit 50 requires at least two control valves, that is, a four-port servo valve 52 and a four-port switching valve 53, the cost of the hydraulic circuit 50 is low. In addition to increasing the size and size, it is necessary to control the switching of the two control valves, which complicates the control system of the controller, resulting in a decrease in control accuracy and an increase in the cost of the control system.

The present invention has solved the problems existing in such conventional techniques. By reducing the number of control valves, the cost and size of the hydraulic circuit including the control system can be reduced and the control accuracy can be improved. An object is to provide a hydraulic circuit of an injection molding machine that can contribute.

[0006]

According to the present invention, the front oil chamber 2f of the injection cylinder (hydraulic cylinder) 2 is connected to the port A of the four-port valve, and the rear oil chamber 2r of the injection cylinder 2 is connected to the port B of the four-port valve.
In constructing the hydraulic circuit 1 of the injection molding machine in which the hydraulic pressure source 3 is connected to the P port and the oil tank 4 is connected to the T port, in particular, the pressure controllable four-port servo valve 5 is used as the four-port valve. , 4-port servo valve 5
A bypass circuit 6 having a check valve 7 for blocking the flow from the A port side to the T port side is connected between the A port and the T port in FIG.

[0007]

According to the hydraulic circuit 1 of the injection molding machine according to the present invention, in the injection step, the pressure oil of the hydraulic pressure source 3 passes from the P port of the four-port servo valve 5 to the B port and the rear oil of the injection cylinder 2. It is supplied to the chamber 2r. As a result, the injection cylinder 2
Of the four-port servo valve 5 and the screw of the four-port servo valve 5
Is returned from the A port to the oil tank 4 through the T port. In this case, the check valve 7 prevents oil from flowing into the bypass circuit 6.

On the other hand, in the metering process, the piston of the injection cylinder 2 retreats due to the back pressure generated by the retreat of the screw, so the oil discharged from the rear oil chamber 2r in the injection cylinder 2 is discharged from the B port of the four-port servo valve 5. While passing through the T port and being returned to the oil tank 4, the oil in the oil tank 4 flows into the front oil chamber 2f of the injection cylinder 2 by the negative pressure through the check valve 7, that is, the bypass circuit 6.

[0009]

Next, preferred embodiments according to the present invention will be described in detail with reference to the drawings.

First, the structure of an injection molding machine including the hydraulic circuit 1 according to this embodiment will be described with reference to FIG.

In the figure, reference numeral 20 denotes an injection device in an injection molding machine, which has a heating cylinder 21 having an injection nozzle 22 at the front end and a hopper 23 at the rear part. Heating cylinder 2
A screw 24 is inserted into the inside of 1, and a screw driving unit 25 is connected to the rear end of the heating cylinder 21. The screw drive unit 25 includes an injection cylinder (hydraulic cylinder) 2 having a double rod type piston 27 built therein.
The front rod 27f of No. 7 is coupled to the rear end of the screw 24, and the rear rod 27r is spline coupled to the shaft of the oil motor 28 disposed at the rear end of the injection cylinder 2.

On the other hand, the injection cylinder 2 has a hydraulic circuit body 1
1 are connected to form a hydraulic circuit 1 according to the present invention. The hydraulic circuit main body 11 is provided with a four-port servo valve 5, and the A port in the four-port servo valve 5 is in the front oil chamber 2f of the injection cylinder 2, the B port is in the rear oil chamber 2r of the injection cylinder 2, and the P port is logic. Each of the valves (pilot operated check valve) 12 is connected to a discharge port 12o. On the other hand, the supply port 12i of the logic valve 12 is connected to a hydraulic pressure source 3 including an accumulator and a hydraulic pump, and the hydraulic pressure source 3 and the oil tank 4 are connected to a three-port switching valve 13
Is connected to the pilot port 12p of the logic valve 12 via.

A check valve 7 is connected between the A port and the T port of the four-port servo valve 5 to form a bypass circuit 6. In this case, the check valve 7 is connected so as to prevent the flow from the A port side to the T port side.

Next, the operation of the hydraulic circuit 1 according to this embodiment will be described.

First, when the switching valve 13 is switched to the symbol b, the pressure oil of the hydraulic pressure source 3 is supplied to the pilot port 12p, so that the logic valve 12 is closed. Therefore, the supply of pressure oil to the injection cylinder 2 is stopped.

On the other hand, in the injection process, the switching valve 13 is switched to the symbol a and the four-port servo valve 5 is switched to the symbol b. As a result, the pilot port 12p of the logic valve 12 is opened to the oil tank 4, so that the logic valve 12 is opened and the pressure oil of the hydraulic pressure source 3 is injected from the P port of the four-port servo valve 5 through the B port. Cylinder 2
Is supplied to the rear oil chamber 2r. As a result, the injection cylinder 2
Since the piston 27 (screw 24) of the four cylinders moves forward, the oil in the front oil chamber 2f of the injection cylinder 2 is discharged from the four-port servo valve 5
Is returned from the A port to the oil tank 4 through the T port. In this case, the check valve 7 allows the bypass circuit 6
There is no oil flowing in. Therefore, by controlling the four-port servo valve 5, pressure control (speed control) on the screw 24 can be performed.

On the other hand, in the measuring process, the switching valve 13 is switched to the symbol b to shut off the hydraulic pressure source 3, and the four-port servo valve 5 is switched to the symbol a. In the measuring step, the screw 24 is rotated by the oil motor 28 to carry out the measurement, and the piston 27 also moves backward due to the backward movement of the screw 24. As a result, the oil discharged from the rear oil chamber 2r of the injection cylinder 2 is returned from the B port to the oil tank 4 through the T port, and the front oil chamber 2f of the injection cylinder 2 has a negative pressure in the front oil chamber 2f. The oil in the oil tank 4 flows in through the bypass circuit 6. Therefore, at this time, by controlling the four-port servo valve 5, back pressure control on the screw 24 can be performed.

As described above, according to the hydraulic circuit 1 of the present embodiment, the pressure control (speed control) in the injection process can be performed only by adding the bypass circuit 6 using the check valve 7 to the four-port servo valve 5. ) And back pressure control in the measuring process can be easily realized. Therefore, the number of control valves is reduced, and the cost and size of the hydraulic circuit 1 including the control system can be reduced. Also, the simplification of the control system can contribute to the improvement of control accuracy.

The embodiment has been described in detail above.
The present invention is not limited to such an embodiment.
For example, although the injection cylinder is illustrated as the hydraulic cylinder, the invention can be similarly applied to any other hydraulic cylinder such as a mold clamping cylinder. In addition, the detailed configuration and the like can be arbitrarily changed without departing from the scope of the present invention.

[0020]

As described above, according to the present invention, the A port of the four-port valve is the front oil chamber of the hydraulic cylinder, the B port is the rear oil chamber of the hydraulic cylinder, the P port is the hydraulic source, and the T port is the oil tank. In the hydraulic circuit of the injection molding machine in which each of these is connected, a pressure controllable 4-port servo valve is used for the 4-port valve, and
Since a bypass circuit having a check valve that blocks the flow from the A port side to the T port side is connected between the port and the T port, only a check valve (bypass circuit) is added to the 4-port servo valve. Thus, pressure control (speed control) in the injection process and back pressure control in the metering process can be easily realized, and the cost and size of the hydraulic circuit including the control system can be reduced by reducing the number of control valves, and the control system can be achieved. There is a remarkable effect that the control precision can be improved by simplifying

[Brief description of drawings]

FIG. 1 is a configuration diagram of a hydraulic circuit of an injection molding machine according to the present invention,

FIG. 2 is a configuration diagram of a hydraulic circuit of an injection molding machine according to a conventional technique,

[Explanation of symbols]

 1 hydraulic circuit 2 injection cylinder (hydraulic cylinder) 2f front oil chamber 2r rear oil chamber 3 hydraulic power source 4 oil tank 5 four-port servo valve 6 bypass circuit 7 check valve

Claims (2)

(57) [Claims] 1. A four-port valve has an A port as a front oil chamber of a hydraulic cylinder and a B port as a rear oil chamber of a hydraulic cylinder.
In a hydraulic circuit of an injection molding machine in which a hydraulic pressure source is connected to the P port and an oil tank is connected to the T port, a pressure controllable 4-port servo valve is used as the 4-port valve, and a 4-port servo valve has an A port. A hydraulic circuit for an injection molding machine, characterized in that a bypass circuit having a check valve for blocking the flow from the A port side to the T port side is connected between the T ports. 2. The hydraulic circuit for an injection molding machine according to claim 1, wherein the hydraulic cylinder is an injection cylinder.