JP3133259B2 - Injection plunger operation method for pre-plastic injection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of operating an injection plunger in a pre-plastic injection apparatus in which plasticization and injection of a material resin are performed by different cylinders.

[0002]

2. Description of the Related Art In general, a pre-plasticization type injection device has a plasticizing cylinder containing a plasticizing screw or a plunger arranged side by side with an injection cylinder containing an injection plunger. Connected to the tip of the injection cylinder, the resin melted and kneaded by the plasticizing cylinder (hereinafter referred to as plasticization) is fed to the front of the injection cylinder by pressure, and the injection plunger is measured while retracting. Injection is performed by moving forward.

[0003]

A clearance is provided between the injection cylinder and the injection plunger in order to reduce the resistance of the injection plunger against the forward and backward movements. This clearance is designed to have a minimum size that makes it difficult for the molten resin to enter, but the resin enters during repeated measurement and injection regardless of the clearance.

[0004] As long as the resin that has entered the clearance is in a molten state and is thinly interposed between the injection cylinder and the injection plunger, it does not adversely affect the advance / retreat movement of the injection plunger. If it intervenes in the state, the movement resistance increases and a pressure loss is caused.
In addition, misalignment occurs between the injection cylinder and the injection plunger, resulting in galling.

[0005] As means for removing the obstacle of the residual resin in the clearance, the shaft of the injection plunger is formed to have a smaller diameter than the tip, and the resin that has entered the clearance around the tip around the shaft of the injection plunger is used. It is conceivable to provide a required clearance to be leaked to the rear side, and to sequentially discharge the resin leaked and left in the clearance from a resin hole formed in the rear portion of the cylinder by retreating the injection plunger. However, such a solution is limited to a case in which the resin is in a heated state and has fluidity, and cannot exclude a resin that has lost fluidity due to solidification.

[0006] Generally, the heater zone of the injection cylinder in which the injection plunger is housed is defined as the stroke range of the injection plunger. However, even if the heater is provided to the rear of the hole, resin that adheres to the shaft of the injection plunger is stuck. The solidification of the injection plunger cannot be prevented, and this moreover acts as a movement resistance of the injection plunger.

[0007] Even if the frictional resistance due to the resin solidified by the sticking is small, the resin in the pre-plastic injection device is measured by injecting the material resin plasticized by the plasticizing device through the resin passage at the tip end of the injection cylinder. And pressurizes the tip of the injection plunger with the resin pressure, and moves the injection plunger to which a predetermined pressure (back pressure) is applied by the hydraulic cylinder, while moving the plasticized resin into the cylinder tip. Accumulation has a significant effect on weighing.

As means for removing the resin stuck to the shaft portion of the injection plunger, a sleeve or the like scratches around the inside of the cylinder behind a hole formed in the injection cylinder wall behind the part corresponding to the retreat limit of the tip of the injection plunger. It is considered that a take-out member is provided, and when the injection plunger is moved backward for measurement, the scraping member scrapes the solidified resin stuck. This removal means had a certain effect, but the movement stroke of the injection plunger during the injection / metering process was limited to the measurement range, and the injection stroke of the resin was small, and the molding stroke was short. The scraping amount of the resin by the scraping member during the molding stroke is also small, and most of the residual resin stagnates by filling the clearance around the shaft of the injection plunger. This stagnation of the residual resin causes a movement resistance of the injection plunger to give a subtle change, and also causes a disturbance in the injection speed and the injection pressure.

[0009] The present invention is to solve this new problem as well as the above-mentioned conventional problems, and an object of the present invention is to perform the operation of moving the injection plunger back and forth other than during the injection / metering process. It is an object of the present invention to provide an injection plunger operation method for a pre-plastic injection apparatus, which can reduce the movement resistance of the injection plunger due to residual resin remaining in a clearance around a shaft portion of the plunger.

[0010]

SUMMARY OF THE INVENTION According to the present invention, there is provided an injection device in which an injection plunger having a shaft portion whose diameter is smaller than that of a tip portion is provided so as to be able to move forward and backward, and a plasticizing device. A part of the injection plunger communicates with a part corresponding to the forward end of the injection plunger, and a cutout hole is provided in the injection cylinder wall behind the part corresponding to the retreat limit of the tip of the injection plunger. In a prepra-type injection device in which the residual resin in the clearance between the injection cylinder and the injection plunger shaft by the member is scraped by the retreat of the injection plunger and discharged into the above-described hole, the advancing and retreating operation of the injection plunger is performed by injection pressure,
In comparing the set values such as the injection speed, the filling time, the weighing time, the plunger most advanced position, and the pressure in the mold with the detected values, the detected value after molding of a predetermined number of shots is at least one upper limit of the above set values. Alternatively, the injection or metering process is stopped and performed when the value deviates from the lower limit.

Further, according to the present invention, the advancing and retreating operation of the injection plunger includes an injection pressure, an injection speed, a filling time, a measuring time,
In the comparison between the set value such as the plunger most advanced position and the pressure in the mold and the detected value, when the detected value after the start of molding deviates from at least one of the upper and lower limits of the set value, the injection or measuring step is performed. Stop it and do it.

In the above configuration, even during injection or metering, for example, if the filling time detected and calculated by the position sensor exceeds a set value, the residual resin in the clearance becomes a forward resistance of the injection plunger. It is determined that it took a long time, the injection or metering process is immediately stopped, and the operation of moving the injection plunger is switched to the retreat operation up to the full stroke by the control device. By retreating to the position corresponding to the retraction limit of the tip of the injection plunger, most of the resin remaining in the clearance between the cylinder and the shaft of the injection plunger is forcibly fed to the hole, and at the same time, the injection plunger is moved by the scraping member. Is shaved, and the resin stuck around the shaft is scraped off. As a result, most of the resin remaining in the clearance is discharged out of the injection cylinder through the hole, and the resistance of the injection plunger to movement due to the resin remaining in the clearance becomes extremely small, so that the measurement accuracy and the injection accuracy as set in advance are maintained. become.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings, reference numeral 1 denotes an injection device, 2 denotes a plasticizing device juxtaposed on the injection device, and both devices are resin paths 3 at a position corresponding to a forward end of an injection plunger tip at the tip of an injection cylinder. To communicate with each other.

The injection device 1 has an injection plunger 10 mounted therein so as to be able to advance and retreat, and has an injection cylinder 12 provided with a nozzle 11 at the tip, and a piston 13 connected to the rear end of the injection cylinder 12 to connect a piston 13 to the injection plunger 10. And a hydraulic cylinder 14 for injection. Between the shaft 10a of the injection plunger 10 and the inner peripheral surface of the injection cylinder 12, a clearance 18 required for the reciprocation of the injection plunger 10 is provided except for the tip 10b of the injection plunger.

The injection cylinder 12 has an inflow path 15 for the resin path 3 above a position corresponding to the forward end of the injection plunger tip 10b of the tip 12a. A hole 16 is formed in the injection cylinder wall behind the injection plunger 10 at a position corresponding to the retreat limit of the injection plunger tip 10b.
The band heater 17 is provided to the outer periphery of the cylinder after the hole 16.

The clearance 18 around the shaft of the injection plunger 10 is formed to have a smaller diameter than the tip 10b of the injection plunger and is enlarged so that the tip 10 of the injection plunger 10 is formed.
The sliding resistance at the tip 10b of the injection plunger is reduced by facilitating the backward movement of the molten resin that has entered the clearance b. Due to the expansion of the clearance 18, the resin that has entered the fine clearance around the tip 10 b of the injection plunger adheres to and remains on the injection cylinder wall of the clearance 18 when the injection plunger 10 moves forward. When the plunger tip 10b retreats, the trailing edge forms
Will be able to be rushed towards.

A sleeve 19 for scraping is provided around the inside of the injection cylinder after the hole 16 and the shaft 10 of the injection plunger 10 is provided.
a is provided with a required gap (0.02 to 0.05 mm). The sleeve 19 expands the inner diameter of the injection cylinder 12 to the rear of the hole 16, inserts the sleeve 19 from the opening at the tip of the injection cylinder into the expanded portion, and installs the sleeve 19 at the rear of the hole 16. The inside diameter of the cylinder liner 12b, which is the same as the inside diameter of the rear part of the cylinder, is sandwiched and fixed by the end of the cylinder liner 12b.

The injection device 1 and the plasticizing device 2 are mounted and fixed on a support 21 provided on the hydraulic cylinder 14 of the injection device 1 by holding and holding the holding cylinder 22 of the plasticizing device 2 up and down.
The hydraulic cylinder 14 of the injection device 1 is mounted and fixed on a slidable base block 6 integrally connected to a step and connected to a fixed plate 4 of a mold clamping device via a nozzle touch cylinder 5. It is installed on 7.

In the above configuration, the material resin is plasticized by the rotation of the screw (not shown) in the plasticizing device 2, and the plasticized resin is sequentially pressure-fed into the tip end of the injection cylinder 12 via the resin path 3. . The plasticized resin is accumulated in the distal end of the injection cylinder 12 while pressing the distal end surface of the injection plunger 10 to move the injection plunger 10 backward. This accumulation is performed until the injection plunger 10 retreats to the set position, which is generally called weighing.

When the injection plunger 10 retreats from the preset molding stroke A (see FIG. 3), the completion of the weighing is detected by the position sensor 31 of the injection plunger 10 shown in FIG. The valve (not shown) provided on the device 2 side closes, the screw stops rotating, and the pressure feed of the plasticized resin stops. In addition, the switching valve 32 of the hydraulic circuit of the hydraulic cylinder 14 enters the neutral state, and the injection plunger 10 stops at the measuring position.

After the stop, the switching valve 32 is switched to the right by a command from the control device 30, and the injection plunger 10
Moves forward and the metering resin is injected and filled into the mold 23 from the nozzle 11. This filling pressure is constantly detected by a pressure sensor 33 provided in the mold. The injection plunger pressure is constantly detected by a pressure sensor 34 provided in a hydraulic circuit, and the detection values of both pressure sensors 33 and 34 are
Input to 0.

When the injection plunger 10 advances the molding stroke A, the injection filling is completed, and the injection time is measured, the valve on the plasticizing device 2 side opens according to a command from the control device 30, and the switching valve 32 Is switched to the right side, and the plasticized resin is again pressure-fed to the injection device side via the resin path 3 and shifts to a new measurement. In addition, 35 is a pressure adjusting valve.

By the forward movement of the injection plunger 10 during the injection step, the resin that has entered the clearance around the distal end portion 10b adheres to the cylinder wall side of the clearance 18 and remains. Also, the residual resin is scraped off by the rear edge of the distal end portion 10b of the injection plunger 10 that moves backward at the time of measurement and accumulates in the clearance 18. However, the distal end portion 10b moves toward the above-described hole 16 by the moving stroke. You will be able to be scraped. By repeating such reciprocating movement of the injection plunger 10,
Resin remaining in the clearance 18 sequentially reaches the rear hole 16 and is discharged out of the cylinder. Also injection plunger 1
The resin sticking to the shaft portion 10a of the sleeve 1
9 is scraped into the hole 16 to prevent the clearance 18a from entering the clearance 19 after the sleeve 19.

The movement stroke of the injection plunger 10 in the above-described injection / metering process, that is, the molding stroke A
In the molding, the injection filling amount of the resin into the mold 23 is short, and the discharge amount of the residual resin in the molding stroke A and the scraping amount by the sleeve 19 are small. For this reason, most of the residual resin is in the clearance 18 before the sleeve 19.
And the resin is deteriorated for a long time, and often causes a movement resistance of the injection plunger 10. When the movement resistance increases, the backward movement of the injection plunger 10 becomes difficult to perform smoothly.
The molding stroke A cannot be completely retracted due to the resin pressure from the plasticizing device side, resulting in abnormal measurement and the molding machine is stopped. In addition, the increase in movement resistance is caused by the injection plunger 1.
This is a resistance to forward movement of 0, and in particular, a difference in resistance at the start of injection causes an unstable injection filling amount.

Therefore, in addition to the injection / metering step, the operation of moving the injection plunger 10 is performed over the entire stroke B of the preset retreat limit of the injection plunger tip 10b, and the resin remaining in the clearance 18 is discharged. The retracting operation of the injection plunger 10 over the entire stroke B can be appropriately performed based on the number of molding shots, since the degree of accumulation of the residual resin can be determined. In addition, in the forward / backward operation of the entire stroke B, the injection or the weighing process is immediately stopped according to the process at that time.

Also, automatically, the set values of the injection pressure, injection speed, filling time, weighing time, plunger most advanced position, pressure in the mold, etc., which are set in advance for each molding, and the detected value at the time of operation are automatically determined. The comparison is performed when the detected value deviates from at least one of the upper limit value and the lower limit value of the set value. For example, when the filling time detected and calculated by the position sensor 31 exceeds a set value, the residual resin in the clearance 18 becomes a forward resistance of the injection plunger 10, and it is determined that a long time is required. The process is stopped, and the moving operation of the injection plunger 10 is switched by the control device 30 to the backward operation up to the full stroke B.

The moving operation up to the retreat limit of the injection plunger tip portion 10b is repeatedly performed a required number of times. As a result, most of the residual resin stagnated in the clearance 18 is transferred to the shaft 10 of the injection plunger 10 by the sleeve 19.
a, and is pushed out of the through hole 16 to clean the inside of the clearance, the movement resistance of the injection plunger 10 is removed, and the injection plunger 10
Will surely move forward and backward. When the removal of the residual resin by the retreating operation up to the retreat limit of the injection plunger tip 10b is completed, the injection plunger 10 moves forward to the most advanced position and returns to the injection / metering process operation in which the molding stroke A moves forward and backward, and the molding is performed. Continue working.

FIG. 4 is a flowchart of the injection molding in which the above-mentioned scraping step can be performed automatically. The plunger in FIG. Further, it goes without saying that the entire amount of the resin in the injection cylinder at the time of switching to the scraping step is purged from the nozzle 11 by the full stroke movement of the injection plunger 10 regardless of the amount.

[Brief description of the drawings]

FIG. 1 is a partial longitudinal sectional side view of a pre-plastic injection apparatus capable of implementing an injection plunger operation method according to the present invention.

FIG. 2 is an explanatory diagram of an injection plunger operation device.

FIG. 3 is an explanatory view showing a state in which residual resin is eliminated.

FIG. 4 is a flowchart of injection molding employing the injection plunger operation method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Injection apparatus 2 Plasticizing apparatus 3 Resin path 10 Injection plunger 10a Shaft part of injection plunger 10b Tip part 12 Injection cylinder 16 Drainage hole of residual resin 18 Clearance around shaft part 19 Sleeve for scraping

Continuation of the front page (56) References JP-A-4-347614 (JP, A) JP-A-6-23796 (JP, A) JP-A-6-143345 (JP, A) JP-A-9-85787 (JP, A) , A) Registered utility model 3032857 (JP, U) WO 94/11174 (WO, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 45/00-45/84

Claims (2)

(57) [Claims] An injection device in which an injection plunger having a shaft portion whose diameter is smaller than that of a tip portion is provided so as to advance and retreat, and a plasticizing device are communicated with each other at a position corresponding to a forward limit of the tip of the injection plunger at the tip portion of the injection cylinder. A hole is provided in the injection cylinder wall behind the portion corresponding to the retreat limit of the tip of the injection plunger, and a scraping member disposed around the inside of the injection cylinder after the hole allows the injection cylinder and the injection plunger shaft to move. In a prepra-type injection device that scrapes residual resin in a clearance by retreating the injection plunger and discharges the resin into the hole, the reciprocating operation of the injection plunger includes an injection pressure, an injection speed, a filling time, a weighing time, and a plunger most forward position. In the comparison between the set value such as the pressure in the mold and the detected value, the detected value after the lapse of molding of a predetermined number of shots is at least the set value. Injection plunger Operation of preplasticization injection apparatus characterized by performing stop injection or metering process when One of deviated from the upper limit value or lower limit value. 2. The operation of moving the injection plunger back and forth is performed by comparing a set value such as an injection pressure, an injection speed, a filling time, a weighing time, a plunger most advanced position, a pressure in a mold, and a detected value with the detected value. The detected value is at least one of the above set values
2. The injection plunger operation method for a pre-plastic injection device according to claim 1, wherein the injection or metering process is stopped when the value deviates from one of the upper and lower limits.