JP2014140877A - Powder molding die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder molding die that can prevent an outer circumference of a lower punch from being damaged during pressure molding of a powder compact.SOLUTION: A powder molding die 1 includes: a die 2 having a molding hole 3 with an inner circumference undulation part 3a undulating in a radial direction formed in an inner circumference in order to form a large diameter tooth part 54 of a powder compact 50; an upper punch 4 inserted into the molding hole 3 from the upside; and a first lower punch 5 inserted into the molding hole 3 from the downside and undulating in the radial direction in order to form the large diameter tooth part 54, and also formed with an outer circumference undulation part 5b disposed at a predetermined clearance S0 radially inside to the inner circumference undulation part 3a in the outer circumference. A portion forming a tooth bottom of the large diameter tooth part 54 in the outer circumference undulation part 5b is formed to become the same undulation shape as a portion forming a tooth bottom of the large diameter tooth part 54 in the inner circumference undulation part 3a in the state where the outer circumference undulation part 5b is elastically deformed in pressure molding.

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 such a sintered part, for example, a sprocket, a cylindrical main body portion and an annular flange formed on the outer periphery of the main body portion, and a plurality of tooth portions are all on the outer periphery of the flange portion. What is formed over the circumference | surroundings is known (for example, refer patent document 1).

  FIG. 5 is a cross-sectional view showing a conventional powder molding die for pressure-molding such sintered parts. As shown in FIG. 5, a conventional powder molding die 100 includes a die 101 having a molding hole 101a, a cylindrical upper punch 102 inserted into the molding hole 101a of the die 101 from above, and a molding of the die 101. Cylindrical first and second lower punches 103 and 104 inserted into the hole 101a from below and a core rod 105 are provided. The powder molding die 100 presses the metal powder with the lower end portion of the upper punch 102 and the upper end portions of the first and second lower punches 103, 104, whereby the main body portion 201 of the powder molded body 200, The part 202 and the tooth part 203 are molded.

FIG. 6A is an enlarged sectional view taken along the line CC in FIG. 5 and shows a state before pressure molding. As shown in FIG. 6A, an inner peripheral undulating portion 101b for forming the tooth portion 203 of the powder compact 200 is formed on the inner periphery of the forming hole 101a of the die 101 over the entire periphery. Further, on the outer periphery of the first lower punch 103, an outer periphery undulating portion 103a for forming the tooth portion 203 is formed over the entire periphery.
The outer peripheral undulating portion 103a of the first lower punch 103 is formed so as to be offset radially inward over the entire periphery with respect to the inner peripheral undulating portion 101b of the die 101. Therefore, a constant clearance S ′ is provided over the entire circumference between the outer peripheral undulating portion 103 a of the conventional first lower punch 103 and the inner peripheral undulating portion 101 b of the die 101. Accordingly, the first lower punch 103 is slidable in the vertical direction with respect to the molding hole 101a of the die 101 when the powder compact 200 is pressure-molded.

JP 2009-72810 A

When the powder compact 200 is pressure-molded by the conventional powder molding die 100, as shown in FIG. 5, the outer peripheral surface of the main body 201 is radially outside the upper peripheral surface of the first lower punch 103. An internal pressure P ′ that pushes in the direction acts. For this reason, the outer peripheral undulation 103a at the upper end of the first lower punch 103 is elastically deformed so as to bulge outward in the radial direction by the internal pressure P ′. At this time, as shown in FIG. 6B, the outer peripheral undulating portion 103 a of the first lower punch 103 makes a line contact A ′ with the portion of the inner peripheral undulating portion 101 b of the die 101 that forms the tooth bottom of the tooth portion 203. May be elastically deformed. When such elastic deformation occurs, stress concentration occurs in the line contact A ′ portion, so that the outer periphery of the first lower punch 103 slides in the vertical direction while being strongly pressed against the forming hole 101a of the die 101. As a result, there has been a problem in that the outer periphery of the first lower punch 103 is damaged such as seizure or stuffiness.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a powder molding die that can suppress the outer periphery of the lower punch from being damaged during pressure molding of a powder molded body. Yes.

  The powder molding die of the present invention is a powder molding die that press-molds a powder molded body in which a collar is formed on the outer periphery of a cylindrical main body and a tooth is formed on the outer periphery of the collar. A die having a molding hole in which an inner circumferential undulation portion that undulates in the radial direction to mold the tooth portion is formed, an upper punch inserted into the molding hole from above, and the molding hole The outer peripheral undulating portion is formed on the outer periphery, and is inserted from below into the outer peripheral undulating portion, and is undulated in the radial direction so as to form the tooth portion and provided with a predetermined clearance radially inward with respect to the inner peripheral undulating portion. A portion for forming the tooth bottom of the tooth portion in the outer circumferential undulation portion in a state where the outer circumferential undulation portion is elastically deformed during the pressure molding, and the tooth bottom of the tooth portion in the inner circumferential undulation portion It is formed to have the same undulation shape as the part to be molded. The features.

  According to the present invention, the portion forming the tooth bottom of the outer peripheral undulation portion of the lower punch is in a state where the outer peripheral undulation portion is elastically deformed during the pressure molding of the powder molded body, and the teeth in the inner peripheral undulation portion of the die are Since the outer undulations of the lower punch are elastically deformed during the pressure molding of the powder molded body, the teeth of the outer undulations are formed. The part which shape | molds a bottom and the part which shape | molds the said tooth bottom of an internal peripheral undulation part can be surface-contacted. This can disperse the contact surface pressure between the portion of the outer peripheral undulating portion that forms the tooth bottom and the portion of the inner peripheral undulating portion that forms the tooth bottom. It is possible to suppress the occurrence of damage such as seizure or stuffiness on the outer periphery of the punch.

The circumferential length of the outer circumferential undulation portion that is the same undulating shape is 1/3 to 1 / of the circumferential length of the inner circumferential undulation portion from the root to the tip of the tooth portion. It is preferable that the length is set to 2.
In this case, it is possible to further effectively suppress the occurrence of damage such as seizure or stuffiness on the outer periphery of the lower punch during the pressure molding of the powder compact.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that the outer periphery of a lower punch is damaged at the time of the press molding of a powder compact.

It is sectional drawing which shows the metal mold | die for powder molding which concerns on one Embodiment of this invention. The powder molded object pressure-molded with the said metal mold | die for powder shaping | molding is shown, (a) is a top view, (b) is AA arrow sectional drawing of (a), (c) is a bottom view. is there. It is a BB arrow expanded sectional view of Drawing 1, (a) shows the state before pressure forming, and (b) shows the state at the time of pressure forming. It is an expanded sectional view which shows the undulation shape at the time of the elastic deformation of an outer periphery undulation part. It is sectional drawing which shows the conventional metal mold | die for powder molding. FIG. 6 is an enlarged cross-sectional view taken along the line CC in FIG. 5, (a) shows a state before pressure molding, and (b) shows a state during pressure molding.

Hereinafter, embodiments of a 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 first lower punch (lower punch) 5, a second lower punch 6, and a core rod 7. It is used for pressure forming a powder compact 50 of a sprocket that is a sintered part.

2A and 2B show the powder compact 50, where FIG. 2A is a plan view, FIG. 2B is a cross-sectional view taken along the line AA in FIG. 2A, and FIG.
2A to 2C, the powder molded body 50 includes a cylindrical main body 51 and a disk-shaped flange 52 formed on the outer periphery of the main body 51. A small-diameter tooth portion 53 is formed at the lower end of the outer periphery of the main body 51 over the entire circumference. A large-diameter tooth portion (tooth portion) 54 is formed on the outer periphery of the collar portion 52 over the entire periphery.

  In FIG. 1, a powder molding die 1 includes a lower end portion of an upper punch 4 inserted from above into a molding hole 3 of a die 2, and first and second lower punches 5 inserted from below into a molding hole 3 of a die 2. , 6 and the outer peripheral surface of the core rod 7 press the metal powder filled between them from above and below to form the powder compact 50. Hereinafter, the constituent members of the powder molding die 1 will be described in detail.

On the inner periphery of the molding hole 3 of the die 2, an inner peripheral undulation portion 3 a that undulates in the radial direction is formed to form the large-diameter tooth portion 54 of the flange portion 52 over the entire periphery.
The upper punch 4 is made of a cylindrical member, and the upper surface of the main body portion 51 and the upper surface of the flange portion 52 of the powder molded body 50 are formed by the lower surface thereof. Further, on the outer periphery of the upper punch 4, an outer peripheral undulating portion 4 a for forming the large diameter tooth portion 54 is formed.

  The 1st lower punch 5 consists of a cylindrical member, and shape | molds the outer peripheral surface of the main-body part 51 of the powder compact 50, and the lower surface of the collar part 52 by the upper end part. On the inner periphery of the first lower punch 5, an inner peripheral undulation portion 5 a that undulates in the radial direction is formed so as to form the small-diameter tooth portion 53 of the main body 51. Further, on the outer periphery of the first lower punch 5, an outer peripheral undulation portion 5 b that undulates in the radial direction is formed over the entire periphery so as to form the large-diameter tooth portion 54 of the flange portion 52.

  The second lower punch 6 is formed of a cylindrical member, and the lower surface of the main body portion 51 and the lower surface of the flange portion 52 of the powder molded body 50 are formed by the upper surface thereof. On the outer periphery of the second lower punch 6, an outer peripheral undulation portion 6 a that undulates in the radial direction is formed over the entire periphery so as to form the small diameter tooth portion 53 of the main body portion 51.

3 is an enlarged cross-sectional view taken along the line B-B in FIG. 1, (a) shows a state before the pressure molding of the powder molded body 50, and (b) shows the pressure molding of the powder molded body 50. Shows the state.
3A, the outer peripheral undulating portion 5b of the first lower punch 5 is arranged with a predetermined clearance S0 radially inward with respect to the inner peripheral undulating portion 3a of the die 2. Has been. As a result, the first lower punch 5 slides in the vertical direction with respect to the forming hole 3 of the die 2. The clearance S0 is different from the conventional constant clearance S ′ shown in FIG. 7 so that it has a different size between a portion where the root of the large-diameter tooth portion 54 is formed and a portion where the tooth tip is formed. Is formed.

  When the powder compact 50 is pressure-molded from this state, as shown in FIG. 1, the outer peripheral surface of the main body 51 of the powder compact 50 has a radial direction on the inner peripheral surface of the upper end portion of the first lower punch 5. An internal pressure P that presses outward acts. For this reason, as shown in FIG. 3B, the outer peripheral undulation 5b at the upper end of the first lower punch 5 is elastically deformed so as to swell radially outward (upward in the drawing) by the internal pressure P. The undulation shape of the outer circumferential undulation portion 5b is set based on this elastically deformed state. The setting method will be described below.

FIG. 4 is a cross-sectional view showing the undulation shape during elastic deformation of the outer circumferential undulation portion 5b.
As shown in FIG. 4, in the portion forming the root of the large-diameter tooth portion 54 in the outer circumferential undulation portion 5 b, the intermediate point separated by a predetermined length from the deepest point A of the tooth bottom toward the adjacent tooth tip side. The undulating shape up to B is formed to be the same as the undulating shape of the portion forming the root of the large-diameter tooth portion 54 in the inner peripheral undulating portion 3 a of the die 2.
The circumferential length L _AB of the portion having the same undulating shape is the circumferential length (the deepest point of the tooth bottom) that forms from the root to the tip of the large-diameter tooth portion 54 in the inner circumferential undulating portion 3a. It is set in the circumferential direction of the length) length of L _AC of 1 / 3-1 / 2 to the corner point C of the tip from a.

The undulation shape at the circumferential length L _BC forming from the intermediate point B to the corner point C of the outer peripheral undulation portion 5b is compared to the undulation shape from the intermediate point B to the corner point C at the inner peripheral undulation portion 3a of the die 2. The clearance S1 is gradually increased toward the tooth tip. This clearance S1 is set to 0.01 to 0.04 mm, for example.
Further, the undulation shape of the portion forming the tooth tip in the outer peripheral undulation portion 5b is formed by providing a certain clearance S2 with respect to the undulation shape of the portion forming the tooth tip of the inner peripheral undulation portion 3a. . This clearance S2 is set to 0.02 to 0.06 mm, for example.

  As described above, according to the powder molding die 1 of the present embodiment, the portion for molding the bottom of the large-diameter tooth portion 54 in the outer circumferential undulation portion 5 b of the first lower punch 5 is the same as that during the pressure molding of the powder compact 50. Since the outer peripheral undulating portion 5b is elastically deformed, it is formed to have the same undulating shape as the portion forming the root of the large-diameter tooth portion 54 in the inner peripheral undulating portion 3a of the die 2. When the outer peripheral undulating portion 5b of the first lower punch 5 is elastically deformed during the pressure molding of 50, a portion for forming the tooth bottom of the outer peripheral undulating portion 5b and a portion for forming the tooth bottom of the inner peripheral undulating portion 3a Can be brought into surface contact. Thereby, since the contact surface pressure of the part which shape | molds the said tooth bottom of the outer periphery undulation part 5b and the part which shape | molds the said tooth bottom of the inner periphery undulation part 3a can be disperse | distributed, pressurization of the powder compact 50 It is possible to prevent the outer periphery of the first lower punch 5 from being seized or damaged due to stuffiness during molding.

It should be thought that embodiment disclosed this time is an illustration and restrictive at no points. 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, the powder molding die 1 in the present embodiment has been described with respect to the case where the powder molded body 50 of a sprocket that is a sintered part is pressure-molded, but has the main body 51, the flange 52, and the tooth 54. If it is a thing, it can apply to the powder compact of other sintered parts.
In addition, the powder molding die 1 in this embodiment includes two lower punches (first lower punch 5 and second lower punch 6), but at least along the inner peripheral undulation 3a of the die 2. As long as the lower punch having the sliding outer peripheral undulation portion 5b is provided, the lower punch may be constituted by three or more lower punches.

DESCRIPTION OF SYMBOLS 1 Mold for powder shaping | molding 2 Die 3a Inner peripheral undulation part 3 Molding hole 4 Upper punch 5 1st lower punch (lower punch)
5b Peripheral undulation part 50 Powder compact 51 Main body part 52 Gutter part 54 Large diameter tooth part (tooth part)

Claims (2)

A powder molding die for pressure-molding a powder molded body in which a collar is formed on the outer periphery of a cylindrical main body, and a tooth is formed on the outer periphery of the collar,
A die having a forming hole in which an inner peripheral undulation portion that undulates in the radial direction to form the tooth portion is formed on the inner periphery;
An upper punch inserted into the molding hole from above;
An outer peripheral undulation is formed on the outer periphery, which is inserted into the molding hole from below and undulates in the radial direction to form the tooth portion, and is provided with a predetermined clearance radially inward with respect to the inner peripheral undulation. With a lower punch,
The portion for forming the root of the tooth portion in the outer peripheral undulation portion is a portion for forming the tooth bottom of the tooth portion in the inner peripheral undulation portion in a state where the outer peripheral undulation portion is elastically deformed during the pressure molding. A powder molding die, which is formed to have the same undulating shape.   The circumferential length of the outer circumferential undulation portion that is the same undulating shape is 1/3 to 1 / of the circumferential length of the inner circumferential undulation portion from the root to the tip of the tooth portion. The powder molding die according to claim 1, which is set to a length of 2.

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