WO2019181417A1

WO2019181417A1 - Sintered machine component, sintered gear, pulley, coupling, sintered machine component manufacturing method, and powder molding mold

Info

Publication number: WO2019181417A1
Application number: PCT/JP2019/007836
Authority: WO
Inventors: 敏彦毛利; 哲弥栗村; 達夫川瀬
Original assignee: Ntn株式会社
Priority date: 2018-03-23
Filing date: 2019-02-28
Publication date: 2019-09-26

Abstract

A sintered machine component formed by placing one end surface of a green compact, both end surfaces of which have a recess formed therein, on a tray for which the loading surface is a level surface, and carrying out sintering. The surface area ratio of the recess with respect to the one end surface is 5–50%. The depth of the recesses is 0.2–1.0 mm.

Description

Sintered machine parts, sintered gears, boogies, couplings, methods of manufacturing sintered machine parts, and molds for powder molding

The present invention relates to a sintered machine part, a sintered gear, a bouley, a coupling, a method for manufacturing a sintered machine part, and a powder molding die.

Sintered mechanical parts are formed by compressing and molding a plurality of metals in a fine powder state, and maintaining the powder compact (green compact) at a high temperature below the melting point (diffusion bonding of metal particles and Manufactured by powder metallurgy, which is alloyed and baked.

Iron-based sintered machine parts are sintered at a high temperature exceeding 1100 ° C. to ensure strength. When the green compact is sintered, for example, a method is generally used in which the green compact is placed on a tray or a metal net and sintered.

However, the density and accuracy of the green compact are different, the heat and cooling rate received by the green compact are different at the position in the furnace, and the tray is deformed. Variation occurs. In particular, when a product having a large diameter and a small thickness (for example, a spur gear) is formed, warping is likely to occur. For this reason, it is often impossible to obtain the required accuracy by a method in which a green compact is simply placed on a tray or the like and sintered.

Therefore, there is a conventional technique in which a molded body (a green compact) is placed on a fireproof plate (tray) and a weight board is placed on the molded body (Patent Document 1). By configuring in this way, even if there is density non-uniformity at each position of the molded body by pressing the molded body using the weight of the weight plate, the density non-uniformity during the sintering process It is possible to forcibly correct the warp caused by.

Conventionally, there is one in which a plurality of convex portions are provided on a green compact (a cemented carbide compact), and the green compact is placed on a sintered plate and sintered (Patent Document 2). . In this case, the contact area between the green compact and the sintered plate is reduced by bringing the plurality of convex portions of the green compact into contact with the sintered plate. This suppresses the warping of the green compact.

In order to efficiently transmit the power from the shaft to other mechanical elements such as gears that rotate with the shaft, the key is generally provided on the outer diameter surface of the shaft and the inner diameter surface of the gear. A fitting structure including a key groove is used.

By the way, the gear includes a sintered gear which is a sintered machine part. Here, sintered machine parts are compression molding of a plurality of metals in a fine powder state, and sintering by holding this powder compact at a high temperature below the melting point (diffusion bonding and alloying of metal particles). ) And then baked and solidified by powder metallurgy.

For this reason, sintered machine parts are suitable for the production of composite material parts, suitable for mass production, high dimensional accuracy, suitable for forming complex shapes, and material yield. There are advantages such as excellent point.

A sintered gear, which is a sintered machine part, also has a gear with a key groove in which a key groove provided on an inner diameter surface is formed (see Patent Document 3 and Patent Document 4).

JP 2010-209400 A JP 2004-83925 A Japanese Patent Application Laid-Open No. 08-069705 Japanese Patent No. 4046315

The one described in Patent Document 1 requires a heavy stone plate, which increases the number of parts, and requires a work of placing the heavy stone plate, leading to an increase in work processes. In addition, there is a problem in that the number of man-hours for inventory management is increased because it is necessary to make the weight plate different depending on the thickness of the green compact (molded body).

By the way, this Patent Document 1 describes a method of stacking a plurality of green compacts (molded bodies) between a tray and a weight plate. By stacking a plurality of green compacts (molded bodies) in this way, the processing efficiency is improved, and the surfaces of the stacked green compacts (molded bodies) are brought into contact with each other to suppress deformation. This is to further increase the suppression effect.

However, if a plurality of green compacts (molded bodies) are stacked, the green compacts (molded bodies) placed above and below have different weights on the green compacts, which may cause dimensional differences in the sintered bodies. .

The one described in Patent Document 2 is limited as a product because it is necessary to provide a plurality of convex portions on the green compact (super hard alloy green compact). Moreover, when molding a product having such a shape, it is necessary to provide a concave portion corresponding to the convex portion in the mold. However, it is difficult to manufacture a mold having such a shape because, for example, it cannot be turned with a lathe and the like, there is a possibility that the accuracy of the mold is deteriorated and the cost is increased.

The keyway is formed to protrude from the inner diameter surface (cylindrical surface) of the shaft hole to the outer diameter side, and the shape of the inner diameter surface of the shaft hole is an irregular shape. For this reason, when inserting (inserting) the shaft member in which the key is formed into the shaft hole in which the key groove is formed, it is necessary to match the circumferential phase of the key groove and the key. In addition, if the axial direction of the shaft hole and the axial direction of the shaft member are inclined, it becomes difficult to insert them due to mutual interference.

Therefore, chamfering is performed on the insertion start end on the shaft member side, and chamfering is performed on the opening of the key groove. In the case of a general melted material, chamfering to the key groove is performed by machining. However, in the case of having a key groove, the shape of the inner diameter surface of the shaft hole is an irregular shape, and therefore, chamfering is performed in a process different from the inner diameter surface processing.

If such processing is performed, the chamfered portion of the key groove and the chamfered portion of the inner diameter surface may have different shapes and dimensions. If there is a difference in this way, the shaft member cannot be stably inserted, resulting in poor productivity.

Therefore, in view of the above-mentioned problems, the present invention is effective in that a molding die used for molding a green compact may be a simple shape, a product having a large outer dimension and a small thickness, and warping. Provided is a sintered machine part that is prevented. Further, the present invention provides a sintered machine part and a sintered gear having a keyway that is stable in insertion workability and productivity of a shaft member.

According to the first mechanical component of the present invention, a raw material powder filled in a powder filling portion formed between an inner diameter surface of a core and an outer diameter surface of a die is compressed by an upper punch and a lower punch, and compacted. A sintered machine part formed by molding a body, and one end face of a green compact having concave portions formed on both end faces is placed on a tray whose placing face is flat. Sintered, the surface area ratio of the recessed portion to the entire end surface of the one end surface is 5 to 50%, and the depth of the recessed portion is 0.2 mm to 1.0 mm.

According to the first sintered machine part of the present invention, the contact area of the green compact with the tray can be reduced by setting the surface area ratio of the recessed portion to the entire end face at one end face to be 5 to 50%. It is possible to reduce or eliminate the influence of heat history from the tray, friction with the tray during the expansion and contraction of the green compact, and the like. In addition, the product density distribution can be prevented from being deteriorated by setting the depth of the recessed portion to 0.2 mm to 1.0 mm.

The surface area ratio is preferably 10 to 40%, and the depth of the recess is preferably 0.3 mm to 0.6 mm.

The green compact with concave portions formed on both end faces is a disk-shaped body, the concave portion is formed between the inner peripheral portion and the outer peripheral portion, and the concave portion is a concentric ring with an axial hole. The shape is preferred. As described above, since the concave portion has a concentric ring shape with the axial hole, the powder molding die for molding the green compact can be made into a simple shape, and it is easy to manufacture and modify the die. is there.

The second sintered machine part of the present invention compresses the raw material powder filled in the powder filling portion formed between the inner diameter surface of the core and the outer diameter surface of the die with the upper punch and the lower punch, It is a sintered machine part formed by compacting a green compact, and a key groove is formed on the inner diameter surface of the hole, and formed by powder metallurgy, and at each open end of the hole and the key groove A chamfered portion having the same shape and the same size is formed by a chamfered convex portion provided on the upper punch and a chamfered convex portion provided on the lower punch. Here, the same dimension means that the design dimension is the same, and the variation occurring in the manufacturing process is included, and includes a range within the dimensional tolerance. In addition, the same shape means one that allows a certain amount of molding error, for example, one that allows a molding error as much as that formed using the same mold, and includes a range that falls within the geometric tolerance.

According to the second sintered machine component of the present invention, the chamfered portion is provided at each open end of the hole and the key groove. When inserting a shaft member having a key provided on the radial surface, the shaft body of the shaft member is guided (guided) by the chamfered portion of the hole (excluding the key groove) and can be stably inserted. When inserting the key of the member, the key can be stably inserted by being guided (guided) by the key groove chamfer. In addition, since the chamfered portions at the open ends of the hole and the key groove have the same shape and the same dimensions, when the shaft body is inserted into the sintered machine part, the chamfer between the hole and the key groove. There is no difficulty in insertion due to differences in the shape and dimensions of the parts.

It is preferable that the opening end of the chamfered portion is a convex round shape portion. In this way, if the open end is a convex round shape portion, it is possible to avoid a hooking at the time of insertion and insert smoothly.

The chamfered portion includes the convex round shape portion, a taper portion extending from the convex round shape portion to the back side, and a land portion connected to the taper portion. It may be a shape part. In this way, if the land portion is a convex round shape portion, it is possible to smoothly insert the chamfered portion from the chamfered portion, avoiding catching at the time of insertion.

The sintered gear of the present invention is a sintered gear formed by powder metallurgy, and is composed of the sintered machine parts. For this reason, when a shaft member having a shaft main body and a key provided on the outer diameter surface of the shaft main body is inserted into the sintered gear, the shaft main body of the shaft member is chamfered with a hole (a key groove is omitted). It is guided (guided) to the part and can be inserted stably, and when inserting the key of the shaft member, it can be guided (guided) to the keyway chamfered part and stably inserted. Moreover, since the chamfers of the open ends of the hole and the key groove have the same shape and the same dimensions, when the shaft body is inserted into the sintered gear, the chamfered part of the hole and the key groove Does not cause insertion difficulty due to differences in shape and dimensions. Further, the sintered machine component may be a pulley or a coupling.

In the manufacturing method of the sintered machine part of the present invention, the raw material powder filled in the powder filling portion formed between the inner diameter surface of the core and the outer diameter surface of the die is compressed with the upper punch and the lower punch, A method of manufacturing a sintered machine part for forming a green compact, wherein concave parts are provided on both end faces of the green compact, and one end face is placed on a tray having a flat mounting surface. Sintering is performed, and the surface area ratio of the recessed portion to the entire end surface at one end surface is set to 5 to 50%, and the depth of the recessed portion is set to 0.2 mm to 1.0 mm.

According to the method for manufacturing a sintered machine part of the present invention, since the green compact has a surface area ratio of the recessed portion to the entire end face of one end face of 5 to 50%, the contact area of the green compact with the tray , And the influence of friction with the tray during expansion / contraction of the green compact can be reduced or eliminated. In addition, the product density distribution can be prevented from being deteriorated by setting the depth of the recessed portion to 0.2 mm to 1.0 mm.

The powder molding die according to the present invention compresses the raw material powder filled in the powder filling portion formed between the inner diameter surface of the core and the outer diameter surface of the die with an upper punch and a lower punch, A powder molding die for molding powder, which molds a green compact with a key groove formed on the inner diameter surface of the hole, and has a chamfer molding convex portion on each of the upper punch and the lower punch. Are formed with the upper punch and the lower punch, and the chamfered portion forming convex portion has the same shape and the same size at each opening end of the hole portion and the key groove of the green compact. A chamfer is formed.

If the metal mold for compacting of the present invention is used, the chamfered part forming convex part provided on the upper punch and the chamfering part provided on the lower punch at the opening ends of the hole and the key groove. A green compact having a chamfered portion having the same shape and the same size formed by the convex portion can be stably formed. If this green compact is sintered, a sintered machine part having a chamfered portion having the same shape and the same size at each opening end of the hole and the key groove can be formed.

The convex portions for forming the chamfered portion of the upper punch and the lower punch may be formed by electric discharge machining. Here, the electric discharge machining is performed by making the electrode and the object to be processed close to each other without contacting the workpiece and utilizing an electric discharge phenomenon generated between the two. For this reason, a convex part can be shape | molded accurately and the chamfered part of the same shape and the same dimension can be shape | molded stably.

In the present invention, it is possible to reduce or eliminate the influence of the heat history from the tray, the friction with the tray when the green compact is expanded / shrinked, and the deterioration of the product density distribution can be prevented. For this reason, the curvature at the time of sintering can be prevented effectively, and a highly accurate sintered machine part can be provided. In addition, existing trays can be used as they are, and further, parts such as heavy stone plates are not required, so that the sintering workability is excellent and the cost can be reduced. In addition, it is not necessary to make a product such as a convex part that contacts the tray with the green compact, and the mold for molding the green compact can be a simple shape, making it easy to manufacture and modify the mold. Thus, cost reduction can be achieved.

In the present invention, since the chamfered portions at the open ends of the hole and the keyway have the same shape and the same dimensions, workability and productivity at the time of inserting the shaft can be improved.

It is sectional drawing at the time of sintering of the sintering machine component of this invention. It is sectional drawing of the sintering machine component of this invention. It is sectional drawing of the state which is sintering the green compact which does not have a hollow part. It is sectional drawing of the state which is sintering the green compact whose area of a hollow part is large. It is a top view of the gear wheel with a keyway of the present invention. FIG. 6 is an enlarged sectional view taken along line AA in FIG. 5. FIG. 6 is an enlarged sectional view taken along line BB in FIG. 5. It is an expanded sectional view of one opening end side in a state where a chamfered portion of an inner diameter surface is shown and a land portion is not formed in a convex round shape portion. It is an expanded sectional view of the chamfered part on the other opening end side in a state where the chamfered part of the inner diameter surface is shown and the land part is not formed in the convex round shape part. It is an expanded sectional view of one opening end side in the state where the chamfered portion of the key groove is shown and the land portion is not formed in the convex round shape portion. It is an expanded sectional view on the other opening end side in a state where the chamfered portion of the key groove is shown and the land portion is not formed in the convex round shape portion. It is an expanded sectional view of one opening end side in the state where a chamfered portion of an inner diameter surface is shown and a land portion is formed in a convex round shape portion. It is an expanded sectional view of the chamfered part on the other opening end side in a state where the chamfered part of the inner diameter surface is shown and the land part is formed in the convex round shape part. It is an expanded sectional view of one opening end side in a state where a chamfered portion of a key groove is shown and a land portion is formed in a convex round shape portion. The chamfered portion of the key groove is shown, and is an enlarged sectional view on the other opening end side in a state where the land portion is formed in a convex round shape portion. It is sectional drawing of the site | part containing the keyway of a compact. It is sectional drawing of the site | part which does not contain the keyway of a compact. It is sectional drawing of the metal mold | die for powder molding. FIG. 3 is an enlarged cross-sectional view of a main part of an upper punch, showing a mold for powder molding of a chamfered portion of an inner diameter surface. It is a principal part expanded sectional view of the lower punch which shows the metal mold | die for powder shaping | molding of the chamfer part of an internal diameter surface. FIG. 3 is an enlarged cross-sectional view of a main part of an upper punch, showing a mold for powder molding of a chamfered portion of a key groove. FIG. 4 is an enlarged cross-sectional view of a main part of a lower punch, showing a powder molding die for a chamfered portion of a key groove. It is a top view of the pulley of the present invention. It is a top view of the coupling of this invention.

Hereinafter, embodiments of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view of a state in which the green compact 10 is sintered, and FIG. 2 is a cross-sectional view of a sintered gear that is a sintered machine component according to the present invention. The sintered machine part is a spur gear in which concave and convex teeth 1 are formed on the outer peripheral surface and a shaft hole 2 is formed.

In this case, the central portion and the outer peripheral portion (the uneven tooth 1 is omitted) are the

thick portions

3 and 4. Therefore, ring-shaped recessed

portions

7 and 8 are formed on both

end surfaces

5 and 6. In addition, tapered

surfaces

7b, 7c, and 8b that increase in diameter from the bottom surfaces 7a and 8a of the recessed

portions

7 and 8 toward the end surfaces 5 and 6, respectively, are provided at the inner diameter end portion and the outer diameter end portion of the recessed

portions

7 and 8, respectively. , 8c are provided.

For this reason, when forming a sintered machine part having such a shape, it is first necessary to form a green compact 10 (see FIG. 1) having the same shape as the sintered machine part. That is, the green compact 10 is a disc body in which the concave and convex teeth 1 ′ on the outer peripheral surface are formed and the axial hole 2 ′ is formed, and the axial portion and the peripheral portion (the concave and convex teeth 1 ′ are omitted). Are the thick portions 3 'and 4'. For this reason, ring-shaped recessed parts 7 'and 8' are formed on both end faces 5 'and 6'. Tapered surfaces 7b ', 7c', 8b ', and 8c' are provided in the recessed portions 7 'and 8'.

The green compact 10 is molded by this powder molding die (not shown). The powder molding die includes a die, a core inserted into the die, an upper punch, and a lower punch. Concave and convex teeth forming portions are formed on the inner surface of the die. In the metal mold thus configured, first, raw material powder is filled into a powder filling portion (cavity) defined by the outer diameter surface of the core, the inner diameter surface of the die, and the upper end surface of the lower punch. As the raw material powder, a metal powder is used as a main raw material, and various kinds of fillers such as molding aids and solid lubricants are added to and mixed therewith. That is, the raw material powder generally used conventionally for a sintered gear can be used.

After the raw material powder is filled in the powder filling portion (cavity), the upper punch is moved closer to the lower punch (the upper punch is lowered) to compress the raw material powder. As a result, the green compact 10 in which the outer surface irregularities 1 ′ are formed on the inner surface and the ring-shaped concave portions 7 ′ and 8 ′ are formed on the end surfaces 5 ′ and 6 ′ (see FIG. 1). ) Is formed.

The green compact 10 configured as described above is placed on a tray 11 and sintered as shown in FIG. The raw material powder is a powder of sintered alloy steel. In this case, for example, an alloy element such as copper (Cu), nickel (Ni), molybdenum (Mo) is added in addition to iron (Fe). Using. The product (sintered machine part) is a gear (module 0.8) having a diameter (reference circle diameter) of 95 mm and a wall thickness of 6 mm.

The one end face 5 ′ of the green compact 10 is placed on the flat placement surface 11 a that is the upper surface of the tray 11. Thus, if it mounts on the mounting surface 11a, recessed part 7 ', 8' and uneven | corrugated tooth | gear 1 'will not contact the tray 11, but the remaining part of the recessed part 7', 8 'and uneven | corrugated tooth | gear 1' End surfaces 12 ′ and 13 ′ contact the tray 11. Here, the remaining end face 13 ′ is a ring-shaped end face provided on the outer peripheral side of the shaft hole 2, and the remaining end face 12 ′ is a ring-shaped end face provided on the inner peripheral side of the uneven tooth 1 ′. is there. In this case, the area of the recessed portion 7 ′ is 5% to 50%, preferably 10% to 40% of the area of the end surface 5 ′ (the entire end surface when the recessed portion 7 ′ is not provided). The depth of the recess 7 ′ is 0.2 mm to 1.0 mm, preferably 0.3 mm to 0.6 mm. Note that the other end face 6 ′ of the green compact 10 has the same shape as the one end face 5 ′.

Then, the tray 11 on which the green compact 10 is placed is conveyed into a sintering furnace, and the green compact 10 is sintered at a temperature below the melting point (for example, 1250 ° C.). In this case, the green compact 10 has a surface area ratio of the recessed portion 7 'with respect to the entire end surface (end surface when the recessed portion 7' is not provided) in one end surface 5 'is 5 to 50%. The contact area of the powder 10 with the tray 11 can be reduced, and the influence of the heat history from the tray 11 and the friction with the tray 11 when the green compact is expanded or contracted can be reduced or eliminated. In addition, the product density distribution can be prevented from being deteriorated by setting the depth of the recessed portion 7 'to 0.2 mm to 1.0 mm.

On the other hand, as shown in FIG. 3, when the concave portion 7 ′ is not provided, that is, when the entire end surface 5 ′ is in contact with the tray 11, the heat history from the tray 11, the expansion of the green compact, The influence of the friction with the tray at the time of shrinkage is large, and the green compact 10 warps during sintering. The entire end surface 5 ′ is not in contact with the tray 11, but if the area of the recessed portion 7 ′ is less than 5% of the area of the end surface 5 ′ (as much as the entire end surface 5 ′ is in contact with the tray 11. However, the green compact 10 warps during sintering. In FIG. 3, an arrow A indicates heat transfer from the tray, and an arrow B indicates the expansion / extension direction of the green compact 10.

In addition, as shown in FIG. 4, when the area of the recessed part 7 ′ is large (when the area of the recessed part 7 ′ exceeds 50% of the area of the end surface 5 ′), the part that contacts the tray 11 Is a very small part, the heat history from the tray 11 and the friction with the tray 11 during the expansion / contraction of the green compact work locally, and the difference from the concave portion becomes large. 10 warps. In FIG. 4, an arrow A indicates heat transfer from the tray, an arrow B indicates the expansion / extension direction of the green compact 10, and an arrow C indicates the pressing force acting on the concave portion.

For this reason, as described above, the total area size of the recessed portions 7 'is set to 5 to 50%, preferably 10% to 40%, of the entire end face area.

However, even if the size of the area of the recessed part 7 ′ is 5 to 50% of the area of the entire end face, if the depth of the recessed part 7 ′ exceeds 1 mm, it is too deep and the product density distribution deteriorates. , Warping tends to occur. Conversely, if the depth of the recessed portion 7 'is less than 0.2 mm, the bottom surface of the recessed portion is too close to the tray 11 and does not serve as the recessed portion 7', as shown in FIG. As in the case where all end faces are in contact with each other.

In the present invention, it is possible to reduce or eliminate the influence of the heat history from the tray 11 and the friction with the tray 11 when the green compact 10 is expanded / contracted, and also prevent the product density distribution from being deteriorated. It is possible to effectively prevent warping at the time of setting and to provide a highly accurate sintered machine part. Moreover, the existing tray 11 can be used as it is, and further, parts such as a heavy stone plate are not required, the sintering workability is excellent, and the cost can be reduced.

5 shows a plan view of a sintered gear G which is a sintered machine part according to the present invention, FIG. 6 shows an enlarged view of line AA in FIG. 5, and FIG. 7 shows a line BB in FIG. An enlarged view is shown. This sintered gear is a spur gear in which concave and convex teeth 21 are formed on the outer peripheral surface and a hole 22 is formed. A key groove 24 is formed on the inner diameter surface 23 of the hole 22.

Further, as shown in FIGS. 6 and 7, the inner surface 23 of the hole 22 (the inner surface where the key groove 4 is omitted) and the key groove 4 have chamfered portions 25 (25 A, 25 B), 26 at both openings. (26A, 26B) is formed. As shown in FIG. 8A, one chamfered portion 25 A of the inner diameter surface 23 has a convex round shape portion 27 Aa on one opening end side and a diameter reduced from the convex round shape portion 27 Aa to the inner side in the axial direction. The taper portion 27Ab extends and the land portion 27Ac extends radially inward from the taper portion 27Ab. Further, as shown in FIG. 8B, the other chamfered portion 25B of the inner diameter surface 23 is reduced in diameter toward the inner side in the axial direction from the convex round shape portion 27Ba on the other opening end side and the convex round shape portion 27Ba. The taper portion 27Bb extending in this manner and the land portion 27Bc extending radially inward from the taper portion 27Bb.

As shown in FIG. 9A, one chamfered portion 26 A of the key groove 24 is contracted to a convex round shape portion 28 Aa on one opening end side of the key groove 24 and the convex round shape portion 28 Aa inward in the axial direction. The taper portion 28Ab extends so as to have a diameter, and the land portion 28Ac extends from the taper portion 28Ab inward in the radial direction. Further, as shown in FIG. 9B, the other chamfered portion 26B of the key groove 24 includes a convex round shape portion 28Ba on the other opening end side of the key groove 24, and an inner side in the axial direction from the convex round shape portion 28Ba. The taper portion 28Bb extends so as to be reduced in diameter toward the inner side, and the land portion 28Bc extends from the taper portion 28Bb inward in the radial direction.

Therefore, the chamfer 25 (25A) shown in FIG. 8A, the chamfer 25 (25B) shown in FIG. 8B, the chamfer 26 (26A) shown in FIG. 9A, and the chamfer 26 (26B shown in FIG. 9A). ) Are chamfered portions having the same shape and the same dimensions. Moreover, the chamfered portion 25 (25A) and the chamfered portion 26 (26A) are continuously formed, and the chamfered portion 25 (25B) and the chamfered portion 26 (26B) are continuously formed. Here, the same dimension means that the design dimension is the same, and the variation occurring in the manufacturing process is included, and includes a range within the dimensional tolerance. In addition, the same shape means one that allows a certain amount of molding error, for example, one that allows a molding error as much as that formed using the same mold, and includes a range that falls within the geometric tolerance.

By the way, the chamfer 25 (25A) shown in FIG. 8A, the chamfer 25 (25B) shown in FIG. 8B, the chamfer 26 (26A) shown in FIG. 9A, and the chamfer 26 (26B) shown in FIG. 9B. Then, each land part 27Ac, 27Bc, 28Ac, 28Bc is formed with a flat surface extending radially inward, but as shown in FIGS. 10A, 10B, 11A, and 11B, a convex round shape part is formed. 29Ac, 29Bc, 30Ac, 30Bc may be used.

Next, a method for manufacturing the gear G configured as described above will be described. The gear G is a sintered gear that is a sintered machine part. For this reason, powder metallurgy in which a plurality of metals are compression-molded in the form of fine powder and sintered (diffusion bonding and alloying of metal particles) and sintered by holding the powder compact at a high temperature below the melting point. Manufactured by the law.

Therefore, first, the green compact M is molded by compressing the raw material powder using a powder molding die as shown in FIG. The green compact M has the same shape as the sintered gear, which is a sintered machine component shown in FIGS. That is, as shown in FIGS. 12 and 13, the green compact M has an inner surface 23 ′ (inner diameter surface excluding the key groove 24 ′) and a key groove 24 ′ of the hole 22 ′. The taking parts 25 '(25A', 25B '), 26' (26A ', 26B') are formed. As shown in FIG. 15A, one chamfered portion 25A 'of the inner diameter surface 23 has a convex round shape portion 27Aa' on one opening end side and a diameter reduced from the convex round shape portion 27Aa 'inward in the axial direction. The taper portion 27Ab 'extends so as to extend and the land portion 27Ac' extends radially inward from the taper portion 27Ab '. Further, as shown in FIG. 15B, the other chamfered portion 25B of the inner diameter surface 3 is contracted inwardly toward the inner side in the axial direction from the convex round shape portion 27Ba 'on the other opening end side and the convex round shape portion 27Ba'. A tapered portion 27Bb ′ extending so as to have a diameter, and a land portion 27Bc ′ extending radially inward from the tapered portion 27Bb ′.

As shown in FIG. 16A, one chamfered portion 26A 'of the key groove 24' has a convex round shape portion 28Aa 'on one opening end side of the key groove 24' and an axial direction from the convex round shape portion 28Aa '. The taper portion 28Ab ′ extends so as to reduce the diameter inward, and the land portion 28Ac ′ extends from the taper portion 28Ab ′ inward in the radial direction. Further, as shown in FIG. 16B, the other chamfered portion 26B 'of the key groove 24' is formed from a convex round shape portion 28Ba 'on the other opening end side of the key groove 24' and the convex round shape portion 28Ba '. A tapered portion 28Bb ′ extending so as to reduce the diameter inward in the axial direction, and a land portion 28Bc ′ extending inwardly in the radial direction from the tapered portion 28Bb ′.

As shown in FIG. 14, the powder molding die includes a die 35, a core 36 inserted into the die 35, an upper punch 37, and a lower punch 38. An uneven tooth forming portion 40 is formed on the inner diameter surface of the die 35. The core 36 includes a cylindrical core body 36a and a core sub-body 36b disposed on the outer diameter surface of the core body 36 along the axis thereof. That is, the core body 36a forms the inner diameter surface 23 'of the green compact M, and the core sub-body 36b forms the key groove 24' of the green compact M.

Further, a chamfered portion forming convex portion 41 is formed on the lower surface inner diameter portion of the upper punch 37, and a chamfered portion forming convex portion 42 is formed on the upper surface inner diameter portion of the lower punch 38. The chamfered portion forming convex portion 21 includes a main body portion 43A for forming a chamfered portion 25A '(see FIG. 15A) of an inner diameter surface 23' (a portion where the key groove 24 'is omitted), and a chamfered portion of the key groove 24'. 26A ′ (see FIG. 16A) and a sub-portion 44A for molding. Further, the chamfered portion forming convex portion 42 includes a main body portion 43B for forming a chamfered portion 25B ′ (see FIG. 15B) of an inner diameter surface (a portion where the key groove is omitted), and a chamfered portion 26B ′ (see FIG. 16B) and a sub-portion 44B for molding.

That is, as shown in FIG. 15A, the main body portion 43A of the chamfered portion forming convex portion 41 includes a concave round shape portion 43Aa corresponding to the convex round shape portion 27Aa ′ of the chamfered portion 25A ′ and a chamfered portion 25A ′. The taper surface 43Ab corresponding to the taper portion 27Ab 'and the flat portion 43Ac corresponding to the land portion 27Ac' of the chamfered portion 25A '.

Further, as shown in FIG. 16A, the auxiliary portion 44A of the chamfered portion forming convex portion 41 includes a concave round shape portion 44Aa corresponding to the convex round shape portion 28Aa ′ of the chamfered portion 26B ′, and a chamfered portion 26B ′. A taper surface 44Ab corresponding to the taper portion 28Ab 'and a flat portion 44Ac corresponding to the land portion 28Ac' of the chamfered portion 26A '.

Further, as shown in FIG. 15B, the body portion 43B of the chamfered portion forming convex portion 42 includes a concave round shape portion 43Ba corresponding to the convex round shape portion 27Ba 'of the chamfered portion 25A' and a chamfered portion 25A '. The taper surface 43Bb corresponding to the taper portion 27Ab ′ and the flat portion 43Bc corresponding to the land portion 27Ac ′ of the chamfered portion 25A ′.

As shown in FIG. 16B, the sub-portion 44B of the chamfered portion forming convex portion 42 includes a concave round shape portion 44Ba corresponding to the convex round shape portion 28Ba 'of the chamfered portion 26B' and a taper of the chamfered portion 26B '. The taper surface 44Bb corresponding to the portion 28Bb ′ and the flat portion 44Bc corresponding to the land portion 28Bc ′ of the chamfered portion 26B ′ are provided.

Therefore, the main body portion 43A shown in FIG. 15A, the main body portion 43B shown in FIG. 15B, the sub-portion 44A shown in FIG. 16A, and the sub-portion 44B shown in FIG. 16B are convex portions having the same shape and the same dimensions. In addition, the main body portion 43A and the sub portion 44A are continuously formed, and the main body portion 43B and the sub portion 44B are continuously formed.

Incidentally, the chamfered portion forming convex portion 41 of the upper punch and the chamfered portion forming convex portion 42 of the lower punch can be formed by, for example, electric discharge machining. Here, the electric discharge machining is performed by making the electrode and the object to be processed close to each other without contacting the workpiece and utilizing an electric discharge phenomenon generated between the two. For this reason, a convex part can be shape | molded accurately.

In the mold configured as described above, first, the raw material powder is filled into a powder filling portion (cavity) defined by the outer diameter surface of the core 36, the inner diameter surface of the die 35, and the upper end surface of the lower punch 38. . As the raw material powder, a metal powder is used as a main raw material, and various kinds of fillers such as molding aids and solid lubricants are added to and mixed therewith. That is, the raw material powder generally used conventionally for a sintered gear can be used.

After the raw material is powdered in the powder filling portion (cavity), the upper punch 37 is moved relatively close to the lower punch 38 (the upper punch is lowered), and the lower surface 37a of the upper punch 37 and the lower punch 38 are The raw material powder is compressed with the upper surface 38a. As a result, a green compact M is formed for molding the sintered gear G in which the key groove 24 is formed on the inner diameter surface 23 and the uneven teeth 1 on the outer diameter surface are formed.

Further, since the upper punch 17 is provided with a chamfered portion forming convex portion 41 and the lower punch 38 is provided with a chamfered portion forming convex portion 42, the inner diameter surface 23 ′ of the green compact M is provided on the upper punch 17. Chamfered portions 25A 'and 25B' are formed at the axial ends, and chamfered portions 26A 'and 26B' are formed in the key groove 24 'of the green compact M, respectively. The green compact (compressed compact) M is sintered in a gas atmosphere at a temperature below the melting point. As a result, a gear with a keyway as shown in FIG. 5 is formed. After sintering, sizing (recompression) or coining (forging) may be applied as a shaping process to increase dimensional accuracy.

By the way, as shown in FIG. 10A, FIG. 10B, FIG. 11A, and FIG. 11B, when land part 27Ac, 27Bc, 28Ac, and 28Bc are made into convex round shape part 29Ac, 29Bc, 30Ac, 30Bc, after baking, barrel processing or shot The convex round-shaped portions 29Ac, 29Bc, 30Ac, 30Bc can be formed by plasting or the like.

According to the sintered machine component of the present invention, the chamfered

portions

25 and 26 are provided at the opening ends of the hole 22 and the key groove 24. Therefore, the sintered body includes the shaft body and the shaft body. When a shaft member having a key provided on the outer diameter surface of the shaft member is inserted, the shaft body of the shaft member is guided (guided) by the chamfered portion 25 of the hole 2 (excluding the key groove) and can be stably inserted. In addition, when inserting the key of the shaft member, the key can be stably inserted by being guided (guided) by the chamfered portion 26 of the key groove. Moreover, since the chamfered

portions

25 and 26 at the open ends of the hole portion 22 and the key groove 24 have the same shape and the same dimensions, when the shaft body is inserted into this sintered machine part, There is no difficulty in insertion due to differences in the shape and dimensions of the chamfered

portions

25 and 26 from the key groove 24. That is, since the chamfered

portions

25 and 26 at the open ends of the hole 22 and the key groove 24 have the same shape and the same dimensions, it is possible to improve workability and productivity when inserting the shaft.

The open ends of the chamfered

portions

25 and 26 are preferably convex round-shaped portions 27Aa, 27Ba, 28Aa, and 28Ba. As described above, if the open end is the convex round shape portion 27Aa, 7Ba, 28Aa, 28Ba, it is possible to avoid the catch at the time of insertion and insert smoothly.

If the land portions 27Ac, 27Bc, 28Ac, and 28Bc are convex round-shaped portions, they can be smoothly inserted while being able to avoid catching at the time of insertion further from the chamfered portion.

If the metal mold for compacting of the present invention is used, the chamfered portion forming convex portion 41 provided on the upper punch 37 and the lower punch 38 are provided at the opening ends of the hole portion 22 and the key groove 24. The green compact M having the same shape and the same size of the chamfered portions 25 ′ and 26 ′ formed by the chamfered convex portion 42 can be stably molded. If the green compact M is sintered, sintered machine parts having chamfered

portions

5 and 6 having the same shape and the same size at the opening ends of the hole 22 and the key groove 24 can be formed.

The chamfered

convex portions

41 and 42 of the upper punch 37 and the lower punch 38 may be formed by electric discharge machining. Here, the electric discharge machining is performed by making the electrode and the object to be processed close to each other without contacting the workpiece and utilizing an electric discharge phenomenon generated between the two. For this reason, a convex part can be shape | molded accurately and the

chamfered parts

5 and 6 of the same shape and the same dimension can be shape | molded stably.

Incidentally, the sintered machine part according to the present invention may be a pulley as shown in FIG. 17 or a coupling as shown in FIG. That is, even in the pulley shown in FIG. 17 and the coupling shown in FIG. Are chamfered

portions

25 and 26 having the same shape and the same dimensions formed by the chamfered portion convex portion 41 provided on the upper punch 37 and the chamfered convex portion 42 provided on the lower punch 38. Have

As described above, the embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and various modifications are possible. When the sintered machine part to be molded is a gear, the present invention is limited to a spur gear. It may be other gears such as a helical gear.

The shape and size of the chamfered

portions

25 and 26 can be arbitrarily changed as long as they have the same shape and the same dimensions for each sintered machine part. That is, the radius of curvature of the convex round-shaped portions 27Aa, 27Ba, 28Aa, 28Ba and the like can be arbitrarily set. Further, the number of key grooves 24 is not limited to one.

Since the green compact 10 for forming a sintered machine part has the same end face, the end face 5 'is placed on the tray 11 on one side in the above embodiment, but the other end face 6' is placed on the other side. It may be placed on the tray 11.

¡Sintered mechanical parts to be molded are not limited to gears, and may be pulleys, couplings, and the like. Moreover, when it is a gearwheel, it is not restricted to a spur gear, Another gear may be sufficient.

5 ', 6' End surface 7 ', 8' Recess 10, M Green compact 11 Tray 11a Placement surface 22, 22 'Hole 23, 23' Inner surface 24, 24 '

Key grooves

25, 25A, 25B, 26, 26A, 26B Chamfered portion 27Aa, 27Ba, 28Aa, 28Ba Convex round shape portion 27Ab, 27Bb, 28Ab, 28Bb Taper portion 27Ac, 27Bc, 28Ac, 28Bc Land portion 29Ac, 29Bc, 30Ac, 30Bc Convex round shape portion 35 Die 36 Core 37 Upper punch 38

Lower punch

41, 42 Chamfered convex portion

Claims

Sintered machine parts formed by compressing the raw material powder filled in the powder filling portion formed between the inner diameter surface of the core and the outer diameter surface of the die with the upper punch and the lower punch, and forming the green compact Because
One end surface of the green compact with concave portions formed on both end surfaces is placed on a tray whose mounting surface is a flat surface and sintered, and the entire end surface on the one end surface is sintered. A sintered machine component characterized in that the surface area ratio of the recessed portions is 5 to 50%, and the depth of the recessed portions is 0.2 mm to 1.0 mm.
The sintered machine component according to claim 1, wherein the surface area ratio is 10 to 40%.
The sintered machine part according to claim 1 or 2, wherein the depth of the recess is 0.3 mm to 0.6 mm.
The green compact in which concave portions are formed on both end faces is a disk-shaped body, and the concave portion is formed between the inner peripheral portion and the outer peripheral portion. Item 4. The sintered machine part according to any one of items 3 to 4.
4. The green compact in which concave portions are formed on both end faces is a disk-shaped body, and the concave portion is a concentric ring shape of an axial hole. 2. A sintered machine part according to item 1.
Sintered machine parts formed by compressing the raw material powder filled in the powder filling portion formed between the inner diameter surface of the core and the outer diameter surface of the die with the upper punch and the lower punch, and forming the green compact Because
A key groove is formed on the inner diameter surface of the hole, and is molded by powder metallurgy, and at each opening end of the hole and the key groove, a chamfer forming convex portion provided on the upper punch and a lower portion are formed. A sintered machine part having a chamfered portion having the same shape and the same dimension formed by a chamfering convex portion provided on a punch.
The sintered machine part according to claim 6, wherein the opening end of the chamfered portion is a convex round shape portion.
The chamfered portion includes the convex round shape portion, a taper portion extending from the convex round shape portion to the back side, and a land portion connected to the taper portion. The sintered machine part according to claim 6 or 7, wherein the sintered machine part is a shape part.
A sintered gear formed by powder metallurgy, comprising the sintered machine component according to any one of claims 6 to 8. .
A pulley formed by powder metallurgy, wherein the pulley is constituted by the sintered machine component according to any one of claims 6 to 8.
A coupling formed by a powder metallurgy method, comprising the sintered machine component according to any one of claims 6 to 8.
Manufacture of sintered machine parts that form green compacts by compressing the raw material powder filled in the powder filling part formed between the inner diameter surface of the core and the outer diameter surface of the die with the upper punch and the lower punch A method,
Concave portions are formed on both end faces of the green compact, and sintering is performed with one end face placed on a tray having a flat placing face. A method for producing a sintered machine part, wherein the surface area ratio of the part is 5 to 50% and the depth of the recessed part is 0.2 mm to 1.0 mm.
A powder molding die that compresses the raw material powder filled in the powder filling part formed between the inner diameter surface of the core and the outer diameter surface of the die with an upper punch and a lower punch, and forms a green compact. There,
Forming green compacts with keyways formed on the inner diameter surface of the hole, forming chamfered convex portions on the upper punch and lower punch, respectively, and compressing with the upper punch and lower punch The chamfered portion having the same shape and the same size is formed at each opening end of the hole portion and the key groove of the green compact at each chamfered portion forming convex portion. Mold.
14. The powder molding die according to claim 13, wherein the chamfered convex portions of the upper punch and the lower punch are formed by electric discharge machining.