JPH0847800A - Method for compacting green compact with step - Google Patents

Abstract

PURPOSE:To simply mass-produce a green compact having a thin wall bulging part being ejected on the outer circumference of end face with a step using a powder compacting press without breaking a die and with the uniform density of the green compact. CONSTITUTION:Using a die being provided with one of upper punch 107 providing a reverse step shape to a step shape of an end face with a step, plural lower punches 103, 104, 105 divided corresponding to the step part of the end face with the step, and a die 102 with the step providing a step part 102a corresponding to thin wall bulging parts 16, 17, the end face with the step is compacted on the upper punch 107 side, and the thin wall bulging parts 16, 17 are compacted between the step part 102a of the die 102 with the step and the upper punch 107.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a green compact in the production of powder metallurgy parts, and more particularly to a method for forming a green compact having a complicated step shape.

[0002]

2. Description of the Related Art According to the basic concept of the conventional method for molding a green compact by uniaxial compression (edited by Japan Powder Metallurgy Association: Sintered Machine Parts-Design and Manufacturing-, Technical Institute (1987)
Years), pp. 159-275), in the case of forming a green compact having a stepped shape in the compression direction, in particular, one side is a stepped end surface with irregularities in the compression direction and the opposite end surface is a flat surface. It is common knowledge that the stepped end surface side is formed by the lower punch and the flat surface side is formed by the upper punch.

Further, when both end surfaces have irregularities, it is general that the more complicated surface of the irregularities is formed by the lower punch and the irregularities on the upper punch side are made as small as possible. The upper punch is divided into two pieces according to the shape, and the upper two steps lower two steps molding method or the upper two steps lower three steps molding method is applied to the green compact having large irregularities on both end surfaces. There is.

Based on the conventional concept of the powder molding method by such uniaxial compression, consider the case of molding the stepped green compact 310 as illustrated in FIG. 5D.
In this stepped green compact 310, one end face in the compression direction is an uneven stepped end face provided with a plurality of step portions 311, 312, 313, and the other end face is a flat surface 314.
Further, a thin projecting portion 315 protruding laterally with respect to the compression direction is provided on the outer periphery of the stepped end surface.

As shown in FIGS. 5 (A) to 5 (C), a thin wall overhang is formed on the basis of the conventional idea that a complicated surface having irregularities is formed by a lower punch and a flat surface side is formed by an upper punch. Protrusion 307a protruding the portion 315 from the upper punch 307
One upper punch 307 on the assumption that it is compressed by
Then, it is considered to apply the upper one-stage lower three-stage molding method in which the raw material powder 301 filled in the die 302 is pressed by using the three lower punches 303, 304, 305 and one core rod 306. To be

FIG. 6 (D) shows a stepped green body 410 having another shape.

That is, this green compact 410 has a plurality of step portions 411, 412, 413 and a thin projecting portion 415 protruding in the lateral direction on the stepped end surface, which is similar to FIG. The difference is that the side surface has a flat surface 414 and one protrusion 416. In this case, FIG.
As shown in (A) to (C), the thin protruding portion 415 is used.
Punch 407 having a protrusion 407a for molding
2 upper punches 407, 40
8 and 3 lower punches 403, 404, 405 and one core rod 406 are used to press the raw material powder 401 filled in the die 402, and an upper 2 lower 3 lower forming method is applied. Can be considered.

[0008]

However, in the case of the stepped green compact 310 illustrated in FIG. 5, if the thin projecting portion 315 of the green compact 310 is attempted to be compacted, the powder necessary for forming the projecting portion 315 is obtained. The amount of powder several times larger than the amount is compressed by the protrusions 307a of the upper punch, and the powder compact density becomes too high, and the protrusions 307a are broken.

That is, in the case of producing a sintered part by powder metallurgy using a mixed powder containing metal powder or alloy powder as a main component, a pressure of up to 8 [ton / square centimeter] is generally mixed in the powder compacting process. Added to the flour. Therefore, if the green compact density of the portion sandwiched by the protrusion 307a of the upper punch and the lower punch 305 becomes higher than that of the other portion during pressurization, the total load of the press is applied to this narrow portion. The protrusion 307a of the upper punch 307 is broken before the molding of the first green compact is completed.
The smaller the projected area of the thin projecting portion 315 in the compression direction, the smaller the width of the upper punch protrusion 307 and the easier it is to break.

The same applies to the case of the green compact 410 illustrated in FIG. 6, and when the thin projecting portion 415 is pressed, the protrusion 407a of the upper punch 407 forms the first green compact. It will break before it is completed.

In order to prevent the breakage of the protrusions 307a, 407a of the upper punches 307, 407 as shown in FIG.
As shown in FIG. 8, it is conceivable to increase the lower punches 305a and 405a corresponding to the thin projecting portions 315 and 415. That is, the thin projecting portions 315 and 415.
Powders P51 and P61 for forming the upper punches 307a and 407a and the increased lower punches 305a and
It is sandwiched between 405a and 405a and forcedly moved downward to be compressed, and it is intended to prevent the powder density from locally increasing.

However, even in this case, a small amount of powder for forming the thin-walled protruding portions 315, 415 must be moved from the upper end to the lower end of the cavity, and it is very difficult to adjust the green compact density.

Further, as compared with the forming method shown in FIGS. 5 and 6, the protrusions 307a and 407 of the upper punches 307 and 407 are compared.
Although the a and the lower punches 305a and 405a are less likely to be damaged, when the protruding widths of the protruding portions 315 and 415 are small, the protruding portions 307a and 407 of the upper punches 307 and 407 are small.
a and the lower punches 305a and 405a have small cross-sectional areas, and not only the protrusions 307a and 407a of the upper punches 307 and 407 but also the lower punch 305a and 405a.
Even a and 405a have a problem that they are easily damaged by a slight deformation.

Further, even if the protrusions 307a and 407a of the upper punches 307 and 407 are divided into two upper punches in FIG. 7 and three upper punches in FIG. 8, the result is the same and they are easily damaged. The upper punches 307, 4
As the distance that 07 enters into the powder-filled cavity and pushes the powder becomes longer, the protrusions 307a and 407a of the upper punches 307 and 407 are more likely to be damaged.

Further, in the case of molding a powder compact 410 having a projection 416 on the end surface opposite to the stepped end surface as illustrated in FIG. 8, even if the upper punch 407 is two as shown in FIG. The dust density of the protrusion 416 and its periphery is lower than that of other portions. Therefore, it causes deformation at the time of sintering, and in the case of a component requiring strength, the strength is insufficient, which is not preferable.

Therefore, in the conventional molding method, as shown in FIG.
6, one side is a stepped end surface, and the projecting portions 315, 41 projecting laterally to the outer periphery of the stepped end surface.
5 could not be economically mass-produced.

The object of the present invention is not the upper punch having the projections which may be damaged as in the conventional molding concept described above, but the novel die structure which has not been seen in the past, that is, the green compact. By using an upper punch having a stepped shape opposite to the stepped end face of, a plurality of lower punches divided corresponding to the stepped portion, and a die including a stepped die,
With no trouble of punch breakage, and with uniform green density,
Moreover, the purpose is to be able to economically mass-produce with a normal molding press.

[0018]

[Means for Solving the Problems]

[Structure and Action of the Invention] In the present invention, contrary to the basic idea of the powder metallurgical molding method by uniaxial compression, in the case where the green compact has irregularities, the complex surface of the irregularities is formed by the upper punch. However, this is a forming method that was devised based on a different idea from the conventional method of forming a flat or uneven surface side with a lower punch.

That is, according to the present invention, one end face in the compression direction is a stepped end face provided with a step portion, and the outer periphery of the stepped end face is a thin-walled overhang projecting in the lateral direction with respect to the compression direction. A method of forming a stepped green compact having a section,
Corresponds to one upper punch with a step shape opposite to the stepped shape of the stepped end surface, a plurality of lower punches divided corresponding to the stepped end surface of the stepped end surface, and the thin-walled overhanging portion It is possible to form a stepped end face on the upper punch side by using a die equipped with a stepped die having a stepped portion to form a thin projecting portion between the stepped portion of the stepped die and the upper punch. Characterize.

The end surface of the green compact opposite to the stepped end surface is a flat surface, which can be applied to the case where a plurality of flat surfaces are formed on the lower punch side, or the end surface of the green compact opposite to the stepped end surface. The end surface on the side has a shape having a flat surface and one or more protrusions, and can be applied to the case where the flat surface and one or more protrusions are formed on the lower punch side.

In the present invention, one upper punch, two or more lower punches having a stepped shape corresponding to the shape of the stepped end face of the stepped green compact to be molded, and the green compact having a perforated shape. In this case, a predetermined shape is given by a mold including a core rod and a stepped die.

That is, the die cavity formed by the stepped die and the lower punch, and in some cases the core rod, is filled with the powder, and the upper punch descends to start the compaction.

Then, as the upper punch is lowered, the movable lower punch is pulled down to a predetermined position so as to obtain a predetermined shape, and the powder above the lower punch is moved downward to be compressed to a predetermined green compact density. .

With respect to the thin projecting portion, pressure is applied between the step portion of the step die and the punch surface of the upper punch. Unlike the conventional case, the upper punch does not have a protruding portion for forming an overhang portion, and powder is pressed by the step portion of the die wall surface and the punch surface of the upper punch.

Therefore, neither the upper punch nor the lower punch has a pressing portion having a small cross section corresponding to the projecting portion,
There is no risk of punch damage.

The flat surface opposite to the stepped end surface, or the flat surface and one or more protrusions are formed by a plurality of lower punches. In the prior art, the flat surface is usually formed by one punch, and this point employs a novel method not found in the conventional method.

The withdrawal of the green compact and the subsequent withdrawal from the molding press are carried out by known methods.

More specifically, the mold used in the present invention is constructed as follows.

There is only one upper punch, and the upper punch surface is provided with unevenness corresponding to the step portion of the stepped end surface of the green compact to be molded.

A stepped die is used to form the thin overhang with the upper punch.

The end surface on the opposite side of the stepped end surface having the step portion is formed by two or more lower punches corresponding to the step portion, one of which is fixed and the remaining lower punches are the lower punches. Since the powder above the punch is moved downward, it is preferable that the powder is forcibly movable.

The fixed lower punch is fixed to a base plate fixed to the press body by a punch retainer, a receiving plate, a holder, etc., and the punch surface is fixed at the lowest part of the die cavity.

The lower punch may have two stepped portions whose stepped end surface sides are spaced from each other and have the same height, and the opposite surface thereof is a flat surface when forming a green compact. Further, in the case of molding a green compact in which the step portions provided separately have different heights and the opposite surface is flat, three lower punches are required.

Furthermore, when the end face opposite to the stepped end face having two spaced step portions has a flat surface and one or more protrusion portions, the same number of protrusion portions as the number of protrusion portions are formed. You need a punch underneath. For example, in the case of having a flat surface and one protrusion, another lower punch is added.

When there are a plurality of protrusions, the heights of the remaining protrusions are set to 80% or more and 120% or less of the height of the reference protrusion with reference to the height of a specific protrusion. It is preferable to set the distance within the range, and it is preferable to set the distance between the protrusions to 1 [mm] or more.

First, regarding the height limitation, a plurality of lower punches forming a plurality of protrusions are usually placed on the same one receiving plate. Although a plurality of lower punches for forming these protrusions can be moved up and down slightly by the force of a spring or the like, they do not have the function of accurately adjusting the green compact density, so the height of these lower punches is high. When the powders are significantly different, the powder density of the powders above the lower punch surface will be different during powder compaction, and depending on the height of the projections, a powder compact with weak projections will be formed. To be done.

In order to prevent this, it is preferable that the height of the plurality of protrusions be 80% or more and 120% or less of the height of the height of a certain specific protrusion.

When the heights of the plurality of protrusions are constant, it is not necessary to move the plurality of split punches up and down by the force of a spring or the like. Further, a through hole may be formed in the base plate and a spring may be set on the yoke plate side so that the lower punches for forming the protrusions act through the through hole.

The limitation of the distance between the plurality of protrusions is as follows.
When it is less than [mm], another lower punch forming this gap surface partially has a thickness of less than 1 [mm], and due to the strength of this other lower punch, it is immediately cracked or the like. The trouble occurs and there is a problem in use.

As described above, it is possible to form the protrusions by providing a plurality of lower punches for forming the protrusions, and the number thereof varies depending on the size and shape of the green compact, etc. However, the gap between the protrusions is 1
It is preferable to limit it to [mm] or more.

In the cavity of the step of the stepped die,
The size of the overhang that can be pressed into powder is 0.5 in the compression direction.
It is preferable that the protrusion dimension is not less than [mm] and not more than 3 [mm].

That is, edited by Japan Powder Metallurgical Industry Association: Sintered machine parts-design and manufacture-, Technical Shoin (1987), 1
According to page 60, the step portion of the stepped die is normally within 2 [mm] from the die wall in the horizontal direction, but it depends on the volume of powder in the cavity adjacent to the cavity of the step portion of the stepped die. Is possible within 3 [mm].

In the compression direction, 0.5 [m
m] or more is appropriate, and if it is thinner than this, part of the powder in the cavity adjacent to the cavity of the stepped portion of the stepped die flows laterally into the powder compact and the powder compact density rises too much, resulting in the powder compact. This is because it is not preferable because troubles such as cracks occur in the density sudden change portion.

As described above, the overhanging portion having such a cross-sectional shape cannot be formed by the upper punch and the lower punch having the same small cross-sectional area, and conventionally, the cutting work has been forced. According to the invention, it has become possible to economically form by powder molding alone. As the shape of the overhanging portion, except the shape that cannot be molded by a known method,
It may have a fan shape, a corrugated shape, or an elongated shape, and the thickness may change in the pressing direction.

Further, if the side surface of the stepped portion of the stepped green compact is parallel to the compression direction, when the green compact is withdrawn after the end of the green compact, the green compact is taken out from the die while being attached to the upper punch having the convex portion. It is preferable that the side surface of the stepped portion has a draft slope, because it may not come off and fall off and continuous molding may not be possible.

[0046]

【Example】

[First Embodiment] The present invention will be described below based on the illustrated embodiment.

FIG. 2 shows an example of a stepped green body g1 molded by the molding method of the present invention. This step green compact g
Reference numeral 1 denotes a ratchet mechanism pawl, which is used, for example, in a seat belt ratchet mechanism of an automobile.

As shown in FIG. 2A, the stepped green body g1 has a stepped end surface having a plurality of stepped portions on one end face in the compression direction. The opposite end face is flat. That is, in this embodiment, there are two projections 2 and 3 spaced apart from each other and having different heights on the left and right ends of one surface of the flat plate 1 as a base.
The end faces 19 and 20 of the flat plate portion 1 and the central end face 18 of the flat plate portion 1 form a stepped structure of three steps on the left and right.

On one side surface of one of the protrusions 2 and 3, which is the higher protrusion 2 in this embodiment, three triangular claws 6 are provided with two triangular valleys 4 and 5 separated from each other. 7 and 8 are continuously provided. At the valleys 4 and 5 between the claws 6 and 7 and the valleys 4 and 5 between the claws 7 and 8, thin-walled projecting portions 16 and 17 projecting in a direction perpendicular to the compression direction are provided.
It is provided at a position offset to the side. Of these, one of the protrusions 16 has a triangular shape in which the side edges 11 and 12 of the projections 2 of the claws 6 and 7 on the side of the end surface 19 are hypotenuses, and the line connecting the vertices of the claws 6 and 7 is the base 10. The other protruding portion 17 is the side edge 1 on the end face 19 side of the protrusion 2 of the claws 7 and 8.
3 and 14 are hypotenuses, and a base line 15 is a triangle that connects the vertices of the claws 7 and 8. Each overhang 16,
The end surface of 17 opposite to the valleys 4 and 5 is the end surface 1 of the protrusion 2.
It is on the same plane as 9.

In this embodiment, the thickness of the projecting portions 16 and 17 in the compression direction is 1 [mm], and as shown in FIG. 2B, the claws 6, 7 and 8 are located at the most recessed portions. Triangular vertices 11a, 13 of each overhanging portion 16, 17
Set the lengths ha and hb of the perpendiculars drawn from a to the bases 6 and 7 to 3
It is set within [mm].

Further, the other projection 3 is provided with a rectangular through hole 3a penetrating in the compression direction.

Next, a method of forming the stepped green compact will be described.

FIG. 1 is an explanatory view briefly showing the forming process of the green compact. In the figure, unnecessary devices are omitted,
Further, the shape of the green compact does not exactly show the shape shown in FIG.

First, the structure of the mold will be briefly described. The mold used for this molding has three protruding surfaces 107a on the left and right corresponding to the shape of the stepped end surface of the stepped green compact g1. 1
07b and 107c, one upper punch 107, two movable lower first and second punches 103 and 104 divided corresponding to each step portion, and one fixed lower third punch 105.
And one core rod 106 having a rectangular cross-sectional shape,
And a stepped die 102 having a stepped portion 102a corresponding to the thin projecting portions 16 and 17. The upper punch 107 is provided with an insertion hole 107d into which the core rod 106 is inserted.

The upper punch 107 is connected to a ram (not shown) on the side of the press body and driven up and down, and the fixed lower third punch 107c is fixed to a base plate fixed to the press body by a punch retainer, a receiving plate, a holder and the like. ,
The punch surface is fixed at the lowest part of the die cavity. The stepped die 102 is fixed to the die plate and is connected to the yoke plate by a guide rod (not shown), and the core rod 106 is supported by a yoke plate connected to a lower ram (not shown) on the press body side and driven up and down. It The movable lower punches 103 and 104 are
The descent timing and descent speed can be adjusted by a control device (not shown).

In FIG. 1, the powder filling process (see FIG. 1A), the pressurizing process (see FIGS. 1B and 1C) and the extracting process (see FIG. 1D) are shown as the molding process. Shows.

In the powder filling process, a raw material powder made of a metal mixed powder mixed at a predetermined ratio is added to the stepped dies 102, 2 as shown in FIG.
The cavity 101 is composed of two movable lower first and second punches 103 and 104, one fixed lower third punch 105, and one core rod 106 having a rectangular cross section.

The filling depth of the powder at this time is expressed by (height of green compact) × (filling ratio), as in the conventional powder metallurgical part molding method. Here, the filling ratio is an amount represented by (compacted powder density) / (apparent density of powder). For example, when an iron-based mixed powder is used, the apparent density is 3.30 [gram / cubic centimeter], and the obtained pressure is Assuming that the density of the powder is 6.93 [gram / cubic centimeter], the filling ratio at this time is 2.1. This filling ratio, that is, the filling depth, should be set to the first lower first, first before the continuous molding is started so that the green compact density of the green compact having irregularities becomes uniform after the green compaction. 2, third punch 103, 104, 1
Each is adjusted by the filling depth adjusting device attached to 05.

When the powder cavity 101 is filled, the upper punch 107 starts descending, and as shown in FIG.
The raw material powder P1 between the first projecting surface 107a of the upper punch 107 and the lower first punch surface 103a is moved downward while being sandwiched so as not to be excessively compressed immediately after the start of compression. The upper surface 103a of the lower first punch 103
Finally, the raw material powder P1 is compressed to a predetermined green compact density while being finally pulled down to a level on the same plane as the lower fixed third punch 105.

The lowering start timing and lowering speed of the lower first punch can be adjusted by a control device (not shown) so that defects such as cracks do not occur in the green compact to be formed.
The first protrusion surface 107a of the upper punch and the lower first punch surface 10
The increase in the green compact density of the raw material powder P1 sandwiched by 3a is adjusted so as not to be significantly different from the increase in the green compact density of the raw material powder in the other adjacent portions.

In this apparatus, if the first projection 103a of the upper punch 107 comes to a predetermined position every one cycle of molding,
It operates automatically by the signal from the molding press.

When the upper punch 107 is further lowered and the second projecting surface 107b of the upper punch 107 begins to push the raw material powder P2 filled in the cavity around the core rod 106, the operation is similar to that of the lower first punch 103. The second protrusion surface 107 b of the upper punch 107 and the lower second punch surface 104.
The raw material powder P2 between a is moved downward while being sandwiched so as not to be excessively compressed immediately after the start of the powder compaction, and finally the lower second punch 104 is fixed to the lower third punch.
While the punch surface 105a is pulled down to the same level as that of the punch surface 105a, the punch surface 105a is compressed to a predetermined powder density.

The lowering timing and the lowering speed of the lower second punch 104 can be adjusted by a control device (not shown) different from that of the lower first punch 103, as compared with the case of lowering the lower first punch 103. Similarly, it is also the same as the automatic operation by a signal from the molding press when the predetermined position is reached.

Further, the upper punch 107 descends and the third protruding surface 107c of the upper punch is filled with the remaining raw material powder, that is, the cavities of the fixed lower third punch 105 and the stepped portion 102a of the stepped die 102. Raw material powder P
3, start to pressurize P4. Thereafter, the die 102 and the core rod 106 start descending, and the three lower first, second and third punches 103, 104, relative to the die 102,
105 is raised to pressurize the lower end portion of the raw material powder to make the upper and lower densities of the green compact uniform.

When the third projection surface 107c of the upper punch compacts the raw material powder P4 filled in the cavity 101a of the stepped portion 102a of the stepped die 102 to a substantially predetermined compacted density, the upper punch 107 and the die are pressed. Reference numeral 102 denotes a third protruding surface 107c of the upper punch and a step lower surface 102 of the stepped die.
In order to keep the distance from a constant, it starts descending at the same speed. Then, the raw material powder P3 present between the third protruding surface 107c of the upper punch 107 and the fixed lower third punch surface 105a.
Is compressed to a predetermined green compact density.

FIG. 1C shows the final powdered state in which the raw material powder thus filled is fully pressed, and the lower first punch 103, the lower second punch 104 and the fixed lower third punch are shown. A flat surface 1 is formed on the lower surface by the three lower punches 105.

Thereafter, the green compact g1 is extracted, but the extraction method is the same as the conventional method. The upper punch 107 is raised, and the die 102 and the core rod 106 are further lowered by one step, as shown in FIG. ), The molded green compact g1 is extracted and then taken out of the molding press.

The stepped end face of the stepped green compact g1 is 1
Although it is formed by the upper punch 107 of the book, if the side surfaces of the projecting portions 2 and 3 that are steps are perpendicular to the surface of the flat plate that is the base, the green compact g1 will be generated when the powder is extracted after the completion of the green compact. Stepped die 102 while being attached to the upper punch 107 having a convex portion
Since it is not taken out and does not fall out and continuous molding is not possible, either or both of the protrusions 2 and 3 or the both sides, except the claws 6, 7, and 8, have a draft slope. Is preferred.

As a final step of one molding cycle, the stepped die 102, the core rod 106, the lower first and second lower punches 103 and 104 are returned to the initial powder filling position. The lower third punch 105 remains for fixing to a base plate (not shown).

[Second Embodiment] FIG. 3 shows a second embodiment of the present invention.

The second embodiment is an embodiment in the case of molding the stepped green body g10 shown in FIG. As shown in FIG. 4A, the stepped green compact g10 is an example in which a flat surface and one protrusion are provided on the surface opposite to the stepped end surface. That is, the stepped green compact g10 is provided with two protruding portions 22 and 23 at different heights which are spaced apart from each other on the left and right ends of one surface of the flat plate 21 as a base, and is similar to the embodiment of FIG. In addition, the end surfaces 39 and 41 of the respective projections 22 and 23 and the central end surface 40 of the flat plate portion 21 form a stepped structure of three steps on the left and right.

One of the protrusions 22 and 23, one side surface of the higher protrusion 22 in this embodiment, is provided with three claws 26, 27 and 28 with two triangular troughs 24 and 25 being separated from each other.
Is provided. Between the claws 26 and 27 and between the claws 27 and 28
In each of the valleys 24 and 25 between them, thin projecting portions 36 and 37 projecting in a direction perpendicular to the compression direction are provided.
Is provided at a position deviated to the end face 39 side. Of these, one of the protrusions 36 is the protrusion 2 of the claws 26 and 27.
The side edges 31 and 32 on the side of the end face 39 of 2 are hypotenuses, and each claw 2
Each of the protruding portions 37 has a side edge 33, 34 on the end face 39 side of the protrusion 22 of the claw 27, 28 as a hypotenuse, and a line connecting the vertices of 6, 27 with a base 30. It has a triangular shape having a base 35 as a line connecting the vertices of the claws 27 and 28. The troughs 24, 2 of each overhang 36, 37
The end surface on the side opposite to 5 is flush with the end surface 39 of the protrusion 22.

The thickness of the protruding portions 36 and 37 in the compression direction is set to 1 [mm], and, as shown in FIG. 4B, the protruding portions at the most recessed portions of the claws 26, 27 and 28. 36, 37 triangular vertices 31a, 33
Lengths hc and hd of perpendiculars drawn from a to the bottom sides 30 and 35
Is set within 3 [mm].

On the opposite side of the base plate 21,
Along with the flat surface of the flat plate portion 21, there is one protruding portion 38.

On the other hand, the other projecting portion 23 is provided with a round through hole 23a penetrating in the compression direction.

FIG. 3 is an explanatory view briefly showing the forming process of the green compact. In the figure, unnecessary devices are omitted,
Further, the shape of the green compact does not exactly show the shape shown in FIG.

The structure of the mold will be briefly described. The mold used for this molding has three protruding surfaces 208a, 208 on the left and right corresponding to the shape of the stepped end surface of the stepped green compact g10.
b, 208c, one upper punch 208, three movable lower first, second, and third punches 203, 204, 205 divided corresponding to each step, and one fixed lower first. 4 punch 206 and one core rod 2 having a round cross section
07, and the stepped portion 2 corresponding to the thin projecting portions 36 and 37
02a with a stepped die 202. The upper punch 208 is provided with an insertion hole 208d into which the core rod 207 is inserted.

In the powder filling process, a raw material powder made of a metal mixed powder mixed in a predetermined ratio is added to the stepped dies 202, 3 as shown in FIG.
Movable lower first, second and third punches 203, 204, 2
05, one fixed lower fourth punch 206 is filled in the cavity 201 constituted by one core rod 207.

Two protrusions 22 of the stepped green compact g10,
Projection 3 on the surface opposite to the stepped end surface provided with 23
8 is formed by a lower fourth punch 206 fixed to a base plate (not shown). As in the case of the first embodiment, the amount of the raw material powder filled in each upper part of each lower punch surface, that is, so that the green compact density of the green compact having irregularities becomes uniform after the green compaction, that is, The filling ratio is adjusted in advance by a filling depth adjusting device (not shown).

When the raw material powder is filled in the cavity 201, the upper punch 208 having three steps of projecting surfaces 208a, 208b, 208c corresponding to the upper surface shape of the green compact to be molded starts to descend, and FIG. As shown in (B), the first protruding surface 208a of the upper punch 208 starts to push the powder P10 filled in the cavity 201. After that, the upper punch 208, the lower first punch 203, and the lower second punch 204
Since the operating condition of is the same as that of the first embodiment, the description is omitted here. However, the difference from the first embodiment is that the lower first punch surface 203a and the lower second punch surface 204 are
a is finally lowered to a predetermined level of the movable lower third punch surface 205a.

Further, the upper punch 208 descends, and the third protruding surface 208c of the upper punch 208 has the remaining raw material powder, that is, the upper portion of the lower third punch 205 and the lower fourth punch 206 and the stepped portion of the stepped die 202. Cavity 20 at 202a
Raw powder P12, P13, P14 filled in 1a
Start to pressurize. After this, the die 202 and the core rod 2
The descent of 07 starts, and as a result, the four lower first, second, third and fourth punches 203, 204, 205,
This is the same as the increase in 206, which makes the density of the green compact uniform.

In order to move the raw material powder P12 between the third protruding surface 208c of the upper punch 208 and the lower third punch surface 205a downward while sandwiching it in a sandwich form so as not to excessively compress it immediately after the start of pressing. The lower third punch 205
The raw material powder P12 is pressed to a predetermined pressed density while lowering the upper surface 205a of the above to the level of a final final lower third punch surface 205a '.

The timing and the descending speed of the lowering of the lower third punch 205 are such that the lower first and second lower punches 2 (not shown) are
It can be adjusted by a control device other than 03 and 204,
In order to prevent defects such as cracks from being generated in the green compact to be molded, the increase in the green compact density of the raw powder P12 sandwiched between the third protruding surface 208c of the upper punch and the lower third punch surface 205a is adjacent to each other. As in the case of the lower first and second lower punches 203 and 204, the adjustment should be made so as not to be significantly different from the increase in the apparent density of the raw material powder in other portions. This device can automatically operate by a signal from the molding press if the third projecting surface 208c of the upper punch 208 comes to a predetermined position for each cycle of molding. , 204.

The third projection surface 208c of the upper punch 208 is the cavity 201a of the step portion 202a of the stepped die 202.
When the raw material powder P14 filled in the above is pressed to a substantially predetermined pressed density, the upper punch 208 and the die 202 are pressed.
Starts to descend at the same speed in order to keep the distance between the third protruding surface 208c of the upper punch and the stepped portion 202a of the stepped die constant.

Then, the third protruding surface 208c of the upper punch
Between the fixing lower fourth punch surface 206a and the fixing portion 3
The raw material powder P13 for forming 8 is compressed to a predetermined green compact density.

FIG. 3 (C) shows the final powdered state in which the raw material powder thus filled is fully pressed.
Punch 203, lower second punch 204, lower third punch 20
The flat bottom surface 21 is formed by the three lower punches 5 and the single protruding portion 38 is formed by the fixed lower fourth punch 206.

Normally, only up to three lower punches can be attached to the tool set, but in this embodiment, the device is specially devised to add another lower punch receiving plate to set four lower punches to the tool set. It is attached to.

The subsequent extraction method is the same as the conventional method, in which the upper punch 208 is raised and the die 202 and the core rod 207 are further lowered by one step. At this time, the wedge (not shown) attached to the die plate is The sliding block (not shown) is pushed away, whereby the lower first, second and third punches 203, 204, 205 are lowered together with the die 202 and the core rod 207, and are lowered to the same level as the fixed lower fourth punch surface 206a.
As shown in (D), the stepped green compact g10 is extracted and then taken out of the molding press.

As a final step of one molding cycle, the stepped die 202, core rod 207, lower first, second and third punches 203, 204 and 205 are returned to the initial powder filling position. The lower fourth punch 206 remains for fixing to a base plate (not shown).

[0090]

As described above, according to the present invention, a complicated stepped end surface having unevenness is formed by one upper punch, and a flat or uneven surface side is formed by a plurality of lower punches. This is based on a different idea from the conventional method, that is, not an upper punch having a protrusion that may be damaged, but an upper punch having a stepped shape opposite to the stepped end surface of the green compact, By using a die consisting of a plurality of lower punches and step dies that are divided corresponding to the steps, there is no punch breakage trouble, the powder density is uniform, and a normal forming press machine is used. It became possible to mass-produce economically.

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing the operation of a mold according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an example of a stepped green compact that is molded by the molding process of the first embodiment of the present invention.

FIG. 3 is an explanatory view schematically showing the operation of the mold according to the second embodiment of the present invention.

FIG. 4 is a diagram showing an example of a stepped green compact molded by a molding process of a second embodiment of the present invention.

FIG. 5 is an operation explanatory view of a mold showing an example of a method for forming a stepped green compact according to a conventional technique.

FIG. 6 is an operation explanatory view of a mold showing an example of another method for forming a stepped green compact according to the related art.

FIG. 7 is an operation explanatory view of a die showing an example of another forming method of the stepped green compact according to the conventional technique.

FIG. 8 is an operation explanatory view of a die showing an example of another forming method of another stepped green compact according to the related art.

[Explanation of symbols]

 16, 17, 36, 37 Thin projecting portion 107, 208 Upper punch 102, 202 Stepped die 103, 203 Movable lower first punch 104, 204 Movable lower second punch 105 Fixed lower third punch 205 Movable lower third punch 206 Lower fixed fourth punch 106,207 Core rod

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[Procedure amendment]

[Submission date] November 14, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0050

[Correction method] Change

[Correction content]

In this embodiment, the overhang portions 16 and 17 are
The thickness in the compression direction of 1 is [mm], and Fig. 2 (b)
As shown in, the triangular vertices 11a of the projecting portions 16 and 17 at the most recessed portions of the claws 6, 7, and 8,
The length ha of the perpendicular drawn from 13a to the bases 10 and 15,
hb is set within 3 [mm].

Claims (3)

[Claims] 1. An end face in the compression direction is a stepped end face having a step portion, and a thin projecting portion projecting laterally to the compression direction is provided on the outer periphery of the step end face. A method for forming a stepped green body, comprising: an upper punch having a stepped shape opposite to the stepped shape of the stepped end surface; and a stepped portion corresponding to the stepped end surface. Using a mold having a plurality of lower punches and a stepped die having a step corresponding to the thin projecting portion, a stepped end surface is formed on the upper punch side, and the thin projecting portion is stepped. A method for forming a stepped green body, which comprises forming between a stepped portion of an attached die and an upper punch. 2. The stepped green compact according to claim 1, wherein the end surface of the green compact opposite to the stepped end surface is a flat surface, and the flat surface is formed on the lower punch side. Molding method. 3. An end surface opposite to the stepped end surface of the green compact has a shape having a flat surface and one or more projections, and the flat surface and one or more projections are formed on the lower punch side. The method for molding a stepped green body according to claim 1, wherein