JPH0752221A - Safety device of hydraulic injection molding machine - Google Patents

Abstract

PURPOSE:To prevent a vice that high pressure hydraulic oil is scattered at the time of an exchange of screws or maintenance and further that a screw collides with an inner wall of a heating oylinder or hazard is generated on an operator. CONSTITUTION:One or at least two condition detecting parts 4, 5 detecting a condition of an accumulator 3 making hydraulic regeneration unnecessary, for example, the condition detecting part 4 detecting suspension of a pump motor 2m of a hydraulic pump 2, the condition detecting part 5 detecting a start of maintenance by a method wherein a safety cover of injection molding machine is removed and an automatic discharge control part 6 which allows to discharge hydraulic oil of an accumulator 3 to a drain circuit Cd when at least the one condition detecting part 4 or 5 detects the foregoing condition are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a safety device for a hydraulic injection molding machine having a hydraulic circuit connected to an accumulator for accumulating the hydraulic pressure of a hydraulic pump.

[0002]

2. Description of the Related Art Conventionally, a hydraulic injection molding machine has a built-in hydraulic circuit for driving various hydraulic actuators such as an injection cylinder, and an accumulator for accumulating the hydraulic pressure of a hydraulic pump is connected to the hydraulic circuit. Realized stable hydraulic control.

By the way, the accumulator accumulates pressure by the operation of the hydraulic pump, but depending on the screw replacement or maintenance method, the operation of the hydraulic pump is stopped and the pressure oil in the accumulator is discharged to the drain circuit before starting the work. Was there. The reason for this is to prevent the harmful effect that the high pressure oil is scattered due to the accumulated pressure remaining in the accumulator during the disassembly of the hydraulic circuit.

However, in reality, it is determined that the hydraulic pump need only be stopped if the user is not aware of the harmful effect caused by the accumulated pressure in the accumulator, such as when the user replaces the screw of the hydraulic injection molding machine. Then, the pressure oil discharged from the accumulator is rarely forgotten, and there is a problem that the above-mentioned adverse effects cannot be reliably prevented.

During screw replacement or maintenance, as shown in FIG. 4, the connecting mechanism 62 provided at the tip of the piston 61 incorporated in the injection cylinder is disassembled to remove the screw 63, and at this time, the screw 63 is placed in an obstructive position. Often the existing position sensor 64 is also removed. On the other hand, when the screw is replaced, the screw 63 may be moved forward to remove the residual resin in the heating cylinder or to perform a test movement. In this case, if the position sensor 64 is removed, the feedback signal in the feedback control loop is not fed back, and the servo operation amount increases without control. As a result, there is a problem that the screw immediately advances at the maximum speed due to the accumulated pressure in the accumulator, the screw collides with the inner wall of the heating cylinder, and the operator is in danger.

The present invention solves the problems existing in the prior art as described above. The problem is that high pressure oil is scattered during screw replacement and maintenance, and further the screw collides with the inner wall of the heating cylinder. An object of the present invention is to provide a safety device for an injection molding machine, which reliably prevents a harmful effect on the operator.

[0007]

The present invention is a hydraulic circuit C to which an accumulator 3 for accumulating the hydraulic pressure of a hydraulic pump 2 is connected.
When configuring the safety device 1 of the hydraulic injection molding machine including the above, one or more state detection units 4 and 5 that detect a state in which the accumulator 3 does not need to store pressure, for example, the pump motor 2m of the hydraulic pump 2 The state detection unit 4 that detects a stop and the state detection unit 5 that detects the start of maintenance due to removal of the safety cover H of the injection molding machine, and at least one state detection unit 4 or 5 detects the state. Then, the automatic discharge control unit 6 for discharging the pressure oil of the accumulator 3 to the drain circuit Cd is provided.

A safety device 1 for a hydraulic injection molding machine according to another embodiment of the present invention has, in addition to the above-mentioned configuration, a low pressure oil supplied to a hydraulic actuator by operating an operation switch 7.
For example, it is characterized by including an auxiliary control unit 8 using an open loop control circuit that can be supplied to the injection cylinder 9.

[0009]

According to the safety device 1 of the hydraulic injection molding machine according to the present invention, first, the state in which the accumulator 3 does not need to store pressure, that is, the state at the time of starting screw replacement or maintenance is one or more. It is detected by the state detection units 4 and 5. That is, the state detecting unit 4 detects the stop of the pump motor 2m of the hydraulic pump 2, and the state detecting unit 5 detects the start state of the maintenance by removing the safety cover H of the injection molding machine. To be done.

When at least one state detecting section 4 or 5 detects the above state, the automatic discharge control section 6 automatically discharges the pressure oil of the accumulator 3 to the drain circuit Cd. Therefore, it is possible to prevent the pressure oil from scattering during screw replacement and maintenance.

On the other hand, when the screw is moved forward during maintenance, since the auxiliary control section 8 using the open loop control circuit is provided, operating the operation switch 7 will cause low pressure oil to be injected into the injection cylinder (hydraulic actuator). 9 and the screw advances. Therefore, hydraulic control is performed by an open loop control system that is different from the feedback control system including the position sensor, and even if the position sensor is removed, the screw does not collide with the inner wall of the heating cylinder and the operator is prevented from danger. To be done.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS 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 safety device 1 according to the present invention will be described with reference to FIG.

In FIG. 1, an injection molding machine M is an injection device 1.
Equipped with 0. The injection device 10 has an injection nozzle 12 at the front end,
The heating cylinder 11 provided with the hopper 13 at the rear is provided,
The screw 14 is inserted into the heating cylinder 11, and the screw driving unit 15 is connected to the rear end of the heating cylinder 11. The screw drive unit 15 is an injection cylinder (hydraulic actuator) 9 having a double rod type piston 16 built-in.
And the front rod 16f of the piston 16 has a screw 14
The rear rod 16r is spline-coupled to the shaft of the oil motor 18 arranged at the rear end of the injection cylinder 9 while being coupled to the rear end.

On the other hand, a hydraulic circuit C including a control circuit 20 is connected to the injection cylinder 9. The hydraulic circuit C includes a 4-port servo valve 21, the A port of the servo valve 21 being in the front oil chamber 9f of the injection cylinder 9, the B port being the rear oil chamber 9r of the injection cylinder 9, and the P port being the hydraulic pump 2. , T ports are connected to the oil tank 22, respectively. Further, the accumulator 3 is connected to the oil feed line Lp between the hydraulic pump 2 and the P port, and the oil feed line Lp is further connected.
An oil tank 22 is connected to p via an open / close control valve 23.

On the other hand, the control circuit 20 detects a position of the screw 14 and includes a position sensor 24 for obtaining a speed detection value Vd, and a difference detector for obtaining a deviation value between the speed detection value Vd and the speed setting value Vs. 26, a speed compensator 27 for obtaining a speed operation amount Vc that is speed-compensated for a deviation value obtained from the difference detector 26, a switch function unit 28 for selecting the speed operation amount Vc, and a servo valve 21 for controlling the speed operation amount Vc. A servo command unit 29 for converting into a command signal Sc is provided, and this command signal Sc is given to the command signal input unit of the servo valve 21. The above constitutes a feedback control system for controlling the speed of the screw 14.

Further, the safety device 1 according to the present invention is connected to the control circuit 20. The safety device 1 includes a control unit 30, and a pump motor 2m of the hydraulic pump 2 is provided on the input side of the control unit 30.
A limit switch 3 is connected to a stop switch 31 for stopping the operation of the control unit 30 and detects that the safety cover H mounted on the injection molding machine M has been removed.
Connect two. The stop switch 31 and the limit switch 32 both detect a state in which pressure accumulation in the accumulator 3 is unnecessary, and in particular, the stop switch 31 constitutes a state detection unit 4 that detects a stop of the pump motor 2m of the hydraulic pump 2. To do. In this case, the stop switch 31 may be a power switch or the like for stopping the pump motor 2m, or a sensor for directly detecting whether or not the pump motor 2m is rotating, as long as it can detect the stop of the pump motor 2m.
On the other hand, the limit switch 32 constitutes the state detection unit 5 that detects the start of maintenance. That is, as shown in FIG. 3, since the injection molding machine M is detachably attached with the molding machine body Mo or the safety cover H for protecting the operator,
At the start of maintenance, the safety cover H is always removed. Therefore, if the limit switch 32 that is turned on when the safety cover H is removed is attached to the molding machine body Mo side, it is possible to detect that the safety cover H has been removed by the limit switch 32 and also to detect the start of maintenance. On the other hand, a forward switch 7s (operation switch 7) for advancing the screw 14 by open loop control is connected to the input side of the control unit 30.

On the other hand, the output side of the control unit 30 is connected to the command signal input unit of the opening / closing control valve 23. The control unit 30 and the opening / closing control valve 23 constitute the automatic discharge control unit 6, and at least one of the state detection units 4 and 5 is the state detection unit 4
Alternatively, if the detection result is given from 5, the control unit 30 gives the discharge command signal So to the opening / closing control valve 23, and the pressure oil remaining in the accumulator 3 is drained by the drain circuit Cd (oil tank 2).
Discharge to 2). In this case, the opening / closing control valve 23 is normally located on the symbol a side and shuts off the drain circuit Cd and the oil supply line Lp, but is switched to the symbol b side by giving the discharge command signal So, Drain circuit C
d and the oil feed line Lp are connected.

A switch function unit 33 is provided with a speed set value Vm on the input side. This speed setting value V
At the time of maintenance, m supplies low-pressure pressure oil to the injection cylinder 9 by open loop control, and the screw 14 is rotated at a low speed.
Select a size that can move forward. On the other hand, the output side of the switch function unit 33 is connected to the servo command unit 29. The switch function units 28 and 33 are controlled to be opened and closed by the control unit 30. As described above, the auxiliary control unit 8 using the open loop control circuit is configured.

Next, the operation of the safety device 1 of the hydraulic injection molding machine according to this embodiment will be described with reference to the flow charts shown in FIGS.

First, the basic operation will be described. During speed control of the screw 14, the control unit 30 turns on the switch function unit 28 and turns off the switch function unit 33. The open / close control valve 23 is switched to the symbol a side. Then, from the difference detector 26, the speed setting value Vs
And a deviation value of the speed detection value Vd is obtained, this deviation value is given to the speed compensating unit 27, and the speed compensating unit 27 obtains the speed-compensated speed operation amount Vc.
This speed operation amount Vc is given to the servo command unit 29.
In the servo command unit 29, the speed operation amount Vc is converted into a command signal Sc for controlling the servo valve 21, and this command signal Sc is given to the control signal input unit of the servo valve 21 so that the oil feed line Lp is supplied. The flow rate is controlled. As a result, pressure oil whose flow rate is controlled is supplied to the rear oil chamber 9r of the injection cylinder 9, and the screw 14 moves forward. Further, since the actual speed detection value Vd is obtained from the speed detection unit 25,
As a result, the command signal Sc changes, and feedback control is performed so that the forward speed of the screw 14 matches the speed set value Vs.

On the other hand, when the screw 14 is replaced or maintained, the safety device 1 operates as follows. First, when the stop switch 31 is operated to stop the operation of the pump motor 2m of the hydraulic pump 2, this state is detected by the state detection unit 4, and the detection result is given to the control unit 30 (step 51). As a result, the control unit 30 gives the discharge command signal So to the opening / closing control valve 23, and switches the opening / closing control valve 23 to the symbol b side. Therefore, the oil supply line Lp connected to the accumulator 3 is connected to the drain circuit Cd, and the pressure oil remaining in the accumulator 3 is automatically discharged to the drain circuit Cd (step 53).

On the other hand, when performing maintenance or the like without stopping the pump motor 2m, the safety cover H is detached from the molding machine body Mo before the maintenance is started. It is detected by 32, and the detection result is given to the control unit 30 (step 52). As a result, the control unit 30 gives the discharge command signal So to the opening / closing control valve 33 to output the symbol b.
Switch to the side. Therefore, also in this case, the oil supply line Lp to which the accumulator 3 is connected is connected to the drain circuit Cd, and the pressure oil of the accumulator 3 is automatically discharged to the drain circuit Cd (step 53). At this time, the hydraulic pump 2 in operation is in an unload state (step 56).

Therefore, the pump motor 2m of the hydraulic pump 2
By detecting the stop of or the start of maintenance, the pressure oil remaining in the accumulator 3 is automatically discharged, and the harmful effects of high pressure oil splashing during screw replacement or maintenance are reliably prevented.

When the screw 14 is moved forward during maintenance, the screw operation switch is turned on because the auxiliary control section 8 using the open loop control circuit is provided.
If the forward switch 7s is turned on (step 54) under the condition that it is being operated (step 55), the control unit 30 turns off the switch function unit 28 and turns on the switch function unit 33.
As a result, the speed setting value Vm is set to the servo command unit 29.
Granted to. Then, the command signal Sc based on this is given from the servo command unit 29 to the servo valve 21, low-pressure oil is supplied to the injection cylinder 9, and the screw 1
4 moves forward at a low speed (steps 57 and 58). That is, since the hydraulic control is performed by the open loop control system different from the feedback control system including the speed detection unit 25, even if the position sensor 24 in the speed detection unit 25 is removed, the screw 14 is attached to the inner wall of the heating cylinder 11. The harmful effects of collision and danger to the operator are prevented.

The embodiment has been described in detail above.
The present invention is not limited to such an embodiment.
For example, although the embodiment shows the case of being configured by hardware, the same processing may be executed by software.
Also, the example in which the state detection unit that detects the start of maintenance detects that the safety cover has been removed has been given, but any number of arbitrary state detection units that can detect the start of maintenance such as the rotating position of the heating cylinder can be used. Only available. In addition, the detailed configuration, quantity, method, etc. can be arbitrarily changed without departing from the scope of the present invention.

[0027]

As described above, according to the present invention, in the safety device of the hydraulic injection molding machine including the hydraulic circuit connected to the accumulator for accumulating the hydraulic pressure of the hydraulic pump, the state in which the accumulator does not need to accumulate the pressure is detected. If two or more state detection units and at least one state detection unit detect the state, an automatic discharge control unit that discharges the pressure oil of the accumulator to the drain circuit is provided, and further, a low pressure pressure is set by operating the operation switch. Since the auxiliary control unit using the open loop control circuit capable of supplying oil to the hydraulic actuator is provided, the following remarkable effects are achieved.

[0028] It is possible to reliably prevent the harmful effects of high pressure oil being scattered during screw replacement or maintenance.

It is possible to reliably prevent the screw from colliding with the inner wall of the heating cylinder and causing a danger to the operator during screw replacement or maintenance.

[Brief description of drawings]

FIG. 1 is a block diagram of a main part of an injection molding machine including a safety device according to the present invention,

FIG. 2 is a flowchart showing the operation of the safety device,

FIG. 3 is an external side view showing a part of the injection molding machine,

FIG. 4 is a partial cross-sectional side view showing a screw connecting mechanism of the injection molding machine;

[Explanation of symbols]

 1 Safety Device 2 Hydraulic Pump 2m Pump Motor 3 Accumulator 4 State Detection Unit 5 State Detection Unit 6 Automatic Discharge Control Unit 7 Operation Switch 8 Auxiliary Control Unit 9 Injection Cylinder C Hydraulic Circuit Cd Drain Circuit H Safety Cover

Front Page Continuation (72) Inventor Takahito Shioiri 2110 Nanjo, Osamu, Shiroki-cho, Hanashina-gun, Nagano Nissei Plastic Industry Co., Ltd.

Claims (7)

[Claims] 1. A safety device for a hydraulic injection molding machine comprising a hydraulic circuit to which an accumulator for accumulating the hydraulic pressure of a hydraulic pump is connected, and one or more state detectors for detecting a state where accumulator pressure accumulation is unnecessary. A safety device for a hydraulic injection molding machine, comprising an automatic discharge control unit for discharging pressure oil from an accumulator to a drain circuit when at least one state detection unit detects the state. 2. The safety device for a hydraulic injection molding machine according to claim 1, wherein the state detection unit detects stop of the pump motor of the hydraulic pump. 3. The safety device for a hydraulic injection molding machine according to claim 1, wherein the state detection unit detects the start of maintenance. 4. The safety device for a hydraulic injection molding machine according to claim 3, wherein the state detection unit detects that the safety cover of the injection molding machine has been removed. 5. A safety device for a hydraulic injection molding machine comprising a hydraulic circuit to which an accumulator for accumulating the hydraulic pressure of a hydraulic pump is connected, and one or more state detecting units for detecting a state where accumulator pressure accumulation is unnecessary. , If at least one state detection unit detects the above state, an automatic discharge control unit that discharges the pressure oil of the accumulator to the drain circuit, and an open loop control that can supply low pressure oil to the hydraulic actuator by operating the operation switch. A safety device for a hydraulic injection molding machine, comprising an auxiliary control unit using a circuit. 6. The safety device for a hydraulic injection molding machine according to claim 5, wherein the state detection unit detects the start of maintenance. 7. The safety device for a hydraulic injection molding machine according to claim 6, wherein the state detection unit detects that the safety cover of the injection molding machine has been removed.