Manufacturing method of pressing spring device

Abstract

To provide a pressing spring device capable of outputting a high load in a saved space.SOLUTION: A pressing spring device 1 comprises a first leaf spring 11 and a second leaf spring 12 extending in a length direction X, and a length of an intermediate part 24 of the second leaf spring along a surface of the second leaf spring in a view in a plate width direction Y is shorter than a length of an intermediate part 23 of the first leaf spring along a surface of the first leaf spring in the view in the plate width direction. A manufacturing method of the pressing spring device includes: a first leaf spring forming step of forming the first leaf spring; and a bonding step of bonding both ends 21 of the first leaf spring in the length direction to both ends 22 of the second leaf spring in the length direction. In the first leaf spring forming step, the first leaf spring is formed in such a manner the size of the first leaf spring in the length direction becomes larger than the size of the second leaf spring in the length direction. In the bonding step, both the ends of the first leaf spring in the length direction are bonded to both the ends of the second leaf spring in the length direction in a state where the first leaf spring is elastically deformed so as to reduce the size of the first leaf spring in the length direction.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a compression spring device. [Background technology]

[0002] 2. Description of the Related Art Conventionally, as shown in, for example, Patent Document 1 below, there is known a compression spring device in which a pressed body is sandwiched and pressed in the plate thickness direction by the apexes of curved first and second leaf springs. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5040228 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional compression spring devices, the space required to output a high load tends to be bulky, making it difficult to output a high load in a small space.

[0005] The present invention provides a method for manufacturing a compression spring device that is space-saving and capable of outputting a high load. [Means for solving the problem]

[0006] A method for manufacturing a compression spring device according to one aspect of the present invention includes a first leaf spring and a second leaf spring extending in a longitudinal direction, both end portions of the first leaf spring in the longitudinal direction are stacked and joined to both end portions of the second leaf spring in the longitudinal direction in a plate thickness direction, intermediate portions of the first leaf spring and the second leaf spring in the longitudinal direction face each other while being spaced apart in the plate thickness direction, a length of the intermediate portion of the second leaf spring along a surface of the second leaf spring as viewed in the plate width direction is shorter than a length of the intermediate portion of the first leaf spring along the surface of the first leaf spring as viewed in the plate width direction, and the intermediate portion of the first leaf spring is located between the center of the second leaf spring along the plate thickness direction as viewed in the plate width direction. a first leaf spring forming step of forming the first leaf spring and a joining step of joining both longitudinal ends of the first leaf spring to both longitudinal ends of the second leaf spring, wherein the first leaf spring forming step forms the first leaf spring so that its longitudinal size is larger than that of the second leaf spring, and the joining step joins both longitudinal ends of the first leaf spring to both longitudinal ends of the second leaf spring while the first leaf spring is elastically deformed so that the longitudinal size of the first leaf spring is reduced.

[0007] Since the compression spring device comprises a first leaf spring and a second leaf spring, when the compression spring device is sandwiched between a pair of pressed bodies in the plate thickness direction and a pressing load from the second leaf spring along the plate thickness direction is applied to the middle portion of the first leaf spring, a longitudinal tensile force is applied to the second leaf spring via both longitudinal ends of the first leaf spring. In this case, the length of the middle part of the second leaf spring along the surface of the second leaf spring, viewed in the leaf width direction, is shorter than the length of the middle part of the first leaf spring along the surface of the first leaf spring, viewed in the leaf width direction. Therefore, regardless of the material, etc. of the second leaf spring, the second leaf spring suppresses deformation of the first leaf spring, making it possible to increase the spring constant of the compression spring device that is developed and to output high loads in a space-saving manner.

[0008] The manufacturing method for the compression spring device includes a first leaf spring forming process for forming the first leaf spring so that its longitudinal size is larger than that of the second leaf spring, and a joining process for joining both longitudinal ends of the first leaf spring to both longitudinal ends of the second leaf spring while elastically deforming the first leaf spring so that the longitudinal size of the first leaf spring is reduced.Therefore, in the manufactured compression spring device, a tensile stress is applied to the outer surface side, which is opposite the second leaf spring in the plate thickness direction, at the intermediate portion of the first leaf spring in a direction along the outer surface of the first leaf spring when viewed from the plate width direction (hereinafter referred to as the first specific direction). Therefore, the compressive stress in the first specific direction that occurs when a compression load from the second leaf spring along the plate thickness direction is applied to the outer surface side of the middle portion of the first leaf spring is alleviated, and even if the compression spring device is significantly compressed in the plate thickness direction, it is possible to suppress the load generated in the middle portion of the first leaf spring, thereby improving durability.

[0009] The joining process may include applying a longitudinal compressive force to both longitudinal ends of the first leaf spring in a direction that brings them closer to each other in the longitudinal direction when elastically deforming the first leaf spring so that the longitudinal size of the first leaf spring is reduced.

[0010] During the joining process, a longitudinal compressive force is applied to both longitudinal ends of the first leaf spring in a direction that brings them closer together in the longitudinal direction, so that a compression spring device in which a tensile stress in the first specific direction is applied to the outer surface side of the middle part of the first leaf spring can be easily and reliably manufactured.

[0011] The joining process may involve, when elastically deforming the first leaf spring so that the longitudinal size of the first leaf spring is reduced, applying a load toward the opposite side of the second leaf spring in the thickness direction to the longitudinal central portion of the intermediate portion of the first leaf spring while supporting outer surfaces of each portion located on both sides of the longitudinal central portion of the intermediate portion of the first leaf spring that face the opposite side of the second leaf spring in the thickness direction.

[0012] During the joining process, while the outer surfaces of each part located on both sides of the longitudinal center of the intermediate portion of the first leaf spring are supported, a load is applied to the longitudinal center portion toward the opposite side of the second leaf spring along the plate thickness direction. As a result, the intermediate portion of the first leaf spring is bent at three points, and a compression spring device in which a tensile stress in the first specific direction is applied to the outer surface side of the intermediate portion of the first leaf spring can be easily and accurately manufactured. Effect of the Invention

[0013] According to the above-described aspect of the present invention, a compression spring device capable of outputting a high load while saving space can be obtained. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a perspective view of a compression spring device according to an embodiment. [Diagram 2] 2 is a view of the pressure spring device of FIG. 1 as viewed from the plate width direction. [Diagram 3] 5A to 5C are diagrams illustrating a manufacturing method of the compression spring device of the first embodiment. [Figure 4] 10A to 10C are diagrams illustrating a manufacturing method of the compression spring device of the second embodiment. [Diagram 5] 13 is a view showing a pressure spring device of a modified example as viewed from a plate width direction. FIG. [Figure 6] 10A to 10C are diagrams illustrating a method for manufacturing a compression spring device of a modified example by the manufacturing method of the first embodiment. [Figure 7] 13A to 13C are diagrams illustrating a method for manufacturing a compression spring device of a modified example by the manufacturing method of the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, one embodiment of the pressure spring device will be described with reference to FIGS. As shown in Figs. 1 and 2, the compression spring device 1 of this embodiment includes a first leaf spring 11 and a second leaf spring 12 extending in a length direction X, and is used by being sandwiched in a plate thickness direction Z between a pair of pressed bodies. Both ends of the first leaf spring 11 and the second leaf spring 12 in the longitudinal direction X are stacked in the plate thickness direction Z and joined by, for example, brazing, bonding, welding, ultrasonic bonding, etc. Both ends of the first leaf spring 11 and the second leaf spring 12 in the longitudinal direction X extend straight in the longitudinal direction X. Hereinafter, both ends of the first leaf spring 11 in the longitudinal direction X will be referred to as first fixing portions 21, and both ends of the second leaf spring 12 in the longitudinal direction X will be referred to as second fixing portions 22.

[0016] The first leaf spring 11 and the second leaf spring 12 have the same size in the longitudinal direction X. Both end edges of the first leaf spring 11 and the second leaf spring 12 in the longitudinal direction X are connected without any step in the plate thickness direction Z. The first leaf spring 11 and the second leaf spring 12 may have different sizes in the longitudinal direction X, and both end edges of the first leaf spring 11 and the second leaf spring 12 in the longitudinal direction X may be connected in the plate thickness direction Z via a step. The intermediate portions 23, 24 of the first leaf spring 11 and the second leaf spring 12 in the longitudinal direction X face each other while being spaced apart in the plate thickness direction Z. The length of the intermediate portion 24 of the second leaf spring 12 along the surface of the second leaf spring 12 as viewed from the plate width direction Y is shorter than the length of the intermediate portion 23 of the first leaf spring 11 along the surface of the first leaf spring 11 as viewed from the plate width direction Y.

[0017] When viewed from the width direction Y, the middle portion 23 of the first leaf spring 11 is curved in the thickness direction Z so as to present a protruding curved shape toward the side away from the middle portion 24 of the second leaf spring 12. The second leaf spring 12 extends straight in the longitudinal direction X over the entire length of the longitudinal direction X when viewed from the plate width direction Y. Note that the middle portion 24 of the second leaf spring 12 may be curved to present a protruding curved shape in a direction approaching or receding in the plate thickness direction Z relative to the middle portion 23 of the first leaf spring 11 when viewed from the plate width direction Y.

[0018] The compression spring device 1 of this embodiment includes a third leaf spring 13 having an intermediate portion 28 provided on the opposite side of the intermediate portion 23 of the first leaf spring 11 that sandwiches the intermediate portion 24 of the second leaf spring 12 in the plate thickness direction Z when viewed from the plate width direction Y. When viewed from the plate width direction Y, the intermediate portions 24, 28 of the second leaf spring 12 and the third leaf spring 13 are spaced apart in the plate thickness direction Z.

[0019] In the illustrated example, the third leaf spring 13 is provided separately on both sides of the first leaf spring 11 in the plate width direction Y. Both end portions of the third leaf spring 13 in the longitudinal direction X extend straight in the longitudinal direction X, are formed integrally with the first fixing portion 21 of the first leaf spring 11, and protrude from the first fixing portion 21 in the plate width direction Y. The first leaf spring 11 and the third leaf spring 13 are formed of a single plate body having the same plate thickness over the entire area. Hereinafter, both ends of the third leaf spring 13 in the longitudinal direction X will be referred to as protruding portions 27.

[0020] The intermediate portion 28 of the third leaf spring 13 connects the protruding portions 27 located at both ends in the longitudinal direction X in the longitudinal direction X. When viewed from the transverse direction Y, the intermediate portion 28 of the third leaf spring 13 is curved in the thickness direction Z to present a protruding curved shape toward the side away from the intermediate portion 23 of the first leaf spring 11. When viewed from the transverse direction Y, the center of the intermediate portion 28 of the third leaf spring 13 in the longitudinal direction X is located on the opposite side to the intermediate portion 23 of the first leaf spring 11, sandwiching the intermediate portion 24 of the second leaf spring 12 in the thickness direction Z.

[0021] When viewed from the width direction Y, the intermediate portions 28, 23 of the third leaf spring 13 and the first leaf spring 11 are symmetrical with respect to a line that passes through the center of the first fixing portion 21 and the protruding portion 27 in the thickness direction Z and extends in the length direction X. The intermediate portions 28, 23 of the third leaf spring 13 and the first leaf spring 11 are the same size.

[0022] In a state in which the first leaf spring 11 and the third leaf spring 13 are compressed and deformed in the length direction X within their elastic range, the first fixed portion 21 and the second fixed portion 22 are joined together. As a result, a tensile stress is applied uniformly in the longitudinal direction X over the entire area of ​​the second leaf spring 12, and a tensile stress is applied in a direction along the outer surfaces 23a, 28a of the intermediate portions 23, 28 of the first leaf spring 11 and the third leaf spring 13, respectively, on the outer surfaces 23a, 28a side, which is the opposite side of the second leaf spring 12 along the plate thickness direction Z, as viewed from the plate width direction Y, and a compressive stress is applied in a direction along the inner surfaces 23b, 28b of the intermediate portions 23, 28 of the first leaf spring 11 and the third leaf spring 13, respectively, on the inner surfaces 23b, 28b side, which is the side of the second leaf spring 12 along the plate thickness direction Z, as viewed from the plate width direction Y.

[0023] The tensile stress applied to the outer surface 23a of the intermediate portion 23 of the first leaf spring 11 decreases along the thickness direction Z toward the inner surface 23b of the intermediate portion 23 of the first leaf spring 11. The compressive stress applied to the inner surface 23b of the intermediate portion 23 of the first leaf spring 11 decreases along the thickness direction Z toward the outer surface 23a of the intermediate portion 23 of the first leaf spring 11. The intermediate portion of the intermediate portion 23 of the first leaf spring 11 in the thickness direction Z includes a region with no internal stress.

[0024] The tensile stress applied to the outer surface 28a of the middle portion 28 of the third leaf spring 13 decreases along the thickness direction Z toward the inner surface 28b of the middle portion 28 of the third leaf spring 13. The compressive stress applied to the inner surface 28b of the middle portion 28 of the third leaf spring 13 decreases along the thickness direction Z toward the outer surface 28a of the middle portion 28 of the third leaf spring 13. The middle part of the middle portion 28 of the third leaf spring 13 in the thickness direction Z includes a region with no internal stress. The distribution and magnitude of internal stress in the intermediate portions 23, 28 of the first leaf spring 11 and the third leaf spring 13 are the same. However, the distribution and magnitude of internal stress in the intermediate portions 23, 28 of the first leaf spring 11 and the third leaf spring 13 may be different from each other.

[0025] Next, a manufacturing method for the pressure spring device 1 configured as above will be described.

[0026] First, the flat plate material for the first leaf spring 11 and the flat plate material for the third leaf spring 13, which extend straight over the entire length in the length direction X, are bent so that the outer surfaces 23a, 28a of the portions to form the intermediate portions 23, 28 become protruding, to form the first leaf spring 11 and the third leaf spring 13 (first leaf spring forming process, third leaf spring forming process). The flat plate material for the first leaf spring 11 and the flat plate material for the third leaf spring 13 are connected in the plate width direction Y to form a single flat plate.

[0027] In this case, as shown in Fig. 3, the size of each of the first leaf spring 11 and the third leaf spring 13 in the length direction X is larger than the size of the second leaf spring 12 in the length direction X. In addition, the radius of curvature of each of the intermediate portions 23, 28 of the first leaf spring 11 and the third leaf spring 13 as viewed from the plate width direction Y is larger than that of the compression spring device 1 in which the first fixing portion 21 and the second fixing portion 22 are joined, as shown by the two-dot chain line in Fig. 3. The amount of bulging of the intermediate portion 23 of the first leaf spring 11 in the plate thickness direction Z relative to the first fixing portion 21 is smaller than that of the compression spring device 1 in which the first fixing portion 21 and the second fixing portion 22 are joined, as shown by the two-dot chain line in Fig. 3. The amount of bulging of the intermediate portion 28 of the third leaf spring 13 in the plate thickness direction Z relative to the protruding portion 27 is also smaller than that of the compression spring device 1, as shown by the two-dot chain line in FIG.

[0028] Next, the second fixing portion 22 of the second leaf spring 12, which extends straight over the entire length in the longitudinal direction X and is in an unloaded state in the longitudinal direction X, is joined to the first fixing portion 21 of the first leaf spring 11 (joining step). At this time, the first fixing portion 21 is joined to the second fixing portion 22 in a state in which the first leaf spring 11 and the third leaf spring 13 are elastically deformed so that the size of each of the first leaf spring 11 and the third leaf spring 13 in the longitudinal direction X is reduced.

[0029] As a result, the first fixing portion 21 and the second fixing portion 22 are joined together while the first leaf spring 11 and the third leaf spring 13 are compressed and deformed within their elastic range in the longitudinal direction X, thereby obtaining a compression spring device 1 in which a tensile stress is applied uniformly to the entire second leaf spring 12 in the longitudinal direction X. At this time, the first leaf spring 11 and the third leaf spring 13 are compressed and deformed in the longitudinal direction X, so that the radius of curvature of the intermediate portions 23, 28 of the first leaf spring 11 and the third leaf spring 13, respectively, as viewed from the width direction Y becomes smaller as shown by the dotted line in FIG. 3, the amount of bulging of the intermediate portion 23 of the first leaf spring 11 in the thickness direction Z relative to the first fixing portion 21 becomes larger as shown by the dotted line in FIG. 3, and the amount of bulging of the intermediate portion 28 of the third leaf spring 13 in the thickness direction Z relative to the protrusion portion 27 also becomes larger as shown by the dotted line in FIG. 3.

[0030] In the present embodiment, when the first leaf spring 11 and the third leaf spring 13 are elastically deformed in the joining step so that the size of each of the first leaf spring 11 and the third leaf spring 13 in the longitudinal direction X is reduced, a compressive force in the longitudinal direction X in a direction in which the first leaf spring 11 and the third leaf spring 13 approach each other in the longitudinal direction X is applied to both ends of the first leaf spring 11 and the third leaf spring 13. At this time, with both end edges of the first leaf spring 11 and the third leaf spring 13 in the longitudinal direction X pressed in the longitudinal direction X, both ends of the first leaf spring 11 and the second leaf spring 12 in the longitudinal direction X, i.e., the first fixing portion 21 and the second fixing portion 22, are sandwiched in the plate thickness direction Z and joined.

[0031] As described above, the compression spring device 1 of this embodiment is equipped with the first leaf spring 11 and the second leaf spring 12. Therefore, when the compression spring device 1 is sandwiched between a pair of pressed bodies in the plate thickness direction Z and a pressing load from the second leaf spring 12 along the plate thickness direction Z is applied to the intermediate portion 23 of the first leaf spring 11, a tensile force in the longitudinal direction X is applied to the second leaf spring 12 via the first fixed portion 21 of the first leaf spring 11. In this case, the length of the intermediate portion 24 of the second leaf spring 12 along the surface of the second leaf spring 12 when viewed from the leaf width direction Y is shorter than the length of the intermediate portion 23 of the first leaf spring 11 along the surface of the first leaf spring 11 when viewed from the leaf width direction Y. Therefore, regardless of the material, etc. of the second leaf spring 12, the second leaf spring 12 suppresses deformation of the first leaf spring 11, making it possible to increase the spring constant of the compression spring device 1 that is developed, and a high load can be output in a space-saving manner.

[0032] The method for manufacturing the compression spring device 1 according to this embodiment includes a first leaf spring forming step and a third leaf spring forming step of forming the first leaf spring 11 and the third leaf spring 13 so that the size of the first leaf spring 11 and the third leaf spring 13 in the length direction X is larger than the size of the second leaf spring 12 in the length direction X, and a second leaf spring forming step of forming the first leaf spring 11 and the third leaf spring 13 in a state in which the first leaf spring 11 and the third leaf spring 13 are elastically deformed so that the size of each of the first leaf spring 11 and the third leaf spring 13 in the length direction X is reduced. The manufacturing process also includes a joining process for joining the first fixing portion 21 of the first leaf spring 11 to the second fixing portion 22 of the second leaf spring 12. Therefore, in the manufactured compression spring device 1, a tensile stress is applied to the outer surfaces 23a, 28a of the intermediate portions 23, 28 of the first leaf spring 11 and the third leaf spring 13, respectively, on the opposite side of the second leaf spring 12 along the plate thickness direction Z, in a direction along the outer surfaces 23a, 28a when viewed from the plate width direction Y (hereinafter referred to as the first specific direction). Therefore, the compressive stress in the first specific direction that occurs when a pressing load from the second leaf spring 12 along the plate thickness direction Z is applied to the outer surfaces 23a, 28a of the intermediate portions 23, 28 of the first leaf spring 11 and the third leaf spring 13, respectively, is alleviated, and even if the compression spring device 1 is significantly compressed and deformed in the plate thickness direction Z, it is possible to suppress the load generated in the intermediate portions 23, 28 of the first leaf spring 11 and the third leaf spring 13, respectively, and durability can be improved.

[0033] During the joining process, a compressive force in the longitudinal direction X is applied to both ends of the first leaf spring 11 and the third leaf spring 13 in a direction in which they approach each other in the longitudinal direction X, so that the compression spring device 1 in which a tensile stress in the first specific direction is applied to the outer surfaces 23a, 28a of the intermediate portions 23, 28 of the first leaf spring 11 and the third leaf spring 13, respectively, can be easily and reliably manufactured.

[0034] Next, a method for manufacturing the compression spring device 1 according to the second embodiment of the present invention will be described with reference to FIG. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and their description will be omitted, with only the differences being described.

[0035] In the manufacturing method of the compression spring device 1 of this embodiment, in the joining process, when the first leaf spring 11 and the third leaf spring 13 are elastically deformed so that the size of each of the first leaf spring 11 and the third leaf spring 13 in the longitudinal direction X is reduced, a load is applied to the central portion in the longitudinal direction X toward the opposite side of the second leaf spring 12 along the plate thickness direction Z in a state in which the outer surfaces 23a, 28a of each part located on both sides of the central portion in the longitudinal direction X of the intermediate portions 23, 28 of the first leaf spring 11 and the third leaf spring 13 are supported. In the illustrated example, at this time, outer surfaces 23a, 28a of both ends in the longitudinal direction X of intermediate portions 23, 28 of first leaf spring 11 and third leaf spring 13 are supported.

[0036] At the same time, as in the first embodiment, both end edges in the longitudinal direction X of each of the first leaf spring 11 and the third leaf spring 13 may be pressed in the longitudinal direction X, or in the intermediate portions 23, 28 of each of the first leaf spring 11 and the third leaf spring 13, the outer surfaces 23a, 28a of the portions located on both sides of the central portion in the longitudinal direction X in between may be pressed in a direction approaching each other in the plate thickness direction Z when viewed from the plate width direction Y.

[0037] As described above, according to the manufacturing method of the compression spring device 1 of the present embodiment, in the joining step, in the intermediate portions 23, 28 of the first leaf spring 11 and the third leaf spring 13, the outer surfaces 23a, 28a of each portion located on both sides of the central portion in the longitudinal direction X are supported, and a load is applied to the central portion in the longitudinal direction X toward the opposite side of the second leaf spring 12 along the plate thickness direction Z. This means that the intermediate portions 23, 28 of the first leaf spring 11 and the third leaf spring 13 are bent at three points, and the compression spring device 1 in which tensile stress in the first specific direction is applied to the outer surfaces 23a, 28a of the intermediate portions 23, 28 of the first leaf spring 11 and the third leaf spring 13 can be easily and accurately manufactured.

[0038] The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0039] For example, the third leaf spring 13 does not need to be provided. As shown in FIG. 5, the first leaf spring 11, the second leaf spring 12, and the third leaf spring 13 may be made to have the same size in the plate width direction Y, the first leaf spring 11, the second leaf spring 12, and the third leaf spring 13 may be separate bodies and positioned at the same position in the plate width direction Y, the second fixing portion 22 may be sandwiched in the plate thickness direction Z between the first fixing portion 21 and the protruding portion 27, the intermediate portions 24, 23 of the second leaf spring 12 and the first leaf spring 11 may face each other in the plate thickness direction Z, and the intermediate portions 24, 28 of the second leaf spring 12 and the third leaf spring 13 may face each other in the plate thickness direction Z. The compression spring device 2 shown in FIG. 5, as shown in FIGS. 6 and 7, can also be manufactured by the same method as that described with reference to FIGS.

[0040] In addition, within the scope of the invention, the components in the above-described embodiments may be replaced with well-known components as appropriate, and the above-described embodiments and variations may be combined as appropriate. [Explanation of symbols]

[0041] 1, 2 Pressure spring device 11 First leaf spring 12 Second leaf spring 21 First fixing portion (both ends in the longitudinal direction of the first leaf spring) 22 Second fixing portion (both ends in the longitudinal direction of the second leaf spring) 23 Middle part of first leaf spring 23a Exterior 23b Inside 24 Middle part of second leaf spring X length direction Y Plate width direction Z Thickness direction

Claims

1. a first leaf spring extending in a longitudinal direction and a second leaf spring; Both ends of the first leaf spring in the longitudinal direction are laminated and joined to both ends of the second leaf spring in the longitudinal direction in the plate thickness direction, The first leaf spring and the second leaf spring have longitudinal intermediate portions opposed to each other while being spaced apart from each other in a plate thickness direction, A length of an intermediate portion of the second leaf spring along a surface of the second leaf spring as viewed in a leaf width direction is shorter than a length of an intermediate portion of the first leaf spring along a surface of the first leaf spring as viewed in a leaf width direction; a middle portion of the first leaf spring is curved in a plate thickness direction so as to have a protruding curved shape toward a side away from the middle portion of the second leaf spring when viewed in a plate width direction, a first leaf spring forming step of forming the first leaf spring; a joining step of joining both ends of the first leaf spring in a longitudinal direction to both ends of the second leaf spring in a longitudinal direction, The first leaf spring forming step forms the first leaf spring so that a size in a longitudinal direction of the first leaf spring is larger than a size in a longitudinal direction of the second leaf spring, The joining process of this method for manufacturing a compression spring device includes joining both longitudinal ends of the first leaf spring to both longitudinal ends of the second leaf spring while elastically deforming the first leaf spring so that the longitudinal size of the first leaf spring is reduced.

2. 2. The manufacturing method of a compression spring device according to claim 1, wherein the joining step includes applying a longitudinal compressive force to both longitudinal ends of the first leaf spring in a direction in which the ends approach each other longitudinally when the first leaf spring is elastically deformed so that the longitudinal size of the first leaf spring is reduced.

3. 3. The method for manufacturing a compression spring device according to claim 1 or 2, wherein, in the joining step, when the first leaf spring is elastically deformed so that the longitudinal size of the first leaf spring is reduced, a load is applied to a longitudinal central portion of the intermediate portion of the first leaf spring in a direction toward the opposite side of the second leaf spring in the plate thickness direction while supporting outer surfaces of each portion located on both sides of a longitudinal central portion of the intermediate portion of the first leaf spring, the outer surfaces facing the opposite side of the second leaf spring in the plate thickness direction.

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