JP2007061833A - Powder molding die assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a die assembly for molding a green compact with a shape in which boss parts and a rim part are connected with a plurality of arm parts and with a structure using a lower punch with a horn part, in which cracks are hard to occur at the root of the horn part, and whose service life is held for a long period of time. <P>SOLUTION: In the die assembly for molding the green compact 60 with a shape where boss parts 62a, 62b, and a rim part 64 are connected with a plurality of arm parts provided between adjoining flange holes 65, a die 10 and a core part 20, a lower punch 41 with the horn part 42 supported to the lower ram side and an internal lower punch 40, an external upper punch 31 having a horn part guiding hole 32 fitted to the horn part 42 supported to the upper ram side and an internal upper punch 30 are provided, and further, in a state where the respective punches are arranged at powder compression completion positions, the clearance between the horn part 42 on the lower punch with the horn and the horn part guiding hole 32 on the external upper punch side is larger at the vicinity of each edge part located in the horn part circumferential direction than that at the inside part and the outside part in the horn part 42. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention particularly relates to a mold apparatus for molding a green compact having a shape in which a central boss portion and an outer peripheral rim portion are connected by a plurality of arm portions.

  Examples of the sintered product having a shape in which the center boss portion and the outer rim portion are connected by a plurality of arm portions include a pulley and a tri-limiter of a rotation transmission device. 4 and 5 show examples of the shape of such a molded body. In each figure, even if the shapes are different, parts having the same functions and roles are denoted by the same reference numerals. The boss portion 62 forms a hole edge of the shaft hole 61. The boss portion 62 has an upper boss 62 a on one end side and a lower boss 62 b on the other end side, and is connected to the rim portion 64 by a plurality of arm portions 63. Around the boss portion 62, there are a plurality of flange holes 65 that define the arm portion 63 and the rim portion 64.

  By the way, as a molding die apparatus for a green compact as described above, a prior art document could not be found, but there is something similar to FIG. 1 to which the present invention is applied. It is a structure like this. That is, the main part of the apparatus includes, between the die 10 and the core 20, the inner and lower punches 40 that fit the core 20 and press the end of the lower boss 62 b of the green compact 60 from the lower side. The lower punch 40 is fitted between the die 10 and has a surface that forms the lower surface of the arm portion 63 and the outer periphery of the lower boss 62b, and has an angled (one) portion 42 that protrudes upward to form the flange hole 65. The cornered lower punch 41 and the outer lower punch 43 that forms the lower surface of the rim portion 64 are fitted together. The cornered lower punch 41 is made of a hard mold material such as high-speed tool steel. For example, in the case of a molded product shape shown in FIG. 4C, the shape shown in FIG. is doing. The cornered lower punch 41 and the outer lower punch 43 may be integrated without being divided as shown in FIG.

  On the other hand, above the die 10, the inner upper punch 30 that fits with the core 20 and presses the end face of the upper boss 62 a, and the corner portion 42 of the cornered lower punch 41 that fits with the inner upper punch 30 and the die 10. And an outer upper punch 31 for shaping the outer periphery of the upper boss 62a, the upper surface of the arm portion 63, and the rim portion 64.

  A feature of the molding die apparatus as described above is that a cornered lower punch 41 having a structure in which a corner portion 42 for forming a flange hole 65 of a green compact is integrated with a lower punch is used, The upper boss 62 a is provided on the body, and the outer periphery thereof is formed by the inner peripheral surface of the outer upper punch 31. This is because the construction of the lower punch 41 with corners has an effect that the manufacturing process is reduced as compared with, for example, a structure in which the corner portion is manufactured separately and the lower punch is provided with a fitting hole and combined.

  In the powder molding using the above-described mold apparatus, a predetermined amount of powder is filled in the cavity formed by the die 10, the core 20, and the lower punches 40, 41, 43, and the powder is filled by the upper punches 30, 31. Is performed by moving the powder sandwiched between the inner lower punch 40 and the inner upper punch 30 upward to form a powder similar to the target green compact, and then releasing the green compact. .

  The powder molding die apparatus as described above has the advantage that the mold structure is simple and inexpensive by using the cornered lower punch 41, but the cornered lower punch 41 shown in FIG. The base portion (r) of the corner 42 is cracked and easily damaged, and the mold life is shortened. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems relatively easily so that mold cracks hardly occur and the mold life can be maintained long.

  In order to solve the above-described problems, the present invention is specified with reference to the drawings. The center boss portion (62) and the outer peripheral rim portion (64) are provided between adjacent flange holes (65). And a die (10) having an inner wall for shaping the outer periphery of the rim portion (64) in a mold apparatus for forming a green compact (60) having a shape connected by a plurality of arm portions (63). The core (20) for forming the shaft hole of the boss portion (62) and the die (10) are fitted to press the lower surface of the rim portion (64) and the lower surface of the arm portion (63). An end surface, an inner surface that forms the outer periphery of the lower boss (62b) side of the boss portion (62), and a corner with a corner portion (42) that protrudes upward from the upper end surface that forms the flange hole (65). The lower punch (41), the inner side surface of the lower punch (41) with corners, and An inner and lower punch (40) that fits with the core (20) and presses the lower boss (62b), is provided on the upper ram side on the die, fits into the die (10), and the rim A lower end surface that presses the upper surface of the portion (64) and the upper surface of the arm portion (63), an inner surface that forms the outer periphery of the upper boss (62a) side of the boss portion (62), and the cornered lower punch (41 The outer upper punch (31) having a corner guide hole (32) fitted to the corner (42) of the outer upper punch (31) and the inner surface of the outer upper punch (31) and the core (20). An inner upper punch (30) for pressing the boss (62a), and the corners (42) of the lower punch with corners and the outer upper punches in a state where the punches are arranged at the powder compression completion positions. Clearance (gap between opposing faces) between the corner guide holes (32) of the punch is the corner End portion positioned in the circumferential direction of the corner portion (42) than in the inner portion and the outer portion 42) is characterized that it is large.

  In the above powder molding die apparatus, when the distance from the outer periphery of the inner / upper punch (30) to the end portions on both sides located in the circumferential direction of the corner portion (42) is the same, both the vicinity of both end portions are used as the clearance. When the distance from the outer periphery of the inner and upper punch (30) to the end portions on both sides located in the circumferential direction of the corner portion (42) is different, only the vicinity of the shorter end portion is larger as the clearance. (Claim 2), the clearance is a maximum clearance of 0.03 to 0.15 mm, more preferably 0.06 to 0.10 mm in the vicinity of the end of the end portion located in the circumferential direction of the corner portion (42). The rim of the corner portion (42) is gradually continuous from the maximum clearance toward the inner portion and the outer portion of the corner portion (42). That divides the outer peripheral portion for pressing the lower surface (64) as the lower outer punch (43) (claim 4) is preferable.

The powder molding die apparatus of the present invention has the following effects.
In the first aspect of the present invention, in particular, the corners (42) of the lower corner punch (41) and the corner guide holes (32) of the outer upper punch (31) are not equalized at each portion without equalizing the clearance. If the vicinity of the end portion located in the circumferential direction of the corner portion (42) is made larger than the inner portion and the outer portion of the portion (42), the base (r) of the corner portion (42) is less likely to crack, and the mold The service life can be greatly extended. For this reason, the present invention can provide economic effects such as reducing mold costs and molding operation stoppage associated with mold replacement. At the same time, when the powder is compressed by the clearance configuration, the air contained in the powder can be easily discharged from the portion having the large clearance, and the effect of smoothing the powder molding can be obtained.
In the inventions of claims 2 and 3, the function and effect of claim 1 can be obtained more accurately.
In the invention of claim 4, the degree of freedom in manufacturing the cornered lower punch (41) can be expanded.

  The best mode of the present invention will be described below with reference to the drawings. The drawings are exaggerated for easy understanding. The molding die apparatus of the present invention has a green compact 60 as illustrated in FIGS. 4 and 5, that is, between the flange holes 65 adjacent to each other, the central boss 62 and the outer rim 64. The green compact 60 connected by the provided arm parts 63 is manufactured, and has a structure shown in FIGS.

  That is, the mold apparatus of FIG. 1 has a die 10 having an inner wall (inner peripheral wall of the die hole 11) for modeling the outer periphery of the rim portion 64 and a core for modeling the shaft hole 61 (see FIG. 4) of the boss portion 62. 20, an inner lower punch 40 and a cornered lower punch 41 and an outer lower punch 43 supported by a lower ram (not shown), and an inner upper punch 30 and an outer upper punch supported by an upper ram (not shown). 31.

  Of these, the lower punch 41 with corners may be formed integrally with the outer lower punch 43a on the outer periphery as shown in FIG. 2 (b), in addition to a configuration in which a separate outer lower punch 43 is fitted on the outer periphery. . Then, the lower punch 41 with corners is fitted into the die hole 11 of the die 10 via the outer lower punches 43 and 43a and presses the lower surface of the green compact rim portion 64 and the lower surface of the arm portion 63. , And an inner side surface that forms the outer periphery of the lower boss 62 b side of the boss portion 62, and a corner portion 42 that protrudes upward from the upper end surface that forms the flange hole 65. Further, the lower punch 40 is fitted to the inner surface of the cornered lower punch 41 and the core 20, and can press the end surface of the lower boss 62b.

  On the other hand, the outer upper punch 31 fits into the die hole 11 of the die 10 and presses the upper surface of the green compact side rim portion 64 and the upper surface of the arm portion 63, and the upper boss of the boss portion 62. It has at least the corner | angular part guide hole 32 fitted with the inner side surface which shape | molds the 62a side outer periphery, and the corner | angular part 42 of the corner | angular lower punch 41. FIG. The inner / upper punch 30 is fitted to the inner surface of the outer / upper punch 31 and the core 20 so that the upper boss 62a can be pressed.

  Moreover, in the above die apparatus, in the state which each punch 30, 31, 40, 41 has been arrange | positioned in the powder compression completion position, between the corner | angular lower punch side corner | angular part 42 and the outer upper punch side corner | angular part guide hole 32, The clearance between them (the gap between the opposing surfaces) is devised as follows.

  That is, in the cross section of the mold apparatus of FIG. 3A, the core 20 is located at the center, the inner and upper punches 30 are fitted to the outer side of the core 20, and the cornered lower punch side corner portion 42 and the outer and upper punches are fitted. The side corner portion guide hole 32 is in a fitted state. And the clearance gap (one side clearance) between each metal mold | die member is manufactured in the range of 0.02-0.05 mm similarly to the case of a general metal mold apparatus. The corner portion 42 has a shape corresponding to (b) in the shape of the molded product shown in FIG. 4 (that is, the end portions on both sides located in the circumferential direction of the corner portion 42 from the outer periphery of the inner / upper punch 30 as the mold configuration). The inner surface and the both end portions of the outer surface are concentric, and the intermediate portion of the outer surface protrudes and becomes a compact shape. In this case, only the vicinity of both end portions in the circumferential direction of the corner portion 42 is made at least 0.01 mm larger than the inner and outer portions of the corner portion 42. The clearance in the vicinity of both ends is set to a maximum of 0.15 mm, more preferably a maximum of 0.10 mm, and the clearance is gradually connected toward the inner periphery and the outer periphery of the corner portion 42. Reference numeral 50 in FIG. 3 indicates the majority of this clearance. This large clearance 50 is a value when the outer upper punch 31 and the lower cornered punch 41 approach each other in the same manner as in the compression molding without filling the powder. In addition, this clearance structure is, for example, a corner portion so that the corner portion 42 of the cornered lower punch 41 is easily fitted into the corner portion guide hole 32 of the outer upper punch 31 and the green compact is easily released. 42 may be formed into a thin shape, but this is not the clearance between the thinned portion and the outer punch side.

  As described above, when the clearance in the vicinity of the end portion of the corner portion 42 is made at least 0.01 mm larger than the inner and outer portions of the corner portion 42, the durability of the mold is improved. For example, a molding die apparatus having a large clearance (maximum 0.15 mm) near the end of the corner 42 and a conventional molding mold apparatus having a uniform clearance (maximum 0.05 mm). As a result of operating and comparing under the same conditions, the durability of the mold was more than three times higher in the former compacting than in the latter compacting. The reason is estimated as follows. First, in the cross-sectional view of the molding die apparatus shown in FIG. 1, assuming that the molded body (green compact 60) does not have the upper boss 62a, the inner upper punch 30 and the outer upper punch 31 have compression surfaces. Since they are the same, the load received by the corner portion 42 of the cornered lower punch 41 is applied in a balanced manner between the boss side green compact portion and the rim side green compact portion and is fitted and held in the corner portion guide hole 32 in a stable state. Uneven load does not act on the corner 42.

  On the other hand, in the shape with the upper boss 62a as shown in FIG. Thus, the compressive load expands the thin portion 31a, which presses the corner portion 42 toward the outside (radial direction), and depending on the degree of deformation of the thin portion 31a of the outer upper punch 31 and the other portions. It is presumed that torsional bending and tensile load are concentrated on the end portion in the circumferential direction of the corner 42, and this is repeatedly applied each time the green compact is formed, resulting in fatigue failure. In this respect, in the present embodiment, the clearance at the end portion in the circumferential direction of the corner portion 42 is increased so that the clearance portion 50 escapes or absorbs the deformation of the outer punch 31. It is considered that the unbalanced load on the end portion is reduced and fatigue is reduced.

  FIG. 3B shows a case in which the cross-sectional shape of the corner portion 42 is different, and the molded body has a shape as shown in FIG. In this embodiment, the shape of the corner portion 42 is such that one end side in the circumferential direction is close to the outer periphery of the inner upper punch 30 (in other words, the thin portion 31a of the outer upper punch 31 is thin) and is concentric with the core 20. Yes, and the other end side in the circumferential direction extends in a direction away from the outer periphery of the inner upper punch 30 (in other words, a state in which the thin portion 31a of the outer upper punch 31 is thicker). In this case, the large clearance 50 is only in the vicinity of one end of the corner 42 on the side close to the outer periphery of the inner / upper punch 30. The reason why the large clearance portion is not provided on the other end side of the corner portion 42 is that the other end side has a large distance from the outer periphery of the inner / upper punch 30 and inevitably the thin portion 31a of the outer / upper punch 31 is not thin. This is because diameter expansion deformation during powder molding hardly occurs. Of course, a large clearance portion may be provided on the other end side, and the same effect as the large clearance portion 50 on the one end side is obtained. In this way, by making the vicinity of the end portion in the circumferential direction of the corner portion 42 the large clearance portion 50, the thin portion 31a of the outer upper punch 31 is compressed by the upper boss portion 62a of the molded body (green compact) during powder compression. As in the case described above, the effect of delaying the breakage of the corner portion 42 is exerted by expanding the diameter by pressure and relaxing or absorbing the stress concentration applied to the end portion in the circumferential direction of the corner portion 42.

  The present invention is not limited to the above-described embodiment except for the requirements specified in claim 1, and the details of each punch and the like can be variously changed.

It is a longitudinal cross-sectional view which shows the molding die apparatus of this invention form in the state at the time of powder molding. (A) shows a cornered lower punch in the molding die apparatus of FIG. 1, and (b) is a schematic external view showing an example in which a cornered lower punch and an outer lower punch are integrated. (A) And (b) is a metal mold | die cross-sectional view explaining the clearance of the said shaping | molding die apparatus principal part. (A)-(d) is the top view which showed the example of the shape of the green compact manufactured with the molding die apparatus of this invention. It is the sectional view on the AA line of FIG.4 (d) which shows the detailed shape of the said green compact.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Die 20 ... Core 30 ... Inner / upper punch 31 ... Outer / upper punch 31a ... Thin part 32 ... Corner | angular part guide hole 40 ... Inner / lower punch
41 ... Lower punch with corner 42 ... Corner
43 ... Outer and lower punch 50 ... Most of clarance 60 ... Green compact 62 ... Boss part 63 ... Arm part
64 ... Rim 65 ... Flange hole

Claims (4)

In a mold apparatus for molding a green compact having a shape in which a central boss part and an outer rim part are connected by a plurality of arm parts provided between adjacent flange holes,
A die having an inner wall for shaping the outer periphery of the rim portion;
A core for modeling the axial hole of the boss part;
From the upper end surface that fits the die and presses the lower surface of the rim portion and the lower surface of the arm portion, the inner surface that forms the lower boss side outer periphery of the boss portion, and the upper end surface that forms the flange hole A cornered lower punch having a corner protruding upward;
An inner and lower punch that fits with the inner surface of the cornered lower punch and the core and presses the lower boss;
An inner surface that is provided on the upper ram side on the die and that fits the die and presses the upper surface of the rim portion and the upper surface of the arm portion, and an inner surface that forms the upper boss side outer periphery of the boss portion And an outer upper punch having a corner guide hole that fits into a corner of the lower punch with corners,
With an inner upper punch that fits with the inner surface of the outer upper punch and the core and presses the upper boss,
In the state where each punch is arranged at the powder compression completion position, the clearance between the corner portion of the cornered lower punch and the corner guide hole of the outer upper punch is larger than the inner portion and the outer portion of the corner portion. A powder molding die apparatus characterized in that the vicinity of the end located in the circumferential direction of the corner is large.   When the distance from the outer periphery of the inner upper punch to both ends located in the circumferential direction of the corner is the same, the clearance is increased in the vicinity of both ends, and from the outer periphery of the inner upper punch to the periphery of the corner. The powder molding die apparatus according to claim 1, wherein when the distance to the end portions on both sides located in the direction is different, only the vicinity of the end portion with the shorter distance is made larger as the clearance.   The clearance is a maximum clearance of 0.03 to 0.15 mm in the vicinity of the end of the end portion located in the circumferential direction of the corner portion, and gradually decreases from the maximum clearance toward the clearance of the inner side portion and the outer side portion of the corner portion. The powder molding die apparatus according to claim 1 or 2, which is continuous with the above. The powder molding die apparatus according to any one of claims 1 to 3, wherein an outer peripheral portion that presses a lower surface of the rim portion is divided as an outer lower punch among the cornered lower punches.

Images