JPH0825450A - Protection device for injection molding machine - Google Patents

Abstract

PURPOSE:To eliminate trouble such that a resin is injected at high speed in an unprepared state even when power failure is generated. CONSTITUTION:A hydraulic cylinder 2 having a double-rod type piston 3 built therein, for example, an injection cylinder 2i and the servo valve 4 controlling the driving of the injection cylinder 2i are provided and a cut-off circuit 5 having a control valve 6 for opening an oil sending line L at the time of non- power failure and cutting off the same at the time of power failure is connected to the oil sending line L supplying pressure oil to the injection cylinder 2i.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection system for an injection molding machine equipped with a hydraulic cylinder containing a piston of a double rod type and a servo valve for driving and controlling the hydraulic cylinder.

[0002]

2. Description of the Related Art Conventionally, there has been known an injection molding machine equipped with an injection cylinder containing a piston of a double rod type and a servo valve for driving and controlling the injection cylinder (for example,
(See Japanese Patent Laid-Open No. 5-50483).

FIG. 4 shows a schematic structure of this type of injection molding machine. In the figure, an injection molding machine 50 includes an injection device 51 and a mold clamping device 52. The injection device 51 includes a heating cylinder 54 containing a screw 53, an injection nozzle 55 at the front end of the heating cylinder 54, and a hopper 56 at the rear of the heating cylinder 54 for supplying a molding material. An injection cylinder 57 that drives the screw 53 in the front-rear direction is provided at the rear end of the heating cylinder 54. The injection cylinder 57 contains a piston 58 of a double rod type, and the rear end of the screw 53 is connected to the front end of the piston 58. Furthermore, the injection cylinder 57
An oil motor 59 is provided at the rear end, and a rotary shaft 60 of the oil motor 59 is spline-connected to the rear end of the piston 58. On the other hand, the front oil chamber and the rear oil chamber of the injection cylinder 57 are connected to the pressure oil supply unit 62 via the four-port servo valve 61.
And the oil tank 63. The pressure oil supply unit 6
2 is a hydraulic pump 64, a load / unload control valve 65 for the hydraulic pump 64, a check valve 66, and an accumulator 67.
Is provided. On the other hand, 68 is a control circuit for controlling the servo valve 61, and power is supplied to the control circuit 68 from a power supply section 69.

[0004]

An injection molding machine 50 of this type is provided with an injection cylinder 57 having a double rod type piston 58 built therein, and a servo valve 61 drives and controls the injection cylinder 57. The position control (stop control) for 53 can be easily performed.

On the other hand, depending on the type of molded product, it may be desirable to complete the injection filling in a short time in order to avoid the progress of solidification before the completion of the injection filling.
The injection speed is increased by connecting the accumulator 67 to the side and increasing the capacity of the servo valve 61.

However, when the position control for the screw 53 is performed in the injection molding machine 50 having such a high speed, the injection cylinder 57 is stopped even if the piston 58 is stopped.
The hydraulic pressure is always applied to the front oil chamber and the rear oil chamber in the above. Therefore, a power failure occurs, and tp shown in FIG.
At this point, when the AC power supply voltage drops to 0 volt, the power supply input voltage E (+ E, −E) of the control circuit 68 does not instantaneously drop as shown in FIG. The command signal Sc given to the valve 61 is as shown in FIG.
In the section Zc shown in (C), the uncontrolled state is extremely unstable. Since this unstable section Zc is a short time,
In the case of a general injection molding machine, there is almost no problem, but in the case of a high-speed injection molding machine, the injection is completed in about 0.1 seconds, so the high speed from the injection nozzle 55 at a short time when a power failure occurs. There was a problem that the resin of squirt.

In order to prevent the resin from scattering during normal high-speed injection, the operation of the screw 53 is interlocked with a purging cover to prevent the screw 53 from moving forward unless the purging cover is closed. In the control state, such protective measures are ignored, and the resin spouts in an inadvertent state.

The present invention solves the problems existing in the prior art as described above, and reliably solves the problem that the resin spouts at high speed in an unprepared state even when a power failure occurs. An object of the present invention is to provide a protection device for an injection molding machine that can be used.

[0009]

A protection device 1 according to the present invention
Is a hydraulic cylinder 2 having a built-in double rod type piston 3, for example, in an injection molding machine M including an injection cylinder 2i and a servo valve 4 that drives and controls the injection cylinder 2i, supplies pressure oil to the injection cylinder 2i. The oil supply line L is connected to a power cutoff circuit 5 having a control valve 6 that opens the oil supply line L when there is no power failure and shuts off the oil supply line L when there is a power failure.

In this case, the control valve 6 opens the oil supply line L by energization from the side of the power source 8 which supplies power to the control circuit 7 which controls the servo valve 4, and shuts off the oil supply line L by stopping energization. Can be configured as Further, it is desirable to provide the oil supply line L with a flow rate reduction circuit 10 that reduces the flow rate of the pressure oil when the position of the screw 9 coupled to the piston 3 is controlled.

[0011]

According to the protection device 1 of the present invention, in the normal state during non-power failure, the control valve 6 is energized from the power source section 8 side, so that the switching circuit of the control valve 6 cuts off the circuit during a power failure. 5 is in a distribution state. Therefore, the oil transfer line L
Is opened and normal control is performed in which the injection valve 2i is driven and controlled while the servo valve 4 is controlled by the control circuit 7.

On the other hand, when a power failure occurs, the control valve 6
Since the energization from the power supply unit 8 side to the is stopped, the control valve 6 is switched, the oil supply line L is cut off by the cutoff circuit 5 at the time of power failure, and the supply of the pressure oil to the injection cylinder 2i is stopped. In this case, since the control valve 6 is controlled by energization from the power supply unit 8 side, the supply of the pressure oil to the injection cylinder 2i is stopped before the control circuit 7 that controls the servo valve 4 is in the uncontrolled state. Therefore, the purging cover is not closed during position control, that is,
Even if a power failure occurs in an unprepared state, the problem that the resin spouts at high speed does not occur.

Further, by providing the flow rate reducing circuit 10 in the oil feed line L, the flow rate during position control can be reduced, and the responsiveness (close speed) of the control valve 6 when a power failure occurs during position control. Can be increased.

[0014]

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 M including the protective device 1 according to this embodiment will be described with reference to FIG.

In the figure, the injection molding machine M comprises an injection device 11 and a mold clamping device 12. The injection device 11 includes a heating cylinder 13 having a screw 9 therein, an injection nozzle 14 at the front end of the heating cylinder 13, and a hopper 15 at the rear of the heating cylinder 13 for supplying a molding material. Also, the heating cylinder 1
An injection cylinder 2i that drives the screw 9 in the front-rear direction is provided at the rear end of the screw 3. The injection cylinder 2i has a piston 3 of a double rod type built therein, and the front end of the piston 3 is connected to the rear end of the screw 9. Further, an oil motor 16 is provided at the rear end of the injection cylinder 2i.
The rotary shaft 17 of is splined to the rear end of the piston 3.

On the other hand, the front oil chamber 2f and the rear oil chamber 2r of the injection cylinder 2i are connected to the A port and the B port of the four-port servo valve 4, respectively. Further, the P port of the servo valve 4 is connected to the outflow side of the protection device 1 according to the present embodiment via the oil feed line L, and the T port of the servo valve 4 is connected to the oil tank 23.

The protection device 1 comprises a large flow circuit 21 and a small flow circuit 22 connected in parallel. The large flow circuit 21 includes a logic valve 24 and a control valve 25 for controlling the logic valve 24. When the control valve 25 is switched to the symbol a, the logic valve 24 is closed and the large flow circuit 21 is shut off. , If the control valve 25 is switched to the symbol b, the logic valve 24 is opened to bring the large flow circuit 21 into the flow permitting state.

On the other hand, the small flow rate circuit 22 is constituted by connecting the check valve 26, the control valve 6 and the throttle valve 27 which constitute the cutoff circuit 5 at the time of power failure in cascade. Accordingly, when the control valve 6 is switched to the symbol a, the small flow rate circuit 22 is turned off, and when the control valve 6 is switched to the symbol b, the small flow rate circuit 22 is allowed to flow. In this case, the control valve 6 has a built-in check valve and is of a type that completely shuts off leakage when closed. The control valve 6 is switched to the symbol b by energization, and when the energization is stopped, it is switched to the symbol a by the return spring. Further, the throttle valve 27 constitutes the flow rate reducing circuit 10 that reduces the flow rate.

The inflow side of the protection device 1 is connected to the outflow side of the check valve 28 and the accumulator 2 via the oil feed line L.
9, and the inflow side of the check valve 28 is connected to the hydraulic pump 31 via the load / unload control valve 30.
Connect to. In addition, 31m shows a pump motor.

On the other hand, a control circuit 7 has a function of controlling the servo valve 4 and the control valve 25. Also, 8 is AC
The power supply unit is a power supply unit, and the power supply unit 8 supplies power to the control circuit 7 and also supplies power to the control valve 6. In this case, it is desirable that the power supply to the control valve 6 be applied with a potential on the AC power supply side in the power supply unit 8 so that the control valve 6 can be closed as quickly as possible during a power failure. Therefore, the power may be directly supplied by the AC power source.

Next, the operation of the protection device 1 according to this embodiment will be described with reference to FIGS.

First, in steps other than the position control of the screw 9, the control circuit 7 causes the control valve 25 to move to the symbol b.
, And the logic valve 24 is open. Further, in the normal state during non-power failure, the control valve 6 is energized from the power supply section 8, so that the control valve 6 is switched to the symbol b as shown in FIG. Becomes
Therefore, both the large flow rate circuit 21 and the small flow rate circuit 22 are in the flow permitting state, and the oil feed line L is opened. As a result,
The servo valve 4 is controlled by the control circuit 7 while the injection cylinder 2i is driven and controlled normally (high-speed control).
Is done.

On the other hand, when the position of the screw 9 is controlled, as shown in FIG. 1, the control circuit 25 switches the control valve 25 to the symbol a and the logic valve 24 is closed. As a result, the large flow rate circuit 21 is shut off, and only the small flow rate circuit 22 is in the flow permitting state. Therefore, since the small flow rate circuit 22 includes the throttle valve 27, the flow rate of the oil feed line L is reduced. During position control, the injection cylinder 2i
Since the hydraulic pressure acts on both the front oil chamber 2f and the rear oil chamber 2r and the position control (stop control) is performed by the pressure balance between both chambers 2f and 2r, a small flow rate is sufficient.

On the other hand, assume that a power failure occurs during such position control. In this case, the energization of the control valve 6 from the power supply unit 8 side is stopped, so that the control valve 6 is switched to the symbol a as shown in FIG. As a result,
The oil supply line L is cut off by the cutoff circuit 5 during a power failure, and the supply of pressure oil to the injection cylinder 2i is stopped. On this occasion,
Since the control valve 6 is energized from the power supply section 8 side, the supply of pressure oil to the injection cylinder 2i is stopped before the control circuit 7 enters the uncontrolled state. Therefore, even if a power failure occurs while the purging cover is not closed during the position control, the problem that the resin is spouted at high speed is solved.

Next, a protection device 1 according to a modified embodiment of the present invention will be described with reference to FIG. In addition, in FIG.
The same parts as those in FIG. 1 are designated by the same reference numerals to clarify the configuration thereof, and detailed description thereof will be omitted.

In the modified embodiment, the small flow rate circuit 22 is removed from the circuit shown in FIG.
It was made to function as. Therefore, in this case, the logic valve 24 constitutes the control valve 6, and the logic valve 24 and the control valve 25 constitute the interruption circuit 5 at the time of power failure according to the present invention. In addition, the energization line 8e of the power supply unit 8 that energizes the control valve 6 shown in FIG. 1 is used to energize the control valve 25. Therefore, at the time of non-power failure, the control valve 25 is switched to the symbol b and the oil feeding line L is opened, and at the time of power failure, the control valve 25 is switched to the symbol a and the oil feeding line L is shut off, and the oil feeding line L of FIG. Functions like a circuit.

In the embodiment of FIG. 1, since the oil flow line L has the flow rate reducing circuit 10, it is possible to reduce the flow rate during the position control, and a power failure occurs during the position control. Although the responsiveness (closing speed) of the control valve 6 can be increased, in the modified embodiment, the large flow rate is directly shut off by the logic valve 24, so the responsiveness is lower than that of the embodiment of FIG.

The embodiment has been described in detail above.
The present invention is not limited to such an embodiment.
For example, although the injection cylinder 2i is illustrated as the hydraulic cylinder 2, it can be similarly applied to other hydraulic cylinders such as a mold clamping cylinder. Further, the structure of the cutoff circuit 5 at the time of power failure including the control valve 6 can be arbitrarily implemented. In addition, the detailed configuration, format, and the like can be arbitrarily changed without departing from the scope of the present invention.

[0030]

As described above, according to the present invention, in a protection device for an injection molding machine equipped with a hydraulic cylinder having a double rod type piston built therein and a servo valve for driving and controlling the hydraulic cylinder, pressure oil is supplied to the hydraulic cylinder. Even if a power failure occurs, the oil supply line to be supplied is connected to a power cutoff circuit that has a control valve that opens the oil supply line when there is no power outage and shuts off the oil supply line due to a power failure. ,
The remarkable effect is that it is possible to surely eliminate the problem that the resin spouts at high speed in an unprepared state.

[Brief description of drawings]

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

FIG. 2 is a circuit configuration diagram showing a main part of the protective device in a state in which a control valve is switched,

FIG. 3 is a circuit configuration diagram showing a main part of a protection device according to a modified embodiment of the present invention;

FIG. 4 is a configuration diagram of an injection molding machine according to a conventional technique,

FIG. 5 is a time chart of voltage waveforms at various parts of the injection molding machine,

[Explanation of symbols]

 1 Protective Device 2 Hydraulic Cylinder 2i Injection Cylinder 3 Piston 4 Servo Valve 5 Interruption Circuit at Power Failure 6 Control Valve 7 Control Circuit 8 Power Supply Section 9 Screw 10 Flow Reduction Circuit L Oil Transmission Line M Injection Molding Machine

Claims (4)

[Claims] 1. A protective device for an injection molding machine, comprising: a hydraulic cylinder containing a piston of both rod types; and a servo valve for driving and controlling the hydraulic cylinder, in an oil feeding line for supplying pressure oil to the hydraulic cylinder, A protective device for an injection molding machine, characterized in that the oil supply line is opened when there is no power outage, and a shutoff circuit at the time of power failure that has a control valve that shuts off the oil supply line due to a power outage is connected. 2. The protection device for an injection molding machine according to claim 1, wherein the hydraulic cylinder is an injection cylinder. 3. The control valve opens the oil feed line by energization from a power source side that supplies power to a control circuit for controlling the servo valve, and shuts off the oil feed line by stopping energization. The protective device for an injection molding machine as described in 1 or 2. 4. The injection molding machine according to claim 1, wherein the oil feed line is provided with a flow rate reducing circuit for reducing the flow rate of the pressure oil when controlling the position of the screw coupled to the piston. Protective device.