JP5019165B2 - Screw for injection molding machine, injection molding apparatus and injection molding method - Google Patents

Description

The present invention relates to an injection molding machine screw used in a resin injection molding machine, an injection molding apparatus, and an injection molding method, and relates to a check ring mechanism disposed at a screw tip of an injection molding machine screw and its operation accuracy and resin The present invention relates to a screw for an injection molding machine, an injection molding apparatus, and an injection molding method capable of performing high-precision injection and metering operations by enhancing sealing properties.

Conventionally known injection molding screws are a screw body and a seal ring in which flights for supply, compression, and metering are formed in the direction of injecting resin in order from the raw material supply side on the screw rear side. (Also referred to as a rear seat), a check ring (also referred to as a check ring) for preventing back flow of resin, and a screw head.

Usually, the check ring is mounted in a state of being fitted to the small diameter portion of the screw head, and is arranged on the head portion of the screw head (the portion of the screw head in the direction of injecting resin) and the screw main body portion. It arrange | positions so that a slight distance can be moved to the screw axial direction of a screw longitudinal direction between seal ring parts. The check ring moves to the head side (resin injection direction side) during measurement, so that the molten resin on the seal ring side (screw body direction side) can flow to the head part side. ing.

The check ring has a structure that seals the resin so that the resin on the head side does not flow back to the seal ring side by moving to the seal ring side and coming into contact with the seal ring at the time of injection. The above-described mechanism for opening and closing the resin flow path between the seal ring side and the head portion side by moving the check ring back and forth of the screw is generally called a check ring mechanism (check ring mechanism). Is sometimes called)

The conventional general check ring mechanism uses a pressure difference between the resin generated before and after the check ring (resin pressure during injection, resin pressure during measurement, etc.) to attach the check ring to the head part. It is often configured to open and close the resin flow path by moving to the side or the seal ring side.
However, the movement of the check ring is not only a movement using the pressure difference of the resin, but also a technique disclosed in, for example, Patent Documents 1 to 5 briefly described below is known.
In this specification, in order to simplify the description, the direction in which the resin is injected by the screw is referred to as the front side or the front side of the screw, and the direction of the screw material supply side opposite to the direction is the rear side of the screw, or Sometimes referred to as the rear. In addition, the direction of rotation of the screw that is rotated when measuring the resin is the normal direction of rotation of the screw.

Japanese Patent Laid-Open No. 04-119812

Patent Document 1 discloses a check ring in which a one-tapered claw is formed, and the claw of the check ring engages and slides in a groove formed in the screw head.
In the technique disclosed in Patent Document 1, the screw is reversely rotated after weighing, and the claw is slid in the groove to move the check ring to the rear of the screw. Form.

JP-A-62-19423

  Further, Patent Document 2 has a structure in which the head portion of the screw head and the check ring are in contact with each other at an inclined surface, and the check ring moves to the rear of the screw by reverse rotation of the screw. In Patent Document 2, the check ring is moved forward of the screw by resin pressure.

JP 2004-9554 A

  In the technique disclosed in Patent Document 3, a screw head and a check ring are connected by a cam mechanism, and the check ring moves forward or backward of the screw by forward rotation or reverse rotation.

JP 2000-309042 A

  In the technique disclosed in Patent Document 4, a circumferential flow path is formed at the connecting portion of the screw head and the check ring, and the check ring moves forward or backward of the screw by forward rotation or reverse rotation. It has a configuration.

JP 07-214619 A

  In the technique disclosed in Patent Document 5, the screw head and the check ring are connected by a screw structure, and the check ring moves forward or backward of the screw by forward rotation or reverse rotation.

By the way, a conventional general check ring mechanism that opens and closes the resin flow path by moving the check ring forward or backward of the screw using the pressure difference of the resin, and circulates or blocks the resin flow. Then, when the pressure difference of the resin changes during injection or weighing, the opening / closing operation changes. For example, during continuous molding, if the temperature of the molten resin changes, the resin pressure during molding slightly changes, and the opening / closing operation of the check ring becomes unstable. There was a problem of affecting the weighing time.

Moreover, the technique disclosed by patent document 1, 2 is performing the sealing of a non-return ring reliably by reversely rotating a screw after measurement. Therefore, the back flow of the resin at the time of injection can be surely prevented, and the stability is high.
However, the techniques disclosed in Patent Documents 1 and 2 use the resin pressure in the same manner as the general prior art for the mechanism in which the check ring moves during measurement. Therefore, the timing varies and the operation is unstable. Therefore, there is a problem that weighing accuracy and weighing time are unstable as in the general prior art described above.
In addition, the above-described method using the resin pressure has a drawback that the additive is easy to be re-separated when the additive or the like is contained because a sudden pressure change of the resin occurs at the moment when the check ring starts to move. Furthermore, there is a problem that the resin temperature tends to become unstable due to a change in the resin flow path area from the moment when the check ring starts to move until the opening is completed.

Each of the techniques disclosed in Patent Documents 3 to 5 opens and closes the resin flow path by moving the check ring back and forth without using the resin pressure difference.
However, the techniques disclosed in Patent Documents 3 to 5 are all complicated in the shape of the resin flow path formed by the check ring, resulting in resistance to resin flow, and resin replacement failure due to resin retention. There was a problem that it was easy to cause the problem.

The present invention pays attention to the above-mentioned problems of the prior art, and without using the resin pressure difference, the check ring can be reliably moved back and forth to freely open and close the resin flow path, It is another object of the present invention to provide an injection molding screw, an injection molding apparatus, and an injection molding method provided with a check ring opening / closing mechanism having a simple structure for the resin flow path.

In order to achieve the above object, a screw for an injection molding machine according to the present invention comprises: (1) a substantially conical head portion and a substantially cylindrical small diameter portion which is attached to the seal ring portion side of the screw body. A screw head, and a non-return ring that is slidably fitted to the small diameter portion and can move in the axial direction of the screw from the head portion to the seal ring portion,
A gap through which resin can flow is formed between the inner peripheral surface of the check ring and the outer peripheral surface of the small diameter portion to form a resin flow path, and the check ring is brought into contact with or separated from the seal ring portion. by, in screw injection molding machine of the resin to be cut off or circulating flow path of the resin, the end face of the head portion side of said reverse stop ring, tilting the protrusion portion at a predetermined angle with respect to the screw axis by forming, on both sides of the side surface of the protrusion portion with tilting in the same direction relative to the screw axis, projecting engage the raised portions, by protrusion portion is rotated around the screw axis, said By forming a groove in the head portion that slides on the protrusion and moves the check ring in the axial direction, the check ring is separated from the seal ring when the screw is rotated in the rotation direction during measurement. In the direction of the screw Is rotated in the direction of the rotational direction opposite said reverse stop ring is moved in contact with the direction to the seal ring.

An injection molding apparatus according to the present invention comprises:
(2) The injection molding screw according to (1) was provided.

The injection molding method according to the present invention comprises:
(3) An injection molding method using an injection molding apparatus including the injection molding screw according to (1), wherein a screw is rotated and a desired amount of resin is measured, and then the screw is held while the screw position is maintained. The check ring and the seal ring part were brought into contact with each other by reversely rotating and then the resin was injected by an injection operation.

According to the injection molding screw of the present invention, since the check ring can be reliably moved back and forth using the rotation of the screw, the effect of preventing the back flow of the resin after measurement (sealability) is high. Since the resin sent to the front of the screw does not flow backward to the screw body during injection, stabilization of the product weight can be achieved.
In addition, the shape of the resin flow path formed by the check ring is simple and does not hinder the flow of the molten resin during measurement, so that quality can be stabilized during measurement, and at the same time, resin replacement failure due to retention occurs. It has the excellent effect of being difficult.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.
1 and 2 relate to a preferred embodiment according to the present invention, FIG. 1 is an explanatory view for conceptually explaining the structure of an injection molding machine screw, (A) shows the time of measurement, (B ) Shows the case where the screw is rotated backward before injection after weighing. FIG. 2 is an explanatory diagram for explaining the overall configuration of an injection apparatus including the screw for an injection molding machine shown in FIG. FIG. 3 is a diagram for explaining an angle θ formed by the protrusion and the screw shaft.

First, the structure of the screw 1 for injection molding which is embodiment of this invention is demonstrated.
In FIG. 1, a screw 1 includes a screw body 4, a seal ring 3, a check ring 5, and a screw head 2. The screw 1 is inserted and arranged in the heating cylinder 31A during molding as shown in FIG.

The screw body 4 is formed with flights for supply, compression and weighing in order from the raw material hopper side. Moreover, the opening part by which the internal thread was processed is formed in the edge part of the screw front side of the screw main body 4, and the screw head 2 mentioned later is attached in the state which pinched | interposed the seal ring 3. FIG.

As shown in FIG. 1, the screw head 2 attached to the screw body 4 has one end formed in a substantially conical shape as a head portion 2A and the other end formed as a cylindrical small-diameter portion 2B. An unillustrated male screw portion is formed at one end of the small diameter portion 2B, and the male screw portion is in a state in which the seal ring 3 is sandwiched between the small diameter portion 2B and the screw main body 4, and the screw main body described above. 4 and the female threaded portion.
In the embodiment shown in FIG. 1, when the screw body 4 and the small diameter portion 2B of the screw head 2 are attached by being screwed together with the seal ring 3 sandwiched therebetween, the small diameter portion 2B is inserted into a check ring 5 described later. It is configured to be attached.

Hereinafter, the configuration of the check ring 5 will be described.
As shown in FIG. 1, the check ring 5 in the present embodiment has an annular body as in the conventional check ring 5, and the check ring 5 An annular portion, which is a main body portion, is fitted, and at that time, the seal ring 3 is sandwiched between the screw head 2 and the screw main body 4. At this time, a gap for flowing resin is formed on the outer peripheral surface of the small diameter portion 2B of the screw head 2 and the inner peripheral surface of the main body annular portion of the check ring 5.

The check ring 5 is movable forward and backward in the axial direction of the screw outside the small diameter portion 2B of the screw head 2, and when the check ring 5 moves to the screw body 4 side, it comes into contact with the seal ring 3 and the head portion. The molten resin on the 2A side is prevented from flowing back to the screw body 4 side.

In the present embodiment, a plurality of convex portions 5B are formed on the end surface of the check ring 5 on the head portion 2A side. Therefore, even when the check ring 5 is moved to the end face side of the head part 2A in the weighing step described later, there is a convex part 5B between the check ring 5 and the end face of the head part 2A. A gap through which the resin can flow is formed.

In the present embodiment, the reverse flow ring mechanism including the check ring 5 and the seal ring 3 is configured such that the screw head 2 and the seal ring 3 are detachably attached between the screw main body 4 by the above-described configuration. become.
Therefore, replacement is easy when the check ring 2 or the seal ring 3 is worn or damaged due to long-term continuous use. Of course, when the seal ring 3 is not damaged, a part of the screw body may be integrated as a seal ring, and such a structure is within the scope of application of the present invention.

Further, in the present embodiment, at least one protrusion 5A inclined at a predetermined angle with respect to the screw longitudinal direction is provided on the end surface of the check ring 5 on the head 2A side (screw front) (FIG. 1). In the embodiment shown in FIG. 2, two locations are formed so as to face each other across the screw head rotation center axis.

In the present invention, the protrusion 5A is inclined at a predetermined angle (θ degrees) with respect to the screw axis direction. In the present embodiment, as a preferred example of the protrusion 5A, the screw longitudinal direction However, the scope of application of the present invention is not limited to this, and is preferably between 15 and 75 degrees, and preferably between 30 and 50 degrees. The period up to is particularly preferable.
In addition, the rotation direction of the screw 1 shown to FIG. 1 (A) shows the case where it rotates in the clockwise direction seeing from the screw front.

FIG. 3A shows a diagram for explaining the angle θ described above as a reference.
The rotation direction of the screw 1 shown in FIG. 3 (A) shows a case where the screw 1 is rotating in the clockwise direction when viewed from the front of the screw, as in FIG. 1 (A). As shown in FIG. 3A, the aforementioned angle θ is the angle θ formed by the center line of the protrusion 5A and the screw shaft.
In addition, the protrusion 5A may be spiral because it engages with a groove 2C formed in a conical head portion described later, and in this case, the center line of the protrusion 5A is also spiral. Therefore, in such a case, the angle formed by the screw shaft when the spiral center line is developed and opened is defined as θ.

Accordingly, the head portion 2A of the screw head 5 is formed with a groove portion 2C that opposes the protrusion portion A of the check ring 5 and engages with the protrusion portion 5A, and the check ring 5 is fitted to the small diameter portion 2B. In this case, the groove 2C and the protrusion 5A are configured to engage with each other.
Therefore, as shown in FIG. 1A, when the screw 1 is rotated in the measuring direction, the protrusion 5A slides while sliding on the groove 2C, and as a result, the check ring 5 moves forward in the axial direction of the screw. Move to the side. Therefore, the check ring 5 moves away from the seal ring and moves to the end face side of the head portion 2A, and a gap through which the resin can flow as described above is formed.
Further, when the screw 1 is rotated in the direction opposite to the measuring direction as shown in FIG. 1B, the protrusion 5A slides while sliding in the groove 2C, and the check ring 5 is moved in the axial direction. It moves to the screw rear side, and it has the structure where the end surface of the non-return ring 5 contacts the seal ring.

Hereinafter, the configuration of the injection molding apparatus 100 used in the present embodiment will be briefly described.
The injection molding apparatus 100 illustrated in FIG. 2 includes a mold 10, a mold clamping apparatus 20, an injection apparatus 30, and a control apparatus 60.

The structure of the mold 10 will be described.
The mold 10 includes a fixed mold 13 attached to the fixed platen 11 and a movable mold 14 attached to the movable platen 12, and the mold cavity is formed with the fixed mold 13 and the movable mold 14 fitted together. Form.

  As shown in FIG. 2, the mold clamping apparatus 20 includes a fixed platen 11, a movable platen 12, and a toggle type mold clamping mechanism 20 that is moved by a mold clamping servomotor 20B. The movable platen 12 is guided by a tie bar (not shown) installed between the fixed platen 11 and the end plate, and can be moved forward and backward together with the movable die 14 by a toggle type mold clamping mechanism 21.

In this embodiment, a stroke sensor (not shown) is attached to the crosshead drive shaft of the link drive mechanism provided in the mold clamping device 20 in order to detect the position of the crosshead. It is possible to control with high accuracy, and a mold clamping force measuring sensor (not shown) for measuring the mold clamping force is arranged to detect the mold clamping force.

  Next, the injection device 30 shown in FIG. 2 includes, as the injection device 30, a heating cylinder 31A, a screw 1 built in the heating cylinder 31A, a raw material hopper for supplying a thermoplastic resin material to the heating cylinder 31A, and a screw 1 A screw drive device 31C that moves forward or backward is provided. A heater (not shown) is attached to the outer peripheral surface of the heating cylinder 31A.

  Further, the injection device 30 is configured such that when the screw 1 rotates, the thermoplastic resin material is supplied from the raw material hopper into the barrel 31A, and the supplied thermoplastic resin material is supplied from the heating cylinder. Heated by a heater attached in 31 </ b> A, melted by receiving a kneading compression action by the rotation of the screw 1, and sent to the front of the screw 1. The molten resin sent to the front of the screw 1 is filled into the mold cavity by the screw 1 from the nozzle 31B attached to the tip of the barrel 31A through a valve or the like attached to the fixed die 13.

  The control device 60 controls the mold clamping control unit that controls the opening and closing of the mold and the mold clamping force, and the injection device to control the plasticization of the thermoplastic resin material and the filling of the molten resin into the mold cavity. A control unit is provided.

  The mold clamping control unit of the mold clamping device 20 can set the opening / closing position of the movable mold 4 as necessary, and can set the opening / closing speed of the movable mold 14 to change according to the mold opening / closing position as necessary. A condition setting machine is provided. The mold clamping control unit of the mold clamping apparatus 20 can control the opening / closing position and opening / closing speed of the movable mold 14 during mold opening / closing based on the set value, and can control the mold clamping force to be a desired value during molding.

Next, the operation of the injection molding apparatus 100 configured as described above will be briefly described, and a preferable example of the operation of the injection molding screw 1 will be described.
First, as a first step, a toggle type mold clamping mechanism 21 (sometimes referred to as a link drive mechanism 21) of the mold clamping device 20 is operated, and the movable platen 12 is moved toward the fixed platen 11 while extending the toggle mechanism. The mold apparatus 10 is moved and clamped to a predetermined state.

In parallel with the first step, the injection device 30 rotates the screw 1 as shown in FIG. 1A with the shut-off nozzle 31 closed (in this embodiment, as viewed from the front of the screw). Rotate clockwise).
As described above, the screw 1 according to the present embodiment has two protrusions A that are inclined at a predetermined angle with respect to the screw longitudinal direction on the end surface of the check ring 5 on the head 2A side. Furthermore, since the head portion 2A of the screw head 2 is formed with a groove portion 2C that engages with the projection portion A so as to face the projection portion A of the check ring 5, as shown in FIG. When the screw 1 is rotated, the protrusion 5A slides while sliding on the groove 2C, and as a result, the check ring 5 moves to the axial front side of the screw.

In this state, the check ring 5 moves away from the seal ring 3 and moves toward the end face side of the head portion 2A, and a gap through which the resin can flow is formed. Further, as described above, a gap for flowing resin is formed on the outer peripheral surface of the small-diameter portion 2B of the screw head 2 and the inner peripheral surface of the main body annular portion of the check ring 5. Even when moved to the end face side of the head part 2A, since there is the convex part 5B between the check ring 5 and the end face of the head part 2A, a gap through which resin can flow is formed.
That is, according to the present invention, at the start of measurement, by utilizing the rotation of the screw 1, the check ring 5 is quickly moved to the head portion 2 </ b> B side to move from the screw body side 4 to the head portion 2 </ b> A side. A resin flow path through which the resin flows is formed. Therefore, the operation is quick and stable as compared with the conventional method in which the check ring 5 is moved only by the resin pressure.
Moreover, the flow path of the resin which distribute | circulates by the non-return ring 5 vicinity formed by this embodiment, ie, opening a non-return ring mechanism, is very simple. Therefore, it is possible to effectively suppress the resin replacement failure due to the retention of the resin, which is a problem of the prior art, due to the complicated shape of the resin flow path.

  Then, the metering process starts from the start of metering, and the resin supplied from the raw material hopper by the rotation of the screw 1 during the metering process is the screw body 4 while being heated, compressed, kneaded, etc. The desired amount is weighed through the resin flow path near the check ring 5 described above.

After the measurement is completed, when the screw 1 is rotated in the direction opposite to the rotation direction at the time of measurement in a state where the position of the screw 1 is held, the protruding portion 5A becomes a groove portion as shown in FIG. The end face of the check ring 5 comes into contact with the seal ring 3 by sliding while sliding on 2C and the check ring 5 moves to the screw rear side. When the check ring 5 comes into contact with the seal ring 3, the flow path through which the resin can flow is blocked. Then, after the resin flow path is blocked, the rotation of the screw 1 is stopped.

Next, the injection process is started with the resin flow path blocked by the above-described process.
In the injection process, after opening the shut-off valve 31B, the injection device 30 is operated to inject and fill the resin into the mold 10.

In the present embodiment, at the start of injection, the resin flow path through which resin flows from the head portion 2A side to the screw body 4 side is blocked. Therefore, compared to the conventional method in which the check ring 5 is moved by the resin pressure at the time of injection, the operation is quick and stable, and the resin does not flow backward from the head portion 2A side to the screw body 4 side. .

After filling the mold 10 with the resin, the resin in the mold 10 is cooled by holding for a predetermined time.
Then, after the cooling is completed, the toggle mold clamping mechanism 21 of the mold clamping device 20 is operated to move the movable plate 12 away from the fixed plate 11 while bending the toggle mechanism, and the mold 10 is opened to a predetermined state. After that, take out the product.

In the present invention, the resin that can be molded is not particularly limited as long as it is a resin generally used for injection molding. As a resin generally used for injection molding, for example, as a thermoplastic resin material, an olefin resin such as polypropylene or polyethylene, an acrylic resin such as polystyrene or polymethyl acrylate, a polyamide resin such as 6-nylon, or a polyester Examples thereof include resins, ABS resins, polycarbonate resins, and thermoplastic elastomers.

Moreover, if it is this invention using rotation of the screw 1, the interruption | blocking or distribution | circulation of the resin flow path by the check ring 5 can be performed freely at a desired timing. Therefore, the present invention is particularly suitable for foam molding or the like in which foam gas leakage is a problem during molding.
The present invention effectively prevents the flow of foaming gas that escapes from the screw body 4 to the head part 2A and the backflow of foaming gas from the head part 2A to the screw body 4 by quickly closing the check ring 5 after completion of measurement. This is particularly preferable when a resin containing a foaming agent is injected and foamed.

In addition, it does not specifically limit as a foaming agent used in that case, A chemical foaming agent and a physical foaming agent can be used. Examples of the chemical foaming agent include inorganic foaming agents represented by sodium bicarbonate and organic foaming agents represented by azodicarbonamide (ADCA). Examples of the physical foaming agent include inert gas such as carbon dioxide, nitrogen, and a mixed gas of carbon dioxide and nitrogen, air, and the like. These foaming agents may be used alone or in combination.

As described above, in the present embodiment, the structure of the check ring 5 does not hinder the flow of the molten resin at the time of metering, so that quality stabilization at the time of metering can be obtained, and at the same time, the resin after metering at the time of injection Since the resin that has been sent to the front of the screw 1 does not flow back to the screw body 4 side, stabilization of the product weight can be achieved.
Moreover, in this embodiment, since the resin flow path formed by the check ring 5 has a simple and smooth structure, there is little resin retention and resin replacement is easy. Furthermore, if it is invention of this embodiment, since it is only necessary to remodel a screw head and a non-return ring, it is not necessary to change the generally used non-return ring mechanism greatly, versatility is high.

It is explanatory drawing for demonstrating notionally the structure of the screw for injection molding machines concerning embodiment of this invention, (A) shows the time of measurement, (B) shows before injection. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall view illustrating a configuration of an injection apparatus including an injection molding machine screw according to an embodiment of the present invention. It is a figure explaining the angle (theta) which a protrusion part and a screw axis | shaft make according to embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Screw 2 Screw head 2A Head part 2B Small diameter part 2C Groove part 3 Seal ring 4 Screw main body 5 Check ring 5A Protrusion part 5B Convex part 10 Mold 11 Fixed platen 12 Movable platen 13 Fixed type 14 Movable type 100 Injection molding apparatus

Claims (3)

A screw head comprising a substantially conical head portion and a substantially cylindrical small diameter portion, the small diameter portion being attached to the seal ring portion side of the screw body;
A non-return ring that is slidably fitted to the small diameter portion and is movable in the screw axial direction from the head portion to the seal ring portion;
A gap through which resin can flow is formed between the inner peripheral surface of the check ring and the outer peripheral surface of the small diameter portion to form a resin flow path, and the check ring is brought into contact with or separated from the seal ring portion. In the resin injection molding machine screw that blocks or circulates the resin flow path,
The end surface of the head portion side of said reverse stop ring, by forming a protrusion digits inclined at a predetermined angle with respect to the screw axis, on both sides of the side surface of the protrusion portion in the same direction relative to the screw axis Tilt and
A groove is formed in the head portion that engages with the protrusion and slides about the screw shaft to move the check ring in the axial direction by rotating about the screw shaft. By
When the screw is rotated in the rotational direction during measurement, the check ring moves in a direction away from the seal ring,
An injection machine screw characterized in that when the screw is rotated in a direction opposite to the rotation direction, the check ring moves in a direction in contact with the seal ring. An injection molding apparatus comprising the injection molding screw according to claim 1. An injection molding method using an injection molding apparatus including the injection molding screw according to claim 1, wherein a desired amount of resin is measured by rotating the screw, and then the screw is reversely rotated while the screw position is maintained. An injection molding method comprising injecting a resin by an injection operation after bringing the check ring and the seal ring portion into contact with each other.

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