JPS5935603A - Molding device of green compact - Google Patents

Abstract

PURPOSE:To permit molding and compression of a green compact having a recess on the inside circumferential surface of a bore part in one stage in the stage of compressing and molding metallic powder, etc. by disposing a rigid body in part of molding dies and constituting said body projectable and retreatable into and from the molding cavity. CONSTITUTION:A core guide 31 is provided in the outside circumferential part of a core rod 30 disposed in a die 25 and the rod 30 is made movable along a core 31 in a compressing and molding device for metallic powder, etc. At the same instant, a hole part 31a to be inserted with a rigid body 34 of a hard ball or the like for forming a recess 41b of a green compact 41 having a spherical recess 41b in a bore part 41a is formed to the guide 31. Said body 34 is projected into a cavity 35 by the support of the rod 30 and is retreated by the descending of the rod 30 in the stage of compressing and molding the green compact 41 composed of metallic powder in the cavity 35 by means of an upper punch 28 and a lower punch 27, whereby the green compact having the recess on the inside circumferential surface of the bore is easily molded.

Description

[Detailed Description of the Invention] This invention is a method for using metals and metal oxides in powder metallurgy technology.
The present invention relates to a powder compacting device that compresses powder made of nitride, boride, carbide, etc. into a desired shape.

As a conventional powder compacting apparatus, there is one shown in FIG. 1, for example. That is, in the figure, 1 is an upper punch, 2 is a lower punch, and 3 is a die.

4 is a core rod in which an annular cavity 5 is formed by a lower punch 2, a die 3, and a core rod 4. When performing powder compaction using such an apparatus, a first powder is placed in the cavity 5 shown in FIG.
As shown in Figure (b), the raw material powder 6 is filled, and then the first
As shown in FIG. 1(C), the die 3 is also lowered at the same time as the upper punch 1 is lowered, and the raw material powder 6 is compressed in the cavity 5 by the upper punch 1 and the lower punch 2, and then, as shown in FIG. As shown in d), the green compact 7 was taken out by raising the upper punch 1 and further lowering the die 3.

By using such conventional powder compacting equipment,
Although it is possible to obtain a powder compact 7 with a somewhat complicated shape in a short period of time, conventional shapes that can be formed include an uneven portion 11a in the forming direction, such as a sprocket gear 11 shown in FIG.
, llb, and those having convex portions 12a and 13a in a direction perpendicular to the molding direction, such as parts 12 and 13 shown in FIGS. 3 and 4.
Parts 14 and 15 shown in Figs. 5 and 6 have spherical recesses 14a and 15a in the inner hole in the same direction as the molding direction (undercut shape), as shown in Fig. 1. In the past, it has been difficult to obtain a healthy compact by compression molding the powder in one step. The reason for this is that during the basic compression molding process, it is impossible to extract the product due to structural problems of the molding die. For this reason, conventional methods for manufacturing such parts include first compression molding into a ring shape and then machining to form a spherical part in the inner hole after molding or sintering. A method has been used to obtain a desired shape by integrating compression molded bodies or sintered bodies divided into the above parts by joining such as diffusion bonding, welding, or press fitting.

However, with these conventional methods, there are problems such as an increase in the number of machining steps and a shortened cutting tool life due to poor machinability when using machining, and when using bonding, manufacturing is labor-intensive. The actual situation was that it was not suitable for mass production due to problems such as this and the tendency for distortion to occur during bonding.

The present invention has been made by focusing on such conventional problems, and has corrected the above-mentioned conventional drawbacks, and has made it possible to improve the pressure resistance of an article having a spherical shape or the like on the inner circumferential surface of the inner hole. It is an object of the present invention to provide an apparatus capable of molding powder in one compression molding process.

The present invention includes a die having a hollow part, a core rod disposed in the die, and a compacted powder body having an inner hole by compressing powder supplied into a cavity formed by the die and the core rod. In the green compact forming apparatus equipped with a punch, a core guide is disposed on the outer periphery of the core rod to enable the core opening/end to move along the core guide, and the core guide includes:
A hole is formed in the inner hole of the powder compact to accommodate a hard body for forming a recess at a predetermined position, and the hard body in the hole can be protruded into the cavity by support of the core rod, and the core rod is supported by the core rod. It is characterized by being retractable by movement.

Hereinafter, embodiments of the present invention will be described in more detail based on the drawings.

FIG. 7 is a view showing a green compact forming apparatus according to an embodiment of the present invention, and shows a state where it is installed in a hydraulic press. In the figure, 21 is the frame of the hydraulic press, 22
23 is a lower block fixed to the lower ram of the hydraulic press, and 23 is an upper block fixed to the niram of the press, each of which is movable in the vertical direction. Further, 24 is a base plate that can be attached to the frame 21, 25 is a die having a hollow part 25a, and 26 is a die 25 and a lower prong 2.
A rod connecting the base plate 2 with the base plate 24 slidably passes through the base plate 24.

Furthermore, 27 is a lower punch mounted upright on the base plate 24, and is slidably fitted into the die 25. Reference numeral 28 denotes an upper punch that is attached to the upper block 23 and has an outer diameter that allows it to slide within the hollow portion 25a of the die 25. Furthermore, 29 is a receiving block with a built-in hydraulic cylinder mechanism attached to the lower block 22; 30 is a core rod whose lower end side is connected to a piston portion 29a of a hydraulic cylinder mechanism that slides vertically inside the receiving block 29; 31, the lower end side is the block 2
9 is fixed to the lower block 22 via the upper end of the die 25, and its upper end side is always kept in the same plane as the upper surface of the die 25, and is slidably fitted into the hole 27a in the lower punch 27, and the core rod 30 is This is a core guide that is slidable, and 32 and 33 are piping that supply and discharge hydraulic pressure to and from the hydraulic cylinder mechanism. Further, 34 is a hard body, such as a hard ball, and this hard body 34 is arranged in a hole 31a formed in the core guide 31. The diameter of this hole 31a is slightly smaller than the diameter of the hard body 34, and when the hard body 34 is supported by the core rod 3o, the die 2
5, the lower punch 27, and the core guide 31. Further, 35' is a long hole formed in the core guide 31, and 36 is a pin fixed to the core rod 30 and fitted into the long hole 35'.The movement of the core rod 30 is controlled by the long hole 35' and the pin 36. It is regulated.

The compacted powder compacting apparatus according to the present invention is constructed as described above.Next, the movement of each part of this apparatus will be explained in order of the powder compacting process.

FIG. 8 is a diagram showing the positional relationship of only the main parts constituting the molding apparatus in the order of the powder molding process. First, during powder molding, the core rod 30 is raised by the oil sent to the hydraulic cylinder mechanism through the piping 33, and during this rise, the tapered surface 30a provided on the circumference of the tip of the core rod 30
The hard body 34 in the hole 31a of the core guide 31 is moved laterally, and as shown in FIG.
A part of the hard body 34 is made to protrude into the cavity 35 from 1a, and while supporting the hard body 34 on the side surface of the core rod 30,
It is in a state where it comes into contact with the upper end surface of the core guide 31 and stops. This is the state shown in FIG. 7, and the core rod 3
After completing the operation of No. 0, the raw material powder 40 is filled into the cavity 35 to a height that matches the upper surface of the die 25 as shown in FIG. As shown in FIG.
The powder 40 in 5 is compressed. During this compression, in order to obtain a green compact with uniform density, the lower block 22 is lowered and the die 25, core rod 30. The core guide 31 is lowered at the same time. Note that the core rod 30 remains lifted by the hydraulic mechanism until the powder compression is completed. Furthermore, in the process of compressing the powder 40 in the cavity 35, the spherical surface of the hard body 34 protruding from the outer peripheral surface of the core guide 31 absorbs the stress acting perpendicularly to the molding direction of the powder 40 to be compressed. A portion of the core guide 31 receives the core and is about to be pushed back into the core guide 31. however,
The hard body 34 is in contact with the - part of the outer peripheral surface of the core rod 30 within the core kite 31 and receives a reaction force, so that it remains stationary until compression is completed.

After completion of compression molding, as shown in FIG. 8(C), -1,...
Raise the lower bunch 28 in the direction of the arrow and open the cavity 35.
Pull it out from inside. Thereafter, by supplying pressure oil from the piping 32 of the hydraulic mechanism, the core rod 30 is lowered until the pin 36 hits the lower end of the elongated hole 35, and the tip of the core rod 30 is inserted into the hard body 34 in the hole 31a of the core guide 31. lower it to a position where it does not come into contact with the Subsequently, by lowering the lower block 22 via the ram of the hydraulic press,
At the same time, dice 25. Core rod 30 and core guide 3
1 is lowered, and as shown in FIG. 8(d), the die 25
and the upper surface of the lower punch 27. At the point when this dice 25 descends,
The core rod 3o and the core guide 31 also descend in conjunction with each other, but when the descent starts, the hard body 34 that is in contact with the powder compact 41 comes into contact with the powder compact 41 because the core guide 31 descends. Shear force is applied to the surface. At this point, since the hard body 34 is not in contact with the core rod 30 inside the core kite 31, a part of the four parts 4ip formed in the powder compact 41 receives a reaction force, and as shown in FIG. It is easily pushed back toward the core rod 30 in the direction of the arrow, and comes into contact with the tapered surface 30a of the tip of the core rod 30 and stops. At this time, it is necessary that the hard body 34 is completely pushed back into the core guide 31 so that no part of it remains on the outer peripheral surface of the core guide 31, that is, within the cavity 35. This is core rod 3
The necessary positional relationship can be obtained by changing the taper angle of the tapered surface 30a provided on the circumference of the tip end of the core rod 30, the length of the core rod 30, etc. However, as a positional relationship that prevents the hard body 34 from being pushed back into the core guide 31 too much, the hard body 34 is pushed back into the hole 31a.
We need to make sure that we can return to the inside.

In addition, as long as the positional relationship described above is within the range,
As will be described later, it is also possible to provide a plurality of holes 31a in the core guide 31 and insert the hard bodies 34 into each hole.

After taking out the powder compact 41, the lower block 22 is raised and the die 25. Core rod 30. The core kite 31 etc. are raised to a predetermined height and stopped, and then the core rod 3
0 by hydraulically raising the core guide 3.
After the hard body 34 is pushed back into the hole 31a of the hard body 34, a part of the hard body 34 is made to protrude into the cavity 35, and is returned to the initial state shown in FIG. Thereafter, by filling powder into the cavity 35 and repeating the powder molding process described above, the inner hole 8 and the recess 41 are formed in the same direction as the molding direction.
A compacted powder body 41 having a shape a is obtained. During this compression molding, the powder near the spherical surface moves along the spherical surface, so that the formed surface is clean and a green compact with a relatively uniform density can be obtained. At this time, the core rod 30. Core guide 31. Since the hard body 34 is subjected to considerable stress during compression molding, it is desirable to use hard steel such as cemented carbide or die steel as the material thereof.

Incidentally, as shown in FIGS. 9 and 10 of the above embodiment, the hard body 34 is formed by the die 25. When the core rod 30, core guide 31, etc. are lowered, they can easily collapse into the core guide 31 when they receive the force of being pushed back into the core guide 31, but this collapse can be made smoother. As such, it is preferable to provide a certain taper angle θ to the portion that supports the hard body 34 from its lower part.

11 and 12 are views showing other embodiments of the present invention, in which spherical recesses 41b, 41b are formed at two axially symmetrical locations in the inner hole 41a of the powder compact 41. It is something that In this embodiment, forming a tapered surface 30a at the upper end of the core rod 30 is similar to the embodiment described above, but the core guide 31 has two holes 31a, 31.
A is formed, and a hard body 34 is inserted into each of both holes 31a. The dimensions of a specific example of the compacted powder body 41 molded in this example are an outer diameter of 80 mm, an inner tub of 60 mm,
The height is 30ffffl, and the maximum depth of the four spherical portions 41b is 5III. At this time, for example, as raw material powders, 2% by weight of atomized pure iron powder, 1% by weight of graphite powder, and 0.75% by weight of zinc stearate powder for mold lubrication are added to reduced pure iron powder for 30 minutes. Use the mixture in a mold mixer. After filling the obtained mixed powder into the cavity 35, the upper punch 28
was lowered, and compression molding was performed at a molding load of 5 Oton/cm2. Figure 12 shows the green compact 4 after compression molding.
1 is a diagram illustrating a state in the middle of extracting 1. FIG. At this time, a carbide pole with a diameter of 15 mm was used as the hard body 34. As a result, a clean spherical four part 41 with no cracks is obtained.
Green compact 4 with density 6.8 g/C113 having b, 41b
I was able to get 1.

FIG. 13 and FIG. 14 are diagrams showing still another embodiment of the present invention, in which a compacted powder body 41 has four spherical parts 41b, 41b attached to its inner hole 41a at two coaxial locations. This is what is shown. In the molding apparatus according to this embodiment, two holes 31a and 3 are provided in the core guide 31 in the axial direction.
1a, each containing a hard body 34 and 34, and a dogleg-shaped tapered surface 30b is formed on the core rod 30, and the tapered surface 30b is a hole 31a.

31a, both hard bodies 34.34 are retracted from inside the cavity 35, and are rotated by a rotary drive mechanism 45 provided at the lower end of the core rod 30, so that the side surface of the core rod 30 is rotated by the hard body 34.34. 34, the rigid body 34.34 can protrude into the cavity 35. The rotational drive mechanism 45 in the illustrated example includes a pinion 46 fixed to the lower end of the core rod 30, a rack 47 that engages with the pinion 46, a hydraulic cylinder 48 that reciprocates the rack 47, and a stopper mechanism 49.50. It is equipped with the following.

The dimensions of the compacted powder body 41 molded in this example are as follows: outer diameter 80+nm, inner diameter 60vn, height 4.
0 mm, and the maximum depth of the four spherical portions 41b is 5111ffl at both locations. FIG. 14 shows a state in which the green compact 41 is being extracted after compression molding. That is,
As described above, in order to project the hard body 34 into the cavity 35 during compression molding, the core rod 30 is rotated by the rotation drive mechanism 45, and the hard body 34 is supported on the outer peripheral surface (circumferential surface) of the core rod 30. Next, the green compact 4
1, the core rod 30 is rotated so that the hard body 34 can be moved laterally to the surface 30b of the core rod 30, and then the die 2 is removed as described above.
5. Core rod 30. The green compact 41 is extracted by lowering the core guide 31 and the like at the same time. In this case, as the hard body 34, a carbide pole having the same dimensions as in the previous embodiment was used. As a result, in this embodiment, the density is 6, which has two spherical recesses 41b, 41b in series without cracks.
A green compact 41 weighing 8 g and 7 cm3 was obtained.

In each of the above embodiments, as the upper punch 28 descends, the die 25 and the core rod 30. Although the case of the with draw method in which the core guide 31 is lowered is shown, it is of course possible to lower only the upper punch 28, or it is also possible to make both the upper punch 28 and the lower punch 27 movable. .

Further, in the above embodiment, the powder compact 41 has a perfect annular shape having a concentric inner hole 41a, but it is not limited to such a shape. As shown in FIGS. 15(&) to (d), the inner hole 41a is elliptical, the outer shape is rectangular, the inner hole 41a is polygonal, and the inner hole 41a is not concentric. It can also be applied to things that are rectangular.

As explained above, according to the green compact molding apparatus according to the present invention, a hard body is disposed in a part of the mold, and the hard body can be moved into a cavity and retracted from the cavity. Because of this structure, it is possible to easily obtain a green compact having a concave portion on the inner circumferential surface of the inner hole in a single molding and compression process, which has been considered difficult in the past.

[Brief explanation of the drawing]

FIGS. 1(a) to 1(d) are cross-sectional explanatory diagrams sequentially showing the process of forming a green compact using a conventional green compact forming apparatus, and FIGS.
FIG. 4 is a diagram showing the shape of a green compact that can be molded by a conventional molding device, in which (a) in each figure is a cross-sectional view, and (a) in each figure is a cross-sectional view.
b) is a plan view, and FIGS. 5 and 6 are diagrams showing the shape of a green compact that is difficult to mold with conventional molding equipment,
In each figure, (a) is a sectional view, (b) is a plan view, FIG. 7 is an explanatory longitudinal cross-sectional view of a compacted powder forming apparatus according to an embodiment of the present invention, and FIGS. 8(a) to (d) 9 and 10 are explanatory diagrams sequentially showing the process of molding a green compact using the molding device shown in FIG. 7, and FIGS. 9 and 10 show the hard material in the molding device shown in FIG. FIG. 11 is a diagram showing the positional relationship between the core rod and the core rod, in which (a) of each figure is an explanatory enlarged vertical cross-sectional view, (b) of each figure is an explanatory horizontal cross-sectional view passing through the center of the hard body, and FIG. FIG. 12 is a cut perspective explanatory view of a compacted powder body and an enlarged cross-sectional explanatory view of a hard body portion of a molding device according to another embodiment of the present invention, and FIGS. 13 and 14 are according to still another embodiment of the present invention. A cut perspective explanatory view of the green compact, a vertical cross-sectional view of the main part of the molding device, and Fig. 15 (a
) to (d) are explanatory plan views showing other examples of shapes of the powder compact. 25...Dice, 25a...Hollow part, 27.28.
... Punch, 30... Core rod, 30a, 30b.
...Tapered surface, 31... Core guide, 31a... Hole, 34... Hard body, 35... Cavity also 40...
・Powder, 41...Powder compact, 41a...Inner hole, 41
b... recess. Patent applicant: Nissan Motor Co., Ltd. Patent attorney Yutaka Oshio Figure 2 (b) Figure 3 (b) 18- Figure 4<0) Figure 5 (21) (b) Figure 9 (b) 11- Figure 10 (b) (8) (b) (C) (d) 21-

Claims (1)

[Claims] (1) A die having a hollow portion, a core rod disposed within the die, and a punch that compresses powder supplied into a cavity formed by the die and core rod to form a green compact having an inner hole. In the apparatus for forming a green compact, a core guide is disposed on the outer periphery of the core rod, the core rod is movable along the core guide, and the green compact is attached to the core guide. A hole is formed at a predetermined position in the inner hole for inserting a hard body for forming the four parts, and the hard body in the hole can be protruded into the cavity by support of the core rod and retracted by movement of the core rod. A compacted powder compacting device characterized by: