JPH0825449A - 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:In an injection molding machine equipped with a hydraulic cylinder having a double-rod type piston built therein, for example, an injection cylinder and the servo valve 4 driving and controlling the injection cylinder, a power failure detection circuit Ua detecting power failure and a power failure signal applying circuit Ub applying a neutral signal Sn controlling the servo valve 4 to a neutral position to the command signal input line Lc to the servo motor 4 by the detection of power failure due to the power failure detection circuit Ua are provided.

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. 6 shows a schematic structure of an injection molding machine of this type. 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 switching valve 65 of 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, a power failure detection circuit Ua for detecting a power failure, When a power failure is detected by the power failure detection circuit Ua, a command signal input line Lc for the servo valve 4 is provided with a power failure signal providing circuit Ub that provides a neutral signal Sn for controlling the servo valve 4 to a neutral position. And

In this case, the power failure signal giving circuit Ub can be constructed by including an open / close switch Ka that is closed by detecting a power failure by the power failure detection circuit Ua by connecting between the command signal input line Lc and the ground line G. Further, it is desirable to connect capacitors C1 and C2 for storage between the power input lines L1 and L2 to the servo valve 4 and the ground line G.

On the other hand, in the oil feed line L for supplying pressure oil to the hydraulic cylinder 2i, the control valve 6 which opens the oil feed line L when there is no power failure and shuts off the oil feed line L due to the power failure.
It is desirable to connect the cut-off circuit 5 at the time of power failure.
At this time, the control valve 6 is configured so that the oil supply line L is opened by energization from the power supply section 8 side that supplies power to the control circuit 7 that controls the servo valve 4, and the oil supply line L is shut off by stopping energization. it can. In addition, the piston 3
It is desirable to provide a flow rate reducing circuit 10 that reduces the flow rate of the pressure oil when controlling the position of the screw 9 coupled to the.

[0012]

According to the protective device 1 of the present invention, the power failure detection circuit Ua does not detect a power failure in a normal state when there is no power failure, so that the open / close switch Ka in the power failure signal providing circuit Ub is open. Therefore, the command signal input line Lc is not in contact with the ground line G, and the command signal Sc is directly applied to the servo valve 4 from the control circuit 7. Further, since the control valve 6 is energized from the power supply section 8 side, the control valve 6 is switched and the cutoff circuit 5 at the time of power failure is in the flow state. As a result, the oil supply line L is opened, and normal control is performed in which the injection cylinder 2i is drive-controlled while the servo valve 4 is controlled by the command signal Sc from the control circuit 7.

On the other hand, when a power failure occurs, the power failure detection circuit Ua detects the power failure, so that the command signal input line Lc of the servo valve 4 neutralizes the servo valve 4 from the power failure signal providing circuit Ub. Neutral signal Sn for controlling position
Is given. That is, by closing the open / close switch Ka, the command signal input line Lc and the ground line G are connected, and a zero potential is applied to the command signal input line Lc.
As a result, the servo valve 4 is fixed at the neutral position, and the problem that the command signal Sc becomes unstable due to the occurrence of power failure is resolved.

Further, the power input line L1 of the servo valve 4
Between the L2 and the ground line G, a capacitor C1, for storing electricity,
Since C2 is connected, the capacitor C
Due to the storage effect of C1 and C2, the original power input voltage + E, and
-E is added to each, and the command signal Sc is stabilized from the side of the power supply input voltage to the servo valve 4.

Further, the power supply from the power source 8 side to the control valve 6 is also stopped, and the control valve 6 is switched, so that the oil supply line L is shut off by the shutoff circuit 5 at the time of power failure. As a result, the supply of 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. By providing the flow rate reduction circuit 10 in the oil feed line L, the flow rate during position control can be reduced, and the responsiveness (closing speed) of the control valve 6 when a power failure occurs during position control is increased. You can

Therefore, even if a power failure occurs in the state where the purging cover is not closed during the position control, that is, in an inadvertent state, the resin does not spout at high speed.

[0017]

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

First, the structure of the 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 in the parallel circuit of the large flow rate circuit 21 and the small flow rate circuit 22 forming a part of the protection device 1 according to the present embodiment via the oil feed line L, and T of servo valve 4
The port is connected to the oil tank 23.

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. And control valve 2
When 5 is switched to the symbol b, the logic valve 24 is opened and the large flow rate circuit 21 is brought 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.

A large flow rate circuit 21 and a small flow rate circuit 22
The inflow side of the parallel circuit is connected to the outflow side of the check valve 28 and the accumulator 29 via the oil feed line L, and the inflow side of the check valve 28 is connected to the hydraulic pressure via the load / unload switching valve 30. Connect to pump 31. 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. Further, the control circuit 7 incorporates the protection device 1 according to the present embodiment.

Next, the structure of the protection device 1 will be specifically described with reference to FIG. The control circuit 7 is the control circuit body 7
The servo valve 4 is provided with four signal lines to the control circuit body 7m, that is, the positive power source input line L1,
Connection is made by the negative power source input line L2, the ground line G, and the command signal input line Lc. In this case, the diodes D1 and D2 are connected in the positive power supply input line L1 and the negative power supply input line L2, respectively. Further, between the power supply input lines L1 and L2 of the servo valve 4 and the ground line G, capacitors C1 and C2 for storing electricity having a large electrostatic capacitance, such as electrolytic capacitors, are connected, respectively.

On the other hand, a power failure detection circuit Ua for detecting a power failure is provided. The power failure detection circuit Ua has an input connected to an AC power supply (commercial AC power supply), detects a power failure due to a drop in the power supply voltage due to the power failure, and outputs the detection result. Further, an open / close switch Ka, which constitutes a power failure signal giving circuit Ub, is connected between the command signal input line Lc and the ground line G. The open / close switch Ka is open during a power failure, but is closed by the power failure detection circuit Ua detecting a power failure, and has a function of connecting the command signal input line Lc to the ground line G.

Reference numeral 8 denotes a power supply section to which an AC power source is input. The power supply section 8 supplies power to the control circuit 7 and also supplies power to the control valve 6 as shown in FIG. In this case, the control valve 6 is energized so that the control valve 6 can be closed as quickly as possible in the event of a power failure.
It is desirable to apply a potential on the AC power source side in the power source unit 8. Therefore, the power may be directly supplied by the AC power source.

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

First, in the steps other than the position control for the screw 9, the control circuit 25 causes the control valve 25 to move to the symbol b.
, And the logic valve 24 is open. Further, in a normal state during non-power failure, the control valve 6 is energized from the power source section 8, so that the control valve 6 is switched to the symbol b and the power interruption circuit 5 is in the distribution state 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,
While the servo valve 4 is controlled by the command signal Sc given from the control circuit 7, normal control (high-speed control) for driving and controlling the injection cylinder 2i is performed.

On the other hand, when the position of the screw 9 is controlled, as shown in FIG. 3, the control circuit 7 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.

Further, in a normal state at the time of non-power failure,
Since the power failure detection circuit Ua does not detect a power failure, the open / close switch Ka in the power failure signal providing circuit Ub is in an open state. Therefore, the command signal input line Lc is not in contact with the ground line G, so that the command signal Sc is directly applied from the control circuit 7 to the servo valve 4.

On the other hand, assume that a power failure occurs at the time tp shown in FIG. 2 (A) during such position control. In this case, a power failure is detected by the power failure detection circuit Ua, and based on this, the neutral signal Sn is output from the power failure signal providing circuit Ub to the command signal input line Lc of the servo valve 4.
Is given. That is, by closing the open / close switch Ka, the command signal input line Lc and the ground line G are connected, and the command signal input line Lc is given a zero potential (neutral signal Sn) as shown in FIG. 2C. To be done. As a result, the servo valve 4 is immediately fixed to the neutral position, and the problem that the command signal Sc becomes unstable due to the occurrence of power failure is resolved.

Further, the power input line L1 of the servo valve 4
A capacitor C for storage connected between L2 and the ground line G
1 and C2, even if a power failure occurs, the power supply input lines L1 and L2 of the servo valve 4 are supplied with the original power supply input voltages + E and -E, respectively, for a certain period of time, as shown in FIG. The stabilization of the power input voltage to the servo valve 4 can be achieved.

Further, since the power supply from the power source 8 side to the control valve 6 is stopped, 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. At this time, the control valve 6 is connected to the power source 8
Since the power is supplied from the side, the supply of the 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 position control,
The problem that resin is ejected at high speed is solved. Therefore, stabilization is achieved from the side of pressure oil supply to the servo valve 4.

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 (closing speed) of the control valve 6 when a power failure occurs during position control. Can be increased.

As a result, even if a power failure occurs while the purging cover is not closed during position control,
The problem that resin is ejected at high speed is solved.

Next, a modified embodiment of the present invention will be described with reference to FIG.
Will be described with reference to. In FIG. 5, the same parts as those in FIG. 3 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 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. Further, the energization line 8e of the power supply unit 8 which energizes the control valve 6 shown in FIG. 3 is used for energizing the control valve 25. Therefore, at the time of non-power failure, the control valve 25 is switched to the symbol b, the oil supply line L is opened, and at the time of power failure, the control valve 25 is switched to the symbol a,
The oil supply line L is shut off and functions in the same manner as the circuit of FIG.

In the embodiment shown in FIG. 3, since the flow rate reducing circuit 10 is provided in the oil feed line L, the flow rate during position control can be reduced, and when a power failure occurs during position control. Although the responsiveness (closing speed) of the control valve 6 can be enhanced, 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 capacitors C1 and C2 need not necessarily be connected, and the large flow rate circuit 21 and the small flow rate circuit 22 need not necessarily be provided. In addition, the detailed configuration, format, and the like can be arbitrarily changed without departing from the scope of the present invention.

[0041]

As described above, the present invention provides a power failure detection circuit for detecting a power failure 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. , By the detection of a power failure by this power failure detection circuit, the command signal input line to the servo valve is provided with a signal supply circuit at the time of power failure that provides a neutral signal for controlling the servo valve to the neutral position,
Even if a power failure occurs, the remarkable effect that the problem that the resin spouts at high speed in an unprepared state can be reliably solved is achieved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an electric circuit of a protection device according to the present invention,

FIG. 2 is a time chart of voltage waveforms in each part of the protection device,

FIG. 3 is a configuration diagram of an injection molding machine including a protection device according to the present invention,

FIG. 4 is a configuration diagram of a hydraulic circuit in a state in which a control valve provided in the protective device is switched,

FIG. 5 is a configuration diagram of a hydraulic circuit provided in a protection device according to a modified embodiment of the present invention,

FIG. 6 is a configuration diagram of an injection molding machine according to a conventional technique,

FIG. 7 is a time chart of voltage waveforms in each part of the injection molding machine,

[Explanation of symbols]

 1 Protective Device 2 Hydraulic Cylinder 2i Injection Cylinder 3 Piston 4 Servo Valve 5 Cutoff Circuit at Power Failure 6 Control Valve 7 Control Circuit 8 Power Supply Section 9 Screw 10 Flow Reduction Circuit M Injection Molding Machine Ua Power Failure Detection Circuit Ub Power Failure Signaling Circuit Lc Command Signal input line Sn Neutral signal G Ground line Ka Open / close switch L1 Power input line L2 Power input line C1 Capacitor C2 Capacitor L Oil supply line

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area // F15B 9/09 Z

Claims (7)

[Claims] 1. A power failure detection circuit for detecting a power failure, and a power failure by this power failure detection circuit in a protection device for an injection molding machine equipped with a hydraulic cylinder containing a piston of both rod types and a servo valve for driving and controlling the hydraulic cylinder. A protection device for an injection molding machine, characterized in that a command signal input circuit for applying a neutral signal for controlling the servo valve to a neutral position is provided to a command signal input line for the servo valve by the detection of. 2. The injection according to claim 1, wherein the power failure signal giving circuit is provided with an opening / closing switch which is connected between the command signal input line and the ground line to close when a power failure is detected by the power failure detection circuit. Molding machine protection device. 3. A protection device for an injection molding machine according to claim 1, wherein a capacitor for storing electricity is connected between a power supply input line and a ground line for the servo valve. 4. An oil supply line for supplying pressure oil to a hydraulic cylinder is connected to a power cutoff circuit having a control valve for opening the oil supply line when there is no power failure and for shutting off the oil supply line due to a power failure. The protection device for an injection molding machine according to claim 1, wherein: 5. The control valve opens the oil feed line by energization from a power source side that supplies power to a control circuit that controls the servo valve, and shuts off the oil feed line by stopping energization. The protective device for an injection molding machine according to item 4. 6. The protective device for an injection molding machine according to claim 4, 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. . 7. The protection device for an injection molding machine according to claim 1, wherein the hydraulic cylinder is an injection cylinder.