JP6503583B2 - Method of producing green compact - Google Patents

Description

  The present invention relates to a method of producing a green compact. More particularly, the present invention relates to a method of producing a green compact from a powder material using a mold.

  Powder metallurgy is a technology for producing machine parts having relatively complicated shapes. In this method, powder materials of various compositions including iron-based materials are pressure-formed into a desired shape, and the obtained green compact is heated and sintered. A sintered body is manufactured through such forming and sintering steps.

  The green compact is usually manufactured using a press molding machine equipped with a die such as a die, upper and lower punches and a core. For example, the green compact W having the shape shown in FIG. 3 is press-molded with a die having a die 30, a lower punch 31, an upper punch 32, a center core 33 and a side core 34 as shown in FIGS. Manufactured using a machine. (A) of FIG. 3 is a plan view of the green compact W, and (b) of the same is a cross-sectional view taken along the line AA of (a) of FIG.

  The green compact W is formed of a short cylindrical body having a first round hole 35 at the center, and four second round holes 36 are formed at equal intervals around the first round hole 35. Further, a plurality of teeth T are formed on the outer periphery of the green compact W. The green compact W can be used, for example, as a pulley.

  The die 30 for producing the green compact W having such a structure has a round hole 37 as an opening at the center. The lower punch 31, the upper punch 32, the center core 33, and the side core 34 are disposed so as to be positioned in the round hole 37 when viewed in plan. Specifically, the lower punch 31 is disposed in the circular hole 37 of the die 30, and the upper punch 32 is disposed in the circular hole 37 of the die 30 above the lower punch 31. A center core 33 is disposed inside the lower punch 31. Furthermore, a side core 34 is disposed in the round hole 37 of the die 30 so as to penetrate the lower punch 31. Four side cores 34 are disposed corresponding to the number of second round holes 36 of the green compact W. The lower punch 31 and the upper punch 32 are respectively formed with holes through which the side core 34 can penetrate.

  Each punch has a cylindrical shape, and each punch, center core 33 and side core 34 can be operated by hydraulic pressure, a motor or a mechanical mechanism. The lower punch 31 is disposed at such a position that the upper end surface 31a can be in contact with the lower surface 38 (the lower surface in FIG. 3B) of the green compact W. On the other hand, the upper punch 32 is disposed at a position where the lower end surface 32a can be in contact with the upper surface 39 (upper surface in FIG. 3B) of the green compact W.

  A plurality of recesses having a shape corresponding to the teeth T of the powder compact W are formed along the circumferential direction on the inner periphery of the die 30. Further, on each outer periphery of the lower punch 31 and the upper punch 32 sliding on the inner periphery of the die 30, teeth having a shape corresponding to the recess, that is, teeth having the same shape as the teeth T of the powder compact W are circumferentially A plurality is formed along with.

The green compact W is manufactured through the steps shown in FIGS.
First, as shown in (a) of FIG. 4, various kinds of iron-based materials are contained in a space defined by the die 30, the lower punch 31, the center core 33 and the side core 34 using a powder feeder (not shown) The powder material P of the composition of FIG. At this time, the upper punch 32 stands by above the lower punch 31.

  Next, as shown in (b) of FIG. 4, the upper punch 32 is lowered to compact the powder material P filled in the space to produce a green compact W. At this time, in conjunction with the lowering of the upper punch 32, the die 30 descends by a predetermined distance, and the center core 33 and the side cores 34 descend to an arbitrary position in a motion different from the die 30.

The compression molding of the powder material P is completed by the steps of (a) to (b) in FIG. 4. The green compact W obtained by compression molding is taken out of the mold by the steps shown in (c) to (e) of FIG.
First, as shown in FIG. 5C, the die 30 is lowered by a predetermined distance. The die 30 is lowered until its upper surface 30 a is located slightly lower than the lower surface 38 of the green compact W. While the compacting of the green compact W is completed and the die 30 is moved downward, the upper punch 32 applies a hold-down pressure of a predetermined magnitude to the green compact W. Although this hold down pressure changes with shapes, sizes, etc. of the green compact W, generally it is about 5 to 20 t. The hold down pressure is applied to the green compact W until the step of raising the upper punch 32 described later.

Next, as shown in (d) of FIG. 5, the center core 33 and the side cores 34 are lowered. The center core 33 and the side cores 34 are lowered to a position where their upper end faces 33 a and 34 a are substantially flush with the upper surface 30 a of the die 30.
Finally, as shown in FIG. 5E, the upper punch 32 is raised to take out the green compact W from the mold.

However, the conventional manufacturing method described above has the following problems.
That is, although the die 30 is lowered in the step of taking out the green compact W after compression molding, at this time, due to the above-mentioned hold down pressure and the spring back pressure of the green compact W The force to work acts. Since the side core 34 is a relatively long member, the side core 34 is deformed into a curved shape by this force, and when extracted from the hole formed in the upper punch 32, the side core 34 is strong with the edge of the hole. By rubbing against each other, there is a risk that the surface of the side core 34 may be muffled. Once the mussel occurs, the resistance at the time of extraction from the hole is further increased, and in some cases, the side core 34 may be broken.

  This invention is made in view of such a situation, and when taking out the green compact after compression molding from a mold, manufacture of a green compact which can control damage to a side core which constitutes a mold. It is intended to provide a way.

The method for producing a green compact according to an aspect of the present invention (hereinafter, also simply referred to as “production method”) comprises a short cylindrical body having a first opening at the center, and a plurality of second cylinders around the first opening. A method of producing a green compact having an opening formed therein using a mold,
The mold includes a die having a round hole at the center, a lower punch disposed in the round hole of the die, and an upper punch disposed in the round hole of the die above the lower punch. A center core disposed inside the lower punch for forming the first opening, and disposed through the lower punch in a round hole of the die for forming the second opening It has a side core and
After the compacting step of the green compact is completed, the inner core side and the outer diameter side of the green compact are opened by pulling out the center core in synchronization with the die, and the springback pressure and the upper pressure of the green compact are obtained. Remove the punch hold down pressure to the inner diameter side and the outer diameter side, and then pull out the side core.

  According to the above-mentioned invention, when taking out the green compact after compression molding from a metallic mold, damage to the side core which constitutes the metallic mold can be controlled.

It is process explanatory drawing of one Embodiment of the manufacturing method of the green compact of this invention. It is process explanatory drawing of one Embodiment of the manufacturing method of the green compact of this invention. (A) is a top view of an example of green compact, (b) is the sectional view on the AA line. It is process explanatory drawing of the conventional manufacturing method of green compact. It is process explanatory drawing of the conventional manufacturing method of green compact.

Description of the embodiment of the present invention
First, the embodiments of the present invention will be listed and described.
The manufacturing method according to one aspect of the present invention is
(1) A method of manufacturing a green compact comprising a short cylindrical body having a first opening at the center and having a plurality of second openings formed around the first opening using a mold,
The mold includes a die having a round hole at the center, a lower punch disposed in the round hole of the die, and an upper punch disposed in the round hole of the die above the lower punch. A center core disposed inside the lower punch for forming the first opening, and disposed through the lower punch in a round hole of the die for forming the second opening It has a side core and
After the compacting step of the green compact is completed, the inner core side and the outer diameter side of the green compact are opened by pulling out the center core in synchronization with the die, and the springback pressure and the upper pressure of the green compact are obtained. Remove the punch hold down pressure to the inner diameter side and the outer diameter side, and then pull out the side core.

  In the manufacturing method according to this aspect, unlike the conventional method, the center core is extracted from the green compact in synchronization with the die instead of extracting only the die from the green compact after completion of compression molding. Thereby, the outer diameter side and the inner diameter side of the green compact are opened. As a result, the spring back pressure and the hold down pressure can be uniformly applied to the side core in the radial direction, and deformation or deviation of the side core can be suppressed. This makes it possible to reduce the resistance between the surface of the side core and the edge of the hole formed in the upper punch, and to prevent the occurrence of mussel on the surface of the side core. As a result, the life of the side core is extended. can do.

Details of the Embodiment of the Present Invention
Hereinafter, embodiments of the manufacturing method of the present invention will be described in detail with reference to the attached drawings. The present invention is not limited to these exemplifications, but is shown by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

Since the green compact W1 manufactured by the manufacturing method according to the present embodiment has the same structure as that shown in FIG. 3, the description of the green compact W1 will be omitted for the sake of simplicity.
The green compact W1 is manufactured using a press molding machine provided with a die having a die 10, a lower punch 11, an upper punch 12, a center core 13 and a side core 14 as shown in FIGS.

  The die 10 has a round hole 17 at the center as an opening. The lower punch 11, the upper punch 12, the center core 13, and the side cores 14 are disposed so as to be positioned in the round hole 17 when viewed in plan. Specifically, the lower punch 11 is disposed in the round hole 17 of the die 10, and the upper punch 12 is disposed in the round hole 17 of the die 10 above the lower punch 11. A center core 13 is disposed inside the lower punch 11. Furthermore, a side core 14 is disposed in the round hole 17 of the die 10 so as to penetrate the lower punch 11. Four side cores 14 are disposed corresponding to the number of second round holes 36 of the green compact W1. The lower punch 11 and the upper punch 12 are respectively formed with holes through which the side core 14 can penetrate.

  Each punch has a cylindrical shape, and each punch, center core 13 and side core 14 can be operated by hydraulic pressure, a motor or a mechanical mechanism. The lower punch 11 is disposed at a position where the upper end surface 11a can be in contact with the lower surface 38 (the lower surface in FIG. 3B) of the green compact W1. On the other hand, the upper punch 12 is disposed at a position where the lower end surface 12a can be in contact with the upper surface 39 (upper surface in FIG. 3B) of the powder compact W1.

  On the inner periphery of the die 10, a plurality of recesses having a shape corresponding to the teeth T of the green compact W1 are formed along the circumferential direction. Further, on each outer periphery of the lower punch 11 and the upper punch 12 sliding on the inner periphery of the die 10, teeth having a shape corresponding to the recess, that is, teeth having the same shape as the teeth T of the powder compact W1 are circumferentially A plurality is formed along with.

The green compact W1 is manufactured through the steps shown in FIGS.
First, as shown in FIG. 1 (a), various kinds of iron-based material are contained in a space defined by the die 10, the lower punch 11, the center core 13 and the side core 14 using a powder feeder (not shown). The powder material P of the composition of FIG. At this time, the upper punch 12 stands by above the lower punch 11.

  Next, as shown in (b) of FIG. 1, the upper punch 12 is lowered to compact the powder material P filled in the space, thereby producing a green compact W1. At this time, in conjunction with the lowering of the upper punch 12, the die 10 and the center core 13 are synchronously lowered by the same predetermined distance, and the side core 14 is lowered to an arbitrary position. When the process of FIG. 1B is completed, the upper limit position of the die 10 and the upper limit position of the center core 13 are the same, and the upper limit position of the side core 14 is slightly larger than the upper limit positions of the die 10 and the center core 13 It is located above.

  The compression molding of the powder material P is completed by the steps of (a) to (b) in FIG. The process up to such compression molding differs from the conventional one in that the center core 13 and the die 10 are synchronized. The green compact W1 obtained by compression molding is removed from the mold by the steps shown in (c) to (e) of FIG.

  In the present embodiment, as shown in (c) of FIG. 2, the center core 13 is synchronized with the die 10 instead of lowering the die 10 only and taking out the powder compact W 1 as in the prior art. The powder compact W1 is drawn down by a predetermined distance. The die 10 and the center core 13 are lowered until their upper end faces 10a and 13a are located slightly lower than the lower surface 38 of the green compact W1. While the compacting of the green compact W1 is completed and the die 10 and the center core 13 move downward, the upper punch 12 applies a hold-down pressure of a predetermined magnitude to the green compact W1. Although this hold down pressure changes with shapes, sizes, etc. of the green compact W1, generally it is about 5 to 20 t. The hold down pressure is applied to the green compact W1 until the upper punch 12 raising step described later. Further, a spring back pressure acts on the green compact W1.

  In this regard, in the present embodiment, as described above, since the outer diameter side and the inner diameter side of the powder compact W1 are opened, the springback pressure and the holddown pressure are equal to the side core 14 in the radial direction. Can act on. Thereby, the deformation or deviation of the side core 14 can be suppressed, and the resistance between the surface of the side core 14 and the edge of the hole formed in the upper punch 12 can be reduced. As a result, it is possible to prevent the occurrence of a conventional mussel on the surface of the side core 14, and the life of the side core 14 can be extended.

Next, as shown in (d) of FIG. 2, the side core 14 is lowered. At this time, as described above, since the deformation or deviation of the side core 14 is suppressed, the resistance between the surface of the side core 14 and the edge of the hole formed in the upper punch 12 can be reduced. The side core 14 is lowered to a position where its upper end surface 14 a is substantially flush with the upper surface 10 a of the die 10.
Finally, as shown in FIG. 2E, the upper punch 12 is raised to take out the green compact W1 from the mold.

[Other Modifications]
The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims.
For example, in the above-described embodiment, four second round holes are formed around the center first round hole of the green compact W1, but the number of second round holes is limited to four. For example, it may be three, or five or more, and may be appropriately selected according to the application of the green compact W1. Also, the size and shape of the plurality of second round holes may be different from one another. For example, the second round hole can be configured by two round holes and two long round holes.

  Further, in the above-described embodiment, the teeth T are formed on the outer periphery of the green compact W1, but a green compact having no such teeth T may be used.

10: Die 10a: Upper surface 11: Lower punch 11a: Upper end surface 12: Upper punch 12a: Upper end surface 13: Center core 13a: Upper end surface 14: Side core 14a: Upper end surface 17: Round hole 30: Die 30a: Upper surface 31: Lower Punch 31a: upper end face 32: upper punch 32a: lower end face 33: center core 33a: upper end face 34: side core 34a: upper end face 35: first round hole 36: second round hole 37: round hole 38: lower face 39: upper face P: powder material T: tooth W: green compact W1: green compact

Claims (1)

A method of manufacturing a green compact comprising a short cylindrical body having a first opening at the center and having a plurality of second openings formed around the first opening using a mold.
The mold includes a die having a round hole at the center, a lower punch disposed in the round hole of the die, and an upper punch disposed in the round hole of the die above the lower punch. A center core disposed inside the lower punch for forming the first opening, and disposed through the lower punch in a round hole of the die for forming the second opening It has a side core and
After the compacting step of the green compact is completed, the inner core side and the outer diameter side of the green compact are opened by pulling out the center core in synchronization with the die, and the springback pressure and the upper pressure of the green compact are obtained. A method for producing a green compact, wherein the hold down pressure of the punch is removed to the inner diameter side and the outer diameter side, and then the side core is extracted.

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