Manufacturing method of spring

Abstract

To provide a manufacturing method of a spring which can inhibit deterioration of processing accuracy.SOLUTION: A manufacturing method of a spring includes: a through hole formation step in which a plurality of through holes 34 each serving as a second slit 14 are formed at intervals in a circumferential direction of the cylinder member 30 in the cylinder member 30; and a slit formation step in which slits 37 serving as first slits 13, communicating with the through holes 34 respectively and extending from the through holes 34 to the sides opposite to each other in a circumferential direction of the cylinder member 30, are formed at both sides of each through hole 34 in an axial direction of the cylinder member 30.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a spring. [Background technology]

[0002] As shown in FIG. 12, Patent Document 1 discloses a cylindrical spring 110 having an annular peripheral wall 111. The peripheral wall 111 has a plurality of slit groups 112 formed at intervals in the axial direction of the peripheral wall 111. Each slit group 112 has two first slits 113 extending in the circumferential direction of the peripheral wall 111 and formed at an interval in the circumferential direction. The peripheral wall 111 has a plurality of second slits 114 that connect the first slits 113 of two slit groups 112 adjacent to each other in the axial direction.

[0003] The peripheral wall 111 has two opposing surfaces 115 that face each other in the circumferential direction across the second slit 114. The opposing surfaces 115 are parallel to each other and extend in the axial direction.

[0004] The spring 110 expands and contracts as the width of the first slit 113 in the axial direction expands and contracts. The spring 110 is manufactured by, for example, wire electric discharge machining using a wire electrode. In this case, first, the wire electrode approaches the tubular member from the outer periphery side of the tubular member, thereby forming a plurality of first slits 113. Then, the wire electrode travels back and forth between two adjacent first slits 113 in the axial direction of the tubular member along different paths, thereby forming second slits 114 that connect the two first slits 113 to each other. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Design Registration No. 1226279 Summary of the Invention [Problem to be solved by the invention]

[0006] When multiple first slits 113 are formed in the tubular member, the rigidity of the tubular member decreases. As a result, the tubular member may bend due to its own weight, and the planned positions for forming the second slits 114 may differ from the actual positions for forming them. As a result, the processing accuracy of the spring may decrease. Note that this problem becomes more pronounced as the spacing between the first slits 113 decreases, i.e., the thickness of the portion of the tubular member between two adjacent first slits 113 decreases. [Means for solving the problem]

[0007] Various aspects of a method for manufacturing a spring to solve the above problems will be described. [Embodiment 1] A method for manufacturing a spring having an annular peripheral wall, wherein the peripheral wall has a plurality of slit groups formed at intervals in the axial direction of the peripheral wall, each of the slit groups having a plurality of first slits extending circumferentially of the peripheral wall and formed at intervals in the circumferential direction, and a plurality of second slits connecting the first slits of two of the slit groups adjacent to each other in the axial direction and formed at intervals in the circumferential direction, the manufacturing method comprising: a through hole forming step of forming a plurality of through holes as the second slits in a tubular member at intervals in the circumferential direction of the tubular member; and a slit forming step of forming slits as the first slits on both sides of each of the through holes in the axial direction of the tubular member, the slits communicating with the through holes and extending from the through holes to opposite sides in the circumferential direction of the tubular member.

[0008] If a through-hole communicating with the slit is formed after the slit is formed in the cylindrical member, there is a risk that the cylindrical member will bend due to its own weight at the time the slit is formed. In this regard, according to the above method, after a through hole is formed in the tubular member, a slit communicating with the through hole is formed. At the time when the through hole is formed in the tubular member, the rigidity of the tubular member is less likely to decrease compared to after the slit is formed, so the tubular member is less likely to bend compared to after the slit is formed. This makes it possible to suppress a decrease in the positional accuracy of the through hole, i.e., the positional accuracy of the second slit. Therefore, it is possible to suppress a decrease in the processing accuracy of the spring.

[0009] [Mode 2] A method for manufacturing a spring as described in [Mode 1], wherein a plurality of through holes formed at intervals around the circumferential direction of the tubular member are defined as a through hole group, and each of the two axial ends of the tubular member is defined as a first end and a second end, the through hole forming process forms a plurality of through hole groups at intervals in the axial direction of the tubular member, the through hole groups having different phases around the circumferential direction of the tubular member, and the slit forming process forms the slits in order from the through hole group on the side where the first end is located to the through hole group on the side where the second end is located.

[0010] According to the above method, slits are formed in order from the side where the first end of the tubular member is located to the side where the second end is located. Therefore, slits are formed in order in the parts of the tubular member where no slits are formed, i.e., in the parts of the tubular member that are less likely to bend under their own weight. This makes it possible to prevent a decrease in the processing accuracy of the first slits. Therefore, it is possible to prevent a decrease in the processing accuracy of the spring.

[0011] [Embodiment 3] A method for manufacturing a spring according to [Embodiment 1], wherein in the through hole forming step, each of the through holes is formed to have a circular cross section. According to the above method, a through hole having a circular cross section is formed in the cylindrical member by removal processing such as cutting or electric discharge machining, and the through hole can be used as the second slit, which makes it easy to form the second slit and, ultimately, the spring. [Effects of the Invention]

[0012] According to the present disclosure, it is possible to suppress a decrease in the processing accuracy of the spring. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view showing a spring according to one embodiment. [Figure 2] FIG. 2 is a front view of the spring of FIG. [Figure 3] FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line 4-4 in FIG. [Figure 5] FIG. 5 is an enlarged front view showing the second slit of the spring in FIG. [Figure 6] FIG. 6 is a front view showing the spring of FIG. 1 in an expanded state. [Figure 7] FIG. 7 is a front view showing the spring of FIG. 1 in a compressed state. [Figure 8] FIG. 8 is a front view showing a tubular member in which a through hole is formed. [Figure 9] FIG. 9 is a front view showing a state in which a slit is partially formed in the cylindrical member of FIG. [Figure 10] FIG. 10 is a cross-sectional view showing a state in which a connecting portion is formed on the tubular member of FIG. [Figure 11] FIG. 11 is a front view showing a state in which all the slits have been formed in the cylindrical member of FIG. [Figure 12] FIG. 12 is a perspective view showing a conventional spring. DETAILED DESCRIPTION OF THE INVENTION

[0014] An embodiment of a method for manufacturing a spring will now be described with reference to Figures 1 to 11. The term "annular" as used in this description can refer to any structure that forms a loop, or a continuous shape with no ends, as well as a generally loop-shaped structure with a gap, such as a C-shape. Note that "annular" shapes include, but are not limited to, circles, ellipses, and polygons with pointed or rounded corners.

[0015] First, the configuration of the spring 10 will be described with reference to FIGS. (Spring 10) 1, the spring 10 is cylindrical and has an annular peripheral wall 11. In this embodiment, the peripheral wall 11 is circular when viewed from the axial direction. The spring 10 is made of a metal material.

[0016] Hereinafter, the direction along the central axis C1 of the peripheral wall 11 will be referred to as the "axial direction." The circumferential direction of the peripheral wall 11 centered on the central axis C1 will be simply referred to as the "circumferential direction." The radial direction of the peripheral wall 11 centered on the central axis C1 will be simply referred to as the "radial direction."

[0017] 1 and 2, the peripheral wall 11 has a plurality of slit groups 12 formed at intervals in the axial direction. Each slit group 12 extends in the circumferential direction and has a plurality of first slits 13 formed at intervals in the circumferential direction. Each first slit 13 penetrates the peripheral wall 11 in the radial direction. The width of each first slit 13 in the axial direction is constant throughout the entire circumferential direction.

[0018] 3 and 4, each slit group 12 has, for example, two first slits 13. The multiple slit groups 12 are formed at intervals in the axial direction with a phase shift of 45° on one side in the circumferential direction. Therefore, the phases of two first slits 13 adjacent to each other in the axial direction are shifted by 45° in the circumferential direction.

[0019] 1 and 2, the peripheral wall 11 has a plurality of second slits 14. Each second slit 14 penetrates the peripheral wall 11 in the radial direction. Each second slit 14 connects the first slits 13 of two axially adjacent slit groups 12. The two axially adjacent slit groups 12 communicate with each other via two second slits 14 located on opposite sides in the radial direction across the central axis C1.

[0020] Each second slit 14 communicates with the ends of two adjacent first slits 13 in the axial direction. The two second slits 14 connected to both ends of each first slit 13 extend from the first slit 13 in opposite directions in the axial direction.

[0021] The peripheral wall 11 has a plurality of leaf spring portions 22 formed at intervals in the axial direction. A group of slits 12 is formed between two adjacent leaf spring portions 22 in the axial direction. Each leaf spring portion 22 has a plurality of arc portions 23 that extend in an arc shape in the circumferential direction and face each other in the circumferential direction with gaps between them.

[0022] 3 and 4, each leaf spring portion 22 has, for example, two arc portions 23. The leaf spring portions 22 are formed at intervals in the axial direction with a phase shift of 45° on one side in the circumferential direction. Therefore, the phases of two arc portions 23 adjacent to each other in the axial direction are shifted by 45° in the circumferential direction.

[0023] The peripheral wall 11 has a plurality of connecting portions 24. Each connecting portion 24 connects the arc portions 23 of two axially adjacent leaf spring portions 22. The two axially adjacent leaf spring portions 22 are connected via two connecting portions 24 located on opposite sides in the radial direction across the central axis C1.

[0024] Each connecting portion 24 connects the ends of two adjacent arc portions 23 in the axial direction. The two connecting portions 24 connected to both ends of each arc portion 23 extend in opposite directions in the axial direction from the arc portion 23. Both ends of each arc portion 23 extend in a cantilevered manner from the connecting portion 24 in the circumferential direction.

[0025] Two first slits 13 of the slit group 12 are formed by gaps between two adjacent leaf spring portions 22 in the axial direction and two connecting portions 24 connecting the two leaf spring portions 22. Two second slits 14 are formed by gaps between two adjacent arc portions 23 in the circumferential direction.

[0026] 5, each arcuate portion 23 has opposing surfaces 15 at both ends in the circumferential direction that face the ends of other arcuate portions 23. Each leaf spring portion 22 has a total of four opposing surfaces 15. Each opposing surface 15 forms a second slit 14.

[0027] Each of the two opposing surfaces 15 (hereinafter, sometimes simply referred to as the two opposing surfaces 15) that face each other across the second slit 14 includes a concave surface 16. In this embodiment, the entire opposing surface 15 is the concave surface 16. The two concave surfaces 16 of the two opposing surfaces 15 face each other in the circumferential direction. Each concave surface 16 extends over the entire radial direction of the arc portion 23. Therefore, each concave surface 16 is continuous with the outer peripheral surface and the inner peripheral surface of the arc portion 23.

[0028] The two concave surfaces 16 intersect with the axial direction. More specifically, the two concave surfaces 16 are curved in an arc shape along the same imaginary circle V, which is centered on a central axis C2 that is perpendicular to the axial direction and passes through the second slit 14. The two concave surfaces 16 are located on the circumference of the same imaginary circle V. The central axis C2 of the imaginary circle V is a straight line extending in the radial direction that passes through the center of the second slit 14 in the axial direction and intersects with the central axis C1 of the peripheral wall 11. The diameter of the imaginary circle V is larger than the width of the arc portion 23 in the axial direction and smaller than the sum of the width of the arc portion 23 in the axial direction and the width of the two first slits 13 adjacent to the arc portion 23.

[0029] Each second slit 14 has a first region A1 and two second regions A2 located on either side of the first region A1 in the axial direction. The first region A1 is a region where the distance between two opposing concave surfaces 16 is a first distance d1. The second region A2 is a region where the distance between the two concave surfaces 16 is a second distance d2 that is smaller than the first distance d1. The first distance d1 is the distance between the deepest portions of the two concave surfaces 16. The second distance d2 is the distance between the portions of the two concave surfaces 16 excluding the deepest portions. Any region of the second slit 14 other than the first region A1 can be the second region A2. The second distance d2 decreases as the distance from the first region A1 increases in the axial direction. For convenience, FIG. 5 illustrates the minimum second distance d2.

[0030] 6 and 7, the spring 10 expands and contracts as each arc portion 23 elastically deforms in the axial direction starting from the connecting portion 24. When the spring 10 expands, the arc portions 23 deform in directions away from each other in the axial direction, thereby expanding the width of each first slit 13. When the spring 10 contracts, the arc portions 23 deform in directions approaching each other in the axial direction, thereby reducing the width of each first slit 13. The portions of each arc portion 23 that extend cantilevered in the circumferential direction from the connecting portion 24 do not elastically deform when the spring 10 expands or contracts, and therefore do not contribute to the expansion or contraction of the spring 10.

[0031] (Method for manufacturing spring 10) Next, a method for manufacturing the spring 10 will be described. 8 to 11, the spring 10 is manufactured by cutting a tubular member 30 using, for example, a multi-tasking machine (not shown) (hereinafter simply referred to as a processing machine). The tubular member 30 has a circular shape when viewed from the axial direction. The tubular member 30 is made of a metal material.

[0032] In the following description, both ends of the cylindrical member 30 in the axial direction will be referred to as a first end 31 and a second end 32, respectively. The method for manufacturing the spring 10 includes a through-hole forming step of forming a plurality of through-holes 34 in the tubular member 30, and a slit forming step of forming a plurality of slits 37 in the tubular member 30.

[0033] The through-hole forming step is performed, for example, with the second end 32 of the tubular member 30 clamped by a chuck (not shown) of a multi-tasking machine. This chuck has the function of rotating the tubular member 30 around the central axis C1 of the tubular member 30 at any rotation angle.

[0034] 8 , in the through hole forming step, a processing machine forms a plurality of through hole groups 33 in the tubular member 30, which communicate between the inside and outside of the tubular member 30. Each through hole group 33 has a plurality of through holes 34 as second slits 14 formed at intervals in the circumferential direction of the tubular member 30. Each through hole group 33 has, for example, two through holes 34 formed at equal intervals in the circumferential direction of the tubular member 30. The processing machine forms the through holes 34 having a circular cross section using, for example, a drill. As a result, the concave surface 16 of the second slits 14 is formed as part of the inner circumferential surface of the through hole 34.

[0035] In the through hole forming process, a processing machine forms a plurality of phase-shifted through hole groups 33 on one circumferential side of the tubular member 30 at intervals in the axial direction of the tubular member 30. In this embodiment, the phases of two axially adjacent through hole groups 33 are shifted by 45° in the circumferential direction.

[0036] The plurality of through holes 34 formed in the tubular member 30 includes a plurality of first through holes 35 and a plurality of second through holes 36. The plurality of first through holes 35 are formed at intervals on a spiral first imaginary line V1 extending along the outer peripheral surface of the tubular member 30. The plurality of second through holes 36 are formed at intervals on a spiral second imaginary line V2 extending along the outer peripheral surface of the tubular member 30. The first imaginary line V1 and the second imaginary line V2 extend parallel to each other. Each through hole group 33 has one first through hole 35 and one second through hole 36.

[0037] The N-th first through-hole 35, counting from the side where the first end 31 is located on the first imaginary line V1, and the N-th second through-hole 36, counting from the side where the first end 31 is located on the second imaginary line V2, face each other across the central axis C1 of the tubular member 30. N is a natural number.

[0038] As shown in FIG. 9, in the slit forming step, a processing machine forms a plurality of slits 37 in the tubular member 30 as first slits 13 that connect the inside and outside of the tubular member 30. In the slit forming step, first, the processing machine forms two slits 37 at the first end 31 of the tubular member 30 at a distance from each other in the circumferential direction of the tubular member 30. This forms two first slits 13 that constitute the slit group 12. The two slits 37 each communicate with one of two through holes 34 formed at a distance from each other in the circumferential direction of the tubular member 30, on the side where the first ends 31 are located. More specifically, one of the two slits 37 communicates with the first through hole 35 of the through hole group 33, and the other of the two slits 37 communicates with the second through hole 36 of the through hole group 33.

[0039] 10 , the processing machine forms the slits 37 using, for example, a disk-shaped metal saw M having multiple cutting blades formed on its outer periphery. The metal saw M moves sequentially along two paths that are perpendicular to the axial direction of the cylindrical member 30 and parallel to each other on opposite sides of the central axis C1 of the cylindrical member 30. As a result, two slits 37 are formed in the cylindrical member 30. At this time, two unmachined portions that are not machined by the metal saw M are left between the two paths. These two unmachined portions function as the connecting portions 24 of the spring 10.

[0040] Next, the processing machine rotates the cylindrical member 30 by a predetermined angle around the central axis C1. As shown in FIG. 9 , the processing machine then forms two other slits 37 in the tubular member 30 at positions offset by a predetermined pitch from the two slits 37 toward the second end 32 in the axial direction. These two slits 37 are formed on one side of the tubular member 30 in the circumferential direction, more specifically, at positions offset by a predetermined phase in the same direction as the phase offset direction of two adjacent through-hole groups 33, relative to the two previously formed slits 37. Each of the two slits 37 communicates with a first through hole 35 of one through-hole group 33 on one axial side and with a second through hole 36 of the other through-hole group 33 on the other axial side. The predetermined pitch is, for example, the same as the pitch of the through-hole groups 33 in the axial direction. The predetermined phase is, for example, the same as the phase difference between the two adjacent through-hole groups 33.

[0041] As described above, in the slit forming process, the processing machine forms slits 37 on both sides of each through hole 34 in the axial direction of the tubular member 30, the slits 37 communicating with the through hole 34 and extending from the through hole 34 to opposite sides in the circumferential direction of the tubular member 30. The two slits 37 communicating with both sides of each through hole 34 in the axial direction of the tubular member 30 are formed at positions where the axial distances from the center of the through hole 34 are equal to each other.

[0042] 11, in the slit forming step, the processing machine forms slits 37 in order from the through-hole group 33 on the side where the first end 31 is located toward the through-hole group 33 on the side where the second end 32 is located. As a result, two slits 37 adjacent to each other in the axial direction communicate with each other via the through holes 34. In this manner, the spring 10 is manufactured.

[0043] <Operation of this embodiment> If the through-hole 34 communicating with the slit 37 is formed after the slit 37 is formed in the tubular member 30, there is a risk that the tubular member 30 will bend at the time the slit 37 is formed.

[0044] In this regard, according to the manufacturing method of the spring 10 of this embodiment, after the through holes 34 are formed in the tubular member 30, the slits 37 that communicate with the through holes 34 are formed. At the time when the through holes 34 are formed in the tubular member 30, the rigidity of the tubular member 30 is less likely to decrease compared to after the slits 37 are formed, and therefore the tubular member 30 is less likely to bend compared to after the slits 37 are formed.

[0045] <Effects of this embodiment> (1) In the through hole forming process, a plurality of through holes 34 serving as second slits 14 are formed in the tubular member 30 at intervals in the circumferential direction of the tubular member 30. In the slit forming process, slits 37 serving as first slits 13 are formed on both sides of each through hole 34 in the axial direction of the tubular member 30, the slits 37 communicating with the through holes 34 and extending from the through holes 34 to opposite sides in the circumferential direction of the tubular member 30.

[0046] According to the above method, it is possible to suppress a decrease in the positional accuracy of the through-holes 34, that is, the positional accuracy of the second slits 14. Therefore, it is possible to suppress a decrease in the processing accuracy of the spring 10. (2) In the through hole forming process, a plurality of through hole groups 33 having different phases in the circumferential direction of the tubular member 30 are formed at intervals in the axial direction of the tubular member 30. In the slit forming process, slits 37 are formed in order from the through hole group 33 on the side where the first end 31 is located to the through hole group 33 on the side where the second end 32 is located.

[0047] According to the above method, the slits 37 are formed in the tubular member 30 in order from the side where the first end 31 of the tubular member 30 is located to the side where the second end 32 is located. Therefore, the slits 37 are formed sequentially in the parts of the tubular member 30 where the slits 37 are not formed, i.e., in the parts of the tubular member 30 that are less likely to bend under its own weight. This makes it possible to suppress a decrease in the processing accuracy of the first slits 13. Therefore, it is possible to suppress a decrease in the processing accuracy of the spring 10.

[0048] (3) In the through-hole forming step, each of the through-holes 34 is formed to have a circular cross section. According to the above method, by forming the through hole 34 having a circular cross section in the tubular member 30 by removal processing such as cutting or electric discharge machining, the through hole 34 can be used as the second slit 14. Therefore, the second slit 14, and therefore the spring 10, can be easily formed.

[0049] <Example of change> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0050] The cross-sectional shape of the through hole 34 may be an oval shape formed by two semicircles connected by two parallel lines. The through hole 34 can be formed, for example, by intersecting the axial direction of the end mill with the axial direction of the cylindrical member 30 and linearly moving the end mill in a direction perpendicular to both the axial direction of the end mill and the axial direction of the cylindrical member 30.

[0051] The cross-sectional shape of the through hole 34 may be a shape in which multiple circles of the same diameter partially overlap each other. The through hole 34 can be formed, for example, by drilling at multiple arbitrary locations on the outer circumferential surface of the tubular member 30.

[0052] The through-hole 34 does not have to have a circular cross section. The through-hole 34 may have a rectangular cross section, for example. In the slit forming step, the slits 37 do not have to be formed in order from the side where the first end 31 is located to the side where the second end 32 is located. In the slit forming step, multiple slits 37 may be formed in any order.

[0053] In the slit forming step, the metal saw M may reciprocate along the same path to form two slits 37 spaced apart in the circumferential direction of the cylindrical member 30. In this case, for example, the metal saw M passes through a path that is perpendicular to the axial direction of the cylindrical member 30 and does not intersect with the central axis C1 of the cylindrical member 30, thereby forming one of the two slits 37. Thereafter, the cylindrical member 30 is rotated around the central axis C1 by the chuck of the multi-tasking machine, and then the metal saw M passes through the same path again to form the other of the two slits 37.

[0054] The first slit 13 and the second slit 14 may be formed by various machining methods. For example, at least one of the first slit 13 and the second slit 14 may be formed by electrical discharge machining, including wire electrical discharge machining and die-sinking electrical discharge machining.

[0055] The spring 10 may be made of a material other than a metal material, such as a resin material. However, if the material of the spring 10 is not electrically conductive, it is difficult to manufacture the spring 10 by electrical discharge machining, which processes the spring by dielectric breakdown between the material and the electrical discharge. In this case, it is preferable to manufacture the spring 10 by cutting, as in this embodiment.

[0056] The two slits 37 communicating with the through hole 34 may be formed at positions that are different distances from the center of the through hole 34 in the axial direction. In this case, the central axis C2 of the imaginary circle V may pass through the second slit 14 at a position that is offset from the center of the second slit 14 in the axial direction to one side in the axial direction. In addition, the central axis C2 of the imaginary circle V may pass through the first slit 13.

[0057] The plurality of slit groups 12 may be formed at intervals in the axial direction, shifted by any angle on one side in the circumferential direction. The slit group 12 may have three or more first slits 13.

[0058] The width of the first slit 13 and the width of the arc portion 23 can be changed as appropriate. The spring 10 does not have to be circular when viewed in the axial direction. For example, the spring 10 may have a peripheral wall 11 that is polygonal when viewed in the axial direction. The spring 10 may also have a peripheral wall 11 that is frustum-shaped, with the peripheral wall 11 tapering toward one side in the axial direction. [Explanation of symbols]

[0059] A1…First area A2…Second area C1…Central axis line C2…Central axis line d1...first distance d2…Second distance M...Metal saw V...imaginary circle V1...First imaginary circle V2: Second imaginary circle 10...Spring 11...Peripheral wall 12...Slit group 13...First slit 14...Second slit 15...Opposite surface 16...Concave 22...Leaf spring part 23...Arc section 24...Connection part 30...Cylindrical member 31...first end 32…Second end 33...Through hole group 34...Through hole 35...First through hole 36...Second through hole 37...Slit 110...Spring 111...Peripheral wall 112...Slits 113...First slit 114...Second slit 115...Opposite surface

Claims

1. A method for manufacturing a spring having an annular peripheral wall, comprising: The peripheral wall is a plurality of slit groups formed at intervals in the axial direction of the peripheral wall, each of the slit groups having a plurality of first slits extending in the circumferential direction of the peripheral wall and formed at intervals in the circumferential direction; a plurality of second slits that communicate with the first slits of two of the slit groups that are adjacent to each other in the axial direction and are formed at intervals in the circumferential direction, The manufacturing method includes: a through-hole forming step of forming a plurality of through-holes as the second slits in the cylindrical member at intervals in a circumferential direction of the cylindrical member; a slit forming step of forming slits as the first slits on both sides of each of the through holes in the axial direction of the cylindrical member, the slits communicating with the through holes and extending from the through holes to opposite sides in the circumferential direction of the cylindrical member, Spring manufacturing method.

2. a plurality of the through holes formed at intervals in the circumferential direction of the cylindrical member are defined as a through hole group, When both ends of the cylindrical member in the axial direction are defined as a first end and a second end, In the through hole forming step, a plurality of through hole groups having different phases in the circumferential direction of the cylindrical member are formed at intervals in the axial direction of the cylindrical member, In the slit forming step, the slits are formed in order from the through-hole group on the side where the first end is located to the through-hole group on the side where the second end is located. The method for manufacturing a spring according to claim 1.

3. In the through hole forming step, each of the through holes is formed to have a circular cross section.

3. The method for manufacturing a spring according to claim 1 or 2.

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