JP2005205498A - Method for producing cylindrical part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce a cylindrical part having excellent surface roughness on the inner peripheral surface of a through hole and high surface precision on the end surfaces in the axial direction, with working of mainly forging-work. <P>SOLUTION: This method for producing the cylindrical part is performed as the followings, that is, projecting parts 56, 58 protruded in the axial direction are formed in a coining-forging process (figure (c)); blind holes 90, 92 are formed in an extrusion-forging process (figure (d)); a through hole 12 is formed by punching out the bottom part 112 of the blind holes 90, 92 with a blank-punch in a punch-out process (figure (e)); and burnishing is applied to the inner peripheral surface of the through hole 12 by pushing a burnisher from the reverse side to the inserting side of the blank-punch in a surface-finishing process (figure (f)) and also, the tip end parts of the projecting parts 56, 58 are plastically deformed by compressing from the axial direction to obtain the dimensional precision in the part. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a cylindrical part, and more particularly to a technique for manufacturing mainly a forging process.

  For example, Patent Document 1 discloses that a helical gear is manufactured by a process mainly including forging. However, since it is necessary to forcibly rotate the punch along the tooth trace of the helical gear, the movable part There are many and the structure becomes complicated. Further, since the tooth portion of the helical gear is forcibly formed by forging, the material flow is not sufficiently performed, and there is a possibility that sagging or chipping occurs. In addition, gear forming by hermetic forging is performed, but depending on the tooth shape, high pressure must be applied to fill the material sufficiently, and there is a problem with the durability and life of the mold It was.

On the other hand, because of the good material yield, which is the merit of forging, and the good machining accuracy, which is the merit of cutting, to form a tooth by cutting the cylindrical material preformed by forging Can be considered. In this case, as a method of manufacturing a cylindrical material by forging, for example, as shown in FIG. 11, first, in (a), a rough material 200 having a predetermined length is cut out from a cylindrical round bar, and (b ) Is forged from the axial direction so as to have an outer diameter that is substantially equal to the outer diameter of the target cylindrical part 202 (see (d)). Further, in (c), a bottomed hole 206 having a diameter substantially equal to the through-hole 204 to be formed is formed by extrusion forging, and in (d), the bottom portion 208 of the bottomed hole 206 is punched by a punching punch. A cylindrical part 202 is obtained. 11 is a center line, and the left half is a cross-sectional view.
Japanese Patent Application Laid-Open No. 8-206772

  However, in such a manufacturing method of the cylindrical part 202, burrs due to shear remain in the portion of the inner peripheral surface of the through hole 204 where the bottom 208 is present, and sufficient surface accuracy (surface roughness, etc.) is obtained. There was a problem that it was not possible. Further, the surface accuracy of the end surface 210 in the axial direction (perpendicularity, flatness, etc. with respect to the center line) is not sufficiently obtained, and the processing accuracy is impaired when gear cutting or the like is performed using the end surface 210 as a reference surface after that. There was another problem. That is, in the extrusion forging of (c), when the punch is pushed into the bottomed hole 206, the material of the portion flows in the axial direction, but sufficient surface accuracy is obtained such that it is not necessarily uniform around the center line. It is not possible. After punching of (d), it is conceivable to increase the accuracy of the end surface 210 by compressing in the axial direction while restraining the outer peripheral surface and the inner peripheral surface. Therefore, it is difficult to obtain high surface accuracy.

  The present invention has been made against the background of the above circumstances, and a first object of the present invention is to make it possible to manufacture a cylindrical part whose surface roughness of the inner peripheral surface of the through hole is excellent mainly by forging. Thus, the second object is to improve the surface accuracy of the end surface in the axial direction in addition to the surface roughness of the inner peripheral surface of the through hole.

  In order to achieve such an object, the first invention is a method of manufacturing a metal cylindrical part having a through hole having a circular cross section, and (a) a predetermined rough material having a diameter substantially equal to that of the through hole. A bottomed hole processing step for forming the bottomed hole by forging, and (b) a punching step of inserting a punching punch into the bottomed hole and punching the bottom to form the through hole, and (c) the punching It has a surface finishing process in which a burnishing tool is pushed into the through hole from the side opposite to the punch insertion side and the inner peripheral surface of the through hole is burnished.

  The second invention is a method for manufacturing a metal cylindrical part having a through-hole having a circular cross section at the center, wherein (a) a predetermined rough material is forged so that the outer diameter is the cylinder. The cylindrical part has a columnar shape that is substantially equal to the outer diameter of the cylindrical part and whose axial length is shorter than the axial length of the cylindrical part, and is at least one end face in the axial direction and outside the through hole. A first intermediate product manufacturing step for manufacturing a first intermediate product, in which a ring-shaped convex portion protruding in the axial direction is provided in a part of the portion substantially concentrically with the cylindrical center line; (b) By constraining the outer peripheral surface of the first intermediate product and forming a bottomed hole having a diameter substantially equal to the through hole at the center of the first intermediate product by forging, the axial length is the cylindrical part. A second intermediate product manufacturing process for manufacturing a second intermediate product substantially equal to the axial length of A third intermediate product manufacturing step of manufacturing a cylindrical third intermediate product by inserting a punch into the bottomed hole of the second intermediate product to punch out the bottom of the bottomed hole to form the through hole. And (d) compressing the third intermediate product from the axial direction while preventing deformation of the outer peripheral surface and the inner peripheral surface of the third intermediate product, thereby forming the tip surface of the annular convex portion into a predetermined shape. And a surface finishing step of pressing the burnishing tool into the through hole from the side opposite to the insertion side of the punching punch and burnishing the inner peripheral surface of the through hole.

  In the first invention, after a bottomed hole is formed by forging, when a through hole is formed by punching the bottom of the bottomed hole with a punch, a burnishing tool is pushed in from the side opposite to the insertion side of the punch. Since the inner peripheral surface of the through hole is burnished, burrs formed when punching with a punching punch are crushed by burnishing, and high surface accuracy (surface roughness, etc.) is obtained. In particular, the burnishing tool is pushed in from the side opposite to the insertion side of the punching punch, so that the burr is pushed back so that it is pressed against the broken part of the inner peripheral surface, that is, the bottom part of the bottomed hole broken by the punching punch. Accuracy is obtained. In other words, when the burnishing tool is pushed in from the same direction as the punching punch, the burr is further stretched and is only pushed against the inner peripheral surface of the bottomed hole formed by the bottomed hole processing, and the portion is built up. Therefore, high surface accuracy is not necessarily obtained. Since the burr is a metal structure that has been shredded by a punch, the burr is not completely removed even if the burnishing tool is moved in the same direction as its pulling direction, that is, the insertion direction of the punch. It is crimped to the peripheral surface.

  The second invention substantially corresponds to one embodiment of the first invention, and the second intermediate product manufacturing process and the third intermediate product manufacturing process correspond to a bottomed hole machining process and a punching process, respectively, Is formed with high surface accuracy (surface roughness, etc.). In addition, a ring-shaped convex portion is provided on a part of the portion that is at least one end face in the axial direction and outside the through hole in the first intermediate product manufacturing step, and the second intermediate product manufacturing step and the third intermediate product are provided. After the through-hole is provided in the product manufacturing process, the surface finish process is compressed from the axial direction while preventing deformation of the outer peripheral surface and the inner peripheral surface, so that the tip surface of the convex portion is accurately shaped into a predetermined shape. The tip surface of the convex portion is formed with high surface accuracy (eg, perpendicularity or flatness with respect to the axis). That is, since accuracy is not necessarily required for portions other than the tip end surface of the convex portion of the end surface, a gap can be provided between the mold and the metal flow receiving tray accompanying compression, and the outer peripheral surface and inner peripheral surface can be provided. Regardless of restraint or the like, the tip surface of the convex portion can be reliably plastically deformed by compression, and high surface accuracy can be obtained. As a result, for example, it is possible to perform gear cutting processing in a subsequent process with high accuracy using the tip surface of the convex portion as a reference surface.

  On the other hand, since the convex portion is formed in a cylindrical shape, the mold structure is easily configured as compared with the case where the convex portion is formed after the through hole is formed. Further, in the second intermediate product manufacturing process, the metal in the bottomed hole portion is caused to flow in the axial direction. Therefore, when the bottomed hole is formed from the end surface side where the convex portion is provided, the end surface shape including the convex portion is formed. However, since the outer diameter of the first intermediate product is maintained, the end surface on the outer peripheral side of the bottomed hole is simply pushed in the axial direction, and the protrusion is greatly deformed so that the convex portion is not understood. Rather, in the surface finishing process, the tip end surface of the convex portion is reliably plastically deformed over the entire circumference, and the accuracy is obtained.

  The present invention is preferably applied to the manufacture of cylindrical parts used as gear coarse materials such as helical gears, but can also be applied to the manufacture of cylindrical parts other than gear coarse materials.

  The tip surface of the convex portion provided on the end surface is generally a flat surface perpendicular to the center line, but may be inclined by a predetermined angle from a plane perpendicular to the center line. It is appropriately set according to the usage form of the cylindrical part.

  In the second invention, the convex portion is provided before the through hole is formed, and the accuracy of the tip end surface of the convex portion is determined after the through hole is formed. After forming the protrusions, the protrusions may be provided by forging (such as coining) or other processes, and then the protrusions may be compressed to increase the accuracy of the tip surface.

  Although only one of the end surfaces may be provided as the convex portion, it is desirable to provide the both end surfaces for ease of subsequent handling. Further, the convex portion is provided in a part of the end face in the product state (cylindrical part), that is, on the inner peripheral side, the outer peripheral side, or the intermediate position of the annular end face. In some cases, it is desirable to provide it on the inner peripheral part that is not related to the teeth. It is determined appropriately according to the above.

  The first intermediate product manufacturing process includes, for example, (a) a cutting step of cutting out a columnar coarse material from a round bar with an outer diameter smaller than the outer diameter of the cylindrical part, and (b) an outer diameter dimension of the cylindrical part. A swaging forging step of swaging the columnar coarse material in the axial direction so that the axial length is substantially equal to the outer diameter and shorter than the axial length of the cylindrical part; and (c) a subsequent coining process. It is desirable to have an indentation forging process in which a convex part is formed on the end face by, for example. That is, a columnar coarse material having a columnar shape whose outer diameter is substantially equal to the outer diameter of the cylindrical component and whose axial length is shorter than the axial length of the cylindrical component is cut out from a round bar or the like. It is also possible to prepare a convex portion on the end face of the cylindrical coarse material by forging (such as coining), but there is strain on the cut surface and the metal structure (metal flow) is cut. This is not preferable because a convex portion is provided on the cut surface. A round bar is generally used for forging because the metal flow is generally aligned in the axial direction.

  The bottomed hole provided in the first intermediate product in the second intermediate product manufacturing process is preferably provided from both end surfaces of the first intermediate product, but it is not necessarily one of the end surfaces (the end surface provided with the convex portion). ) May be formed only from the bottom. The bottomed hole processing step of the first invention is the same, and it is desirable to form the bottomed hole from both sides of the portion where the through hole is to be formed, but the bottomed hole may be formed from only one surface. . Also in the bottomed hole machining step of the first invention, it is desirable to forge the bottomed hole by constraining the outer peripheral surface in order to form a highly accurate through-hole. It is not a requirement.

  When the tip of the convex part is compressed by compression forging or the like to obtain accuracy, it is desirable to constrain with a constraining die to prevent deformation of the outer peripheral surface and inner peripheral surface of the cylindrical part. When there is no risk of deformation of the outer peripheral surface or inner peripheral surface due to plastic deformation due to compression of the convex portion, such as when the amount of compressive deformation of the convex portion is small or the convex portion is formed at an intermediate position between the inner and outer peripheral surfaces It is not always necessary to constrain those surfaces. The term “while preventing deformation” in the second aspect of the invention refers to preventing deformation by restraining with a constraining die or the like when deforming along with compression forging, but is not necessarily special when there is no fear of deformation during compression forging. There is no need to provide the restraining means, and it is only necessary to provide the restraining means as necessary so as not to be deformed.

  In the surface finishing process of the second invention, for example, the burnishing tool is pushed into the through hole for burnishing, and the inner peripheral surface is constrained by the burnishing tool and compressed from the axial direction to increase the accuracy of the tip surface of the convex portion. However, it is also possible to perform the burnishing of the through hole with a burnishing tool and the accuracy of the front end surface of the convex portion in different pressing processes. The restriction of the inner peripheral surface by the burnishing tool is particularly effective when a convex portion is formed on the inner peripheral side portion of the end surface.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram illustrating a procedure for manufacturing a cylindrical part 10 according to the method of the present invention. The cylindrical part 10 is a metal cylindrical part having a through-hole 12 having a circular cross section at the center, and annular ends projecting in the axial direction toward the inner peripheral side on both end faces 14 and 16 respectively. Shaped convex portions 14a and 16a are provided, and tip surfaces of the convex portions 14a and 16a are flat surfaces perpendicular to the center line. This cylindrical part 10 is a coarse material of an external gear such as a helical gear, and teeth are formed by cutting on the outer peripheral side of the convex portions 14a and 16a in the subsequent process. 14a or 16a is used as a reference plane. All the dashed-dotted lines in each of the drawings (a) to (f) in FIG. 1 represent the center line, and the left half of the center line is a cross-sectional view.

  FIG. 1A shows a cutting step, in which a round bar having an outer diameter smaller than the outer diameter of the target cylindrical part 10 is cut to a predetermined length to prepare a cylindrical coarse member 20. The round bar material is obtained by drawing or the like, and the metal flow is aligned in the axial direction, and the columnar coarse material 20 is the same, but strain at the time of cutting remains on both end faces 22 and 24. . In the present embodiment, cutting is performed by press shearing, and there is distortion due to shear.

  FIG. 1B shows a swaging forging step, in which the columnar coarse material 20 is swept in the axial direction, so that the outer diameter is substantially equal to the outer diameter of the cylindrical component 10 and the axial length is the same. A substantially cylindrical intermediate product 30 shorter than the axial length of the cylindrical part 10 is manufactured. The forging device 32 shown in FIGS. 2 and 3 is an example of a forging device that performs upset forging shown in FIG. 1B. FIG. 2 shows that the columnar coarse material 20 is substantially vertical on the lower die 34 by a conveying device (not shown). Is positioned with the presser punch 36. The presser punch 36 is urged downward by a spring 38. The cylindrical coarse member 20 is positioned and held on the lower die 34 according to the urging force of the spring 38, while the upper die 40 is lowered. When the sliding member 44 reaches the upper moving end by being relatively pushed into the accommodation hole 42, the lower end surface of the presser punch 36 is substantially matched with the forming surface (lower end surface) of the forming punch 46. Then, when the upper die 40 is further lowered in this state, the cylindrical coarse material 20 is disposed on the presser punch 36, the forming punch 46, the lower die 34, and the lower die 34 as shown in FIG. In the substantially sealed space surrounded by the ring die 48, the intermediate product 30 is compressed in the axial direction. The inner diameter of the ring die 48 is substantially equal to the outer diameter of the cylindrical part 10. A slight gap exists between the molding punch 46 and the ring die 48 at the bottom dead center, and a knockout pin 50 is disposed at the center of the lower die 34.

  By performing upset forging in this manner, distortion generated during cutting is corrected, and the weight balance around the axis is improved. In addition, the lower surface of the inner wall surface of the ring die 48 is provided with an inclined surface (tapered surface) so that the diameter dimension gradually decreases, and the outer peripheral surface 54 on the one end 52 side of the intermediate product 30 is an inclined surface. The taper surface has a slightly smaller diameter as the end portion 52 is approached.

  FIG. 1C shows a coining forging step, in which both end surfaces of the intermediate product 30 are subjected to coining, so that a part of the portion outside the through hole 12, specifically the convex portion 14 a. 16a, an intermediate product 60 is produced in which annular-shaped convex portions 56, 58 projecting in the axial direction are provided substantially concentrically with the center line on the inner peripheral side portion that continues to the through hole 12 so as to correspond to 16a. . The convex portions 56 and 58 have substantially the same shape with the same width dimension and protruding dimension, and the protruding dimension is about 0.55 mm. The forging device 62 shown in FIGS. 4 and 5 is an example of a forging device that performs the coining forging shown in FIG. 1 (c). FIG. 4 shows that the intermediate product 30 is disposed in the die 64 by a conveying device (not shown), FIG. 5 shows a state in which the forging is performed by the die 64 and the punch 68 and the intermediate product 60 having the convex portions 56 and 58 is formed. The intermediate product 30 is arranged in an upside down posture so that the end 52 side, that is, the side on which the tapered outer peripheral surface 54 is formed, is upward, and when the intermediate product 30 is pressed by the punch 68 as shown in FIG. The coarse material is prevented from overflowing from between the opening of the die 64 and the punch 68.

  The presser punch 66 is urged downward by a spring 70, and positions and fixes the intermediate product 30 according to the urging force of the spring 70, while the upper die 72 is lowered and is relatively moved into the accommodation hole 74. When the sliding member 76 reaches the upper moving end, the lower end surface of the presser punch 66 is substantially matched with the lower end surface of the first ring punch 78. The presser punch 66 has an outer diameter dimension substantially equal to the inner diameter of the through-hole 12, that is, the inner diameter of the convex part 56, and the inner diameter dimension of the first ring punch 78 is substantially equal to the outer diameter dimension of the convex part 56. The second ring punch 80 is disposed so that the lower end surface is recessed by the protruding dimension of the convex portion 56. The presser punch 66, the first ring punch 78, and the second ring punch 80 constitute a punch 68.

  The die 64 includes a knockout pin 82, a first ring die 84, a second ring die 86, and an outer peripheral surface constraining die 88. The knockout pin 82 has an outer diameter dimension substantially equal to the inner diameter of the through hole 12, that is, the inner diameter of the convex portion 58, and the inner diameter dimension of the first ring die 84 is substantially equal to the outer diameter dimension of the convex portion 58. The second ring die 86 is disposed such that the upper end surface is recessed by the protruding dimension of the convex portion 58. The outer peripheral surface constraining die 88 is disposed on the first ring die 84, and the inner diameter thereof is substantially equal to the outer diameter of the cylindrical component 10, that is, the outer diameter of the intermediate product 30, and the intermediate product. Indentation forging is performed in a state in which 30 is positioned concentrically and the outer peripheral surface is constrained.

  In this embodiment, the cutting process shown in FIG. 1 (a), the upset forging process shown in FIG. 1 (b), and the coining forging process shown in FIG. 1 (c) correspond to the first intermediate product manufacturing process of the second invention. The intermediate product 60 corresponds to the first intermediate product.

  FIG. 1 (d) shows an extrusion forging process, in which the outer peripheral surface 60f of the intermediate product 60 is constrained, and the center of both end surfaces, that is, the inner portions of the convex portions 56 and 58 have a bottomed diameter of the same diameter as the through hole 12. By forming the holes 90 and 92, an intermediate product 94 having an axial length substantially equal to the axial length of the cylindrical part 10 is manufactured. A forging device 96 in FIG. 6 is an example of a forging device that performs the extrusion forging in FIG. 1 (d), and an intermediate product 60 that has bottomed holes 90, 92 that is subjected to extrusion forging by the punch 98 and the die 100 to the intermediate product 60. 94. The extrusion forging process of FIG. 1 (d) is a second intermediate product manufacturing process of the second invention and corresponds to the bottomed hole machining process of the first invention, and the intermediate product 94 corresponds to the second intermediate product.

  The punch 98 includes a center punch 102 having an outer diameter substantially equal to that of the through hole 12 and a ring punch 104 disposed on the outer peripheral side thereof. A recess corresponding to the convex portion 56 is formed on the inner peripheral side of the ring punch 104. Is provided so that the convex portion 56 of the intermediate product 60 is maintained in a substantially unchanged shape. The center punch 102 protrudes larger than the protruding dimension of the convex portion 56 in the intermediate product 60, thereby forming a bottomed hole 90. The die 100 includes a knockout pin 106 having an outer diameter equal to that of the through hole 12, a ring die 108 having a width dimension equal to the width dimension of the convex portion 58, and an outer diameter of the cylindrical part 10. The outer peripheral surface constraining die 110 is equal in size to the outer diameter of the intermediate product 60. The knockout pin 106 protrudes upward from the upper end surface of the ring die 108 sufficiently larger than the protruding dimension of the convex portion 58, and the punch 98 is lowered and the intermediate product 60 is pressed against the knockout pin 106. The knockout pin 106 bites into the intermediate product 60 and the portion of the coarse material is caused to flow into the annular space between the knockout pin 106 and the outer peripheral surface restraining die 110, thereby forming a bottomed hole 92 deeper than the bottomed hole 90. In addition, an intermediate product 94 having an axial length substantially equal to the axial length of the cylindrical part 10 is obtained. Although the rough material of the bottomed hole 90 portion is caused to flow downward in the axial direction, the outer diameter size of the intermediate product 60 is maintained by the outer peripheral surface constraining die 110, and therefore the convex portion 58 and the end surface outside it are simply shafts. Only by being pushed downward in the direction, the shape of the convex portion 58 when it is the intermediate product 60 is maintained as it is. Further, the intermediate product 60 is positioned and held concentrically by being inserted into the outer peripheral surface restraining die 110. A slight gap remains between the lower end portion of the molded intermediate product 94, strictly speaking, the convex portion 58 and the upper end surface of the ring die 108.

  FIG. 1 (e) shows a punching process, in which a punching punch is inserted into one bottomed hole 92 of the intermediate product 94, thereby punching out the bottom 112 existing between the bottomed holes 90 and 92, and the through hole. 12 is formed, and a cylindrical intermediate product 114 is manufactured. A press machine 116 in FIG. 7 is an example of a press machine that performs the punching process (piercing process) in FIG. 1 (e), and the bottom 112 of the intermediate product 94 is punched out by a cylindrical presser punch 118 and a cylindrical punching punch 120. The intermediate product 114 having the through hole 12 is formed. The punching process of FIG. 1 (e) corresponds to the punching process of the first invention in the third intermediate product manufacturing process of the second invention, and the intermediate product 114 corresponds to the third intermediate product.

  The lower end surface of the presser punch 118 has an outer diameter that is the same as or slightly smaller than the outer diameter of the intermediate product 94, and an inner diameter that is the same as or slightly larger than the inner diameter of the convex portion 56, and corresponds to the convex portion 56. A concave portion is provided to maintain the shape of the convex portion 56. The upper end surface of the punching punch 120 is slightly smaller in outer diameter than the inner diameter of the bottomed hole 92, and a shearing blade is provided on the outer peripheral edge thereof, and the intermediate product 94 is pressed downward by the presser punch 118. Accordingly, the punching punch 120 is relatively inserted into the bottomed hole 92, and the bottom 112 is punched upward by a shearing blade. A positioning die 122 having an inner diameter approximately equal to the outer diameter of the intermediate product 94 is disposed concentrically around the punching punch 120 so that the intermediate product 94 is positioned concentrically. In addition, the punched bottom portion 112 is sequentially pushed upward in the cylinder of the presser punch 118 as the new bottom portion 112 is punched upward as the punching process is repeated, and discharged from the discharge hole 124 to the outside. Is done.

  Here, on the inner peripheral surface of the through hole 12 of the intermediate product 114, a minute step 126 remains in the portion where the bottom 112 is present. FIG. 9A is a diagram showing the metal flow F in a cross section of the intermediate product 114 in a simplified manner. The metal flow F is compressed at the bottom 112 portion and is broken by punching the bottom 112 by the punching process. At the same time, the broken portion of the metal flow F remains in the through hole 12 as a burr and forms a step 126. FIG. 9B is an enlarged view of the vicinity of the step (burr) 126. When the bottom 112 is punched upward by the punching punch 120, the metal flow F is shredded and remains in an upwardly inclined state. .

  FIG. 1 (f) is a surface finishing step, in which a burnishing tool is pushed into the through hole 12 from the side opposite to the insertion side of the punching punch 120, and the inner peripheral surface of the through hole 12 is burnished. The intermediate product 114 is compressed from the axial direction while restraining the outer peripheral surface and the inner peripheral surface of the product 114, and the tip surfaces of the convex portions 56 and 58 are brought into a predetermined shape. The forging device 130 of FIG. 8 is an example of a forging device that performs the surface finishing of FIG. 1 (f), and an intermediate product 114 that is disposed upside down in the die 132 so that the convex portion 56 side is directed downward, By being pressed downward by the cylindrical presser punch 134, the columnar burnishing tool 136 is pushed into the through hole 12 from the convex portion 56 side, and the inner peripheral surface of the through hole 12 is burnished. By compressing from the axial direction while restraining the outer peripheral surface with the outer peripheral surface restraining die 138 while constraining the inner peripheral surface with the burnishing tool 136, the accuracy of the tip surfaces of the convex portions 56 and 58 on both end surfaces is increased once. The target cylindrical part 10 is obtained in the pressing process. The surface finishing process of FIG. 1 (f) is the surface finishing process of the first invention and the second invention.

  The lower end surface of the press punch 134 has a depth that is substantially the same as the outer diameter of the intermediate product 114, the inner diameter is substantially the same as the inner diameter of the bottomed hole 12, and is slightly smaller than the protruding dimension of the convex portion 58. The concave portion is provided on the inner peripheral side corresponding to the convex portion 58, and the tip of the convex portion 58 is plastically deformed by pressing the intermediate product 114 downward and compressing, and the lower end surface of the presser punch 134. The convex portion 14a having a shape corresponding to is forged. The projecting dimension of the convex portion 14 a is about 0.50 mm, and is compressed by about 0.05 mm compared to the convex portion 58. The burnishing tool 136 has an outer diameter dimension substantially equal to the inner diameter of the through hole 12 and burnishes the inner peripheral surface by being pushed into the through hole 12, and from the axial direction while being pushed into the through hole 12. When compression forging is performed, the inner peripheral surface of the intermediate product 114 is restrained. Around the burnishing tool 136, a first ring die 140 having an inner diameter dimension substantially equal to the outer diameter dimension of the convex portion 56 is disposed, and the upper end surface of the first ring die 140 is a projection dimension of the convex portion 56 therebetween. The second ring die 142 is disposed so as to be lower than the first ring die 140 by a smaller predetermined dimension. When the intermediate product 114 is pressed downward by the presser punch 134, the tip of the convex portion 56 is second. The convex portion 16 a having a tip surface corresponding to the tip surface shape of the second ring die 142 is forged by being brought into contact with the ring die 142 and plastically deformed. The outer peripheral surface restraining die 138 is disposed on the first ring die 140, and the inner diameter thereof is equal to the outer diameter of the cylindrical part 10, that is, the outer diameter of the intermediate article 114. And forging are performed in a state where the outer peripheral surface is constrained.

  Here, the burnishing tool 136 is pushed into the through-hole 12 from the upper side to the lower side in FIG. 9B on the side opposite to the insertion side of the punching punch 120, that is, the end side having the convex portion 56. Therefore, the burrs are pressed back against the fracture portion of the inner peripheral surface, that is, the cut portion of the bottom portion 112 broken by the punching punch 120, and the step 126 is satisfactorily eliminated and high surface accuracy (surface roughness) is obtained. can get. That is, when the burnishing tool 136 is pushed in from the same direction as the punching punch 120 (the lower side in FIG. 9B), the burr is further extended upward, and the through hole 12 (strictly, the bottomed hole 90 portion) Just by being pressed against the inner peripheral surface, the portion is built up, and high surface accuracy is not necessarily obtained. Since the burr is formed by cutting the metal flow F by the punching punch 120, the burr is completely removed even if the burnishing tool 136 is moved in the same direction as the pulling direction, that is, the insertion direction of the punching punch 120. No, it is crimped to the inner peripheral surface.

  On the other hand, in a state where the intermediate product 114 is compression-forged between the press punch 134 and the second ring die 142, that is, in a state where it is formed into the cylindrical part 10, the cylindrical coarse material 10 and the first ring die 140 As shown in FIG. 10, a slight gap remains between the upper end surface and the tip of the convex portion 56 is reliably plastic over the entire circumference regardless of the restraint of the outer peripheral surface and the inner peripheral surface. The second ring die 142 is deformed and formed into a surface shape corresponding to the upper end surface of the second ring die 142 with high accuracy. Accordingly, the tip surfaces of the convex portions 14a and 16a of the both end faces 14 and 16 of the cylindrical part 10 are both made high with high surface accuracy by compression forging in the surface finishing process of FIG. 1 (f). Molded with high accuracy on a flat surface perpendicular to the center line. The recesses on the upper end surface of the second ring die 142 and the lower end surface of the presser punch 134 are both flat surfaces perpendicular to the center line. In addition, since the gap exists in this way, the forging pressure can be reduced and an excellent die life can be obtained. The projecting dimension of the convex part 16a is also about 0.50 mm, which is compressed by about 0.05 mm as compared with the convex part 56. This compressed dimension is caused by variations in the projecting dimension of the entire circumference of the convex parts 56 and 58, etc. Considering this, it is determined as appropriate so that compression forging is performed over the entire circumference. In addition, a gap may be formed between the outer peripheral side portion (the portion other than the concave portion) of the lower end surface of the presser punch 134 and the cylindrical component 10.

  As described above, the cylindrical part 10 of this embodiment is manufactured by a process mainly composed of forging processes ((b), (c), (d), (f) in FIG. 1), and therefore, the material yield is excellent. In addition, since the metal flow F is connected from both ends to the outer peripheral portion, excellent mechanical characteristics can be obtained particularly on the outer peripheral portion side.

  Further, at the stage of the intermediate product 60, convex portions 56 and 58 protruding in the axial direction are formed on both end faces by coining forging (FIG. 1 (c)), and the surface finishing step (FIG. 1 (f)) is performed after the through holes 12 are formed. ) In the axial direction and the tip portions of the convex portions 56 and 58 are plastically deformed to increase the accuracy, so that the surface accuracy of the tip surfaces of the convex portions 14a and 16a (the perpendicularity to the axis) The flatness of the projections 14a and 16a can be used as a reference surface, and subsequent gear cutting or the like can be performed with high accuracy. In particular, since the convex portions 56 and 58 are formed in a cylindrical shape, the mold structure is easily configured as compared with the case where the convex portions 56 and 58 are formed after the through hole 12 is formed.

  Further, after forming the bottomed holes 90 and 92 in the extrusion forging process (FIG. 1 (d)), the bottoms 112 of the bottomed holes 90 and 92 are punched out by the punch 120 to form the through holes 12 (FIG. 1). (e)) After that, the burnishing tool 136 is pushed in from the side opposite to the insertion side of the punching punch 120 to burnish the inner peripheral surface of the through hole 12 (FIG. 1 (f)). The burrs formed when punching at 120 are crushed by burnishing, and high surface accuracy (surface roughness) is obtained. For this reason, it is possible to use the cylindrical part 10 as it is as a gear coarse material without requiring a finishing process such as a cutting process.

  As mentioned above, although the Example of this invention was described in detail based on drawing, this is an embodiment to the last, and this invention implements in the aspect which added various change and improvement based on the knowledge of those skilled in the art. Can do.

It is a figure explaining an example of the manufacturing process at the time of manufacturing cylindrical parts according to the method of the present invention. It is sectional drawing which shows an example of the forging apparatus used at the upset forging process of (b) of FIG. 1, and is the state in which the workpiece | work was positioned. This is a state in which the upset forging is performed on the workpiece by the forging device of FIG. It is sectional drawing which shows an example of the forging apparatus used at the coining forge process of (c) of FIG. 1, and is the state in which the workpiece | work was positioned. This is a state in which coin forging has been performed on the workpiece by the forging device of FIG. 4. It is sectional drawing which shows an example of the forging apparatus used at the extrusion forging process of (d) of FIG. 1, and is the state by which the extrusion forge was performed to the workpiece | work. It is sectional drawing which shows an example of the press machine used at the punching process of (e) of FIG. 1, and is the state by which the punching process was performed to the workpiece | work. It is sectional drawing which shows an example of the forging apparatus used at the surface finishing process of (f) of FIG. 1, and is a state by which burnishing and compression forging were performed to the workpiece | work. It is a figure explaining the burr | flash which arises with the metal flow F of the intermediate product obtained by the punching process of (e) of FIG. 1, and punching. It is sectional drawing explaining the clearance gap which arises at the time of shaping | molding (bottom dead center) of the forging apparatus of FIG. It is a figure explaining the comparative example of the manufacturing process at the time of manufacturing a cylindrical part by the process which mainly has a forge process.

Explanation of symbols

  10: Cylindrical part 12: Through hole 14a, 16a: Convex part 56, 58: Convex part 60: Intermediate product (first intermediate product) 90, 92: Bottomed hole 94: Intermediate product (second intermediate product) 112: Bottom 114: Intermediate product (third intermediate product) 120: Punching punch 136: Burnishing tool

Claims (2)

A method for producing a metal cylindrical part having a through-hole having a circular cross section,
A bottomed hole processing step of forming a bottomed hole having a diameter substantially equal to the through hole in a predetermined rough material by forging;
A punching step of inserting a punching punch into the bottomed hole and punching the bottom to form the through hole;
A surface finishing step of pressing a burnishing tool into the through hole from the side opposite to the insertion side of the punching punch and burnishing the inner peripheral surface of the through hole. A method of manufacturing a metal cylindrical part having a through-hole having a circular cross section at the center,
By subjecting a predetermined rough material to forging, the outer diameter is substantially equal to the outer diameter of the cylindrical part, and the axial length is shorter than the axial length of the cylindrical part. A ring-shaped convex portion protruding in the axial direction is provided substantially concentrically with the cylindrical center line on a part of at least one end face in the axial direction that is outside the through hole. A first intermediate product manufacturing process for manufacturing one intermediate product;
By forming a bottomed hole having a diameter substantially equal to the through hole at the center of the first intermediate product by forging while restraining the outer peripheral surface of the first intermediate product, the axial length is the cylindrical shape. A second intermediate product manufacturing step for manufacturing a second intermediate product approximately equal to the axial length of the component;
A third intermediate product is manufactured by inserting a punch into the bottomed hole of the second intermediate product to punch out the bottom of the bottomed hole to form the through hole, thereby producing a cylindrical third intermediate product. Process,
While compressing the third intermediate product from the axial direction while preventing deformation of the outer peripheral surface and the inner peripheral surface of the third intermediate product, the tip surface of the annular convex portion can be accurately set to a predetermined shape. And a surface finishing step of pressing the burnishing tool into the through hole from the side opposite to the insertion side of the punching punch and burnishing the inner peripheral surface of the through hole.

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