JP2006315028A - Method for compacting powder-compacting body, powder-compacted body and sintered machine part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To soundly produce a powder-compacted body arranging easily broken projecting part on the outer periphery of the main part by preventing the break of the projecting part at taking out time from a die, and to improve the producing yield of a sintered machine part by the method. <P>SOLUTION: In a compacting process for powder compacted body having the projecting part 5 on the outer periphery of a flange 4, raw material powder is charged into a metallic die, and after compact-forming this powder, the compacted body is taken out from the metallic die, and taking-out is performed so as to prevent the break of the projecting part 5 developed at the taking-out time from the die by forming a draft θ1 of the projecting part 5 at larger than a draft θ2 of the flange 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a molding method for soundly producing a powder molded body provided with protrusions that are easily chipped on the outer periphery of the main portion, a powder molded body obtained by the method, and this molded body (green compact). The present invention relates to a sintered machine part obtained by sintering.

  Among the known sintered machine parts are those shown in FIG. The illustrated sintered machine part 1 is a hooked part used as a camshaft or the like, and includes a protrusion 5 on the outer periphery of the main part 2. The main portion 2 is configured by providing a flange 4 at one end of the boss portion 3, and a protrusion 5 is provided on the outer periphery of the flange 4 so as to protrude in the radial direction. In this sintered sintered machine part, the protrusion 5 is used as a sensor protrusion. Similar parts include a pulley with a sensor projection for power transmission.

  In particular, the sensor protrusions 5 and the like of the above-described parts are easily subject to installation restrictions from the functional aspect, and it may not be allowed to increase the size and increase the mechanical strength. In addition, the protrusion 5 may have to be molded with a die of the mold due to structural limitations of the molding die.

  FIG. 5 shows a general structure of a die set mold used in a powder molding apparatus. The illustrated mold includes a die 11, a lower punch divided into three parts, that is, a lower first punch 12, a lower second punch 13, a lower third punch 14, a core 15, and an upper first punch 16. The upper second punch 17 is combined. This mold has a structure in which the number of punches that can be mounted is limited. For this reason, a molding groove 18 is provided in the die 11 and the projection 5 of the component is molded by the molding groove 18.

  As described above, when the projection formed on a part of the outer periphery of the main portion is formed with a die, the projection is likely to be chipped at the time of so-called die cutting in which the molded body is taken out from the die. The chipping is caused by the fact that the frictional resistance of the portion where the side surface of the protrusion contacts the die exceeds the strength of the protrusion. In powder molding, an axial stress due to a spring back acts on the compact during pressure reduction after compression. At this time, since the outer periphery of the main part of the molded body that is in contact with the die tends to remain in the original position by the frictional force acting on the contact part, an excessive force is applied to the protrusion on the outer periphery of the main part, and the protrusion The part may be chipped or the base of the protrusion may crack.

  Here, in Patent Document 1 below, the inner hole of the die for forming the outer shape of the molded body is provided with a taper of 1/5000 to 1/1000 that expands to the extraction side of the molded body, and the die surface is further rubbed. Although it is stated that the frictional resistance at the time of extraction is reduced by providing a coating layer having a small coefficient, the method disclosed in the document 1 solves the above-mentioned problem of the protrusions on the outer periphery of the molded body. I can't.

In addition, with respect to the above frictional resistance, the flanged sintered machine part 1 of FIG. 4 has a draft taper θ on the side surface 4a (outer periphery) of the collar 4, and a draft taper θ having the same angle as the draft taper θ. Is also attached to the side surface 5 a of the protrusion 5. Increasing the punch taper θ allows the molded product to be extracted from the die without causing the chipping of the protrusion 5, but if the punch taper θ is increased, the required specifications on the product dimension may not be satisfied. When only a small punching taper is allowed for such a reason, the projecting portion is chipped during die cutting due to insufficient angle of the punching taper, and the yield of the product is deteriorated. In addition, a practically acceptable yield may not be realized, and the use of sintered parts that are advantageous in terms of mass productivity and cost may be abandoned.
JP 2002-129201 A

  The present invention makes it possible to produce a powder molded body provided with protrusions that are easily chipped on the outer periphery of the main part by preventing chipping of the protrusions at the time of die-cutting and to produce them soundly, and thereby sintering. The challenge is to increase the manufacturing yield of machine parts.

  In order to solve the above problems, in the present invention, there is provided a molding method of a powder molded body having a projecting portion projecting radially on the outer periphery of a main portion, the raw material powder is put into a mold, and the powder is After compression molding, the molded body is extracted from the mold, and the extraction is performed by making the extraction taper of the protrusion larger than the extraction taper of the main part.

  In the powder molded body obtained by such a molding method, the main portion and the protrusions provided on the outer periphery of the main portion both have a drawing taper, and the drawing taper of the protrusion is larger than the drawing taper of the main portion. . The present invention also provides the powder compact.

The molding method of the present invention can be expected to have a particularly great effect when applied to the powder compacts listed below.
(1) A powder molded body in which the protrusion protrudes from a part of the outer peripheral edge of the extraction side end surface of the main part.
(2) A powder molded body in which the ratio of the thickness Th in the extraction direction of the protrusion to the thickness Tl in the radial direction is set to Tl / Th ≧ 0.5. The wall thickness Th and the wall thickness Tl are compared in maximum dimension.
(3) The ratio of the total circumferential length L including the protrusion installation area of the outer peripheral edge of the extraction side end surface of the main part to the total length Lt of the outer peripheral edge of the protrusion installation area is Lt / L ≦ Powder molded body set to 1/2, more preferably Lt / L ≦ 1/3. In addition, the total length Lt of the outer periphery part of a protrusion installation area means the value which added the peripheral part length of all the protrusion installation areas, when two or more protrusions are installed.
(4) The main portion includes a collar portion having a draft taper, and a projection having a draft taper is provided on the outer periphery of the collar portion so as to project in the radial direction. Powder compact larger than the taper.

  The present invention also provides a sintered machine part obtained by sintering a molded body formed of a metal powder having any one of the constitutions (1) to (4).

  In the molding method of the present invention, the protrusion taper provided on the outer periphery of the main part is made larger than the taper taper of the main part so that the molded body is extracted from the mold. Compared to the case where the punching taper of the main part and the punching taper of the main part are made the same.

  As described above, if the draft taper of the protrusion is made larger than the draft taper of the main part, the friction resistance acting on the draft taper surface of the main part (tapered side surface; the same applies to the following) and the draft taper surface of the protrusion is also achieved. The difference is caused and the stress due to the spring back is received by the main taper surface, so the stress acting on the protrusion is smaller than when there is no difference in the main and protrusion taper, Thereby, chipping of the protrusion is prevented.

  As described above, according to the present invention, the friction resistance acting on the taper surface of the main part and the taper surface of the protrusion is made different, and the stress due to the spring back is received by the main taper surface of the main part to protect the protrusion. Therefore, the degree of the effect depends on the ratio of the installation area of the main tapered taper surface and the projecting tapered taper surface. Therefore, the relationship between the total circumferential length L including the protruding portion installation area of the outer peripheral edge of the extraction side end surface of the main portion and the total length Lt of the protruding edge installation region of the outer peripheral edge is investigated, and Lt / L ≦ It was confirmed that a particularly good effect was obtained when the condition of 1/2, more preferably Lt / L ≦ 1/3 was satisfied.

  Further, according to the present invention, the ratio of the thickness Th in the extraction direction of the protrusion to the thickness Tl in the radial direction is set to Tl / Th ≧ 0.5, or on the outer periphery of the flange portion of the main part. It has also been confirmed that it is particularly effective when a projecting portion projecting in the radial direction is provided projecting in the radial direction and the projecting taper of the projecting portion is larger than the projecting taper of the flange portion.

  Embodiments of the present invention will be described below with reference to FIGS. 1 to 3 of the accompanying drawings. The sintered machine component 1 shown in FIG. 1 is a machined part with a hook in which a flange 4 is provided on the outer periphery of one end of the boss part 3 to constitute a main part 2, and a protrusion 5 protruding radially on the outer periphery of the flange 4. It has. A side taper 4 shown in FIG. 2 is attached to the side surface 4 a of the flange 4 and the side surface 5 a of the protrusion 5, respectively. The extraction taper θ 2 of the flange 4 is smaller than the extraction taper θ 1 of the protrusion 5.

  The difference Δθ (= θ1−θ2) between the draft taper θ2 of the flange 4 and the draft taper θ1 of the protrusion 5 is preferably set to a lower limit of about 0.2 ° in order to sufficiently obtain the protection effect of the protrusion 5. . Further, the draft taper θ1 of the protrusion 5 is preferably 3 ° or less, more preferably 2 ° or less, in order to satisfy the required specifications in terms of the dimensions of the parts.

Further, the ratio of the thickness Th in the extraction direction and the thickness Tl in the radial direction of the protrusion 5 in FIG. 2 is preferably Tl / Th ≧ 0.5, and the outer peripheral edge of the end surface on the extraction side of the flange 4 The ratio of the total circumferential length L including the protrusion installation area of the portion and the total length Lt of the outer peripheral edge of the protrusion installation area (Lt is a value obtained by adding l ₁ to l _N ) is also Lt / L ≦ It is better to set to 1/2, more preferably Lt / L ≦ 1/3.

Example 1
The results of confirming the effect of the invention will be described below. The test was carried out by molding the sintered machine part 1 in FIG. 3 (in the figure, a pulley with a sensor projection for power transmission used in a car engine) by changing the size of the taper taper or the difference in the taper taper. The damage state of the protrusion 5 at that time was examined. The sintered machine part 1 in FIG. 3 was formed by mixing a mixed powder of Fe 96.4% -Cu 2% -C 0.8% -lubricant 0.8% at a mass ratio by applying a surface pressure of 600 MPa at room temperature. .

  The molding was first performed by changing the draft taper θ1 of the protrusion 5 without making a difference between the draft taper θ2 of the flange 4. At this time, the ratio of the thickness Th in the extraction direction of the protrusion 5 to the thickness Tl in the radial direction is Tl / Th = 0.5, and the protrusion installation region at the outer peripheral edge of the end surface on the extraction side of the flange 4 is The ratio Lt / L = 1/24 between the total circumferential length L and the total length Lt of the outer peripheral edge of the protrusion installation region. Table 1 shows the results of molding with N = 5 as the number of tests under each of the above conditions.

  As can be seen from Table 1, in this test, if the draft taper is 3 ° or less and there is no difference in the draft taper between the flange 4 and the projection 5, damage to the projection is inevitable. In addition, when the punch taper of the flange 4 and the protrusion 5 was 3 °, the required dimensions of the product could not be satisfied. Thus, it is necessary to increase the taper for sound molding, which is a limitation on the size and shape of the product. As one example of the form of the protrusion breakage, for example, the sintered machine part of FIG. 4 has the flange 4 and the protrusion 5 when the flange 4 and the protrusion 5 which are a part of the main part are formed with a die. In particular, when molding is performed only by upper pressure with the upper punch, the molding density on the lower surface side tends to be lower than the molding density on the upper surface side. Sometimes, the edge on the lower surface side of the protrusion is easily chipped. In the case of the sintered machine part of FIG. 4, the chipping may occur at the outer peripheral edge on the lower surface side of the flange 4.

-Example 2-
Molding was performed with the difference between the punch taper of the flange 4 and the protrusion 5 and the other conditions being the same as in Example 1. The results are shown in Table 2.

  As a result, the effectiveness of making a difference in the draft taper of the flange 4 and the protrusion 5 appears well. If the punch taper of the collar 4 is zero even if the difference in the taper is added, as shown in the results of Table 2, the collar 4 is damaged.

Example 3
Combination of the taper taper θ2 of the flange 4 and the taper taper θ1 of the protrusion 5, and the entire circumferential length L including the protrusion installation area of the outer peripheral edge of the extraction side end face of the flange 4, and the outer periphery of the protrusion installation area Molding was performed by changing the ratio Lt / L of the total length Lt of the parts in various ways. Other conditions are the same as those in Example 1. The results of this test are shown in Table 3.

  In Table 3, ◯ indicates that the protrusion is not damaged, and Δ indicates that there is partial damage. The results are all good compared to the case where the taper θ1 and θ2 are the same. In particular, it is better to increase the extraction taper difference as the value of Lt / L becomes smaller. Yes.

The perspective view which shows an example of the sintered machine components shape | molded and manufactured with the shaping | molding method of this invention Enlarged cross-sectional view of the main part of the sintered machine part of FIG. Cross-sectional view of sintered machine parts used for effect confirmation test Perspective view showing an example of sintered machine parts Sectional view of a powder molding die used for manufacturing the sintered machine part of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sinter machine part 2 Main part 3 Boss part 4 鍔 4a Side surface 5 Protrusion 5a Side surface 11 Die 12 Lower first punch 13 Lower second punch 14 Lower third punch 15 Core 16 Upper first punch 17 Upper second punch 18 Forming grooves θ, θ1, θ2

Claims (7)

  A method of forming a powder molded body having a projecting portion protruding radially on the outer periphery of the main part, the raw material powder is charged into a mold, and after compression molding this powder, the molded body is extracted from the mold, The method for forming a powder molded body is characterized in that the extraction is performed with the taper of the protrusion of the molded body being larger than the taper of the main portion.   A powder molded body molded by the molding method according to claim 1, wherein both the main portion and the protrusions protruding in the radial direction around the main portion have a drawing taper, A powder compact characterized in that the taper θ1 is larger than the punch taper θ2 of the main part.   The powder molded body according to claim 2, wherein the protrusion is provided so as to protrude from a part of the outer peripheral edge of the extraction side end face of the main part.   The powder compact according to claim 2 or 3, wherein the ratio of the thickness Th in the extraction direction of the protrusion to the thickness Tl in the radial direction is Tl / Th≥0.5.   The ratio of the total circumferential length L including the protruding portion installation region of the outer peripheral edge portion of the main portion extraction side end surface to the total length Lt of the outer peripheral edge portion of the protruding portion installation region is Lt / L ≦ 1/2. The powder molded body according to claim 3, wherein the powder molded body is present.   The main portion includes a flange having a punch taper, and a protrusion having a punch taper is provided on the outer periphery of the flange so as to protrude in the radial direction, and the punch taper of the protrusion is larger than the punch taper of the flange. The powder compact according to any one of claims 2 to 5, characterized in that   A sintered machine part, wherein the molded body according to any one of claims 2 to 6 is formed of metal powder, and the molded body is sintered.

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