JP3459801B2 - Screw for metal injection molding machine - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an injection device of a metal injection molding machine for injection-molding a metal such as magnesium or aluminum and an alloy containing them as a main component (hereinafter referred to as a metal material). The present invention relates to a kneading and ejecting screw.

[0002]

2. Description of the Related Art An injection device of a conventional metal injection molding machine will be described with reference to FIGS.

As shown in FIG. 4, in the metering process, the rotation of the rotary motor 3 is transmitted to the screw 1 via the output shaft 10, and when the screw 1 rotates clockwise as viewed from the nozzle 18, the material hopper 5 heats it. Metallic materials (hereinafter, referred to as material chips) such as particles, cutting pieces, and crushed pieces that have fallen into the cylinder 2 are along a spiral groove (hereinafter, referred to as screw groove) 6 formed on the surface of the screw 1. And sent to the front of the heating cylinder 2 to be heated and kneaded to be in a molten or semi-molten state (hereinafter referred to as molten metal).
Are stored in the front chamber 16 of the heating cylinder 2.

In the next injection process, the entire injection device 17 is moved forward and the nozzle 18 at the tip of the heating cylinder is moved to the mold 1.
4, the pressure oil is supplied to the advancing oil chamber 8 of the injection cylinder, and the injection piston 7
When the screw 1 is driven forward through the output shaft 10 and the screw 1 is moved forward, the molten metal stored in the front chamber 16 of the heating cylinder 2 passes through the nozzle 18 and is filled into the cavity 19 in the mold 14.

As shown in FIG. 3, the screw thread 20 of the conventional screw 1 has a trapezoidal shape in which the screw crest 23 is narrower than the base portion as in the screw of the plastic injection molding machine. It is tilted rearward and the thread rear surface 22 is tilted forward. This shape is intended to make the screw threads 20 strong and to press the material chip or the molten metal in the screw groove 6 against the inner wall surface of the heating cylinder 2 to enhance the conveying force of the screw 1.

As shown in FIGS. 3 to 5, the screw groove 6 is divided into a supply section f, a compression section c and a measuring section m from the material hopper 5 side depending on the shape and role. Although it depends on the type and shape of the metal material to be injection-molded, the supply portion f generally occupies 30 to 70% of the screw groove length, and the height difference between the screw crest 23 and the screw bottom 24 (hereinafter, The screw groove depth) H is the compression portion c and the measuring portion m.
Has been made larger than. The measuring portion m occupies 10 to 30% of the length of the screw groove portion, and the screw groove depth H is smaller than that of the supplying portion f and the compressing portion c. Compression part c
Is located between the supply part f and the metering part m, occupies 10 to 40% of the length of the screw groove part, and the screw groove depth H changes so as to connect the supply part f and the compression part m smoothly. There is.

[0007]

Since the injection device of the conventional metal injection molding machine is constructed as described above, the following problems exist. That is, screw 1
In a region from the latter half of the supply part f to the first half of the compression part c, a small amount of molten metal is mixed in the gap of the solid chips and is conveyed to the rear, that is, the material hopper 5 side by the backward movement of the screw 1 in the measuring process. . The molten metal that has reached the region of the heating cylinder 2 whose inner wall surface temperature is lower than the melting temperature of the material chips is deprived of heat by the surrounding material chips, and part of it adheres to the surface of the screw 1 and the inner wall surface of the heating cylinder 2. And solidify (hereinafter, this deposit is referred to as a re-solidified product).

The re-solidified substance attached to the surface of the screw 1 is
By the forward movement operation of the screw 1 in the next injection process, the heating cylinder 2 is returned to the forward movement position where it is heated to a higher temperature and is heated, and is returned to the molten metal again.

Most of the re-solidified substance adhering to the inner wall surface of the heating cylinder 2 is stripped off by the screw thread 20 of the screw 1 by the forward movement of the screw 1 in the next injection process, returned to the forward movement position and heated again. Although it returns to the molten metal, the rest is left in a state of adhering to the inner wall surface of the heating cylinder 2.

Most of the remaining re-solidified material is scraped off by the material chips moving forward in the next measuring step, but part of the re-solidified material remains attached. This adhered re-solidified product accumulates and increases with the repetition of the molding cycle.

Further, a molten metal, that is, a metal material in a molten or semi-molten state is chemically very active and reacts with oxygen or nitrogen in the air to form an oxygen compound or a nitrogen compound (hereinafter referred to as a compound). It is easy to occur. In particular, since aluminum alloys and magnesium alloys are mixed with other metal elements depending on their uses, various compounds are mixed.

Therefore, if these compounds adhere to the surface of the screw 1 or the inner wall surface of the heating cylinder 2 and solidify in the flow region from the latter half of the compression part c of the screw 1 to the metering part m, they are easily heated again. It does not melt and causes great difficulty in its removal.

When the above compounds and the like adhere to the surface of the screw 1, the cross-sectional area of the screw groove 6 is reduced to impede the flow of the molten metal, and when they adhere to the inner wall surface of the heating cylinder 2, the screw 1 smoothly rotates and straightens. Prevent sliding.

Since the screw thread 20 of the conventional screw 1 is constructed as described above, a small amount of re-solidified substance or compound (hereinafter, re-solidified substance or compound or the like is combined with the inner wall surface of the heating cylinder 2). When the screw 1 is moved forward in the injection step, that is, moved toward the nozzle 18, the adhered and solidified material is pushed toward the rear along the inclination of the screw thread front face 21 and the screw thread is moved forward. 20 into the gap between the heating cylinder 2 and the screw 1
Is fixed to the heating cylinder 2. In this case, even if the screw 1 is rotated in the subsequent measuring step, the adhered solidified matter that has entered the gap between the thread 20 and the heating cylinder 2 is not easily discharged.

Further, in the normal metering process, since the internal pressure of the molten metal stored in the front chamber 16 of the heating cylinder 2 is low, the screw 1 is rotated and at the same time, the pressure oil is supplied to the retreating side oil chamber 9 of the injection cylinder. Then, the screw 1 is forcibly retracted, but when this is done, the state becomes the same as the operation of turning the bolt and pulling it out from the screw hole. I can hardly expect it.

The present invention has been made in order to solve the above problems, and can easily remove the adhered solidified matter adhering to the inner wall surface of the heating cylinder, and the stable rotation and linear sliding of the screw. An object of the present invention is to provide a screw for a metal injection molding machine that does not hinder movement.

[0017]

The present invention has solved the above problems as follows. That is, the screw thread front surface of the screw for kneading and injecting the metal material is inclined at right angles to the axial center or forward, and the screw thread rear surface is inclined forward. In this case, it is preferable that the inclination angle of the front surface of the screw thread is 0 to 30 ° and the inclination angle of the rear surface of the screw thread is 5 to 45 °.

As another invention, the screw thread front surface of the screw near the hopper of the screw for kneading and injecting the metal material is tilted backward, and the screw thread front surface of the other area is set as the axis. Tilt at a right angle or forward and tilt all rear threads forward. In this case, the angle of inclination of the screw thread front surface in the region where the molten metal on the side closer to the material hopper does not contact is 10 to 30 °, the inclination angle of the other screw thread front surface is 0 to 30 °, and all screw thread rear surfaces It is preferable that the inclination angle is 5 to 45 °.

As a result, since the adhered and solidified substance adhered to the inner wall surface of the heating cylinder is scraped off by the rake blade in front of the screw threads and does not accumulate in a large amount during the forward movement and the rotational movement of the screw, the forward movement and the rotational movement of the screw are prevented. Will not be hindered.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described based on examples with reference to the drawings.

The injection device of the metal injection molding machine of the present invention will be described.

As shown in FIG. 4, the heating cylinder 2 is attached to the front part of the injection housing 11 of the injection device 17, and the rotary motor 3 is attached to the rear part. A heater 4 is attached to the outer periphery of the heating cylinder 2, and a material hopper 5 is attached to the rear of the heating cylinder 2. The screw 1 is inserted into the heating cylinder 2 so as to be rotatable and axially movable.

The injection piston 7 built in the injection housing 11 constitutes an injection cylinder together with the injection housing 11, and the forward movement oil chamber 8 and the backward movement oil chamber 9 of the injection piston 7 are formed.
Is formed. The rear portion of the screw 1 is inserted into the front portion of the output shaft 10 which is inserted into the injection piston 7 and is rotatably held, and the rear portion of the screw 1 is inserted while being restrained in the rotational direction, and the rear portion of the output shaft 10 is connected to the rotary motor 3. It is fitted to the front part of the rotary shaft 26 so as to be movable in the axial direction. Further, the screw 1 and the output shaft 10 are connected by a coupling 12.

Next, the operation will be described.

First, in the metering process, when the rotation of the rotary shaft 26 is transmitted to the screw 1 via the output shaft 10, the material chips dropped from the material hopper 5 into the heating cylinder 2 are heated along the screw groove 6 to the heating cylinder. The molten metal is stored in the front chamber 16 of the heating cylinder 2 while being heated and kneaded while being sent to the front of 2. Along with this, the screw 1 retracts. However, since the metal material has a low viscosity of the molten metal and a sufficient pressure is not generated in the molten metal stored in the front chamber 16 for retracting the screw 1, the rotating shaft 26 rotates and the retreating side oil chamber 9 of the injection cylinder 9 simultaneously. In many cases, pressure oil is supplied to forcibly retract the screw 1.

Further, the melting process of the material chips in the measuring process will be described in detail with reference to FIGS. 4 and 5.

The material chips that have fallen into the screw groove 6 of the supply part f of the screw 1 are fed inside the screw groove 6 in the direction of the compression part c by the conveying action of the screw 1 due to the rotation, and the inner wall surface of the heating cylinder 2 is The temperature is raised by the heating of the heater 4 which is transmitted, and part of it is turned into molten metal.

Next, the material chips that have reached the compression section c are continuously heated to further increase the temperature, and the proportion of the molten metal increases, and at the same time, the material chips are compressed due to the decrease in the cross-sectional area of the screw groove 6 to increase the density, It is sent in the direction of part m. The air that was present in the gap between the material chips in this process,
The inert gas supplied by the material hopper 5, the gas such as the gas component contained in the material chip, is pushed back toward the supply section f, and is discharged to the outside through the material hopper 5.

Most of the material chips that have reached the measuring section m are molten metal, and are kneaded while being heated to make the molten state uniform, and then the backflow prevention device 13
And is sent to the front chamber 16 of the heating cylinder 2.

In the case of an injection molding machine for metal, the supply portion f is 30 to 70% of the length of the screw groove portion, and the compression portion c.
Is 10 to 40%, and the measuring unit m is 10 to 30%. As an example, when the screw groove length is 20 pitches, the supply part f has 11 pitches, the compression part c has 5 pitches, and the measuring part m has 4 pitches.

In the next injection step, the injection device 17 as a whole is moved forward, and the nozzle 18 at the tip of the heating cylinder 2 is brought into contact with the sprue bush 15 of the mold 14, and is moved into the forward movement oil chamber 8 of the injection cylinder. Pressure oil is supplied to drive the injection piston 7 in the forward direction, and its operation is transmitted to the screw 1 via the output shaft 10. As a result, when the screw 1 advances, the molten metal stored in the front chamber 16 of the heating cylinder 2 is injected into the mold through the nozzle 18, and is filled in the cavity 19 in the mold.

After the molten metal filled in the cavity 19 in the mold is cooled and solidified, the mold 14 is opened and the metal molded product formed in the shape of the cavity 19 is taken out.

By repeating the above operation, it is possible to efficiently produce a metal molded product having the same shape.

In the screw of one embodiment of the present invention, as shown in FIG. 1, the thread front surface 21 'and the thread rear surface 22 of the thread 20 are inclined forward.

The inclination angle A'of the thread front surface 21 'is 0 to 0.
The inclination angle B of the screw thread rear surface 22 is selected in the range of 30 ° and 5 to 45 °, but A ′ is 5 to 5 from the viewpoint of versatility of molding.
15 ° and B are preferably in the range of 15 to 30 °.

The radii of curvature Ra 'and Rb of the corner curved surfaces of the screw thread front face 21', the screw thread rear face 22 and the screw bottom 24 are 0.3 to 0.7 times and 1 times the screw groove depth H, respectively. It is preferably in the range of 2 times.

The base material of the screw 1 is made of a Ni-based or Fe-based heat-resistant alloy, and the screw crest 23 is coated with a Co-based heat-resistant alloy coating 25 having a screw groove depth H of 0.1 to 0. Three
It is preferable to apply a double thickness. Depending on the type of metal material to be injection-molded, the base material may be made of another heat-resistant alloy and coated with ceramic or the like. In addition, the coating can be stopped for relatively soft metallic materials.

According to the screw of this embodiment, since the adhered solidified substance adhered to the inner wall surface of the heating cylinder 2 is scraped off by the screw thread front face 21 'during the forward movement and the rotational movement of the screw 1, a large amount is not accumulated. The screw 1 can be smoothly advanced and rotated, and continuous molding can be performed for a long period without frequently cleaning the inner wall surface of the heating cylinder 2 and the surface of the screw thread 20 of the screw 1.

When the operation of the machine is stopped with the material chips or the molten metal remaining in the heating cylinder 2,
The adhered solidified material may accumulate in the heating cylinder 2, and the rotation of the screw 1 may become unstable or may not rotate when the operation is restarted. In that case, if the screw 1 is rotated without slowing the forced retreat speed of the screw 1 or forcedly retreating, the adhered solidified material is scraped off, and stable screw rotation becomes possible.

In the screw shown in FIG. 2, the inclination angle of the screw thread front surface 21 'of the screw thread 20 is set to zero, that is, at a right angle to the axis, and the other shapes are the same as those of the above embodiment. In this screw 1, since there is no rake angle on the screw thread front surface 21 ', the ability to scrape off the adhered solidified matter adhering to the inner wall surface of the heating cylinder 2 is reduced, but the screw thread front surface 21' is reduced.
Since the edge angle formed by the crest 23 and the crest 23 is not an acute angle and the strength of the edge increases, it is effective when the hardness of the adhered solidified product is high.

Next, another embodiment will be described.

As shown in FIGS. 3 and 5, the screw according to the present embodiment is a portion of the screw 1 near the material hopper 5 where the molten metal does not come into contact, that is, a screw of the screw thread 20 in the rear half of the feeding portion f. The thread front surface 21 is tilted backward by the tilt angle A, and the other thread threads 20 have the thread front surface 21 'tilted forward by the tilt angle A'or the axial center, as shown in FIGS. And the right angle. Further, all the screw thread rear surfaces 22 are inclined forward.

The inclination angle A of the screw thread front surface 21 in the region near the hopper 5 of the screw 1 where the molten metal does not contact is 10 to 10.
30 °, other angle 21 'of thread front 21' is 0
-30 °, the inclination angle B of all the screw thread rear surfaces 22 is 5-4.
It is selected in the range of 5 °, but in terms of versatility of molding, A
Is 10 to 20 °, A'is 5 to 15 °, and B is 15 to 30 °.
It is preferably in the range of.

Further, the corner curved surface Ra between the screw thread front face 21 and the screw bottom 24 in a region of the screw 1 near the hopper 5 where the molten metal does not come into contact is 0.5 to 1.5 times the screw groove depth H. With a radius of curvature, the corner curved surface Ra ′ between the screw thread front face 21 ′ and the screw bottom 24 in the other regions is set to 0.
The radius of curvature is set to 3 to 0.7 times, and the corner curved surface Rb of all the screw thread rear surface 22 and the screw bottom 24 is set to 1 to the screw groove depth H.
It is preferable that the radius of curvature be doubled.

Further, the region of the screw 1 near the hopper 5 where the molten metal does not come into contact is 30 to 1 from the rear end of the feeding section f.
It is preferably set within the range of 00%.

The base material of the screw 1 and the coating 25 on the crest 23 are the same as those in the above-mentioned embodiment.

According to this embodiment, in the region where the adhered solidified substance does not exist, the screw thread 20 is formed in a shape in which the heat conduction with the heating cylinder 2 is good, so that the temperature of the material chip can be raised quickly. In addition, in the other region, that is, the region where the adhered solidified substance exists, a large amount of the adhered solidified substance adhered to the heating cylinder 2 is not accumulated, so that the forward movement and the rotation operation of the screw 1 can be smoothly performed, and the heating cylinder 2 Even if the inner wall surface and the surface of the screw 1 are not frequently cleaned, continuous molding can be performed for a long time.

[0048]

According to the first to third aspects of the present invention, the adhered and solidified material adhered to the inner wall surface of the heating cylinder is scraped off by the rake blade in front of the screw threads during the forward and rotational operations of the screw and accumulated in a large amount. Therefore, the forward movement and the rotation of the screw are not hindered. In addition, claims 4 to
According to the invention of 7, the material chip is pressed against the inner wall surface of the heating cylinder during the forward movement and rotation operation of the screw in the region where the adhered solidified substance does not exist, so that the heat conduction from the heating cylinder is improved and the material chip rises. The temperature gets faster. In other regions, a large amount of the adhered solidified substance adhered to the heating cylinder does not accumulate, so that the forward movement and rotation operation of the screw are not hindered.

[Brief description of drawings]

1 is a cross-sectional view of a screw thread of a screw of the present invention.

FIG. 2 is a sectional view of a screw thread of another screw of the present invention.

FIG. 3 is a sectional view of a screw thread of a conventional screw.

FIG. 4 is a cross-sectional view of an injection device of a metal injection molding machine.

FIG. 5 is an outside diameter diagram of a screw.

[Explanation of symbols]

1 screw 2 heating cylinder 5 Material hopper 6 screw grooves 20 screw threads 21, 21 'screw thread front 22 Rear of screw thread 23 screw head 24 screw bottom 25 coating

Front Page Continuation (56) References JP 2001-62553 (JP, A) JP 62-259650 (JP, A) JP 50-135692 (JP, A) JP 11-267816 (JP, A) Japanese Patent Laid-Open No. 11-156904 (JP, A) Actual Development 1-71022 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) B22D 17/30 B22D 17/20

Claims (9)

(57) [Claims] 1. A screw (1) for kneading and injecting a metal material, wherein a screw thread front surface (21 ') is tilted at a right angle to a shaft center or forward, and a screw thread rear surface (22) is tilted forward. Screws for metal injection molding machines. 2. The screw thread front surface (21 ') has an inclination angle (A') of 0 to 30 °, and the screw thread rear surface (22) has an inclination angle (B) of 5 to 45 °. The screw of the metal injection molding machine according to claim 1. 3. The thread front (21 ') and the thread bottom (2).
4) and the corner curved surface (Ra ') has a radius of curvature of 0.3 to 0.7 times the screw groove depth (H), and the screw thread rear surface (22)
The screw for a metal injection molding machine according to claim 2, wherein a corner curved surface (Rb) between the screw bottom (24) and the screw bottom (24) has a radius of curvature of 1 to 2 times the screw groove depth (H). 4. A screw thread (1) for kneading and injecting a metal material, the screw thread front surface (21) in a region near the material hopper (5) close to the material hopper (5) is inclined backward, and the screw thread in the other region is inclined. A screw for a metal injection molding machine, characterized in that the front surface (21 ') is inclined at right angles to the axial center or forward, and all the screw thread rear surfaces (22) are inclined forward. 5. The inclination angle (A) of the screw thread front face (21) in a region of the screw (1) near the material hopper (5) where the molten metal does not contact is set to 10 to 30 °, and the other screw thread front faces ( 21 ') has an inclination angle (A') of 0 to 30 °, and all screw thread rear surfaces (22) have an inclination angle (B) of 5 to 45 °.
The screw of the metal injection molding machine according to claim 4, wherein 6. A corner groove curved surface (Ra) between a screw thread front surface (21) and a screw bottom (24) in a region of the screw (1) near the material hopper (5) where the molten metal does not come into contact with the screw groove depth. The radius of curvature is 0.5 to 1.5 times that of (H), and the corner curved surface (Ra ') between the screw thread front face (21') and the screw bottom (24) in the other regions is set to 0 of the screw groove depth. The radius of curvature is 3 to 0.7 times, and all the screw thread rear surface (22) and the screw bottom (2
4) Set the corner curved surface (Rb) to the screw groove depth (H) of 1
The screw for a metal injection molding machine according to claim 5, wherein the screw has a radius of curvature of ˜2 times. 7. The region of the screw (1) near the material hopper (5) where the molten metal does not come into contact is set within a range of 30 to 100% from the rear end of the supply section (f). The screw for a metal injection molding machine according to claim 4, 5 or 6. 8. The base material of the screw (1) is Ni-based or F
The screw of an injection molding machine for metals according to any one of claims 1 to 7, wherein the screw is an e-based heat-resistant alloy. 9. The screw crest (23) of the screw (1) is C
9. The screw for a metal injection molding machine according to claim 8, wherein the screw is coated with an o-based heat-resistant alloy and has a thickness of 0.1 to 0.3 times the screw groove depth (H).