JP2002295475A - Bearing and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an easily manufacturable bearing capable of supporting a rotary shaft satisfactorily and provide a manufacturing method therefor. SOLUTION: An intermediate body 11 (cylindrical body) is formed in such a way that it has a substantially cylindrical shape by forming metallic minute powders into a predetermined shape and sintering them, a first overhang part 11c overhanging to an inner peripheral side is formed at one end 11a, and an end face of the other end 11b is formed into a flat face. A bearing part is constituted of the overhang part 11c in this intermediate body 11. A second lower punch 25 having a projecting part 26 is pressed against an inner peripheral side of the end face of the other end 11b and is pushed into this end face to form a recessed part 27 communicating with an inner peripheral face of the intermediate body 11 on this end face in a correction process, and a material constituting the vicinity of a bottom face of the recessed part 27 on this end face is pushed out and sticks out to an inner peripheral side due to a pushing-in force of the projecting part 26 to form a second overhang part 11e which is a bearing part on the other end 11b side of the intermediate body 11 in order to manufacture the bearing having the bearing parts at both ends.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing manufactured by, for example, sintering a compacted intermediate body and a method for manufacturing the same.

[0002]

2. Description of the Related Art In general, when a rotating shaft of a small motor or the like is supported by a bearing, it is preferable to widen a longitudinal supporting range of the rotating shaft by the bearing in order to stably support the rotating shaft. On the other hand, in order to reduce frictional resistance during rotation of the rotating shaft, it is preferable to reduce the contact area between the bearing and the rotating shaft. In order to satisfy such contradictory conditions, the inner peripheral surfaces of both end portions of the cylindrical body are provided so as to protrude toward the inner peripheral side from the other portions, and the both end portions are supported by the inner peripheral surface to support the rotating shaft. A bearing having a configuration as a part is used. Since this bearing is in contact with the rotating shaft only at the inner peripheral surfaces of both bearing portions and not at other portions, the contact area with the rotating shaft is reduced. Also,
Since these bearing portions are provided apart from each other, the support area in the longitudinal direction of the rotating shaft can be widened while reducing the contact area with the rotating shaft. Furthermore, in this bearing, since both bearing portions are provided integrally, unlike the case where two bearings are simply provided separately from each other,
The adjustment work for matching the axes of the two bearing portions is not required.

[0003] Such a bearing is manufactured, for example, by cutting off the inner peripheral surface of the other portion of the cylindrical body except for both ends forming the bearing portion by machining, or by powder molding. As a method of manufacturing a bearing by powder molding, there is the following manufacturing method. For example, in a method for manufacturing a sintered bearing material described in Japanese Patent Publication No. H8-6124,
First, as shown in FIG.
After inserting the raw material powder between the core 31 and the mold 32 having the step portion 31c formed between the core 31 and the relatively large-diameter portion 31b, the upper and lower punches 33 and 33a are operated along the core 31 to reduce the pressure. Powder molding is performed to obtain a green compact. In the thus obtained green compact, a relatively long large-diameter inner surface 34a is formed by the relatively large-diameter portion 31b, and a portion formed by the relatively small-diameter portion 31a by the step portion 31c is a small-diameter hole. 34b is formed as a sliding surface. Then, the green compact is subjected to a sintering process to form a sintered body 34. Next, the sintered body 34 is subjected to a sizing process. In this sizing, as shown in FIG. 11B, a sizing core 36a and a guide core 36b having the same diameter as the relatively small diameter portion 31a are used.
The sintered body 34 is loaded toward the narrowed portion 38 of the mold 37, and straightened by a small-diameter lower punch 39b operated along the lower guide core 36b and an upper punch 39a pressed down along the sizing core 36a. The desired product 40 by drawing
And This product 40 has a powder compacted bearing surface 40b formed on one end surface side with a relatively large diameter portion 31b, and has a mold 3 on the other end surface with respect to the sizing core 36a.
7 formed by the drawn portion 38 of FIG.
a is formed.

Another manufacturing method by powder molding is described below. In the manufacturing method of the inner diameter intermediate hollow bearing described in Japanese Patent No. 2762037, the metal powder is filled into a die 41 having an upper portion having a large diameter portion 41a and a lower punch 42 having a guide core 42a at a lower portion. The upper punch 46 having the core 44 is pressed down as shown in FIG. 12A to obtain an intermediate molded body 47 formed by compacting with the step portion 47a formed in the large diameter portion 41a. The intermediate molded body 47 has a large-diameter inner hole 47b and a small-diameter inner hole 47c. Next, the intermediate molded body 47 is set upside down on the lower punch 42b of the sizing die 41b, and is pressed by the sizing upper punch 46b guided by the core 46c while being positioned by the guide core 42c of the lower punch 42b. As a result, as shown in FIG. 12 (b), the step 47a is guided by the guide surface 41c of the die 41b, narrowed down, and pressed into the die 41b. By sintering the intermediate molded body 47 after the correction, shaft contact portions 50 and 51 are formed above and below the hollow portion 49, and a bearing 53 whose outer surface is a straight surface 52 is obtained.

[0005]

However, as described above, when a bearing is manufactured by cutting a cylindrical body, the manufacturing cost is increased because the cutting is troublesome.
Also, a very small bearing could not be manufactured. On the other hand, in the method of manufacturing a bearing by powder molding, FIG.
In the former manufacturing method shown in FIG.
Since one end of 4 is narrowed by straightening, the molding cost is increased and the manufacturing cost of the bearing is increased. Further, since the outer diameter of the bearing is different at both ends, when the bearing is mounted on the bearing housing, the support of the bearing tends to be unstable. On the other hand, in the latter manufacturing method shown in FIG. 12, the outer peripheral surface of the bearing is formed to have substantially the same diameter, so that the bearing can be relatively favorably supported by the bearing housing. However, similarly to the former manufacturing method, since one end of the intermediate molded body 47 is narrowed by straightening, an increase in molding cost was inevitable. In both of the former and the latter manufacturing methods of bearings, it is necessary to use a die having a complicated shape at the stage of forming a sintered body or an intermediate molded body before becoming a product, so that management of a mold and Management of molding conditions and other burdens were heavy.
Furthermore, because of the straightening method of squeezing one end of the sintered body or the intermediate molded body before becoming a product, a certain length is required for the sintered body or the intermediate molded body before becoming a product, and the overall length is short. It has been difficult to manufacture bearings, for example bearings with a total length of 5 mm or less. In addition, there is a concern that a sintered body or an intermediate molded body before being formed into a product having such a shape is likely to be deformed during sintering after powder molding.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a bearing that can favorably support a rotating shaft and that can be easily manufactured, and a method of manufacturing the same. And

[0007]

To achieve the above object, the present invention employs the following means. In the bearing according to the present invention, a bearing portion is formed at an axial end of the cylindrical body, and the bearing portion is provided on the inner peripheral side of an end face at an axial end of the cylindrical body. A concave portion communicating with the inner peripheral surface is formed, and a material forming the vicinity of the bottom surface of the concave portion in the cylindrical body is formed to protrude inward. In the present invention, as described above,
A concave portion communicating with the inner peripheral surface of the cylindrical body is formed on the inner peripheral side of the end surface at the end of the cylindrical body, and the material constituting the vicinity of the bottom surface of the concave portion in the cylindrical body protrudes inward to form a bearing portion. With this configuration, the outer peripheral surface of the bearing can be formed to have substantially the same diameter, and the bearing can be favorably supported by the bearing housing. Since this bearing is obtained by simply processing the end face of the cylindrical body, a cylindrical body having a short overall length can be used as the cylindrical body, and a bearing having a short overall length can be obtained.

Further, in the method of manufacturing a bearing according to the present invention, there is provided a powder forming step of forming a substantially cylindrical powder compact from raw material powder, and sintering the powder compact to produce a substantially cylindrical intermediate. A sintering step, and a method of manufacturing a bearing having a straightening step of forming a bearing by subjecting the intermediate to a corrective finishing process, wherein in the straightening step, the compressive force along the axial direction is applied to the intermediate. Is applied, and one end face or both end faces of the intermediate body is pushed toward the other end face side to form a concave portion communicating with the inner peripheral face of the intermediate body on the inner peripheral side of the end face, and the pushing force causes The material forming the vicinity of the bottom surface of the concave portion is protruded inward at one end surface or both end surfaces of the body, and a protrusion is formed at the end of the intermediate body by the protruding portion formed thereby.

In the present invention, in the straightening step, the end face of the intermediate body is pushed into the other end face side to form a concave portion communicating with the inner peripheral face of the intermediate body on the inner peripheral side of the end face, and the pushing force is applied by the pushing force. A material constituting the vicinity of the bottom surface of the concave portion at one end surface or both end surfaces of the intermediate body is extruded so as to protrude inward, and a projection is formed at the end of the intermediate body by the overhang formed thereby. In other words, since the bearing can be formed by simply applying coining to the end face of the intermediate body, unlike the conventional technique of forming the bearing by drawing, the molding cost is reduced and the manufacturing cost of the bearing is reduced. Can be. Then, since a die having a very simple shape can be used when forming the intermediate, it is possible to reduce the burden of managing the mold, managing the molding conditions, and the like. In addition, since the bearing can be obtained by coining the end face of the intermediate body, an intermediate body having a short overall length can be used as the intermediate body, and a bearing having a short overall length can be easily manufactured. Furthermore, the outer diameter of the bearing can be the same at both ends, and when the bearing is mounted on the bearing housing, the support of the bearing can be stabilized. Moreover, because the intermediate has a very simple shape,
It is hardly deformed during sintering after powder molding, the correction is not troublesome, and the molding cost can be reduced. here,
In the manufacturing method of the bearing according to the present invention, the bearing may be formed at one end of the intermediate body in advance, and the bearing may be formed at the other end at the stage of the correction process. Bearing portions may be formed on both end surfaces of the body at the stage of the correction process.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing the shape of the bearing in the present embodiment. Note that the bearing described in the present embodiment is a porous bearing formed by powder molding a metal fine powder (raw material powder) prepared to a predetermined composition and then sintering the powder. This is an oil-impregnated bearing that is impregnated with oil and lubricates between the rotating shaft and the bearing with lubricating oil that seeps out of the bearing. As shown in FIG. 1, in a bearing 1 of the present embodiment, in a bearing body 2 having a substantially cylindrical shape, a bearing portion 3 whose inner peripheral surface protrudes toward the inner peripheral side of the bearing body 2 is provided at both ends 2 a and 2 b. It is formed. This bearing 1
Is in contact with the rotating shaft only on the inner peripheral surface of both bearings 3 and not in the other portions, so that the contact area with the rotating shaft is reduced. Further, the bearing portions 3 are provided apart from each other, and a wide support range in the longitudinal direction of the rotating shaft is obtained while reducing the contact area with the rotating shaft. Further, in the bearing 1, the two bearing portions 3 have the same inner diameter and are integrally provided with their axes aligned.

The bearing 1 is manufactured by the following manufacturing method. 2, 3, and 4 are diagrams illustrating a manufacturing process of the bearing 1 according to the present embodiment. The bearing 1 is formed by first molding a metal fine powder P into a predetermined shape by powder molding in a powder molding step (see FIG. 2), and then sintering the powder compact 10 obtained thereby in a sintering step. Intermediate body 11 serving as a prototype of bearing body 2
(See FIG. 3 (a)), and further, in the straightening step, the intermediate body 11 is subjected to straightening finishing to form the bearing body 2
(See FIG. 3B).

As shown in FIG. 2, in the powder molding step of the process for producing the intermediate 11, the first die 12 is used.
A stepped round rod-shaped first core rod 13 having a stepped portion 13a formed by reducing the diameter of the tip, and a substantially cylindrical first upper punch 14 having a simple substantially annular shape at the tip end surface. When,
A substantially cylindrical first lower punch 15 having a substantially annular flat top surface is used.

The first die 12 has a hole 12a penetrating in the same dimension in the vertical direction. The first core rod 13 is inserted through the first upper punch 14 and the first lower punch 15. The first upper punch 14 is inserted into the hole 12a of the first die 12 from above, and
This is for compressing the metal fine powder P in 2a.
The first lower punch 15 is inserted from below into the hole 12 a of the first die 12, and
Used for compressing the metal fine powder P in 2a. The first core rod 13, the first upper punch 14, and the first lower punch 15 are each driven by a driving device (not shown) to be movable in the vertical direction of the first die 12.
Here, in the present embodiment, the hole 12a of the first die 12
The inner diameter d1 of the first core rod 13 is 6 mm, the outer diameter d2 of the large diameter portion of the first core rod 13 is 2.1 mm, and the outer diameter d3 of the small diameter portion is 2 mm.

Hereinafter, the production process of the intermediate 11 will be described. In the powder molding step, first, as shown in FIG. 2A, the first lower punch 15 is inserted into the hole 12a of the first die 12 from below, and Into the first core rod 13 from below,
In this state, the metal fine powder P is filled into the hole 12a of the first die 12 from above. Subsequently, the holes 12 of the first die 12
The first upper punch 14 is inserted into the hole a from above, and the first upper punch 14 is further pushed down to compress the metal fine powder P in the hole 12a in the axial direction and downward. At this time, the distance between the step 13a of the first core rod 13 and the distal end surface of the first upper punch 14 is 2 mm (in this embodiment, 2 mm).
Just keep them apart. The distal end surface of the first upper punch 14 and the distal end surface of the first lower punch 15 are separated by a distance D2 (6.5 mm in the present embodiment).

By compressing the metal fine powder P in the first die 12 in this way, as shown in FIG. 2 (b), the metal fine powder P is inserted into the hole 12a of the first die 12. The shape of the peripheral surface, the shape of the outer peripheral surface including the step portion 13a of the first core rod 13, the shape of the distal end surface of the first upper punch 14, and the shape of the distal end surface of the first lower punch 15 are transferred and powdered. Molded body 10
Get. Then, the powder compact 10 is sintered to obtain an intermediate 11. As shown in FIG. 3 (a), the intermediate body 11 manufactured in this manner has a substantially cylindrical shape, and has a first overhang portion 11c formed at one end 11a to overhang the inner peripheral side. The end surface of 11b is formed as a flat surface.

After that, the intermediate body 11 is subjected to a straightening process in a straightening process. At the time of the straightening process, as shown in FIG. A second core rod 23 in the form of a round bar having an outer diameter substantially the same as the inner diameter of the first overhang portion 11c of the body 11, a second upper punch 24 having a simple substantially annular shape at the distal end surface, and a convex portion at the distal end surface. A second lower punch 25 having 26 is used.

The second die 22, like the first die 12, has a hole 22a penetrating with the same size in the vertical direction. The second core rod 23 includes a second upper punch 24
And the second lower punch 25 is inserted. Second upper punch 2
4 is for pressing the intermediate body 11 downward in the hole 22a of the second die 22. The second lower punch 25 has a protruding portion 26 provided in a radially inner circumferential side of the distal end surface thereof so as to protrude annularly along the circumferential direction. These second core rod 23, second upper punch 24, second lower punch 25
Are driven by a driving device (not shown), and are movable in the vertical direction of the second die 22. Here, in the present embodiment, the inner diameter d4 of the second die 22 is 6 mm, which is the same as the inner diameter d1 of the first die 12, and the outer diameter d5 of the second core rod 23 is the first core rod 13
Is 2 mm, which is the same as the outer diameter d3 of the small diameter portion.

The straightening process of the intermediate 11 is performed as follows. First, as shown in FIG. 3A, a second lower punch 25 is inserted into the hole 22a of the second die 22 from below, and a second core rod is inserted into the second lower punch 25 from below. 23, and the intermediate 11 is placed on the convex portion 26 of the second lower punch 25 with the second core rod 23 inserted, and the second upper punch 24 is placed above the intermediate 11. Install. Then, the intermediate body 11 is inserted into the hole 22a of the second die 22 from above with the upper and lower end faces of the intermediate body 11 being supported by the second upper punch 24 and the second lower punch 25, respectively. here,
As shown in FIG. 3A, the intermediate body 11
Hole 22a with one end 11a having
Is inserted into.

Thus, the intermediate 11 is completely inserted into the hole 22a of the second die 22, and the second upper punch 24
At the time when the tip side is also inserted, the lowering of the second core rod 23 and the second lower punch 25 is stopped, and by further pressing down the second upper punch 24 in that state,
A compressive force is applied to the intermediate body 11 in the hole 22a in the axial direction. At this time, the distal end surface of the second upper punch 24 and the distal end surface of the second lower punch 25 are separated by a distance D3 (6 mm in the present embodiment) as shown in FIG. 3B. .

Thus, as shown in FIGS. 3B and 4, the material forming the other end 11b of the intermediate 11 is
The second lower punch 25 is crushed upward by the convex portion 26, and a concave portion 27 communicating with the inner peripheral surface of the intermediate body 11 is formed on the inner peripheral side of this end surface. Then, the material forming the vicinity of the bottom surface of the concave portion 27 at this end face is pushed out by the pushing force of the convex portion 26, protrudes into the intermediate body 11, and is pressed against the outer peripheral surface of the second core rod 23. Thus, the second overhang portion 11e, which is the bearing portion 3 on the other end 11b side of the intermediate body 11, is formed. The material protruding to the inner peripheral side at the other end 11b of the intermediate body 11 forms the second overhang portion 11e, and the shape of the outer peripheral surface of the second core rod 23 is transferred to the inner peripheral surface. Will be.

At the time of this processing, one end 11 of the intermediate body 11 is formed.
The first overhanging portion 11c formed on the a is also plastically deformed,
By transferring the shape of the outer peripheral surface of the second core rod 23 to the inner peripheral surface, the upper bearing portion 3 is also formed. As a result, the first and second overhang portions 1 as both bearing portions 3 are formed.
The inner peripheral surfaces of 1c and 11e are formed in the same diameter and coaxially.
Here, in the present embodiment, the axial width D4 of the inner peripheral surface of the first overhang 11c is 2 mm, and the second overhang 1
The axial width D5 of the inner peripheral surface of 1e is 1.5 mm. As described above, the intermediate body 11 is subjected to a corrective finishing process,
The bearing 1 is obtained by manufacturing the bearing main body 2 having the bearing portions 3 formed at both ends.

In this bearing manufacturing method, as described above, the convex portion 26 of the second lower punch 25 is moved by the axial pressing force of the second upper punch
1b is pressed into the end face to form a concave portion 27, whereby the material constituting the vicinity of the bottom surface of the concave portion 27
Is formed as a second overhanging portion 11e, and a bearing portion 3 overhanging inward is formed at the other end 11b.
That is, the bearing 1 can be obtained by coining the end face of the intermediate body 11.

Therefore, according to the bearing manufacturing method of the present embodiment, in the straightening step, the bearing 1 can be obtained by subjecting the end face of the intermediate body 11 to a finishing finish (coining). As shown in FIG. 12, unlike the prior art in which the bearing portion is provided by drawing, the molding cost is reduced and the manufacturing cost of the bearing 1 can be reduced. In addition, since the bearing 1 is obtained by coining the end face of the intermediate body 11 as described above, the bearing 1 can be applied to a short intermediate body having a short overall length. It can be manufactured easily and reliably. Further, since the outer diameter of the bearing 1 can be the same at both ends, when the bearing 1 is mounted on a bearing housing (not shown), the support of the bearing 1 can be stabilized. Works properly.

In the powder compacting step of the powder compact 10 serving as the prototype of the intermediate body 11, a simple die 12 having holes 12a of the same dimensions over the upper and lower sides is used. Since the die 22 having a simple shape is used, it is possible to reduce management of a mold, management of molding conditions, and other burdens. Moreover, intermediate 11
Since has a simple cylindrical shape, it is not easily deformed at the time of sintering after powder molding, so that it does not take much time for correction, and the molding cost can be reduced.

In the above-described embodiment, an example in which the annular second overhang portion 11e is formed by using the convex portion 26 of the second lower punch 25 as the bearing portion 3 at the other end 11b of the intermediate body 11 is described. However, the present invention is not limited to this. For example, as shown in FIG. 5A, the bearing portion 3 is formed by forming a plurality of second projecting portions 11e inward at intervals in the circumferential direction. It may be configured. In this case, the protrusion 26 provided at the tip of the second lower punch 25 is
As shown in FIG. 5B, the second lower punch 25 is formed so as to protrude at intervals along the circumferential direction of the second lower punch 25, whereby the end face of the other end 11 b of the intermediate body 11 has a circumferential direction. A plurality of recesses 27 will be formed at intervals along. That is, the bearing portion 3 can also be configured by forming the second protrusion 11e inward at a plurality of locations in the bearing 1. Even in such a configuration, since the shape of the outer peripheral surface of the second core rod 23 is transferred to the inner peripheral surface of the second overhang portion 11e, the function as a bearing portion is not inferior. In addition, the size, shape, and arrangement of the protrusions 26 provided on the second lower punch 25 (that is, the size, shape, and arrangement of the recesses 27 formed in the intermediate body 11) are appropriately set, and the By securing a sufficient amount of the inner peripheral portion of the end portion of the body 11 protruding to the inner peripheral side, the second overhang portion 11e can be extended to the inner peripheral side over the entire circumference.

The second overhang portion 11 of the intermediate body 11
The length D5 of the second lower punch 25 is not only different depending on the properties of the metal fine powder P constituting the intermediate body 11.
It is not limited to the present embodiment, but depends on the length and width of the convex portion 26 and the pushing force of the second upper punch 24 applied to the intermediate body 11. What is necessary is just to have a length that can be obtained.

[Second Embodiment] In the above-described embodiment, the bearing 3 is provided by extending only the end face of the other end 11b of the intermediate 11 inward in the process of correcting the intermediate 11. Although an example is shown, in this embodiment, the end faces of both ends 11a and 11b of the intermediate body 11 are similarly protruded inward, so that both bearing portions 3 can be formed simultaneously and similarly. Things.

That is, in the present embodiment, in the powder molding step, as shown in FIG. 6, in addition to the first die 12, the first upper punch 14, and the first lower punch 15, the same A first core rod 130 having a diameter is used.
Then, the metal fine powder P in the hole 12a is compressed by the first upper punch 14 and the first lower punch 15 through which the first core rod 130 is inserted, so that the cylindrical powder compact 1 is formed.
00 is formed. Then, after the powder compact 100 is sintered to form a cylindrical intermediate 110, overhangs 110e are formed at both ends 110a and 110b of the intermediate 110 in a correction process.

In the correction step, as shown in FIG.
The second die 22, the second core rod 230, the second upper punch 240, and the second lower punch 250 are used. In this case, the second core rod 230 is formed of the cylindrical intermediate 110. It is formed in a size smaller than the inner diameter.
Further, the distal end of the second upper punch 240 and the distal end of the second lower punch 250 have convex portions 261 and 262 having the same shape on the inner peripheral side, respectively. The second core rod 230, the second upper punch 240, and the second lower punch 250 are each driven by a driving device (not shown) to be movable in the vertical direction of the second die 22.

Then, the second lower punch 250 and the second core rod 230 are inserted into the hole 22a of the second die 22 from below while the second core rod 230 is inserted through the intermediate body 110. The second upper punch 24 is placed on the convex portion 262 of the second lower punch 250 and in this state,
0 is placed on intermediate 110. Then, with the upper and lower end faces of the intermediate body 110 being supported by the second upper punch 240 and the second lower punch 250, respectively, the second die 2
The intermediate 110 is inserted into the second hole 22a from above. Here, the direction in which the intermediate body 110 is inserted into the hole 22a can be arbitrary.

When the intermediate body 110 is completely inserted as shown in the hole 22a of the second die 22 and the distal end side of the second upper punch 240 is also inserted, the second core rod 230 Then, after the lowering of the second lower punch 250 is stopped, the second upper punch 240 is further pressed down in this state, thereby applying a compressive force along the axial direction to the intermediate body 110 in the hole 22a. As a result, the inner peripheral sides of the end surfaces of both end portions 110a and 110b of the intermediate body 110 are pushed in the axial direction by the convex portions 261 and 262 formed on the distal end surfaces of the second upper punch 240 and the second lower punch 250. Thus, concave portions 27 are formed on both end surfaces of the intermediate body 11 so as to communicate with the inner peripheral side. Then, due to the pushing force of the convex portions 261 and 262, the material forming the vicinity of the bottom surface of the groove 27 on both end surfaces of the intermediate body 110 is extruded and protrudes inward.
As shown in FIG. 8, overhangs 110 e as bearings 3 and 3 are formed simultaneously and substantially in the same shape on 110 b.

Therefore, according to this embodiment, in the powder compacting step, a cylindrical powder compact 100 is formed,
Further, after forming a cylindrical intermediate 110 by a sintering process, the intermediate 110 is subjected to coining in a straightening process, so that both ends 110a of the intermediate 110 are formed.
A bearing 10 having overhangs 110e as bearings 3 and 3 formed at 110b and bearings 3 formed at both ends.
Since 1 can be obtained, basically the same functions and effects as those of the above-described embodiment can be obtained. In addition, the direction in which the intermediate body 110 is inserted into the hole 22a of the second die 22 in the straightening step can be set to an arbitrary direction.
Since it is not necessary to control the direction of the intermediate 110 when coining is performed, coining can be easily performed.

[Third Embodiment] In each of the bearings manufactured by the bearing manufacturing methods described in the above embodiments, the outer peripheral surface supported by the bearing housing is formed as a highly accurate cylindrical surface. However, for example, if a mold used during powder molding or straightening is worn, a difference in outer diameter occurs at both ends of the bearing. Also,
In the bearing manufacturing method according to the first embodiment, the intermediate 11 having the first overhang portion 11c formed at one end 11a side is manufactured by powder-forming the metal fine powder P, and further, the stage of the corrective finishing process is performed. By pressing the convex portion 26 into the end face of the other end 11b of the intermediate 11 to form the concave portion 27, the second overhang portion 11e is also formed on the other end 11b side. The bearing 1 obtained by this method of manufacturing a bearing may have a difference in the outer diameter at both ends because the compression of the material is different at both ends. Such a difference in outer diameter at both ends of the bearing is not a problem if the length of the bearing is not so long, but the longer the length of the bearing, the more likely this difference in outer diameter occurs. As a result, the deflection of the shaft center when mounted on the bearing housing becomes large, and the influence may not be ignored.

Therefore, in the bearing manufacturing method described in each of the above embodiments, after the intermediate body is subjected to the corrective finishing process, the end portion of the intermediate body is further subjected to the drawing process as the secondary corrective processing, thereby completing the end of the intermediate body. By making the portion smaller in diameter than the other portions, as shown in FIG.
3, the bearing 30 having a reduced axial contact area with the bearing housing on the outer peripheral surface of the bearing body 302
1 is obtained (hereafter, the correction finish processing first performed on the intermediate is referred to as primary correction processing, and the intermediate subjected to the primary correction processing is referred to as primary correction body 311). here,
FIG. 9 shows an example in which a primary straightening body manufactured by the bearing manufacturing method described in the first embodiment is used as a primary straightening body serving as an original shape of the bearing 301. As described above, by reducing the axial contact range S with the bearing housing on the outer peripheral surface of the bearing main body 302, a difference in outer diameter at both ends in the axial direction at the contact portion with the bearing housing is less likely to occur. While maintaining the length of the bearing 301 itself (the distance between the bearing portions 3 of the bearing 301), it is possible to reduce the deflection of the shaft center when the bearing 301 is mounted on the bearing housing.

Hereinafter, the details of the secondary straightening process will be described. In the secondary straightening process, as shown in FIG. 10, the lower surface 320b of the inner surface is reduced in diameter with respect to the upper surface 320a, and the upper surface 320a and the lower surface 320b are smoothly connected to form a stepped cylindrical surface. The third die 320, a third core rod 330 having a round bar shape having substantially the same outer diameter as the inner diameter of the first overhang portion 11 c of the primary correction body 311, and a third upper punch 340 having a simple substantially annular shape at the tip end surface , And a third lower punch 350 having a simple substantially annular shape at the tip end surface. The third core rod 330, the third upper punch 340, and the third lower punch 350 are each driven by a driving device (not shown) to be movable in the vertical direction of the third die 320. Here, the third die 320
The inner diameter d6 of the upper part 320a is the same as the inner diameter of the die used for the primary straightening, and the inner diameter d7 of the lower part 320b is
The diameter is reduced by 10 to 15 μm from the inner diameter d6 of 20a. Of course, the outside diameter of the portion of the third upper punch 340 that is inserted into the third die 320 is
The inner diameter d6 of the upper part 320a of the first die 320 is substantially the same as the inner diameter d6 of the lower part 320b of the third die 320. Diameter. The outer diameter d8 of the third core rod 330 is the same as the outer diameter of the core rod used for the primary straightening.

The procedure of the secondary correction processing will be described below.
Here, as an example, a case where the primary straightening body manufactured by the bearing manufacturing method described in the first embodiment is used as the primary straightening body 311 will be described. First, the third lower punch 350 is inserted from below the third die 320, the third core rod 330 is inserted into the third lower punch 350 from below, and the primary straightening body 311 is inserted into the third core rod 330. In the inserted state, it is placed on the tip of the third lower punch 350, and the third upper punch 3 is placed above the primary straightening body 311.
40 is installed. Then, the primary corrector 311 is inserted into the third die 320 from above while the upper and lower end surfaces of the primary corrector 311 are supported by the third upper punch 340 and the third lower punch 350, respectively. Then, the primary straightening body 311 is further moved downward, and the lower end thereof is pressed into the narrower lower portion 320b of the third die 320 by a predetermined amount, thereby drawing the portion. By this drawing, the outer diameter of one end of the primary correction body 311 is reduced by 10 to 15 μm with respect to the other parts. At this time, the distal end surface of the third upper punch 340 and the distal end surface of the third lower punch 350 are the same distance as the distance between the distal end surface of the upper punch and the distal end surface of the lower punch during the primary straightening process. Separated. In this manner, by subjecting one end of the primary straightening body 311 to drawing by secondary straightening, the bearing body 3
02 on the outer circumference of one end 302a
Is obtained.

Here, if the contact area S in the axial direction with the bearing housing on the outer peripheral surface of the bearing 301 is as long as necessary to stably support the bearing 301, the clearance 303 in the axial direction of the bearing 301 is provided. Can be set arbitrarily. The escape 303 is
The intermediate may be formed at the stage of manufacturing the intermediate by powder molding, or may be formed at the time of the primary correction processing, but in this case, the relief 303 is formed by using a punch. Will be formed. Here, the bearing body 3
Since the escape amount of the escape 303 with respect to the outer peripheral surface of the punch 02 is extremely small, the thickness of the portion where the escape 303 is formed in the punch becomes extremely thin, and the life of the punch may be shortened. 303 is preferably formed by secondary straightening using the stepped third die 320 as described above. Further, the direction in which the primary correction body 311 is inserted into the third die 320 may be either direction,
When using the primary straightening body manufactured by the bearing manufacturing method described in the first embodiment as the primary straightening body 311, the side of the primary straightening body 311 on which the first overhang portion 11 c is formed at the stage of powder molding. Is turned downward, a compressive force due to the drawing is applied to this end, and it is possible to balance the compression of the material with respect to the end on the side where the concave portion 27 is formed at the stage of the primary correction processing. it can. Thus, a difference in outer diameter between both ends of the bearing 301 is less likely to occur, so that the support by the bearing housing can be stabilized.

[Fourth Embodiment] Here, in the bearing manufacturing method shown in the third embodiment, the primary straightening body 311 is manufactured by the bearing manufacturing method shown in the first embodiment. When using the primary straightening body, the lower part 320b of the inner surface of the third die 320 is replaced with the upper part 320a.
Instead of reducing the diameter, projections along the axis may be formed at a plurality of locations in the circumferential direction in the lower portion 320b, and the secondary straightening process may be performed on the primary straightening body 311 using this die. In the bearing obtained by this, the bearing body 3
At one end 302a of 02, instead of the escape 303, grooves along the axial direction are formed at a plurality of locations in the circumferential direction. At the time of this secondary straightening, a compressive force is applied to the end of the primary straightening body 311 on the side where the first overhang portion 11c is formed, and the recess 27 is formed at the stage of the primary straightening. Since the balance of the compression of the material is balanced with respect to the end on the other side, a difference in outer diameter between both ends of the bearing is less likely to occur, and the support by the bearing housing can be stabilized.

[0039]

As described above, according to the bearing according to the present invention, a recess communicating with the inner peripheral surface of the cylindrical body is formed on the inner peripheral side of the end surface at the end of the cylindrical body, and the concave portion is formed in the cylindrical body. Since the bearing portion is formed by projecting the material forming the vicinity of the bottom surface inward to form the bearing portion, the outer peripheral surface of the bearing can be formed to have substantially the same diameter, so that the bearing can be favorably supported by the bearing housing. Since this bearing is obtained by simply processing the end face of the cylindrical body, a short-length bearing can be obtained by using a cylindrical body having a short overall length as the cylindrical body.

According to the method of manufacturing a bearing according to the present invention, in the straightening step, the end face of the intermediate body is pushed into the other end face side, and the concave part communicating with the inner peripheral face of the intermediate body is formed on the inner peripheral side of the end face. Along with the pushing force,
A material constituting the vicinity of the bottom surface of the concave portion at one end surface or both end surfaces of the intermediate body is extruded so as to protrude inward, and a projection is formed at the end of the intermediate body by the overhang formed thereby. In other words, the bearing can be formed simply by applying coining to the end face of the intermediate body, so that unlike the conventional technique of forming the bearing by drawing, the molding cost is reduced and the manufacturing cost of the bearing is reduced. Can be. Then, since a die having a very simple shape can be used when forming the intermediate, it is possible to reduce the burden of managing the mold, managing the molding conditions, and the like. Further, since the bearing can be obtained by performing the corrective finishing process on the end face of the intermediate body, an intermediate body having a short overall length can be used as the intermediate body, and a bearing having a short overall length can be easily manufactured. Furthermore, the outer diameter of the bearing can be the same at both ends, and when the bearing is mounted on the bearing housing, the support of the bearing can be stabilized. Moreover, since the intermediate has a very simple shape, it is hardly deformed at the time of sintering after powder molding, so that the correction is not troublesome and the molding cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a final shape of a bearing according to a first embodiment of the present invention.

FIG. 2 is a view showing a powder molding step of an intermediate serving as a prototype of the bearing in the manufacturing steps of the bearing according to the first embodiment of the present invention.

FIG. 3 is a view showing an intermediate body correcting step in the bearing manufacturing steps according to the first embodiment of the present invention.

FIG. 4 is a longitudinal sectional view showing an intermediate body correcting step in the bearing manufacturing steps according to the first embodiment of the present invention.

5A is a plan view showing another example of the shape of the bearing according to the first embodiment of the present invention, and FIG. 5B is a perspective view showing the shape of a lower punch used in manufacturing the bearing. FIG.

FIG. 6 is a view illustrating a powder molding step of an intermediate used as a bearing original form in a bearing manufacturing process according to the second embodiment of the present invention.

FIG. 7 is a view showing a process of correcting an intermediate in a process of manufacturing a bearing according to the second embodiment of the present invention.

FIG. 8 is a longitudinal sectional view showing a final shape of a bearing according to a second embodiment of the present invention.

FIG. 9 is a longitudinal sectional view showing a shape of a bearing according to a third embodiment of the present invention.

FIG. 10 is a plan view showing a secondary correction process of an intermediate in a bearing manufacturing process according to a third embodiment of the present invention.

FIG. 11 is a view showing a method for manufacturing a bearing using conventional powder molding.

FIG. 12 is a view showing a method for manufacturing a bearing using conventional powder molding.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1, 101, 301 Bearing 3 Bearing part 10, 100 Powder compact 11, 110 Intermediate body (cylindrical body) 12 First die 12a, 22a Hole 13, 130 First core rod 14 First upper punch 15 First Lower punch 22 Second die 23, 230 Second core rod 24, 240 Second upper punch 25, 250 Second lower punch 26, 261, 26
2 Convex part P Fine metal powder (raw powder)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4E087 BA23 DB13 HA41 4K018 CA00 DA00 FA02 HA03 KA03 KA22

Claims (2)

[Claims] 1. A bearing portion is formed at an axial end of a cylindrical body, and the bearing portion is formed on an inner peripheral surface of the cylindrical body on an inner peripheral side of an end surface at an axial end of the cylindrical body. A recess which is formed in the cylindrical body so as to protrude inward from a material constituting the vicinity of the bottom surface of the recess. 2. A powder molding step of forming a substantially cylindrical powder compact from raw material powder, a sintering step of sintering the powder compact to form a substantially cylindrical intermediate, A straightening step of forming a bearing by performing a straightening process, wherein in the straightening step, a compressive force is applied to the intermediate body in an axial direction, and one end face of the intermediate body or The two end faces are pushed into the other end face side to form a recess on the inner peripheral side of the end face that communicates with the inner peripheral face of the intermediate body, and the pushing force causes the recess to be formed on one end face or both end faces of the intermediate body. A method for manufacturing a bearing, wherein a material constituting the vicinity of the bottom surface is protruded inward, and a protruding portion is formed to form a bearing portion at an end of the intermediate body.