JP5810465B2 - Mold for powder molding - Google Patents

Description

  The present invention relates to a powder molding die for pressure molding a powder molded body.

  Generally, a sintered part is manufactured by sintering a powder compact obtained by pressure-molding metal powder with a mold. As a powder molding die for pressure-molding the metal powder, with the metal powder filled in the cavity formed by the die forming hole and the lower punch, the lower end surface of the upper punch and the upper end surface of the lower punch What press-molds metal powder is known.

  In such a powder molding die, as shown in FIG. 8, the undulations transferred to the powder compact are different from each other on the lower end surface 101a of the upper punch 101 and the upper end surface 102a of the lower punch 102. In some cases, undulations are formed, and undulations are formed on the opening periphery 103a on the upper side of the forming hole 104 in the die 103 in accordance with the undulations of the lower peripheral edge 101b of the upper punch 101 (see, for example, Patent Document 1). ).

JP 2007-237233 A

In the powder molding die, as shown in FIG. 9, the undulation of the upper end surface 102a of the lower punch 102 is transferred to the lower surface of the powder molded body 110. A undulation different from the opening periphery 103a of the die 103 is formed on 110a. For this reason, when the powder molded body 110 is extracted above the molding hole 104 of the die 103, stress that tends to expand due to the spring back on the lower surface of the powder molded body 110 is received by the point contact G at the opening peripheral edge 103 a of the die 103. There is a case. In this case, since stress concentration occurs at the point contact G portion of the powder compact 110, there is a problem that damage such as cracks occurs in the powder compact 110.
The present invention has been made in view of such circumstances, and a powder molding die capable of suppressing damage to the powder molded body when the powder molded body is extracted above the molding hole of the die. The purpose is to provide.

The powder molding die of the present invention is a powder molding die for pressure-molding a powder molded body, and is inserted into the molding hole from above and the powder on the lower end surface. An upper punch formed with undulations to be transferred onto the upper surface of the molded body, and undulations to be transferred to the lower surface of the powder molded body at the upper end surface and inserted into the molding hole from below, and the lower end surface of the upper punch includes a lower punch which undulating different undulations have been formed, and the opening edge which is formed directly on the upper end outer peripheral edge of the upper is a by and the lower punch of the forming hole in the die, the upper end outside of the lower punch The undulation according to the undulation of the periphery is formed.

According to the present invention, the undulations corresponding to the undulations of the upper peripheral edge of the lower punch are formed on the opening peripheral edge formed above the forming hole in the die and immediately above the upper peripheral edge of the lower punch. The same undulation is formed on the opening periphery of the die and the outer peripheral edge of the lower end of the powder compact that is pressure-formed by the lower punch. As a result, when the powder molded body is pulled out above the molding hole, the outer peripheral edge of the lower end of the powder molded body is pulled out along the undulation of the opening peripheral edge of the die. It can be received by line contact at the periphery of the opening. As a result, since the stress can be dispersed by the line-contacted portion, it is possible to suppress the occurrence of damage such as cracks in the powder compact.

  ADVANTAGE OF THE INVENTION According to this invention, when extracting a powder compact to the upper direction of the shaping | molding hole of die | dye, it can suppress that damage, such as a crack, generate | occur | produces in a powder compact.

It is sectional drawing which shows the metal mold | die for powder molding which concerns on one embodiment of this invention. It is a perspective view which shows a sintered component (gear). It is a principal part expanded sectional view of FIG. 1 which shows the metal mold | die for powder molding. It is a top view which shows die | dye. It is sectional drawing which shows die | dye. It is a cross-sectional perspective view which shows die | dye. It is sectional drawing which shows a state when extracting a powder compact from a die | dye. It is sectional drawing which shows the conventional metal mold | die for powder molding. It is a principal part enlarged view of FIG.

Hereinafter, embodiments of the powder molding die of the present invention will be described with reference to the drawings.
FIG. 1 is a sectional view of a powder molding die according to an embodiment of the present invention. The powder molding die 1 includes a die 2 having a molding hole 3, an upper punch 4, a lower punch 5, and a core rod 6, and is a powder for a gear 50 that is a sintered part shown in FIG. 2. Used to pressure-mold a shaped body. In FIG. 2, the gear 50 in the present embodiment is formed so that the thickness t gradually decreases from the tooth bottom 51 toward the tooth tip 52, and the one end surface 53 and the other end surface 54 including the outer peripheral edge are respectively provided. The undulations are formed.

  In FIG. 1, the outer periphery of the die 2 is supported by a die plate 11. The upper punch 4 is inserted into the forming hole 3 of the die 2 from above, and is supported by an upper punch plate 12 driven by an upper ram (not shown). The die plate 11 and the upper punch plate 12 are arranged so as to be relatively movable coaxially by a plurality of guide rods (not shown).

The lower punch 5 is inserted from below into the forming hole 3 of the die 2 and is supported by the base plate 13. The core rod 6 is connected to a yoke plate 14 that is driven by a lower ram (not shown) of the press machine.
The powder molding die 1 configured as described above forms a cavity 7 by the die 2, the lower punch 5 and the core rod 6, and the cavity 7 is filled with metal powder, and the upper punch 4 and the lower punch 5 By pressing metal powder, a powder compact W (see FIG. 7) is molded.

  FIG. 3 is an enlarged cross-sectional view of the main part of FIG. 1 showing the powder molding die 1. In FIG. 3, the lower end surface 4 a of the upper punch 4 is formed with undulations transferred to the upper surface of the powder compact W (a surface corresponding to the one end surface 53 of the gear 50). Specifically, on the outer peripheral portion including the outer peripheral edge (lower peripheral edge) 4a1 of the lower end surface 4a of the upper punch 4, the tooth tip is formed from the tooth bottom forming portion A that forms the one end surface 53 side of the tooth bottom 51 of the gear 50. The one end surface 53 side of 52 is formed in a circular arc shape so that the amount of protrusion downward increases toward the tooth tip forming part B.

  In FIG. 3, the upper end surface 5 a of the lower punch 5 is undulation transferred to the lower surface of the powder compact W (the surface corresponding to the other end surface 54 of the gear 50), and the lower end surface 4 a of the upper punch 4 is undulated. And undulations are formed. Specifically, on the outer peripheral portion including the outer peripheral edge (upper peripheral edge) 5a1 of the upper end surface 5a of the lower punch 5, the tooth tip forming portion C that forms the other end surface 54 side of the tooth bottom 51 of the gear 50 is added. The other end face 54 side of 52 is formed in a circular arc shape so that the upward protrusion amount increases as it goes to the tooth tip forming part D. Thus, the undulation of the upper end surface 5a of the lower punch 5 and the undulation of the lower end surface 4a of the upper punch 4 are formed so as to be opposite to each other.

  FIG. 4 is a plan view of the die 2, and FIG. 5 is a cross-sectional view of the die 2. 4 and 5, the die 2 is formed in a cylindrical shape, and a molding hole 3 is formed by the inner peripheral surface thereof. Further, as shown in FIG. 4, a tooth portion forming portion 2 a for forming a portion from the tooth bottom 51 to the tooth tip 52 of the gear 50 is radially formed on the inner peripheral surface of the die 2. It is formed to undulate toward the direction. As shown in FIG. 5, the tooth portion forming portion 2 a is formed over the entire axial length of the inner peripheral surface of the die 2.

  3, in order to guide the outer peripheral edge 4a1 of the upper punch 4 into the forming hole 3 at the inner peripheral end of the upper surface 2b of the die 2, the outer peripheral end of the tooth part forming part 2a is directed radially outward. Accordingly, a tapered surface 2b1 inclined upward is formed. By guiding the outer peripheral edge 4a1 of the upper punch 4 by the tapered surface 2b1, it is possible to suppress the outer peripheral edge 4a1 from coming into contact with the upper surface 2b of the die 2 and being damaged.

  FIG. 6 is a cross-sectional perspective view of the die 2. 3 and 6, undulations corresponding to the undulations of the upper peripheral edge 5 a 1 of the lower punch 5 are formed on the opening peripheral edge (upper edge of the tooth part forming portion 2 a) 2 a 1 of the die 2. Yes. Specifically, as shown in the enlarged view of the alternate long and short dash line in FIGS. 3 and 4 and FIG. 6, the opening peripheral edge 2 a 1 forms the tooth tip 52 from the tooth bottom forming edge E that forms the tooth bottom 51 of the gear 50. The upward protrusion amount is increased toward the tooth tip forming edge F.

  FIG. 7 is a cross-sectional view showing a state where the powder compact W molded by the powder molding die 1 is extracted from the molding hole 3 of the die 2. As shown in FIG. 7, the same undulation as the opening peripheral edge 2 a 1 of the die 2 is formed on the outer peripheral edge W <b> 1 of the lower end of the powder compact W pressed by the lower punch 5. As a result, when the powder compact W is extracted from the molding hole 3, the lower peripheral edge W1 of the powder compact W is pulled out along the undulation of the opening peripheral edge 2a1 of the die 2, so The expanding stress can be received by line contact at the opening periphery 2 a 1 of the die 2. As a result, since the stress can be dispersed by the line-contacted portion, it is possible to suppress the occurrence of damage such as cracks in the powder compact W.

Table 1 below shows sintered parts that have been test-manufactured using the conventional powder-molding die described in Patent Document 1, and ceramics that have been test-manufactured using the powder-molding die in the present embodiment. It shows the frequency of each defect of the bonded parts. In this test, the metal powder uses Fe-2Cu-0.8C-0.8 lubricant (outer), and the molding conditions are normal temperature molding and density = 6.8 g / cm ³ (molding pressure = 5 ton / cm ² ). The defect frequency is the fraction indicating the total number of sintered parts tested and manufactured in the denominator (100 in this test), and the number of sintered parts in the molecule where damage such as cracks occurred due to test manufacturing. Represents.

  In Table 1, when the failure frequency of the conventional sintered component is compared with the failure frequency of the sintered component of the present embodiment, the failure frequency of the sintered component of the present embodiment is higher than that of the conventional sintered component. small. Thus, it can be seen that the powder molding die in the present embodiment is less susceptible to damage such as cracks in the sintered part than the conventional powder molding die.

  Further, as shown in FIG. 3, the opening peripheral edge 2a1 of the die 2 is formed so that the upward protrusion amount increases from the root forming edge E toward the tooth tip forming edge F. When the metal powder is filled, the upper surface of the metal powder is ground in accordance with the undulations of the opening peripheral edge 2a1 of the die 2, so that the metal powder is filled on the outer peripheral side of the cavity 7 so as to rise upward. In this state, when the lower end surface 4 a of the upper punch 4 is inserted into the molding hole 3, the metal powder filled on the outer peripheral side of the cavity 7 is transferred to the outer periphery of the cavity 7 by the outer peripheral portion protruding below the lower end surface 4 a. It can be effectively pushed into the inner periphery. Thereby, since it can suppress that the shaping | molding density of the metal powder in the outer peripheral side of the cavity 7 becomes high, it can suppress that the lower end outer periphery 4a1 of the upper punch 4 wears. As a result, the occurrence of burrs in the powder compact W can be suppressed.

The embodiment disclosed this time must be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
For example, in the above embodiment, a powder molding die for molding a powder molded body for gears is illustrated, but for powder molding in which different undulations are formed on the lower end surface of the upper punch and the upper end surface of the lower punch. The present invention can be applied to any mold.

DESCRIPTION OF SYMBOLS 1 Powder shaping | molding die 2 Die 2a1 Opening periphery 3 Molding hole 4 Upper punch 4a Lower end surface 5 Lower punch 5a Upper end surface 5a1 Upper end outer periphery W Powder molded object

Claims (1)

A powder molding die for pressure molding a powder molded body,
A die having a forming hole;
An upper punch that is inserted into the molding hole from above and has undulations transferred to the upper surface of the powder compact on the lower end surface;
A lower punch that is inserted into the molding hole from below and has an undulation transferred to the lower surface of the powder molded body on the upper end surface and formed with a undulation different from the undulation of the lower end surface of the upper punch,
And characterized in that the opening edge which is formed directly on the upper end outer peripheral edge of a upper and a lower punch of the forming hole in the die, undulating tailored to relief of the upper peripheral edge of the lower punch is formed Powder molding mold.

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