JPH05156305A - Device for compacting sintered part - Google Patents

Abstract

PURPOSE:To prevent the breakage of a first lower punch due to internal pressure and the gnawing between the first lower punch and die. CONSTITUTION:A tapered part 7 graded upward toward the axial center is previously formed on a pressing face 6 at the tip of a first lower punch 4, and a powder is pressed by the upper punch 3 and the first and second lower punches 4 and 5 from the upper and lower parts of the die 1 to obtain a powder compact C. As the compacting proceeds, an internal pressure P1 is generated to extend the first lower die 4 outward, a pressure P2 opposed to the internal pressure P1 is also produced at the tapered part 7, and the breakage of the first lower punch 4 and gnawing between the punch and die 1 are prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for molding a sintered part, and more particularly to an apparatus for compression-molding a powder compact (compacted powder) to be a hollow cylindrical sintered part having a flange portion at one end.

[0002]

2. Description of the Related Art For example, as shown in FIG. 5, a gear-shaped component W having tooth portions G1 and G2 on a body portion B and a flange portion F integral with the body portion B, respectively. 6 is manufactured by sintering, the powder compact C is molded by the molding device shown in FIG.

The molding apparatus shown in FIG. 6 has a die 1 having a die hole 1a formed therein, a core rod 2 arranged at the center of the die hole 1a, an upper punch 3 and first, first movable members capable of moving relative to each other. The predetermined metal powder P which is composed of two lower punches 4 and 5 and is housed in the die hole 1a.
The powder compact C of the sintered part W shown in FIG. 5 is compression-molded by pressurizing the upper and lower parts of the die 1 with the upper punch 3 and the first and second lower punches 4, 5.

At this time, the upper punch 3 has a powder compact C.
While pressing the end face of the flange portion F side of the
The lower punch 4 and the upper punch 3 together with the flange portion F
In the thickness direction, and the second lower punch 5 presses the end surface of the powder compact C on the side opposite to the flange portion F.

The die 1, the upper punch 3 and the first and second lower punches 4 and 5 have tooth profile portions corresponding to the tooth portions G1 and G2 of the sintered component W shown in FIG.
It is omitted in FIG.

In the molding apparatus as described above, for example, the length dimension a of the body B of the sintered component W shown in FIG. 5 is 10 mm.
When it becomes larger than the dimension b as described above, the first lower punch 4 is expanded outward due to the rise of the internal pressure P ₁ due to the compression as shown by the phantom line e in FIG. 7, and the first lower punch 4 is damaged. Alternatively, even if the first lower punch 4 is not damaged, the clearance G between the die 1 and the first lower punch 4 disappears, and a galling phenomenon occurs between the two, making it difficult to smoothly take out the powder compact C.

Therefore, in order to solve the above problems,
As shown in FIG. 8, there is a so-called counter die method in which the shape of the die hole 31a of the die 31 is approximated to the shape of the sintered component W while the lower punch 34 is formed as a single structure. ..

However, according to this apparatus structure, although the problems such as the breakage of the lower punch 34 as described above do not occur, the shape of the sintered component W and, consequently, the powder compact C thereof has a surplus as shown in FIG. Unless the shape with Q is attached, the powder compact C cannot be compressed to a predetermined density. As a result, if the surplus thickness Q is left as it is in the product shape, the weight of the component increases, and if the surplus thickness Q is removed, machining must be performed in a subsequent process. Is increased, which is not preferable.

The present invention has been made in view of the above problems, and is based on the former mold structure which does not require a surplus to be added to the powder compact, and also causes the damage and galling of the first lower punch. It is intended to provide a structure that prevents the above.

[0010]

According to the present invention, a cylindrical die hole is formed in an apparatus for compression-molding a powder compact which is to be a hollow cylindrical sintered part having a flange portion at one end as described above. A die in which the powder is stored in the die hole, a core rod arranged at the center position of the die hole, and the die is inserted into the die hole from the upper side, and the end face of the powder molded body on the flange side is An upper punch for pressurizing and a hollow cylindrical first member which is inserted into the die hole from the lower side of the die and pressurizes the flange portion of the powder compact together with the upper punch in the thickness direction thereof.
A lower punch, and a second lower punch that is inserted into the first lower punch and is inserted into the die hole from the lower side of the die to press the end surface of the powder compact opposite to the flange portion, The first lower punch is characterized in that a taper portion having an upward slope toward the central axis of the powder compact is formed on the pressing surface at the tip of the first lower punch. More preferably, the inclination angle of the taper portion is 5 to 30 °. The feature is that it is set within the range.

[0011]

According to this structure, as shown in FIG. 1, an internal pressure that tends to push the first lower punch outward is generated as the powder compact is compressed, but at the taper portion at the tip of the first lower punch. A pressure that opposes the internal pressure is generated, which prevents damage to the first lower punch and galling between the first lower punch and the die.

[0012]

1 is a view showing an embodiment of the present invention, in which a taper portion 7 is formed on a pressing surface 6 at the tip of a first lower punch 4 based on the mold structure shown in FIG. It differs from that of FIG. That is, the pressurizing surface 6 at the tip of the first lower punch 4 is formed with a taper portion 7 having an upward slope toward the axial center of the powder compact C, and the inclination angle α of the taper portion 7 is formed.
Is set within a range of 5 to 30 ° depending on the size of the sintered part W and the like as shown in FIG. When the inclination angle α of the taper portion 7 exceeds 30 °, the compression density of the powder at the starting position T ₁ of the taper portion 7 becomes insufficient and the stress concentration at the end position T ₂ of the taper portion 7 causes the burning. The strength of the connecting component W is likely to be reduced. Further, when the inclination angle α is 5 ° or less, the effect of the taper portion 7 described below is not sufficiently exhibited. Therefore, the inclination angle α of the tapered portion 7 is set to 5 to 30 ° as described above.

As shown in FIG. 1 (B), a sintered part W (see FIG. 5) is provided on the inner and outer circumferences of the first lower punch 4.
The tooth profile portions 8 and 9 corresponding to the tooth portions G ₁ and G ₂ of the die are formed. Similar tooth profile portions are formed not only on the inner peripheral surface of the die 1 but also on the outer peripheral surfaces of the upper punch 3 and the second lower punch 5. Of course.

In the structure as described above, as shown in FIG. 1A, a predetermined metal powder P is contained in the die hole 1a of the die 1, and the upper punch 3 and the first and the first punches are arranged from above and below. By pressing with the second lower punches 4 and 5, the metal powder P is pressed and solidified to form a predetermined powder compact C.

Then, as the metal powder P is compressed, the internal pressure P that tends to push the first lower punch 4 outward is expanded.
_{While 1} is generated, at the taper portion 7 at the tip of the first lower punch 4, a pressure P ₂ that opposes the internal pressure P ₁ is generated as a component force of the pressure applied by the upper punch 3 and the first lower punch 4. Therefore, by counteracting the internal pressure P ₁ and the pressure P ₂ generated in the taper portion 7, not only the first lower punch 4 is damaged but also the galling phenomenon between the first lower punch 4 and the die 1 is prevented. You can

FIG. 2 is a diagram showing another embodiment of the present invention. In this embodiment, the taper portion 10 is formed only on the portion of the pressing surface 6 of the first lower punch 4 near the center thereof. The inclination angle α of 10 is set within the range of 5 to 30 ° as in the first embodiment. Also in the case of this embodiment, the same effect as that of the first embodiment can be obtained.

Here, in any of the examples, not only the powder compact C molded by compression but also the sintered part W after firing the powder compact C as shown in FIGS. The traces 7a and 10a of No. 1 remain, but there is no particular problem in terms of the function of the product.

[0018]

As described above, according to the present invention, of the first and second lower punches that press the powder compact from the lower side of the die, the first lower punch located on the outer side of the die rises to the pressing surface. By forming a taper portion having a gradient and more preferably by setting the inclination angle of the taper portion within the range of 5 to 30 °, the internal pressure that tends to push the first lower punch outward with the progress of compression molding is achieved. On the other hand, in the above-mentioned taper portion, a pressure that opposes the internal pressure is generated. Therefore, not only the damage of the first lower punch but also the galling phenomenon between the die and the die can be prevented, so that the formability is improved. Also,
Unlike the conventional counter die method, it is not necessary to add extra thickness to the powder compact, so not only does it increase the weight as a sintered part, but it also eliminates the need for machining to remove the extra thickness. The number of processes can be reduced.

[Brief description of drawings]

1A and 1B are diagrams showing an embodiment of the present invention, in which FIG. 1A is an explanatory view of a main part configuration, and FIG. 1B is an enlarged view of a main part of FIG.

FIG. 2 is an enlarged view of a main part showing another embodiment of the present invention.

3 is a cross-sectional view of a main part of a powder compact molded by the apparatus of FIG.

FIG. 4 is a cross-sectional view of a main part of a powder compact molded by the apparatus of FIG.

FIG. 5 is a sectional view showing an example of a sintered part.

6 is a cross-sectional view of a conventional molding device for molding a powder compact to be the sintered part of FIG.

7 is an enlarged cross-sectional view of a main part of FIG.

FIG. 8 is a sectional view showing another example of a conventional molding apparatus.

9 is a cross-sectional view of a powder compact molded by the molding device of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Die 1a ... Die hole 2 ... Core rod 3 ... Upper punch 4 ... 1st lower punch 5 ... 2nd lower punch 6 ... Pressing surface 7,10 ... Taper part C ... Powder compact F ... Flange part W ... Sintered part

Claims (2)

[Claims] 1. A device for compression-molding a powder compact which is to be a hollow cylindrical sintered part having a flange portion at one end, wherein a cylindrical die hole is formed and powder is contained in the die hole. A core rod arranged at the center position of the die hole; an upper punch that is inserted into the die hole from the upper side of the die and presses the end surface of the powder compact on the flange side; and from the lower side of the die. A hollow cylindrical first lower punch that is inserted into the die hole and presses the flange portion of the powder compact together with the upper punch in the thickness direction thereof; and is inserted into the first lower punch and from the lower side of the die into the die hole. A second lower punch that is inserted into the powder compact and presses an end surface of the powder compact opposite to the flange portion, and a tip of the first lower punch. A molding device for a sintered part, characterized in that a taper portion having an upward slope toward the central axis of the powder compact is formed on the end pressing surface. 2. The inclination angle of the taper portion of the first lower punch is set to 5 to 30 °.
A molding device for a sintered part as described.