JP2857844B2 - 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 means of a screw and a heating cylinder, a delivery plunger and a storage cylinder accumulate plasticized resin during non-weighing, and deliver the resin during metering. A storage device having a delivery cylinder for driving the injection cylinder, an injection plunger and an injection cylinder are used to measure the resin supplied from the plasticizing device and the storage device, and to inject the measured resin and to drive the injection cylinder for driving the injection plunger. For example, Japanese Patent Application Laid-Open No. 4-28661 discloses a prepra-type injection molding machine including an injection device having an opening / closing mechanism having an opening / closing valve for opening and closing a resin passage through which resin supplied to the injection device passes.
A continuous plasticization type injection molding apparatus disclosed in Japanese Patent Application Publication No. 7-107 is known.

[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]

However, the above-described conventional pre-plastic injection molding machine (continuous plasticizing injection molding machine)
Is equipped with a storage device having a delivery cylinder, an injection device having an injection cylinder, and an opening / closing mechanism having an opening / closing valve. By connecting a hydraulic circuit to each cylinder, each cylinder and the opening / closing valve are independently controlled. This requires an independent control system for the storage device, the injection device, and the on-off valve, complicates the configuration of the hydraulic circuit and the control system, and makes it difficult to accurately control the operation timing of each part. There has been a problem that control accuracy and response cannot be improved.

The present invention has solved the problems existing in the prior art as described above, and can simplify the configuration of the hydraulic circuit and the control system, and can achieve high precision and high response of the control. It aims to provide a pre-plastic injection molding machine.

[0006]

According to the present invention, a plasticizing apparatus 2 for plasticizing a molding material by a screw 21 and a heating cylinder 22 is provided.
0, a storage device 30 having a delivery cylinder 34 for driving the delivery plunger 31 while accumulating the plasticized resin during non-metering and sending it out during measurement by the delivery plunger 31 and the storage cylinder 32; An injection cylinder 42 for measuring the resin supplied from the plasticizing device 20 and the accumulating device 30, injecting the measured resin, and having an injection cylinder 44 for driving an injection plunger 41; Valve 53 for opening and closing a resin passage 51 through which resin supplied to the opening and closing cylinder 5 for driving the valve 53
In particular, the first switching circuit 2 connected to the delivery cylinder 34, the second switching circuit 3 connected to the injection cylinder 44, and the hydraulic power source 5 Switching valve 4 connected to an inlet 4i
The first outlet 4a of the switching valve 4 is connected to an oil chamber 52r of the opening / closing cylinder 52 that opens the on-off valve 53 and the first switching circuit 2. On the other hand, the second outlet 4b of the switching valve 4 is connected. Further, the second switching circuit 3 is connected to an oil chamber 52f of the opening / closing cylinder 52 on the side of closing the opening / closing valve 53.

In this case, the first switching circuit 2 includes a switching valve 4
Is switched to the second outlet 4b, and functions as a meter-out circuit for the delivery cylinder 34. The second switching circuit 3 switches the switching valve 4 to the first outlet 4a when the switching valve 4 is switched to the first outlet 4a. Functions as a meter-out circuit.

[0008]

According to the pre-plastic injection molding machine 1 of the present invention, the pressure oil supplied from the hydraulic source 5 is changed by switching the switching valve 4 to the first outlet 4a at the start of the measuring step.
The oil is supplied from the first outlet 4a to the rear oil chamber 52r of the opening / closing cylinder 52 and is also supplied to the first switching circuit 2 connected to the delivery cylinder 34. As a result, the open / close valve 53
Can be displaced in the opening direction to open the resin passage 51 and to control the operation of sending the resin accumulated in the accumulation tube 32 to the resin passage 51. That is, the supply of the pressure oil to the delivery cylinder 34 is interlocked with the opening operation of the resin passage 51. At this time, meter-out control (back pressure control) is performed on the injection cylinder 44 by the second switching circuit 3.

On the other hand, by switching the switching valve 4 to the second outlet 4b at the start of the injection step, the pressure oil supplied from the hydraulic source 5 is supplied from the second outlet 4b to the front oil chamber 52f of the opening / closing cylinder 52. And the injection cylinder 44
Is supplied to the second switching circuit 3 connected to. 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. In this case,
Meter-out control (back pressure control) is performed on the delivery cylinder 34 by the first switching circuit 2.

As described above, since the supply of the pressure oil to the first switching circuit 2 or the second switching circuit 3 is interlocked with the opening / closing control of the opening / closing valve 53, the configurations of the hydraulic circuit and the control system are simplified. In addition, control accuracy and responsiveness are improved.

[0011]

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 the present embodiment will be described with reference to FIGS.

FIG. 2 shows a configuration mainly including a mechanical system of the 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 includes 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 has 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. 3, the resin pressure adjusting mechanism 55 has an opening adjustment valve 56 disposed to face the extrusion port 23, and has a displacement portion 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 which controls 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. FIG. 1 shows a block diagram of a hydraulic system in the pre-plastic injection molding machine 1.
FIG. 5 shows a specific hydraulic circuit diagram.

In the hydraulic circuit 60, reference numeral 5 denotes a hydraulic pressure source, and the discharge side is connected to the inflow port 4i of the switching valve 4. Also,
The first outlet 4a of the switching valve 4 is connected to the rear oil chamber 52r of the open / close cylinder 52, and furthermore, the first outlet 4a
The oil tank 63 is connected to the rear oil chamber 34r and the front oil chamber 34f of the delivery cylinder 34 via the first switching circuit 2. On the other hand, the second outlet 4 b of the switching valve 4 is connected to the front oil chamber 52 f of the opening / closing cylinder 52, and the second outlet 4 b and the oil tank 63 are further connected to the injection cylinder via the second switching circuit 3. 44 is connected to the rear oil chamber 44r and the front oil chamber 44f. The hydraulic source 5 includes a variable discharge type hydraulic pump 66, control valves 67 and 68, a relief valve 69, and the like. The switching circuit 2 includes switching valves 70 and 71 and an electromagnetic proportional relief valve 72, and the switching circuit 3 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. 4 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 4 switches to the left symbol in FIG. Therefore, the pressure oil supplied from the hydraulic pressure source 5 is supplied from the second outlet 4b to the front oil chamber 52f of the opening / closing cylinder 52 and also to the switching circuit 3 for controlling 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 2 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 step is completed, the switching valve 4 switches to the symbol on the right side in FIG. Therefore, the pressure oil supplied from the hydraulic pressure source 5 is supplied from the first outlet 4 a to the rear oil chamber 52 r of the opening / closing cylinder 52 and is also supplied to the switching circuit 2 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 pressure oil to the delivery cylinder 34 is as follows.
It 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 is injected through the resin passage 51. Sent to the cylinder 42,
The resin extruded from the plasticizing device 20 is also supplied to the injection cylinder 42 through the resin passage 51, and is subjected to measurement control (delivery step and measurement step). At this time, the other switching circuit 3
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. 2) of the delivery plunger 31 during accumulation in 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 basically V = L / [tc-ti]
Can be set by In this case, it is desirable to set an arbitrary margin time tr. For example, if the margin time tr is set based on the time required to refresh the resin by the rotation of the screw 21 after the feed plunger 31 is moved forward the most, the forward speed V becomes V = L / [tc-ti-t.
r].

Therefore, the delivery plunger 31 sends out the accumulated resin at a constant flow rate during the entire measurement time te required for the measurement 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 rotation 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. 4, 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 4
Is switched to the left symbol in FIG. As a result, the pressure oil supplied from the hydraulic pressure source 5 is supplied from the second outlet 4b to the front oil chamber 52f of the opening / closing cylinder 52 and to the switching circuit 3 connected to the injection cylinder 44, and the above-described injection is performed. Move to process.

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.

[0036]

As described above, according to the pre-plastic injection molding machine of the present invention, the first switching circuit connected to the delivery cylinder in the storage device, the second switching circuit connected to the injection cylinder in the injection device, A switching valve having an inflow port connected to a hydraulic pressure source, and a first outflow port of the switching valve is connected to an oil chamber of the on-off cylinder that opens the on-off valve and a first switching circuit. Since the oil chamber on the side that closes the on-off valve of the on-off cylinder and the second switching circuit are connected to the outlet, the configuration of the hydraulic circuit and the control system can be simplified, and the control accuracy and response are improved. The remarkable effect that it can aim at is produced.

[Brief description of the drawings]

FIG. 1 is a block diagram of a hydraulic circuit in a pre-plastic injection molding machine according to the present invention;

FIG. 2 is a partial cross-sectional view mainly showing the mechanical system of the prepra-type injection molding machine,

FIG. 3 is a partial cross-sectional configuration view of a resin pressure adjusting mechanism in the pre-plastic injection molding machine.

FIG. 4 is a process diagram of a molding cycle in the pre-plastic injection molding machine.

FIG. 5 is a hydraulic circuit diagram mainly showing a hydraulic system of 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 2 1st switching circuit 3 2nd switching circuit 4 Switching valve 4i Inlet 4a 1st outlet 4b 2nd outlet 5 Hydraulic source 20 Plasticizer 21 Screw 22 Heating cylinder 30 Storage device 31 Sending out Plunger 32 Storage cylinder 34 Delivery cylinder 40 Injection device 41 Injection plunger 42 Injection cylinder 44 Injection cylinder 50 Opening / closing mechanism

Continuation of the front page (56) References JP-A-5-131509 (JP, A) JP-A-5-337993 (JP, A) (58) Fields investigated (Int.Cl. ⁶ , DB name) B29C 45 / 53-45 / 54,45 / 57-45/5 8,45 / 76-45/82

Claims (3)

(57) [Claims] 1. A plasticizing device for plasticizing a molding material by means of a screw and a heating cylinder, a delivery plunger and a storage cylinder for accumulating plasticized resin during non-weighing and delivering the resin at the time of measurement and driving the delivery plunger. A storage device having a delivery cylinder, an injection plunger, and an injection cylinder that measure the resin supplied from the plasticizing device and the storage device, inject the measured resin, and have an injection cylinder that drives the injection plunger. In a pre-plastic injection molding machine including an apparatus, an opening / closing valve for opening and closing a resin passage through which resin supplied to the injection device passes, and an opening / closing mechanism section having an opening / closing cylinder for driving the opening / closing valve, a first connected to a delivery cylinder. Switching circuit, a second switching circuit connected to the injection cylinder, and a switching valve having an inflow port connected to a hydraulic source. Equipped, at the first outlet of this switching valve,
The first switching circuit is connected to the oil chamber on the opening side of the opening / closing valve in the opening / closing cylinder, and the oil chamber on the side closing the opening / closing valve in the opening / closing cylinder is connected to the second outlet of the switching valve. A pre-plastic injection molding machine characterized by being connected. 2. The injection molding machine according to claim 1, wherein the first switching circuit functions as a meter-out circuit for the delivery cylinder when the switching valve is switched to the second outlet. 3. The pre-plastic injection molding machine according to claim 1, wherein the second switching circuit functions as a meter-out circuit for the injection cylinder when the switching valve is switched to the first outlet.