JP2508954B2 - Resin leak prevention method for injection nozzle in injection molding machine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is mainly applied to an injection molding machine for injecting resin into a mold from an injection nozzle pressed against a mold by hydraulically driving to prevent resin leakage from the injection nozzle. Regarding the method.

[0002]

2. Description of the Related Art Conventionally, as a hydraulically driven injection molding machine of this type, a mold clamping cylinder that closes a pair of molds and performs mold clamping, and an injection nozzle (injection unit) are brought into contact with and separated from the molds. A nozzle forward / backward moving cylinder, an injection cylinder for injecting resin into the mold from the injection nozzle, and a screw rotation motor for rotating a screw in the injection unit respectively start and stop these cylinders or motors. 1 via a solenoid valve for controlling flow path switching
It is known to be connected to one variable flow control valve and one variable pressure control valve.

[0003]

By the way, in the above-mentioned conventional hydraulically driven injection molding machine, when so-called nozzle touch molding is performed, that is, the injection nozzle is not always retracted during the molding cycle, but always hits the mold. In the contacted state, the mold clamping cylinder closes the pair of molds, and after the mold is clamped, the resin is immediately injected from the injection nozzle by the injection cylinder into the mold (cavity). The resin is filled and cooled, and then the pair of molds is opened by the mold clamping cylinder to take out the molded product from the mold. In the case of performing such molding, before the mold clamping is completed and before the injection process, the solenoid valve for the nozzle forward / backward cylinder is excited to apply hydraulic pressure to the nozzle forward / backward cylinder, After confirming by the limit switch (proximity switch) that the injection nozzle is in contact with the mold (at the forward end), the resin is injected from the injection nozzle into the mold by the injection cylinder after a predetermined time. I am trying to do it. However, after confirming that the injection nozzle is in contact with the mold (at the forward end) with the limit switch (proximity switch) in this way, the resin is injected from the injection nozzle into the mold after a predetermined time. When injecting, if the hydraulic pressure rises slowly,
The resin may be injected from the injection nozzle before the force of pressing the injection nozzle against the mold by the nozzle forward-backward cylinder reaches a sufficient pressure. And in this case,
There is a problem that the resin leaks from the contact portion between the injection nozzle and the mold.

Therefore, in order to solve the above-mentioned conventional problems, by detecting the pressure increase of the pressing force,
A method of confirming that the injection nozzle is pressed against the mold by sufficient pressing force is adopted, but in this case, it takes time to confirm that the pressing force reaches a predetermined pressure. Therefore, there is a problem that the molding cycle is lengthened by that amount of time.

The present invention has been made in view of the above circumstances, and an object of the present invention is to make it possible to inject a resin into a mold while the injection nozzle is surely pressed against the mold. It is an object of the present invention to provide a resin leakage prevention method for an injection nozzle in an injection molding machine, which can surely prevent the resin from leaking from the contact portion between the nozzle and the mold and shorten the molding cycle.

[0006]

In order to achieve the above object, the present invention presses an injection nozzle against the fixed mold in the mold clamping step after closing the movable mold and the fixed mold. Is.

[0007]

According to the method for preventing resin leakage of the injection nozzle in the injection molding machine of the present invention, after the movable mold and the fixed mold are closed, when the mold is clamped, the injection nozzle is pressed against the fixed mold. As a result, when the mold clamping is completed, the injection nozzle is pressed against the fixed mold with a sufficient pressing force, and immediately after the completion of the mold clamping, the resin is surely injected into the cavity of the mold without leaking from the injection nozzle.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

In the figure, reference numeral 1 is a mold clamping cylinder, and this mold clamping cylinder 1 is fixed to one end side (the left end side in FIG. 1) of an end plate 3 erected on a base 2.
The tip end portion of the piston rod 1a of the mold clamping cylinder 1 penetrates the end plate 3 and is connected to the central portion of the toggle mechanism 4, and the left and right ends of the toggle mechanism 4 that branch up and down are: Each of them is connected to the end plate 3 and the movable platen 5. Further, on the base 2 opposite to the end plate 3 facing the moving plate 5,
The fixed platen 6 is provided upright, and the movable platen 5 and the fixed platen 6 are provided.
A movable die 5a and a fixed die 6a are attached to the respective facing surfaces of the. By moving the piston rod 1a of the mold clamping cylinder 1 forward and backward, the movable platen 5 reciprocates in the horizontal direction via the toggle mechanism 4, and both molds 5a and 6a are closed. As a result, the cavity (void) 7 is formed inside. Further, an ejector cylinder 8 is fixed to the surface of the movable platen 5 opposite to the surface on which the movable die 5a is attached, and the piston rod 8a of the ejector cylinder 8 is moved forward after the die is opened. The tip portion (ejector pin) of the piston rod 8a penetrates the movable platen 5 and the movable die 5a to project the molded product inside the movable die 5a to the outside.

An injection cylinder 9 is provided so as to come in contact with and separate from the fixed platen 6, and an upper portion of the injection cylinder 9 is provided with
A hopper 10 for supplying resin is arranged inside the injection cylinder 9. A screw 11 is inserted inside the injection cylinder 9, and a rotating shaft 12 of the screw rotating hydraulic motor 12 is provided at a base end portion of the screw 11.
a is connected. A piston rod 13a of an injection cylinder 13 is connected to an end of the hydraulic motor 12 for screw rotation opposite to the rotary shaft 12a.
By moving the piston rod 13a forward and backward, the screw 1 is moved through the screw rotation hydraulic motor 12.
1 reciprocates in the horizontal direction. The injection cylinder 9 and the injection cylinder 13 are connected to each other by the connecting member 1.
And the injection cylinder 13
The distal end of the piston rod 15a of the nozzle forward / backward moving cylinder 15 fixed to the base 2 is connected to the base end of the injection cylinder 13 and the screw rotation by rotating the piston rod 15a forward / backward. Hydraulic motor 1
Along with 2, the injection cylinder 9 is adapted to reciprocate horizontally.

Next, each of the cylinders 1, 8, 13, 15
A hydraulic circuit for driving the screw rotation hydraulic motor 12 will be described with reference to FIGS. 2 and 3. In these drawings, reference numeral 20 is a hydraulic pump driven by a motor 21, and an oil tank O is provided at a suction end of the hydraulic pump 20.
The variable flow rate control valve 22 and the relief valve 23 are connected to T and the discharge end, respectively. The variable flow rate control valve 22 controls the flow rate of oil flowing in the valve by a motor 24. The discharge end of the variable flow control valve 22 is connected to one end of a throttle valve 26 via a pilot pipe 25, and the other end of the throttle valve 26 is connected to the load side port of the back pressure solenoid valve DV1. B and relief valve 27
And a pilot end of the relief valve 23 are connected to each other. Then, the back pressure solenoid valve DV
The suction end of the variable pressure control valve 28 is connected to the port P of No. 1, and the discharge end of the variable pressure control valve 28 and the port T of the back pressure solenoid valve DV1 are connected to the oil tank OT. . The variable pressure control valve 28 controls the pressure of oil in the circuit by the motor 29. Further, the discharge ends of the relief valves 23 and 27 and the drain end of the variable flow rate control valve 22 are connected to the oil tank OT.

At the discharge end of the variable flow control valve 22, a mold opening / closing switching solenoid valve DV2, an ejector forward / backward switching solenoid valve DV3, and a nozzle forward / backward switching solenoid valve via a check valve 30. The DV4, the non-reverse reverse switching circuit (hydro valve) 31, and the injection / supply switching electromagnetic valve DV5 are connected to each other. The load side port A of the mold opening / closing switching solenoid valve DV2 is connected to the base end (left end in FIG. 3) of the mold clamping cylinder 1 via a cam valve 32, and the tip of the mold clamping cylinder 1 is , Is connected to the port P of the differential solenoid valve DV6. Further, the port A of the differential solenoid valve DV6 is connected to the load side port B of the mold opening / closing switching solenoid valve DV2, and the port B of the differential solenoid valve DV6 and the mold clamping cylinder 1 are connected.
A check valve 33 is arranged between the base end and the base end of the check valve. The port T of the differential solenoid valve DV6 is connected to the oil tank O.
A solenoid valve D for switching the mold opening / closing, which is connected to T
Each port T of V2 and the cam valve 32 has a throttle valve 34,
It is connected to the oil tank OT via 35.

The ejector forward / reverse switching solenoid valve DV3
The load-side ports A and B of the ejector cylinder 8 are
Of the nozzle forward / reverse switching solenoid valve DV4, the load side ports A and B are connected to the base end and the front end (left and right ends in FIG. 3) of the nozzle forward / backward movement cylinder 15 (FIG. 2). At the left and right ends) respectively. The ports T of the solenoid valves DV3 and DV4 are connected to the oil tank OT. The non-reverse reverse switching circuit 31 is composed of a main switching valve 36 and a non-reverse reverse solenoid valve DV7 that controls switching of the main switching valve 36. 31 main switching valve 3
The port P of 6 is connected to the tip of the injection cylinder 13 (the left end in FIG. 2). The base end of the injection cylinder 13 is connected to the port T of the main switching valve 36 of the non-reverse reverse switching circuit 31 and the load side port A of the injection / supply switching solenoid valve DV5. Further, the load side port B of the injection / supply switching solenoid valve DV5 is connected to one end of the screw rotation hydraulic motor 12, and the port T of the injection / supply switching solenoid valve DV5 has the pressure compensating valve 37. It is connected to the oil tank OT via. The other end of the screw rotation hydraulic motor 12 is
It is connected to the oil tank OT via a check valve 38. Furthermore, the port A of the back pressure solenoid valve DV1 and the pilot end of the pressure compensation valve 37 are connected to one end of the screw rotation hydraulic motor 12 via a pilot pipe 39 and a throttle valve 40, respectively. Then, the solenoid a of the back pressure solenoid valve DV1 and each solenoid valve DV2
The excitation signals from a sequence control unit (not shown) that controls the overall sequence (procedure) of the injection molding process are sequentially input to the solenoids a and b of the DV7.

Next, FIG. 4 shows the case of carrying out the method of the present invention in the injection molding machine configured as described above.
Will be described with reference to. First, the nozzle 9 at the tip of the injection cylinder 9
In a mold open state in which a is separated from the fixed mold 6a of the fixed platen 6 and the fixed mold 6a and the movable mold 5a of the movable platen 5 are separated from each other by a predetermined distance, as shown in FIG. A of the solenoid valve DV2 for use and each solenoid valve DV
When the solenoids b of DV3 and DV6 are respectively excited, the hydraulic oil from the hydraulic pump 20 causes the variable flow control valve 22, the ports P and A of the solenoid valve DV2 for switching the mold opening and closing, and the cam valve 3 to operate.
2 is supplied to the base end of the mold clamping cylinder 1 at a flow rate and pressure according to the variable flow rate control valve 22 and the variable pressure control valve 28, and returns oil from the tip of the mold clamping cylinder 1. Is returned to the base end side of the mold clamping cylinder 1 via the ports P and B of the differential solenoid valve DV6 and the check valve 33, so that the piston rod 1a of the mold clamping cylinder 1 is pushed at a high speed and at a low pressure. By moving forward with pressure, toggle mechanism 4
The movable platen 5 is moved closer to the fixed platen 6 side together with the movable mold 5a via the, and the movable mold 5a and the fixed mold 6a of the fixed platen 6 are closed, while the hydraulic oil from the hydraulic pump 20 has a variable flow rate. Control valve 22, ejector forward / backward switching solenoid valve DV3
Since it is supplied to the tip of the ejector cylinder 8 through the ports P and B, the piston rod 8a of the ejector cylinder 8 is fixed at the retracted end.

Next, at time T1, the movable mold 5a is
When the fixed mold 6a and the fixed mold 6a are closed, the mold clamping process is started, and the solenoid b of the differential electromagnetic valve DV6 is demagnetized, and
Since the solenoid a of the solenoid valve DV4 for nozzle forward / reverse switching is excited, the hydraulic fluid whose flow rate and pressure are controlled by the variable flow rate control valve 22 and the variable pressure control valve 28 is the port P of the solenoid valve DV2 for mold opening / closing switching. , A, cam valve 32
Is continuously supplied to the base end of the mold clamping cylinder 1 via the oil, and the return oil from the tip of the mold clamping cylinder 1 is supplied to the ports P and A of the differential solenoid valve DV6 and the solenoid for switching the mold opening and closing. By being returned to the oil tank OT through the ports B and T of the valve DV2 and the throttle valve 34, the piston rod 1a of the mold clamping cylinder 1 increases the pressing force instead of decelerating the speed from the mold closing time. Further moving forward, the movable die 5a and the fixed die 6a
And the mold are clamped until they reach a predetermined mold clamping force, while the hydraulic oil is used for the check valve 30 and the nozzle forward / reverse switching solenoid valve DV4.
Is supplied to the base end of the nozzle forward / backward moving cylinder 15 through the ports P and B of the nozzle forward / backward moving cylinder 1.
The piston rod 15a of 5 advances, the injection cylinder 9 approaches the fixed plate 6 together with the injection cylinder 13 and the screw rotation hydraulic motor 12, and the nozzle 9a at the tip of the injection cylinder 9 comes into contact with the fixed mold 6a. It is pressed firmly with a predetermined pressing force.

In this case, since the nozzle 9a at the tip of the injection cylinder 9 is pressed against the fixed mold 6a with the mold clamping force applied between the movable mold 5a and the fixed mold 6a, the nozzle 9a is pressed. The force does not cause the fixed mold 6a and the fixed platen 6 to tilt toward the movable platen 5 side, that is, the so-called mold plate tilts. When the mold clamping process is completed at time T2, the advance pressure increase of the nozzle 9a is confirmed, and then the injection process is started. That is, each solenoid valve DV5, DV
The solenoid a of No. 7 is excited to inject the hydraulic oil from the hydraulic pump 20 into the ports P and A of the solenoid valve DV5 for injecting and switching the supply.
And to return the return oil from the tip of the injection cylinder 13 to the oil tank OT from the ports P and B of the main switching valve 36 of the non-reverse reverse switching circuit 31. As a result, the piston rod 13a of the injection cylinder 13 advances. As a result, the screw 1 in the injection cylinder 9 is passed through the screw rotation hydraulic motor 12.
As 1 approaches the fixed plate 6 side, the molten resin in the injection cylinder 9 is injected from the nozzle 9a and filled in the cavity 7 between the movable die 5a and the fixed die 6a. in this case,
After confirming the advance pressure increase of the nozzle 9a, the resin is injected from the nozzle 9a, so that the resin is surely supplied into the mold without leaking outside.

Subsequently, at time T3, when the injection process is completed, the solenoid a of each of the solenoid valves DV5 and DV7 is demagnetized to stop the forward movement of the screw 11 and to rotate the non-reverse solenoid valve DV7. By exciting the solenoid b, the hydraulic oil is supplied to the tip of the injection cylinder 13 from the ports A and P of the main switching valve 36 of the non-reverse reverse switching circuit 31, and the return oil from the base end of the injection cylinder 13 is supplied. Is returned to the oil tank OT via the ports T and B of the main switching valve 36. As a result, the screw 11 in the injection cylinder 9 retreats without rotating, so that the resin pressure in the injection cylinder 9 drops to a predetermined pressure (internal pressure is removed).

Further, at time T4, when the removal of the internal pressure of the injection cylinder 9 is completed, the process goes to the supply step, where the solenoid b of the non-reverse reverse solenoid valve DV7 is demagnetized, and the injection / supply switching solenoid valve DV5 is switched on. Solenoid b and each solenoid valve DV
By energizing the solenoids a of DV1 and DV7 respectively, the hydraulic oil is injected and supplied to the screw rotation hydraulic motor 12 from the ports P and B of the supply switching solenoid valve DV5, and the screw rotation hydraulic motor 12 is As the screw rotates, the screw 11 in the injection cylinder 9 rotates,
Supply of resin from the hopper 10 to the inside and plasticization are started, and the tip of the injection cylinder 13 and the oil tank O are started.
T is communicated with the main switching valve 36 via ports P and B, while the base end of the injection cylinder 13 is connected to the ports A and T of the injection / supply switching solenoid valve DV5 and the pressure compensating valve 37.
Since it is communicated with the oil tank OT via the, the piston rod 13a of the injection cylinder 13 generates a back pressure corresponding to the set pressure of the pressure compensation valve 37 as the screw 11 in the injection cylinder 9 moves backward. Retreat while receiving.

Next, at time T5 when the supply process is completed, the solenoid b of the injection / supply switching solenoid valve DV5 and the solenoid a of each solenoid valve DV1, DV7 are demagnetized and the non-reverse reverse solenoid is operated. By exciting the solenoid b of the valve DV7, the screw 11 in the injection cylinder 9 is retracted again without rotating, and the resin pressure in the injection cylinder 9 is reduced. Then, at time T6, the solenoid a of the nozzle forward / reverse switching solenoid valve DV4 and the solenoid b of the non-reverse reverse solenoid valve DV7 are demagnetized to press the nozzle 9a against the fixed die 6a. And the internal pressure removing step is terminated, and the resin filled in the cavity 7 is cooled until time T7 (cooling step).

When the cooling of the molded product in the cavity 7 is completed, the mold opening step is started, the solenoid a of the mold opening / closing switching solenoid valve DV2 is demagnetized, and the solenoid b of the mold opening / closing switching solenoid valve DV2 is demagnetized. And differential solenoid valve DV
By energizing the solenoid a of No. 6, the hydraulic oil from the hydraulic pump 20 is clamped through the ports P and B of the mold opening / closing switching solenoid valve DV2 and the ports A and P of the differential solenoid valve DV6. The return oil from the base end of the mold clamping cylinder 1 is supplied to the tip of the cylinder 1 and the cam valve 32, the ports A and T of the mold opening / closing switching solenoid valve DV2, and the throttle valve 34.
Since it is returned to the oil tank OT via the, the piston rod 1a of the mold clamping cylinder 1 is retracted, and the movable mold 5a is separated from the fixed mold 6a.

Further, when the movable die 5a is separated from the fixed die 6a by a predetermined distance and the die opening process is completed (at time T8), the solenoid a of the differential solenoid valve DV6 and the solenoid valves DV2 and DV3 are closed. Demagnetize each solenoid b. Then, by alternately exciting the solenoids a and b of the ejector forward / reverse switching solenoid valve DV3 twice at predetermined intervals, the piston rod 8 of the ejector cylinder 8 is excited.
After a is moved forward and backward to release the molded product adhering to the movable mold 5a (see time T9), it stands by in that state until the next molding process is started.

Next, in the second molding step, the solenoid a of the mold opening / closing switching solenoid valve DV2 and the respective solenoid valves DV3, DV6 are moved in the same manner as the first molding step described above.
The mold clamping cylinder 1 is driven by exciting the respective solenoids b of the movable mold 5 and the movable mold 5 with respect to the fixed mold 6a.
After contacting a and completing the mold closing process, the solenoid b of the differential solenoid valve DV6 is demagnetized, and the solenoid a of the nozzle forward / reverse switching solenoid valve DV4 is excited to move the stationary die 6a. The mold 5a and the mold 5a are clamped by a predetermined mold clamping force, and the nozzle 9a at the tip of the injection cylinder 9 in a state where the mold 5a is only in contact with the fixed mold 6a and the pressing force is not applied by the nozzle forward and backward moving cylinder 15. The fixed mold 6a is strongly pressed with a required pressing force.

Then, at time T2, the injection process is started. In this case, like the first molding process,
Compared with the time required to contact the fixed mold 6a with the nozzle 9a, which is separated from the fixed mold 6a by a predetermined distance, and to apply the predetermined pressing force, the pressing force acts only by contacting the fixed mold 6a. Since the time required to press the nozzle 9a against the fixed mold 6a with a predetermined pressing force from the unpressed state is significantly shortened, a sufficient pressing force is applied during the mold clamping process (time T1 to time T2). Is applied and the nozzle 9a is reliably pressed against the fixed mold 6a. Therefore, as in the first molding step, the nozzle 9a is
There is no need to check the advance pressure rise of the mold, and when the completion of the mold clamping process is confirmed by the limit switch that detects the completion of mold clamping (or the timer that notifies the completion of mold clamping), the resin in the mold is immediately removed. Even if the injection is started, the resin does not leak to the outside from the contact portion between the nozzle 9a and the fixed mold 6a, and the resin is reliably filled in the mold.

In this way, by repeatedly performing molding (nozzle touch molding) in a state where the injection nozzle is always in contact with the mold without retracting during the molding cycle, a large number of moldings of good quality are performed. The product is smoothly molded. In this case, the nozzle 9a is pressed against the fixed mold 6a with a predetermined pressing force during the mold clamping process, and the resin is filled into the mold immediately after the completion of the mold clamping. After that, the pressing force of the nozzle 9a against the fixed mold 6a is increased to secure a sufficient pressing force,
Compared with the method of supplying the resin into the mold, the molding cycle can be shortened significantly and the productivity can be improved.

[0025]

As described above, according to the present invention, the injection nozzle is pressed against the mold during the mold clamping process after the pair of molds are closed. When the injection nozzle is pressed against the mold and the mold is clamped, the injection nozzle is pressed against the mold with sufficient pressing force. It is possible to inject into the mold, and it is possible to reliably prevent the resin from leaking from the contact portion between the injection nozzle and the mold, and immediately inject the resin into the mold from the injection nozzle after completion of mold clamping. Therefore, the molding cycle can be shortened.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an injection molding machine showing an embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram for driving the injection molding machine of FIG.

FIG. 3 is a hydraulic circuit diagram connected to FIG.

FIG. 4 is an explanatory diagram showing an operation timing of a solenoid of each solenoid valve.

[Explanation of symbols]

 5 Moving plate 5a Moving type 6 Fixed plate 6a Fixed type 9 Injection cylinder 9a Nozzle

Claims (1)

(57) [Claims] 1. A mold is clamped after closing a movable mold and a fixed mold, and an injection nozzle is pressed against the fixed mold, and a resin is formed in each mold from the injection nozzle. A method for preventing resin leakage of an injection nozzle in an injection molding machine for injecting into a cavity, wherein the injection nozzle is pressed against the fixed mold in the mold clamping step of each mold. Nozzle resin leakage prevention method.