JP2899862B2 - Pre-plastic injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pre-plastic injection molding machine provided with a storage device for accumulating a plasticized resin at the time of non-weighing by a delivery plunger and a storage cylinder, and sending the resin at the time of measurement.

[0002]

2. Description of the Related Art Conventionally, a plasticizing device for plasticizing a molding material by a screw and a heating cylinder, and a storage device for accumulating a plasticized resin during non-weighing by a delivery plunger and a storage cylinder and sending the resin during metering, As a pre-plastic injection molding machine including an injection device for measuring a resin supplied from a plasticizing device and a storage device by an injection plunger and an injection cylinder and injecting the measured resin, for example, Japanese Patent Application Laid-Open No.
There is known a continuous plasticizing injection molding apparatus disclosed in Japanese Patent No. 86617.

[0003] This type of plastic injection molding machine is provided with an accumulating device to temporarily accumulate the plasticized resin extruded from the plasticizing device and to extrude the accumulated resin from the plasticizing device at the time of measurement. Since the plasticizer is supplied to the injection device in addition to the resin to be formed, continuous operation of the plasticizer can be performed, and the plasticization time is prolonged, so that there is an advantage that more uniform plasticization and shortening of the molding cycle time can be achieved.

[0004]

By the way, in the above-mentioned conventional plastic injection molding machine (continuous plasticizing injection molding machine), the amount of resin accumulated in the accumulator is smaller than the total amount of resin required for one measurement. By setting a small amount and sending the resin accumulated in the accumulator at the time of weighing, it is added to the resin extruded from the plasticizing device, and the delivery of the accumulated resin is terminated earlier than the end of the weighing process. Was.

For this reason, depending on the position of the resin to be measured, there are a portion where the accumulated resin is mixed with the resin extruded from the plasticizer and a portion where only the resin is extruded from the plasticizer. However, it is not possible to obtain a uniform resin in a molten state from the side at the time of mixing, and pressure fluctuations occur in the resin extruded from the plasticizing device. There was a problem that a uniform resin could not be obtained.

The present invention has been made to solve the problems existing in the prior art, and it is possible to obtain a homogeneous resin in a molten state at the time of weighing, thereby achieving a homogenized and high quality molded article. It aims to provide a pre-plastic injection molding machine.

[0007]

According to the present invention, a screw 21 is provided.
And a plasticizing device 20 for plasticizing the molding material by the heating cylinder 22, a delivery plunger 31 and a storage cylinder 32, for accumulating the plasticized resin at the time of non-metering and sending it out at the time of measurement, and an injection plunger 41. And injection cylinder 42
In the pre-plastic injection molding machine 1 provided with the injection device 40 for measuring the resin supplied from the plasticizing device 20 and the storage device 30 and injecting the measured resin,
The forward speed V of the delivery plunger 31 at the time of delivery from the storage device 30 is represented by V = L / [tc-ti-tr] (where,
L is the transmission plunger 31 during storage in the storage device 30
, Tc is the molding cycle time, ti is the injection time, and tr is the time required to refresh the resin by rotating the screw after the feed plunger has been moved forward.
It is characterized by being set by:

[0008]

According to the pre-plastic injection molding machine 1 of the present invention, the delivery plunger 31 when the storage device 30 is delivered.
Is set to V = L / [tc-ti-tr], the delivery plunger 31 delivers the accumulated resin at a constant flow rate during the entire period of the measuring time required for the measuring process. Therefore, the resin discharged from the storage cylinder 32 and the resin extruded from the heating cylinder 22 are uniformly mixed at all positions, and the fluctuation of the resin pressure in the resin passage 51 is suppressed. From the aspect of plasticizing ability, the molten state of the resin becomes uniform.

[0009]

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

First, the configuration of a pre-plastic injection molding machine 1 according to this embodiment will be described with reference to FIGS. 1, 2, 4 and 5. FIG.

FIG. 1 shows a construction mainly of a mechanical system of a pre-plastic injection molding machine 1. In the figure, reference numeral 20 denotes a plasticizing device, which includes a heating cylinder 22 into which a screw 21 is inserted. At the front end of the heating cylinder 22, there is provided an extrusion port 23 for plasticized resin, and at the rear, a hopper 24 for supplying molding material.
Having. A screw drive unit 25 is connected to the rear end of the heating cylinder 22. The screw drive unit 25 includes a screw motor 26, and a rotating shaft of the screw motor 26 is coupled to a rear end of the screw 21 via a coupler 27. Reference numeral 28 denotes a rotary encoder that detects the rotation speed of the screw 21.

On the other hand, reference numeral 30 denotes a storage device, which comprises a storage cylinder 32 into which a delivery plunger 31 is inserted. The front end of the storage tube 32 is provided integrally with the front end of the heating tube 22, and the storage tube 32 stands up. In addition, at the front end of the storage tube 32, there is a resin entrance 33, and the direction of the entrance 33 is
At right angles to Further, at the rear end of the storage cylinder 32,
A delivery cylinder (hydraulic cylinder) 34 is connected, and a ram 35 built in the delivery cylinder 34 is provided with a delivery plunger 3.
Bind to 1. Reference numeral 36 denotes a position scale for detecting the position of the delivery plunger 31.

On the other hand, reference numeral 40 denotes an injection device disposed below the plasticizing device 20 and includes an injection cylinder 42 into which an injection plunger 41 is inserted. The front part of the injection cylinder 42 is connected to the front ends of the heating cylinder 22 and the storage cylinder 32 via the opening and closing mechanism 50. Further, an injection nozzle 43 for injecting a resin into a mold (not shown) is provided at a front end of the injection cylinder 42, and an injection cylinder 44 is connected to a rear end. The injection cylinder 44 incorporates a ram 45, which is coupled to the injection plunger 41. Reference numeral 46 denotes a position scale for detecting the position of the injection plunger 41.

The opening / closing mechanism 50 includes a resin passage 5 therein.
1, the outlet of the resin passage 51 communicates with the inside of the injection cylinder 42, and the inlet is at a right angle to the extrusion port 23.
In addition, they communicate with the entrance 33 on the same straight line. on the other hand,
Reference numeral 52 denotes an opening / closing cylinder, which opens and closes the resin passage 51 by displacing an opening / closing valve 53 disposed at an intermediate portion of the resin passage 51.

Further, a resin pressure adjusting mechanism 55 is provided in front of the extrusion port 23. As shown in FIG. 2, the resin pressure adjusting mechanism 55 has an opening adjustment valve 56 disposed opposite to the extrusion port 23, and has a displacement unit 57 for moving the opening adjustment valve 56 forward or backward, Opening control valve 56
The opening of the extrusion port 23 can be adjusted by moving forward or backward. Thus, for example, even if the pressure of the resin delivered from the storage cylinder 32 fluctuates, the pressure of the resin extruded from the heating cylinder 22 can be maintained at a predetermined level, and adverse effects on the plasticizing characteristics can be prevented.

On the other hand, reference numeral 60 denotes a hydraulic circuit, and reference numeral 80 denotes a controller for controlling the entire injection molding machine. The position scales 36 and 46 are connected to the controller 80.

Next, the configuration of the hydraulic circuit 60 will be described with reference to FIG.
This will be described with reference to FIG. 4 shows a configuration mainly including a hydraulic system of the pre-plastic injection molding machine 1, and FIG. 5 shows a block system diagram thereof.

In the hydraulic circuit 60, reference numeral 61 denotes a hydraulic pressure source, and the discharge side is connected to an inlet 62 i of a switching valve 62. The first outlet 62a of the switching valve 62 is connected to the open / close cylinder 5
2 and a first oil outlet 62a and an oil tank 63 are connected to a rear oil chamber 34r and a front oil chamber 34f of the delivery cylinder 34 via a switching circuit 64.
Connect to On the other hand, the second outlet 62b of the switching valve 62
While connected to the front oil chamber 52f of the opening / closing cylinder 52,
Further, the second outlet 62b and the oil tank 63 are connected to the rear oil chamber 44r and the front oil chamber 44f of the injection cylinder 44 via the switching circuit 65. The hydraulic pressure source 61 includes a variable discharge hydraulic pump 66, control valves 67 and 68, a relief valve 69, and the like. Further, the switching circuit 64 includes switching valves 70, 7
The switching circuit 65 includes switching valves 73 and 74 and an electromagnetic proportional relief valve 75.

Next, the operation of the pre-plastic injection molding machine 1 according to the present embodiment will be described with reference to FIGS.

FIG. 3 shows a process chart in one molding cycle. Now, assume that the weighing process is completed. In this case, the delivery plunger 31 is at the most advanced position, and the screw 21 continues to rotate (plasticizing step). In addition, a measured resin is accommodated in an injection cylinder 42 in front of the injection plunger 41. On the other hand, the switching valve 62
In FIG. 4, the symbol is switched to the symbol on the left. Therefore, the pressure oil supplied from the hydraulic pressure source 61 is supplied from the second outflow port 62b to the front oil chamber 52f of the opening / closing cylinder 52,
It is supplied to a switching circuit 65 connected to the injection cylinder 44. As a result, the opening / closing valve 53 is displaced in the closing direction to close the resin passage 51, and the operation of the injection process can be controlled. That is, the supply of the pressure oil to the injection cylinder 44 is interlocked with the closing operation of the resin passage 51.

Therefore, the switching valve 74 is set to the left symbol,
Further, when the switching valve 73 is switched to the symbol on the right side, the injection plunger 41 advances, and the injection control for the mold is performed (injection step). At this time, the other switching circuit 64 functions as a meter-out circuit, and meter-out control (back pressure control) is performed on the delivery cylinder 34.

On the other hand, even during the injection process, since the screw 21 in the plasticizing device 20 continues to rotate, the plasticized resin is accumulated in the accumulation cylinder 32 of the accumulation device 30 through the extrusion port 23 (accumulation). Process). At this time, the switching valve 70
And 71 are switched to the symbols on the right side, respectively, and the back pressure control for the delivery plunger 31 is performed. The screw 21 is rotating at a corrected rotation speed Ns described later.

When the injection process is completed, the switching valve 62 switches to the right symbol in FIG. Therefore, the pressure oil supplied from the hydraulic pressure source 61 is supplied to the first outlet 62
From a, it is supplied to the rear oil chamber 52r of the opening / closing cylinder 52 and to the switching circuit 64 connected to the delivery cylinder 34. As a result, the opening / closing valve 53 is displaced in the opening direction to open the resin passage 51, and the operation control of the sending step of sending the resin accumulated in the storage cylinder 32 to the resin passage 51 becomes possible. That is, the supply of the pressure oil to the delivery cylinder 34 is interlocked with the opening operation of the resin passage 51.

When the switching valve 71 is switched to the left symbol and the switching valve 70 is switched to the right symbol, the delivery plunger 31 moves forward, and the resin stored in the storage cylinder 32 passes through the resin passage 51. The resin is sent out to the injection cylinder 42, and at the same time, the resin extruded from the plasticizing device 20 is supplied to the injection cylinder 42 through the resin passage 51, and the measurement control is performed (delivery step and measurement step). At this time, the other switching circuit 65 functions as a meter-out circuit, and meter-out control (back pressure control) is performed on the injection cylinder 44.

In this case, the forward speed of the delivery plunger 31 and the rotation speed of the screw 21 are set as follows.

First, the setting of the forward speed of the delivery plunger 31 will be described. The retreat distance L (see FIG. 1) of the delivery plunger 31 during the accumulation of the accumulation device 30 is detected by the position scale 36, and the molding cycle time tc and the injection time ti are measured by a timer provided in the controller 80. Therefore, the delivery plunger 3
The forward speed V of 1 is set by V = L / [tc-ti-tr]. In this case, tr is a margin time, and a time required for refreshing the resin by rotation of the screw 21 after the feed plunger 31 is moved forward most can be used.

Therefore, the delivery plunger 31 sends out the accumulated resin at a constant flow rate during the entire measuring time te required for the measuring process. Is uniformly mixed at all positions and the fluctuation of the resin pressure in the resin passage 51 is suppressed, so that the molten state of the resin becomes uniform from the aspect of the plasticizing ability in the plasticizing device 20. In addition, depending on the setting of the surplus time tr, for example, the storage cylinder 32
If the resin sent from the storage tube ends earlier than the end of the measuring step, the resin pressure sent from the storage cylinder 32 is adjusted by the resin pressure adjusting mechanism 55.

Next, the setting of the rotational speed of the screw 21 will be described with reference to the flowchart shown in FIG. First, the theoretical rotational speed No and the extrusion amount qo of resin per one rotation extruded from the heating cylinder 6 are obtained and set in advance based on the performance of the pre-plastic injection molding machine 1 and the setting conditions and the like. . Then, first, the screw 21 is rotated at the theoretical number of revolutions No to perform molding (step S1).
At this time, the actual rotation speed Nd is
Is detected by After the end of the accumulation step in which the resin is accumulated in the accumulation cylinder 32, the actual extrusion amount qd can be calculated based on the total accumulation amount Qd of the resin. That is, if ti is the accumulation time (injection time), Qd = [Nd / 60] · t
Since it is expressed by i · qd, the extrusion amount qd is given by: qd = Qd ·
60 / [Nd · ti] (step S2). On the other hand, the detected Nd is compared with the set No, and the calculated qd is compared with the set qo.
To rotate the screw 21 as it is (step S
3, S4). On the other hand, if any of them does not match, the rotation speed No is corrected, and the rotation of the screw 21 is controlled by the corrected rotation speed Ns (steps S4 to S6).

In this case, the correction for the rotation speed No is performed as follows. Now, the total resin amount based on the target measurement value of the injection cylinder 44 is Qo, and the measurement process (after the accumulation process is completed,
In the period until the next injection process starts), the heating cylinder 22
Assuming that the required amount of resin extruded from the extrusion port 23 is Qs, the relationship of Qs = Qo-Qd is established. Therefore,
Assuming that the corrected rotation speed is Ns and the corrected extrusion amount is qd, Qs is Qs = [Ns / 60] · te · qe = [N
s / 60] · [tc-ti] · qe,
o is Qo = Qd + Qs = ｛[Nd / 60] · ti · q
d｝ + {[Ns / 60] ・ [tc-ti] ・ qe｝. This equation is Ns = ｛[60 if qd = qe is considered.
・ Qo]-[Nd · qd · ti]｝ / ｛qd · [tc−
ti]｝, so that the required rotational speed Ns for the screw 21 can be obtained from this equation (step S5).

Therefore, in the measuring step, the corrected rotational speed N
The screw 21 is rotated by s, and the required resin amount Qs is extruded from the extrusion port 23 (step S6). Therefore, the total resin amount obtained by adding the resin amount Qd sent from the storage cylinder 32 and the resin amount Qs matches the total resin amount Qo based on the target measured value, and continuous plasticization for continuously rotating the screw 21 is enabled. And the end of the weighing process and the storage cylinder 3
The end of the delivery of the resin accumulated in 2 can be matched.

On the other hand, during the measuring step, a cooling step and a mold opening / closing step are performed on the mold side. In FIG. 3, to indicates the cooling time in the cooling step, and tm indicates the mold opening and closing time in the mold opening and closing step.

On the other hand, when the measuring step is completed, the switching valve 6
2 is switched to the left symbol in FIG. This allows
The pressure oil supplied from the hydraulic pressure source 61 is supplied from the second outlet port 62b to the front oil chamber 52f of the opening / closing cylinder 52, and is also supplied to the switching circuit 65 connected to the injection cylinder 44, and shifts to the above-described injection step. I do.

The embodiment has been described in detail above.
The present invention is not limited to such an embodiment,
The detailed configuration, method, and the like can be arbitrarily changed without departing from the gist of the present invention.

[0034]

As described above, in the pre-plastic injection molding machine according to the present invention, the forward speed V of the delivery plunger when the storage device is delivered is set by V = L / [tc-ti-tr]. Therefore, a uniform resin in a molten state can be obtained at the time of weighing, and this has a remarkable effect that the quality and homogeneity of a molded product can be improved.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional configuration diagram mainly showing a mechanical system of a prepra injection molding machine according to the present invention,

FIG. 2 is a partial cross-sectional configuration diagram of a resin pressure adjusting mechanism in the prepra injection molding machine;

FIG. 3 is a process chart of a molding cycle in the pre-plastic injection molding machine.

FIG. 4 is a hydraulic circuit diagram mainly showing a hydraulic system of the pre-plastic injection molding machine,

FIG. 5 is a basic block diagram of a hydraulic circuit in the pre-plastic injection molding machine;

FIG. 6 is a flowchart showing a procedure for setting the number of rotations of a screw in the pre-plastic injection molding machine;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pre-plastic injection molding machine 20 Plasticizing device 21 Screw 22 Heating cylinder 30 Storage device 31 Delivery plunger 32 Storage cylinder 40 Injection device 41 Injection plunger 42 Injection cylinder L Retraction distance of delivery plunger tc Molding cycle time ti Injection time tr Allowance time

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-131509 (JP, A) JP-A-4-286617 (JP, A) JP-A-5-337993 (JP, A) JP-A 8- 216209 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) B29C 45/53-45/54 B29C 45/58 B29C 45/76-45/77

Claims (1)

(57) [Claims] 1. A plasticizing device for plasticizing a molding material with a screw and a heating cylinder, an accumulating device for accumulating plasticized resin during non-metering by a delivery plunger and a storage cylinder, and sending the resin during metering, and an injection plunger. And the injection cylinder measures the resin supplied from the plasticizing device and the accumulating device, and in a pre-plastic injection molding machine having an injection device for injecting the measured resin, the forward speed V of the delivery plunger when the accumulating device is delivered. , V = L / [tc-ti
-Tr] (where L is the retreat distance of the delivery plunger during storage in the storage device, tc is the molding cycle time, ti
Is a time required for refreshing the resin by rotation of the screw after the delivery plunger is moved forward most).