JP2007203342A - Method for manufacturing cylindrical shaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a cylindrical shaft 20 having high roundness over its whole length by bending work. <P>SOLUTION: In a method for manufacturing the cylindrical shaft 20, a metal sheet 10 is worked into such a shape that each of cross-sectional shapes orthogonal to a longitudinal direction is circular, by press-molding it in the width direction. The method includes: a preliminary step of bending a portion of ≥50% in width of the metal sheet 10 into a circular-arc shape; a pre-finish step of working the sheet metal to the stage where the diameter of the metal sheet 10 of the cross section orthogonal to the longitudinal direction, which diameter is parallel to the mating direction of the dies 50, is shorter than the finish diameter of a shaft product, and where the diameter of the metal sheet 10, which diameter is orthogonal to the mating direction of the dies 50, is longer than the finish diameter of the shaft product by using a pair of dies 50, which approach each other and form the metal sheet 10 fed from the preliminary step into a cylindrical shape; and a finish step of finishing the working at the state that the inner surface of the groove is in contact with the surface of the metal sheet 10, by using a pair of dies 60 having grooves, whose inner surfaces have the shapes of a semi-circle having the same inner diameter as the finish diameter of the shaft product, which extend in the longitudinal direction, and which are used as working surfaces. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a cylindrical shaft. More specifically, the present invention relates to a method of manufacturing a cylindrical shaft having a high roundness by bending a metal plate.

There are many techniques for manufacturing cylindrical products by bending metal plates. The following Patent Document 1 discloses a technique for manufacturing a small-diameter tube cylinder by bending a relatively thin metal plate among them. According to the description of Patent Document 1, a core roll that is substantially equal to the inner diameter of the target cylindrical product, a pair of pressing rolls that are pushed around the core roll, and a guide belt that is passed over each roll through a unique path. It is proposed that the metal plate is formed while being in close contact with the core roll. In addition, it is described that it is possible to perform molding without barrel deformation.
JP 2003-245721 A

  However, due to deformation due to residual distribution of processing stress, thickness distribution caused by processing, etc., a long cylindrical shaft product having high roundness until it can be used as a rotating shaft has not been manufactured yet.

  In order to solve the above-described problem, according to the first embodiment of the present invention, a metal plate is processed by press molding that is bent in the width direction of the metal plate, and each of the cross-sectional shapes orthogonal to the longitudinal direction is a cylindrical shaft. A method for manufacturing a product, comprising a pair of steps of bending a metal plate of 50% or more of the width of a metal plate in an arc shape in a cross-section perpendicular to the longitudinal direction into a circular shape and approaching each other to form a cylindrical metal plate after the preliminary step Using the mold, the diameter of the mold alignment direction in the cross section orthogonal to the longitudinal direction is longer than the finished diameter of the shaft product, and the diameter of the metal plate in the preliminary process orthogonal to the mold alignment direction is A pair of molds that process a metal plate that has been processed into a cylindrical shape close to each other and finished before the finishing process, in which processing is stopped at a stage shorter than the finished diameter, and the pair of molds are brought into contact with each other Cross section perpendicular to the longitudinal direction The surface of the metal plate after the pre-finishing process is finished using a mold that forms a groove on the machining surface where the diameter in the mold alignment direction is longer than the finished diameter and the diameter perpendicular to the mold alignment direction is shorter than the finished diameter. And a finishing step of finishing the processing in a state where the inner surface of the groove is in contact therewith.

  In one embodiment, in the finishing step of the manufacturing method, the diameter of the mold alignment direction is shorter than the finished diameter of the shaft product, and the diameter perpendicular to the mold alignment direction is larger than the finished diameter of the shaft product. A short die is used to cancel the spring back of the metal plate, and the shape in the cross section perpendicular to the longitudinal direction after the finishing process is finished into a cylindrical shape. Thereby, the roundness of the cylindrical shaft in the final product can be improved.

  In another embodiment, in the mold used in the finishing process of the manufacturing method, the boundary between the processed curved surface and the surface adjacent to the processed curved surface has a sharp angle. Thereby, the deformation of the metal plate does not occur in the boundary gap between the machining curved surface and the surface adjacent to the machining curved surface during bending, and the roundness on the surface of the cylindrical shaft is improved.

  The above summary of the invention does not enumerate all the necessary features of the present invention, and sub-combinations of these feature groups can also be the invention.

  Hereinafter, the present invention will be described through embodiments of the invention. However, the following embodiments do not limit the claimed invention, and all combinations of features described in the embodiments are included. It is not necessarily essential for the solution of the invention.

  FIG. 1 is a diagram showing the shape of the metal plate 10 before bending into the cylindrical shaft 20. The metal plate 10 is formed with a plurality of convex portions 16 projecting from the end portions at intervals. A plurality of recesses 18 are also formed at the other end portion at intervals. Further, each of the convex portions 16 is disposed at the same position in the direction orthogonal to the longitudinal direction of each of the concave portions 18 and the metal plate 10.

  FIG. 2 is a partially enlarged view of the metal plate 10 having the cylindrical shaft 20 formed by processing described later. As shown in the figure, in a state where the cylindrical shaft 20 is molded, the convex portion 16 and the concave portion 18 are fitted to prevent the joint portion from being opened. Therefore, the cylindrical shaft 20 can be used as a shaft product as it is without any steps such as welding and bonding.

  FIG. 3 shows the shape of a mold 30 used for the first bending process on the metal plate 10. As shown in the figure, the mold 30 includes a die 32 having processing surfaces 31 and 33 having complementary shapes and a punch 34. The processed surfaces of the die 32 and the punch 34 are flat near the center, while both ends have an arcuate cross-sectional shape of approximately 90 degrees.

  Further, the mold 30 extends in the depth direction of the paper surface while maintaining the above-described cross-sectional shape. Further, the processed surfaces of the die 32 and the punch 34 have the same length as the length from the tip end of the convex portion 16 formed at one end portion 12 of the metal plate 10 to the other end portion 14. The metal plate 10 is inserted into the mold 30 having the above structure so that the longitudinal direction thereof coincides with the depth direction of the drawing.

  FIG. 4 is a diagram showing a cross-sectional shape of the metal plate 10 bent by the mold 30 shown in FIG. As shown in the figure, both ends in the short side direction of the metal plate 10 are bent to form bent portions 22 and 24 having arc-shaped cross sections having an inner angle of about 90 °.

  FIG. 5 is a view showing the shape of a mold 40 used for the next bending process for the metal plate 10 shown in FIG. As shown in the figure, the mold 40 includes a die 42 and a punch 44. Here, the die 42 has a processing surface 41 having an arc-shaped cross section and opened upward. On the other hand, the punch 44 has a processed surface 43 having an arc-shaped cross section at the lower end. Furthermore, a clearance narrower than the processing surface 43 is formed above the processing surface 43 in order to avoid the end portions 14 and 12 of the metal plate 10 raised by bending.

  FIG. 6 is a view showing a cross-sectional shape of the metal plate 10 bent by the mold 40 shown in FIG. As shown in the figure, the metal plate 10 is inserted and bent so that the center from the end portion 14 to the tip of the convex portion 16 coincides with the centers of the processing surfaces 41 and 43 of the mold 40. ing.

  Further, in addition to the bent portions 22 and 24 bent into an arc shape by the mold 30, a new bent portion 26 which is also bent into an arc shape is formed. On the other hand, unbent portions 21 and 23 remain between the bent portion 22 and the bent portion 26 and between the bent portion 24 and the bent portion 26, respectively.

  FIG. 7 is a cross-sectional view showing the shapes of the die 52 and the punch 54 attached to the mold 50 used in the pre-finishing process for the metal plate 10 having the shape shown in FIG. As shown in the figure, the mold 50 includes a core mold 56 in addition to a die 52 and a punch 54. The die 52 includes a machining surface 51 having an arcuate cross-sectional shape formed by being slightly lifted from the upper surface thereof. On the other hand, the punch 54 includes a machining surface 53 having an arcuate cross-sectional shape at a position retracted upward from the lower end surface thereof.

  Further, the outer side portion of the processing surface 51 and the tip portion of the punch 54 other than the processing surface 53 are complementary to each other so that they do not collide when the punch 54 is lowered. Has been made. As will be described later, the core die 56 is a round bar having an outer diameter slightly smaller than the inner diameter of the finally obtained cylindrical shaft 20, and is disposed inside the metal plate 10 bent in the mold 40. Set.

  The metal plate 10 that has already been bent by the mold 40 with respect to the mold 50 as described above is first placed on the die 52 so that the outside of the bent portion 26 contacts the inside of the processing surface 51. It is inserted. Next, the core die 56 is placed inside the metal plate 10. Subsequently, when the punch 54 is lowered, the end portion 14 of the metal plate 10 and the end portion 12 including the convex portion 16 approach each other, and eventually the convex portion 16 is fitted into the concave portion 18. Further, when the punch 54 is squeezed, the vicinity of the end portions 12 and 14 including the convex portion 16 and the concave portion 18 is formed so as to form an arc as a whole between the processing surface 53 of the punch 54 and the core die 56. .

  At the same time, below the core die 56, the metal plate 10 including the non-bending portions 21 and 23 is bent between the core die 56 and the processing surface 51 of the die 52. Therefore, the metal plate 10 becomes a cylinder having an annular cross section as a whole by bending with the mold 50.

  FIG. 8 is a diagram showing a processing result of the metal plate 10 by the mold 50 in the pre-finishing step. As shown in the figure, in this embodiment, the processing is stopped before the joint 28 of the metal plate 10 is completely closed. For this reason, the cross-sectional shape of this cylindrical shaft 20 is larger in the vertical direction than in the horizontal direction. Moreover, the diameter in the horizontal direction is shorter than the diameter of the final shaft product, and the diameter in the vertical direction is longer than the diameter of the final shaft product.

  FIG. 9 is a cross-sectional view showing the structure of the mold 60 used in the finishing process of the present embodiment, and shows the shapes of the punch 64, the die 62, and the core mold 56 in a cross section orthogonal to the longitudinal direction of the shaft product. As shown in the figure, the punch 64 and the die 62 used here have a flat surface outside the processing surfaces 61 and 63. Further, the boundaries between the processed surfaces 61 and 63 and the flat surface form sharp corners. Therefore, when the punch 64 is completely squeezed down, the flat surfaces are brought into close contact with each other, and the processed surfaces 61 and 63 form a closed surface without a gap. In the finishing process, the material is processed slightly excessively in consideration of the spring back of the material. Therefore, when the punch 64 and the die 62 come into contact with each other, the processed surfaces 61 and 63 are in the horizontal direction rather than the finished dimensions of the shaft product. Long and short inside diameter.

  FIG. 10 is a view for explaining a state in which the cylindrical shaft 20 after the pre-finishing process shown in FIG. 8 is set in the mold 60 shown in FIG. As shown in the figure, at this stage, the diameter of the cylindrical shaft 20 is long in the vertical direction, and first comes into contact with the punch 64 and the innermost portions of the processed surfaces 63 and 61 of the die 62.

  FIG. 11 shows a state where the punch 64 is lowered in the mold 60 set as shown in FIG. 10 and the finishing process is performed. As shown in the figure, when the punch 64 is lowered and the punch 64 and the die 62 come into contact with each other, the cylindrical shaft 20 is deformed until the horizontal diameter becomes longer than the vertical diameter. Yes.

  FIG. 12 is a view showing a state in which the punch 64 is raised in the mold 60 until the machining stress does not act on the cylindrical shaft 20. As shown in the figure, the cylindrical shaft 20 forms a circular cross-sectional shape by its own spring back.

  Through a series of steps as described above, a cylindrical shaft 20 having a length of 300 mm and an outer diameter of 5 mm was produced using a galvanized steel sheet having a thickness of 0.5 mm. Since it is difficult to achieve high-precision roundness with the mold 50, the processing using the mold 50 is limited to a range in which the cylindrical shaft 20 does not partially bulge. Accordingly, at this stage, the cylindrical shaft 20 is not completely closed. Subsequently, when the finishing process was performed using the mold 60, the cylindrical shaft 20 having high roundness could be produced without causing local bulge. In addition, the cylindrical shaft 20 had little warpage and high straightness. Thereby, it was confirmed that introduction of a finishing process contributes to the cylindrical shaft 20 manufacture of the exact shape.

  As described in detail above, by adding a finishing process, a hollow cylindrical shaft 20 manufactured by bending the metal plate 10 can be manufactured while having high roundness and linearity. The cylindrical shaft 20 can be used in place of a solid metal round bar. Therefore, the material cost can be reduced in many applications in which a machined round bar has to be used due to the limit of component accuracy. Further, since the cylindrical shaft 20 is lighter than the solid material, it is possible to reduce the friction loss during operation as well as the weight of the device by using the cylindrical shaft 20.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

The figure which shows the shape of the metal plate 10 used as the material of the cylindrical shaft 20 concerning this invention. The figure which shows partially the shape of the cylindrical axis | shaft 20 formed with the metal plate 10. FIG. 3 is a cross-sectional view showing a mold 30 used in the first bending process for a metal plate 10. FIG. It is a figure which shows the cross-sectional shape of the metal plate 10 bent by the metal mold | die 30 shown in FIG. 4 is a cross-sectional view showing a mold 40 used for the next bending process on the metal plate 10. FIG. It is a figure which shows the cross-sectional shape of the metal plate 10 bent by the metal mold | die 40 shown in FIG. 4 is a cross-sectional view showing a mold 50 used for the final bending process on the metal plate 10. FIG. FIG. 3 is a cross-sectional view showing the shape of the metal plate 10 after being processed by a mold 50. It is sectional drawing which shows the shape of the die | dye 62 and the punch 64 of the metal mold | die 60 used in the finishing process. It is a figure which shows the state which set the cylindrical shaft 20 of the semi-finished product to the metal mold | die 60. FIG. It is a figure which shows the state which lowered | hung the punch 64 until it contact | abutted to the die | dye 62 in the metal mold | die 60 which set the cylindrical shaft 20. FIG. It is a figure which shows the state which raised the punch 64 until the processing stress no longer acts on the cylindrical shaft 20, after implementing a finishing process.

Explanation of symbols

10 Metal plate, 12, 14 End, 16 Convex, 18 Concave, 20 Cylindrical shaft, 21, 23 Unbending part, 22, 24, 26 Bending part, 28 Seam, 30, 40, 50, 60 Die, 32, 42, 52, 62 Die, 31, 33, 41, 43, 51, 53, 61, 63 Machining surface, 34, 44, 54, 64 Punch, 56 core type

Claims (4)

A metal plate is processed by press molding that bends in the width direction, and each of the cross-sections perpendicular to the longitudinal direction has a method of manufacturing a cylindrical shaft product,
A preliminary step of bending 50% or more of the width of the metal plate into an arc shape in a cross section orthogonal to the longitudinal direction;
Using a pair of dies that process the metal plates that are close to each other and are processed in a preliminary process into a cylindrical shape, the diameter in the direction of alignment of the dies in the cross section perpendicular to the longitudinal direction is shorter than the finished diameter of the cylindrical shaft product, A pre-finishing process that stops processing at a stage where the diameter of the metal plate in the preliminary process that is orthogonal to the mold alignment direction is longer than the finished diameter,
A pair of molds that process a metal plate that is close to each other and finishes the pre-finishing process into a cylindrical shape, and when the pair of molds are brought into contact with each other, Use a die that forms a groove on the machined surface with a diameter longer than the finished diameter and perpendicular to the direction in which the molds are aligned, and shorter than the finished diameter. A cylindrical shaft manufacturing method including a finishing step of finishing processing in a finished state.   In the finishing process, a machining surface is formed in which the diameter of the mold alignment direction is longer than the finished diameter of the cylindrical shaft product and the diameter perpendicular to the mold alignment direction is shorter than the finished diameter of the cylindrical shaft product. The method for producing a cylindrical shaft according to claim 1, wherein a mold is used to cancel the spring back of the metal plate to finish the shape in a cross section perpendicular to the longitudinal direction of the metal plate after the finishing process into a cylindrical shape.   3. The method for manufacturing a cylindrical shaft according to claim 1, wherein, in the mold used in the finishing process, a boundary between the machining curved surface and a surface adjacent to the machining curved surface forms a sharp angle.   The manufacturing method of the cylindrical shaft of Claim 1 or Claim 2 in which a edge part of the process curved surface of the said metal mold | die closely_contact | adheres in a finishing process.

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