Method for manufacturing a disc spring, and disc spring

Abstract

The manufacturing method of the disc spring is as follows: the disc spring has a spring body (1e) formed in a ring shape, the spring body (1e) has an outer peripheral surface (1a) facing the outer side in the radial direction, an inner peripheral surface (1b) facing the inner side in the radial direction, an outer peripheral edge (1c) which is an end surface of the outer side in the radial direction, and an inner peripheral edge (1d) which is an end surface of the inner side in the radial direction, in a state where a support body (11) supporting at least the outer end portion in the radial direction of the inner peripheral surface (1b) exerts an axial compression force along the central axis of the spring body on the spring body, the support body and the spring body are relatively rotated around the central axis while being in sliding contact with each other, so as to exert a compression residual stress on at least the outer end portion in the radial direction of the inner peripheral surface.

Description

Technical Field

[0001] This invention relates to a method for manufacturing a disc spring, and to a disc spring itself.

[0002] This application claims priority based on Japanese Patent Application No. 2020-173168, filed on October 14, 2020, the contents of which are incorporated herein by reference. Background Technology

[0003] Conventionally, as a method for manufacturing disc springs, such as the method shown in Patent Document 1, the disc spring has a spring body formed in a ring shape. This spring body has an outer peripheral surface facing outwards, an inner peripheral surface facing inwards, an outer peripheral edge serving as an outer end face, and an inner peripheral edge serving as an inner end face. In the method shown in Patent Document 1, compressive residual stress is applied to the spring body by rotating and moving a ball supported in a rotatable manner while pressing against the inner peripheral surface of the spring body.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 5209904 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] In conventional disc spring manufacturing methods, the compressive residual stress applied to the spring body is greatest at a predetermined depth between the inner and outer circumferential surfaces. However, the inner circumferential surface, which generates the highest tensile stress during use, is not the greatest, which may make it difficult to improve the durability of the disc spring.

[0009] The present invention was made in view of the above circumstances, and its object is to provide a method for manufacturing a disc spring, and a disc spring that can produce a disc spring in which compressive residual stress is applied over the entire circumferential length of the radially outer end of the spring body, such that it is maximum at the inner circumferential surface and decreases towards the outer circumferential surface.

[0010] Solution for solving the problem

[0011] One aspect of the invention is a method for manufacturing a disc spring, the disc spring having a spring body formed in an annular shape, the spring body having: an outer peripheral surface facing radially outward; an inner peripheral surface facing radially inward; an outer peripheral edge being an end face of radially outward; and an inner peripheral edge being an end face of radially inward. Under a state where a compressive force along the central axis of the spring body is applied to the spring body using a support body supporting at least the radially outer end of the inner peripheral surface, a compressive residual stress is applied to at least the radially outer end of the inner peripheral surface by simultaneously causing the support body and the spring body to slide into contact with each other and rotate relative to each other around the central axis.

[0012] According to the above aspects, when the spring body is subjected to the axial compressive force by the support body at least radially outer end of the inner circumferential surface of the spring body, the support body and the spring body are rotated relative to each other around the central axis while sliding contact is made between them, thereby applying compressive residual stress to at least radially outer end of the inner circumferential surface of the spring body.

[0013] Therefore, it is possible to reliably obtain a disc spring in which a compressive residual stress is applied along the entire circumferential length around the central axis at the radially outer end of the spring body, with the maximum tensile stress occurring at the inner circumferential surface when using the disc spring, and decreasing towards the outer circumferential surface.

[0014] The spring body can also be elastically deformed along the axial direction when the support is used to apply the axial compressive force to the spring body.

[0015] In this case, when the support body applies the axial compressive force to the spring body, the spring body elastically deforms along the axial direction, thereby stretching at least the radially outer end of the inner circumferential surface of the spring body. This allows for the reliable application of high compressive residual stress to the radially outer end of the inner circumferential surface of the spring body.

[0016] The support may also have a plurality of pressing protrusions spaced apart in the circumferential direction, with at least the radially outer end of the inner circumferential surface supported by the plurality of pressing protrusions.

[0017] In this case, at least the radially outer end of the inner circumferential surface of the spring body is supported by a plurality of pressing protrusions spaced apart in the circumferential direction. This increases the contact pressure applied from the support to the inner circumferential surface of the spring body and reliably applies high compressive residual stress to the radially outer end of the inner circumferential surface of the spring body.

[0018] Furthermore, in a longitudinal sectional view along the axial direction and through the central axis, the inner circumferential surfaces that are opposed to each other in the axial direction and the pressing surfaces of the pressing protrusions are inclined in the same direction relative to the horizontal surface orthogonal to the central axis.

[0019] In this case, in the longitudinal sectional view, the inner circumferential surfaces of the spring bodies, which are axially opposed to each other, and the pressing surfaces of the pressing protrusions are inclined in the same direction relative to the horizontal plane. Therefore, when compressive residual stress is applied to the inner circumferential surface of the spring body, it is possible to suppress the excessive load exerted on the pressing surfaces by the corner portion connecting the inner circumferential surface and the outer periphery of the spring body, while simultaneously allowing the inner circumferential surface of the spring body to have a radial width, thus facilitating the application of compressive residual stress.

[0020] With the axial gap provided between the portion of the inner circumferential surface located closer to the radial side than the radial outer end and the pressing surface, the axial compressive force is applied to the spring body.

[0021] In this case, with an axial gap between the portion of the inner circumferential surface of the spring body located closer to the radial side than the radial outer end and the pressing surface, the axial compressive force is applied to the spring body. Therefore, when the support and the spring body slide in contact with each other while rotating relative to each other around the central axis, the sliding resistance generated between the pressing surface and the inner circumferential surface of the spring body can be suppressed, and the residual compressive stress can be locally applied, for example, to the radial outer end of the inner circumferential surface of the spring body. Furthermore, when the spring body is elastically deformed along the axial direction, the amount of axial compressive deformation of the spring body can be adjusted, and the residual compressive stress applied to at least the radial outer end of the inner circumferential surface of the spring body can be easily adjusted.

[0022] Furthermore, the pressing surface of the pressing protrusion, which faces the inner circumferential surface in the axial direction, can be viewed radially as a curved shape protruding in the axial direction.

[0023] In this case, the pressing surface, when viewed radially, exhibits a curved shape that protrudes along the axial direction. Therefore, when compressive residual stress is applied to the inner circumferential surface of the spring body, the load applied to both the pressing surface and the inner circumferential surface of the spring body can be suppressed, while reliably increasing the contact pressure applied from the pressing surface to the inner circumferential surface of the spring body.

[0024] The compressive residual stress can also be applied to multiple disc springs simultaneously while they are connected in series along the axial direction.

[0025] In this case, the compressive residual stress is applied to multiple disc springs simultaneously. This allows for the efficient generation of multiple disc springs with compressive residual stress applied over the entire circumferential length of the outer radial end of the spring body, as described above.

[0026] The compressive residual stress can also be applied to multiple disc springs simultaneously while they are oriented in the same direction as the axial direction and arranged on the same plane.

[0027] In this case, the compressive residual stress is applied to multiple disc springs simultaneously. This allows for the efficient generation of multiple disc springs with compressive residual stress applied over the entire circumferential length of the outer radial end of the spring body, as described above.

[0028] A disc spring according to one aspect of the invention has a spring body formed in an annular shape, the spring body having: an outer peripheral surface facing radially outward; an inner peripheral surface facing radially inward; an outer peripheral edge being an end face of the radially outward; and an inner peripheral edge being an end face of the radially inward. At least at the radially outer end portion of the inner peripheral surface, a compressive residual stress is applied over its entire circumferential length along the central axis surrounding the spring body. The compressive residual stress is maximum at the inner peripheral surface and decreases towards the outer peripheral surface. The surface roughness of the portion of the inner peripheral surface to which the compressive residual stress is applied is less than the surface roughness of the portion located closer to the radially inward.

[0029] Based on the above aspects, compressive residual stress is applied along the entire circumferential length of the radial outer end of the spring body, with the maximum tensile stress occurring at the inner circumferential surface when using a disc spring, and decreasing towards the outer circumferential surface, thus improving the durability of the disc spring.

[0030] In the inner circumferential surface of the spring body, the surface roughness of the radially outer end, where the highest tensile stress is generated when using a disc spring, is less than the surface roughness of the portion located radially closer to the inner side than the portion where the compressive residual stress is applied. Therefore, when using a disc spring, it is possible to suppress situations where stress concentration occurs at the radially outer end of the inner circumferential surface of the spring body, for example, due to damage or surface roughness deviations, and to prevent damage to components supporting the radially outer end of the inner circumferential surface of the spring body.

[0031] Another aspect of the disc spring of the present invention has a spring body formed in an annular shape, the spring body having: an outer peripheral surface facing radially outward; an inner peripheral surface facing radially inward; an outer peripheral edge being an end face of the radially outward; and an inner peripheral edge being an end face of the radially inward. At least at the radially outer end portion of the inner peripheral surface, a compressive residual stress is applied over the entire circumferential length along the central axis surrounding the spring body. The compressive residual stress is maximum at the inner peripheral surface and decreases towards the outer peripheral surface. The hardness of the portion of the inner peripheral surface to which the compressive residual stress is applied is higher than the hardness of the portion located closer to the radially inward.

[0032] Based on the above aspects, compressive residual stress is applied along the entire circumferential length of the radial outer end of the spring body, with the maximum tensile stress occurring at the inner circumferential surface when using a disc spring, and decreasing towards the outer circumferential surface, thus improving the durability of the disc spring.

[0033] In the inner circumferential surface of the spring body, the hardness of the radially outer end, where the highest tensile stress is generated when using a disc spring, is higher than the hardness of the portion located radially closer to the inner side than the portion where the compressive residual stress is applied. Therefore, when using a disc spring, it is possible to suppress wear or stress concentration at the radially outer end of the inner circumferential surface of the spring body, such as due to damage.

[0034] In this configuration, the surface roughness of the portion of the inner circumferential surface to which the compressive residual stress is applied may be less than the surface roughness of the portion located closer to the radial side.

[0035] In this case, the surface roughness of the radially outer end of the inner circumferential surface of the spring body, where the highest tensile stress is generated when using a disc spring, is less than the surface roughness of the portion located radially closer to the inner side than the portion where the compressive residual stress is applied. Therefore, when using a disc spring, it is possible to suppress situations where stress concentration occurs at the radially outer end of the inner circumferential surface of the spring body, for example, due to damage or surface roughness deviations, and to prevent damage to components supporting the radially outer end of the inner circumferential surface of the spring body.

[0036] Invention Effects

[0037] According to the present invention, a disc spring can be obtained in which a compressive residual stress is applied over the entire circumferential length of the radially outer end of the spring body, with the maximum tensile stress occurring at the inner circumferential surface when using the disc spring, and decreasing towards the outer circumferential surface. Attached Figure Description

[0038] Figure 1This is an explanatory diagram illustrating a method for manufacturing a disc spring as shown in the first embodiment of the present invention.

[0039] Figure 2 This is a coordinate graph showing the distribution of the compressive residual stress in the thickness direction of each disc spring in the embodiments and comparative examples.

[0040] Figure 3 This is an explanatory diagram illustrating a method for manufacturing a disc spring as a second embodiment of the present invention.

[0041] Figure 4A This is a side view of the main body of the first support of a manufacturing apparatus used to implement the manufacturing method of the disc spring shown as a second embodiment of the present invention.

[0042] Figure 4B This is a top view of the pressing member of the first support body of the manufacturing apparatus used to implement the manufacturing method of the disc spring shown as a second embodiment of the present invention.

[0043] Figure 5A This is a top view of the shaft portion of the second support body used in a manufacturing apparatus for implementing the manufacturing method of the disc spring shown as a second embodiment of the present invention.

[0044] Figure 5B This is a top view of the flat plate portion of the second support body of a manufacturing apparatus used to implement the manufacturing method of the disc spring shown as a second embodiment of the present invention.

[0045] Figure 6 This is an explanatory diagram illustrating a method for manufacturing a disc spring as shown in the third embodiment of the present invention.

[0046] Figure 7 This is an explanatory diagram illustrating a method for manufacturing a disc spring as shown in the fourth embodiment of the present invention. Detailed Implementation

[0047] (First Implementation)

[0048] The following is for reference Figure 1 The manufacturing method of the disc spring of the present invention and the first embodiment of the disc spring will be described.

[0049] The disc spring 1 is formed by processing a sheet of metal. The spring body 1e of the disc spring 1 is formed into a ring with a central axis O.

[0050] Hereinafter, the direction along the central axis O will be called the axial direction, the direction that intersects the central axis O when viewed from the axial direction will be called the radial direction, and the direction of rotation around the central axis O will be called the circumferential direction.

[0051] The spring body 1e has an outer peripheral surface 1a, an inner peripheral surface 1b, an outer peripheral edge 1c, and an inner peripheral edge 1d.

[0052] The outer peripheral surface 1a faces radially outward, and the inner peripheral surface 1b faces radially inward. Both the outer peripheral surface 1a and the inner peripheral surface 1b are inclined relative to the central axis O. The spring body 1e is formed into an umbrella shape or a file-tipped shape that is open in the axial direction.

[0053] The outer perimeter 1c is the radially outer end face of the spring body 1e, and the inner perimeter 1d is the radially inner end face of the spring body 1e.

[0054] Furthermore, as a disc spring, it can also be configured with an outer claw protruding radially outward from the outer periphery 1c, or an inner claw protruding radially inward from the inner periphery 1d.

[0055] Next, the manufacturing apparatus 10 used for the manufacturing method of the disc spring in this embodiment will be described.

[0056] The manufacturing apparatus 10 applies compressive residual stress to at least the radially outer end of the inner circumferential surface 1b of the spring body 1e. The manufacturing apparatus 10 includes a first support 11 and a second support 12 coaxially arranged. The first support 11 and the second support 12 are formed in the shape of circular plates. The first support 11 and the second support 12 support the spring body 1e from both axial sides while being coaxial with the central axis O of the spring body 1e. The first support 11 and the second support 12 are arranged in a manner that allows them to be relatively close or far apart in the axial direction.

[0057] The first support 11 supports at least the radially outer end of the inner peripheral surface 1b of the spring body 1e, and the second support 12 supports at least the radially inner end of the outer peripheral surface 1a of the spring body 1e.

[0058] The first support 11 is configured to rotate about a central axis O. The first support 11 has a plurality of pressing protrusions 13 spaced apart circumferentially. The plurality of pressing protrusions 13 support at least the radially outer end of the inner circumferential surface 1b of the spring body 1e. The pressing protrusions 13 are located radially outerer than the inner circumferential edge 1d of the spring body 1e. The pressing protrusions 13 are disposed on the surface of the first support 11 opposite the second support 12 axially. Three or more pressing protrusions 13 are provided at equal intervals circumferentially. An even number of pressing protrusions 13 are provided, each pressing protrusion 13 being radially opposite the other pressing protrusions 13.

[0059] Alternatively, the pressing protrusion 13 can be integrally formed with the first support body 11. The pressing protrusion 13 can also be fixed to the first support body 11 by screws or the like. Alternatively, the pressing protrusion 13 may not be provided on the first support body 11.

[0060] exist Figure 1 In the longitudinal sectional view shown along the axial direction and through the central axis O and the circumferential center of the pressing protrusion 13, the inner circumferential surface 1b of the spring body 1e and the pressing surface 13a of the pressing protrusion 13, which are axially opposed to each other, are inclined in the same direction relative to the horizontal plane orthogonal to the central axis O. Furthermore, the pressing surface 13a may also extend along the horizontal plane in the longitudinal sectional view.

[0061] In the longitudinal sectional view, the angle of inclination θ2 of the pressing surface 13a relative to the horizontal plane is smaller than the angle of inclination θ1 of the inner circumferential surface 1b of the spring body 1e relative to the horizontal plane when there is no elastic deformation in the axial direction. Furthermore, these angles θ1 and θ2 can also be the same.

[0062] The pressing surface 13a, when viewed radially, is a curved shape that protrudes axially, and the pressing protrusion 13 is formed as a half-cylinder extending radially.

[0063] The first support 11 and the second support 12 are each provided with a limiting part 16 protruding in a direction opposite to each other in the axial direction. When the first support 11 and the second support 12 move closer together in the axial direction, these limiting parts 16 abut against each other in the axial direction, limiting further axial movement of the first support 11 and the second support 12. This defines the amount of elastic deformation of the spring body 1e in the direction of axial compression. The limiting part 16 is coaxially disposed with the central axis O and inserted into the inner side of the spring body 1e. The outer peripheral surface of the limiting part 16 abuts against or approaches the inner peripheral edge 1d of the spring body 1e.

[0064] Alternatively, the limiting part 16 may not be provided, or it may be provided only on either the first support 11 or the second support 12. Furthermore, the limiting part may be configured to define the amount of elastic deformation of the spring body 1e by abutting against the outer periphery 1c of the spring body 1e.

[0065] Next, the manufacturing method of the disc spring will be explained.

[0066] First, the disc spring 1 is subjected to shot peening for hardening. Alternatively, shot peening of the disc spring 1 may not be performed.

[0067] Next, while the first support 11 and the second support 12 are applying an axial compressive force to the spring body 1e, the first support 11 and the spring body 1e are made to slide into contact with each other while rotating relative to each other around the central axis O. As a result, compressive residual stress is applied to at least the radially outer end of the inner circumferential surface 1b of the spring body 1e over its entire circumferential length.

[0068] In the illustrated example, when an axial compressive force is applied to the spring body 1e, the first support 11 and the second support 12 move closer to each other axially, causing the limiting portions 16 of each support 11 and the second support 12 to abut against each other axially. This causes the spring body 1e to elastically deform by a predetermined amount in the direction of axial compression, thereby generating tensile stress on the inner circumferential surface 1b of the spring body 1e. Alternatively, the spring body 1e may not be elastically deformed axially.

[0069] At this time, an axial gap is pre-set between the portion of the inner circumferential surface 1b of the spring body 1e located closer to the radial side than the radial outer end and the pressing surface 13a of the pressing protrusion 13. That is, even when the spring body 1e is elastically deformed in the direction of axial compression, in the longitudinal sectional view, the inclination angle θ2 of the pressing surface 13a relative to the horizontal plane is smaller than the inclination angle θ3 of the inner circumferential surface 1b of the spring body 1e relative to the horizontal plane.

[0070] Furthermore, at this time, with these tilt angles θ2 and θ3 being the same and the spring body 1e being elastically deformed along the axial direction, it is not necessary to provide an axial gap between the portion of the inner circumferential surface 1b of the spring body 1e that is closer to the radial inner side than the radial outer end and the pressing surface 13a.

[0071] Furthermore, when the first support 11 and the second support 12 apply an axial compressive force to the spring body 1e, and the first support 11 is rotated relative to the spring body 1e around the central axis O, the frictional force generated between the spring body 1e and the second support 12 restricts the rotational movement of the spring body 1e relative to the second support 12, and the pressing surface 13a slides circumferentially on the inner circumferential surface 1b of the spring body 1e.

[0072] At this time, the surface roughness of the portion of the second support 12 that abuts against the spring body 1e is greater than the surface roughness of the portion of the first support 11 that abuts against the spring body 1e. Alternatively, the surface roughness of the former can be set to be lower than that of the latter.

[0073] Furthermore, at this time, the radially outer end of the inner circumferential surface 1b of the spring body 1e is rubbed with almost no wear (maximum number of μm), and its surface roughness is smaller compared to before the first support 11 and the spring body 1e were rotated relative to each other. Even if wear occurs, the distribution of compressive residual stress in the thickness direction will not change solely due to this wear.

[0074] In addition, at this time, the hardness of the radial outer end of the inner circumferential surface 1b of the spring body 1e is higher than that of the first support 11 and the spring body 1e before relative rotation.

[0075] In the disc spring 1 formed as described above, the compressive residual stress is greatest at the inner circumferential surface 1b, where the highest tensile stress is generated when using the disc spring 1, over the entire circumferential length of the radial outer end of the spring body 1e, and decreases towards the outer circumferential surface 1a.

[0076] In the inner circumferential surface 1b of the spring body 1e, the portion of the first support 11 that is in sliding contact with the outer periphery 1c and subjected to compressive residual stress is located between 30%, preferably 20%, of the width W of the spring body 1e radially inward away from it. The width W of the spring body 1e in the longitudinal sectional view is the distance between the outer periphery 1c and the inner periphery 1d along the inner circumferential surface 1b.

[0077] Furthermore, if the portion on the inner circumferential surface 1b of the spring body 1e to which the compressive residual stress is applied is located at a position extending radially inward beyond 30% of the width W of the spring body 1e from the connection portion with the outer periphery 1c, it is difficult to increase the compressive residual stress to the desired level.

[0078] Furthermore, in this disc spring 1, the surface roughness of the portion of the inner circumferential surface 1b to which compressive residual stress is applied is less than the surface roughness of the portion located closer to the radial inner side.

[0079] Furthermore, in this disc spring 1, the portion of the inner circumferential surface 1b to which compressive residual stress is applied has a higher hardness than the portion located on the inner side closer to the radial direction.

[0080] In addition, the surface roughness of the portion of the inner circumferential surface 1b to which compressive residual stress is applied may be less than or greater than the surface roughness of the portion located closer to the radial side, and the hardness of the portion of the inner circumferential surface 1b to which compressive residual stress is applied may be less than or greater than the hardness of the portion located closer to the radial side.

[0081] In addition, the surface roughness of the portion of the inner circumferential surface 1b to which compressive residual stress is applied may be greater than that of the portion located closer to the radial side, and the hardness of the portion of the inner circumferential surface 1b to which compressive residual stress is applied may be greater than that of the portion located closer to the radial side.

[0082] As explained above, in the method for manufacturing a disc spring according to this embodiment, when an axial compressive force is applied to the spring body 1e by using a first support 11 that supports at least the radially outer end of the inner circumferential surface 1b of the spring body 1e, a compressive residual stress is applied to at least the radially outer end of the inner circumferential surface 1b of the spring body 1e by making the first support 11 and the spring body 1e slide into contact with each other while rotating relative to each other around the central axis O.

[0083] Therefore, a disc spring 1 can be reliably obtained such that a compressive residual stress is applied over the entire circumferential length of the radially outer end of the spring body 1e, with the maximum tensile stress occurring at the inner circumferential surface 1b when using the disc spring 1, and decreasing towards the outer circumferential surface 1a.

[0084] When the first support 11 applies an axial compressive force to the spring body 1e, the spring body 1e is elastically deformed along the axial direction, thereby stretching at least the radially outer end of the inner circumferential surface 1b of the spring body 1e. This allows for the reliable application of a high compressive residual stress to the radially outer end of the inner circumferential surface 1b of the spring body 1e.

[0085] At least the radially outer end of the inner circumferential surface 1b of the spring body 1e is supported by a plurality of pressing protrusions 13 spaced apart in the circumferential direction. As a result, the contact pressure applied from the first support 11 to the inner circumferential surface 1b of the spring body 1e can be increased, and a high compressive residual stress can be reliably applied to the radially outer end of the inner circumferential surface 1b of the spring body 1e.

[0086] In the longitudinal sectional view, the inner circumferential surface 1b of the spring body 1e and the pressing surface 13a of the pressing protrusion 13, which are axially opposed to each other, are inclined in the same direction relative to the horizontal plane. Therefore, when compressive residual stress is applied to the inner circumferential surface 1b of the spring body 1e, excessive load on the pressing surface 13a can be suppressed at the corner portion connecting the inner circumferential surface 1b and the outer periphery 1c of the spring body 1e, and compressive residual stress can be easily applied by giving the inner circumferential surface 1b of the spring body 1e a radial width.

[0087] With an axial gap provided between the portion of the inner circumferential surface 1b of the spring body 1e located closer to the radial side than the radial outer end and the pressing surface 13a, an axial compressive force is applied to the spring body 1e. Therefore, when the first support 11 and the spring body 1e slide in contact with each other while rotating relative to each other around the central axis O, the sliding resistance generated between the pressing surface 13a and the inner circumferential surface 1b of the spring body 1e can be suppressed, and the residual compressive stress can be locally applied, for example, to the radial outer end of the inner circumferential surface 1b of the spring body 1e. Furthermore, the axial compressive deformation of the spring body 1e can be adjusted, and the residual compressive stress applied to at least the radial outer end of the inner circumferential surface 1b of the spring body 1e can be easily adjusted.

[0088] The pressing surface 13a, when viewed radially, has a curved shape that protrudes axially. As a result, when compressive residual stress is applied to the inner circumferential surface 1b of the spring body 1e, the load applied to the pressing surface 13a and the inner circumferential surface 1b of the spring body 1e can be suppressed, while the contact pressure applied from the pressing surface 13a to the inner circumferential surface 1b of the spring body 1e can be reliably increased.

[0089] According to this embodiment, the disc spring 1 has a compressive residual stress applied along the entire circumferential length of the outer radial end of the spring body 1e, with the maximum stress at the inner circumferential surface 1b where the highest tensile stress is generated when using the disc spring 1, and the stress decreases as it moves toward the outer circumferential surface 1a. Therefore, the durability of the disc spring 1 can be improved.

[0090] In the inner circumferential surface 1b of the spring body 1e, the surface roughness of the radially outer end that generates the highest tensile stress when using the disc spring 1 is less than the surface roughness of the portion located closer to the radially inner side than the portion where the compressive residual stress is applied. Therefore, when using the disc spring 1, it is possible to suppress situations where stress concentration occurs at the radially outer end of the inner circumferential surface 1b of the spring body 1e due to damage or surface roughness deviations, and to prevent damage to components supporting the radially outer end of the inner circumferential surface 1b of the spring body 1e.

[0091] In the inner circumferential surface 1b of the spring body 1e, the hardness of the radially outer end, where the highest tensile stress is generated when using the disc spring 1, is higher than the hardness of the portion located closer to the radial direction on the inner side than the portion where the compressive residual stress is applied. Therefore, when using the disc spring 1, it is possible to suppress wear or stress concentration at the radially outer end of the inner circumferential surface 1b of the spring body 1e, such as due to damage.

[0092] Next, for each disc spring in the embodiments and comparative examples, the distribution of compressive residual stress in the thickness direction will be explained.

[0093] First, shot peening was performed on each disc spring of Examples 1, 2 and Comparative Examples 1 to 3 under the same conditions.

[0094] Next, in Examples 1 and 2, while the first support 11 and the second support 12 are applying an axial compressive force to the spring body 1e, the first support 11 and the spring body 1e are made to slide into contact with each other while rotating relative to each other around the central axis O. In Comparative Examples 1 and 2, a ball is provided that is rotatably supported on the first support. By pressing the ball against the radially outer end of the inner circumferential surface of the spring body, while the spring body is being subjected to an axial compressive force, the first support is rotated relative to the spring body around the central axis O while the ball is being rotated.

[0095] When an axial compressive force is applied to the spring body, in Example 1 and Comparative Example 1, the spring body is elastically deformed in the direction of axial compression, while in Example 2 and Comparative Example 2, the spring body is not elastically deformed in the axial direction.

[0096] In Comparative Example 3, only shot peening was performed.

[0097] The result is, as Figure 2 As shown, in Examples 1 and 2, it was confirmed that the compressive residual stress applied to the radial outer end of the spring body 1e is maximum at the inner circumferential surface 1b with a depth of zero, and decreases towards the outer circumferential surface 1a. In Comparative Examples 1 to 3, it was confirmed that the compressive residual stress is maximum at a predetermined depth between the inner and outer circumferential surfaces, and is not maximum at the inner circumferential surface with a depth of zero.

[0098] In addition, the compressive residual stress at the inner circumferential surface 1b with a depth of zero was confirmed to be higher in both Examples 1 and 2 than in Comparative Example 3, and further increased after shot peening hardening. It was also confirmed that Example 1 was higher than Example 2.

[0099] (Second Implementation)

[0100] Reference Figures 3-5B A second embodiment of the method for manufacturing the disc spring of the present invention will be described. Furthermore, in the description of this embodiment, configurations identical to those in the first embodiment described above are labeled with the same reference numerals and their descriptions are omitted; only the differences are described.

[0101] In this embodiment, with multiple disc springs 1 connected in series along the axial direction, the compressive residual stress is applied to the multiple disc springs 1 simultaneously. Furthermore, the multiple disc springs 1 are configured such that their axial directions are the same.

[0102] like Figure 3 As shown, the manufacturing apparatus 20 for implementing the disc spring manufacturing method of this embodiment includes a first support 21 and a second support 22. The first support 21 and the second support 22 are respectively configured to be rotatable about a central axis O.

[0103] The first support 21 has a cylindrical main body 23 and multiple pressing parts 24.

[0104] The main body 23 has a cylindrical peripheral wall 23a and a circular plate-shaped bottom 23b connected to the lower end of the peripheral wall 23a. The main body 23 is coaxially arranged with the central axis O of the spring body 1e. An annular cover (not shown) is detachably mounted on the upper end of the peripheral wall 23a.

[0105] like Figure 4AAs shown, a plurality of engaging holes (slits) 23c are formed circumferentially spaced in the peripheral wall portion 23a. The engaging holes 23c extend axially. Alternatively, the engaging holes 23c may not extend to the axial end of the peripheral wall portion 23a, but may be located at the axial center of the peripheral wall portion 23a. The engaging holes 23c may also extend axially over the entire area of ​​the peripheral wall portion 23a. Alternatively, engaging grooves recessed from the inner circumferential surface of the peripheral wall portion 23a toward the outer circumferential surface may be provided instead of engaging holes 23c. By providing engaging grooves, the strength of the peripheral wall portion 23a is increased.

[0106] The pressing member 24 is formed in the shape of a circular plate. The pressing member 24 is coaxially arranged with the central axis O of the spring body 1e. A plurality of pressing members 24 are arranged at intervals in the axial direction. The pressing member 24 supports at least the radially outer end of the inner circumferential surface 1b of the spring body 1e.

[0107] like Figure 4B As shown, a hole 24a is formed in the radial center of the pressing member 24. A limiting portion 25 (described later) is inserted into the hole 24a of the pressing member 24 located on the bottommost side 23b, while a shaft portion 26 of the second support body 22 (described later) is inserted into the hole 24a of the other pressing members 24. A plurality of engaging claws 24b are provided at circumferential intervals along the outer periphery of the pressing member 24. The engaging claws 24b protrude radially outward from the outer periphery of the pressing member 24.

[0108] The pressing member 24 is disposed inside the main body 23. At this time, the engaging claws 24b engage with the engaging holes 23c respectively. Thus, the pressing member 24 is mounted on the main body 23 in a manner that prevents relative rotation but allows relative movement in the axial direction. Therefore, the main body 23 and the pressing member 24 rotate together.

[0109] A limiting part 25 is provided on the first support body 21. The limiting part 25 is arranged coaxially with the central axis O. The limiting part 25 protrudes from the radial center of the bottom 23b of the main body 23 toward the shaft 26.

[0110] The second support 22 has a shaft portion 26 and multiple flat plate portions 27.

[0111] The shaft portion 26 is coaxially arranged with the central axis O. The shaft portion 26 is inserted into the inside of the spring body 1e.

[0112] like Figure 5A As shown, a plurality of engaging grooves 26a are formed circumferentially at intervals on the outer peripheral surface of the shaft portion 26. The engaging grooves 26a extend axially.

[0113] The plate portion 27 is formed in the shape of a circular plate. The plate portion 27 is coaxially arranged with the central axis O of the spring body 1e. A plurality of plate portions 27 are arranged at intervals in the axial direction. The plate portion 27 supports at least the radially inner end of the outer peripheral surface 1a of the spring body 1e.

[0114] like Figure 5B As shown, a hole 27a is formed in the radial center of the flat plate portion 27. Multiple engaging claws 27b are provided at circumferential intervals on the circumferential surface of the hole 27a. The engaging claws 27b protrude radially inward from the circumference of the hole 27a. The shaft portion 26 is inserted through the hole 27a. At this time, the engaging claws 27b engage with the engaging grooves 26a respectively. Thus, the flat plate portion 27 is mounted on the shaft portion 26 in a manner that prevents relative rotation but allows relative axial movement. Therefore, the shaft portion 26 and the flat plate portion 27 rotate integrally.

[0115] An anti-rotation member 28 is provided on the flat plate portion 27. The anti-rotation member 28 restricts the rotational movement of the spring body 1e relative to the second support 22 about the central axis O. The anti-rotation member 28 is provided on the surface of the flat plate portion 27 opposite to the outer peripheral surface 1a of the spring body 1e (in the illustrated example, the surface on the bottom 23b side). In this embodiment, a plurality of inner claws are provided at circumferential intervals along the inner periphery of the spring body 1e, and the anti-rotation member 28 is disposed between the inner claws that are adjacent to each other in the circumferential direction.

[0116] Furthermore, if the spring body 1e does not have an inner claw, the stop member 28 can also be configured to clamp the radial inner end of the spring body 1e from both sides in the axial direction.

[0117] Alternatively, the anti-rotation component 28 may be omitted, and the rotational movement of the spring body 1e relative to the second support 22 may be limited by the frictional force generated between the spring body 1e and the plate portion 27.

[0118] The pressing member 24 and the flat plate portion 27 are alternately inserted into the shaft portion 26. The pressing member 24 and the flat plate portion 27 are arranged axially spaced apart. The spring body 1e is disposed between the pressing member 24 and the flat plate portion 27. The spring body 1e is supported from both sides axially by the pressing member 24 and the flat plate portion 27. Specifically, the pressing member 24 supports at least the radially outer end of the inner peripheral surface 1b of the spring body 1e, and the flat plate portion 27 supports at least the radially inner end of the outer peripheral surface 1a of the spring body 1e.

[0119] The pressing member 24 and the flat plate 27 are movable in the axial direction. That is, the pressing member 24 and the flat plate 27 are configured to be able to approach or move away from each other in the axial direction.

[0120] Furthermore, to reduce friction caused by sliding between the pressing member 24 and the flat plate 27, the surface roughness of the portion of the pressing member 24 that abuts against the flat plate 27 can be made smaller than the surface roughness of other portions, and the surface roughness of the portion of the flat plate 27 that abuts against the pressing member 24 can be made smaller than the surface roughness of other portions. Additionally, a thrust bearing can be provided between the pressing member 24 and the flat plate 27.

[0121] When the first support 21 and the second support 22 move closer together in the axial direction, the limiting part 25 and the shaft part 26 abut against each other in the axial direction, limiting the further axial movement of the first support 21 and the second support 22. That is, the shaft part 26 also functions as a limiting part.

[0122] Next, the manufacturing method of the disc spring using manufacturing apparatus 20 will be described.

[0123] First, the disc spring 1 is shot-peened for hardening. Then, with an axial compressive force applied to the spring body 1e using the first support 21 and the second support 22, the first support 21 and the spring body 1e are made to slide into contact with each other while rotating relative to each other around the central axis O. This applies compressive residual stress to at least the radially outer end of the inner circumferential surface 1b of the spring body 1e over its entire circumferential length.

[0124] In the illustrated example, when an axial compressive force is applied to the spring body 1e, the first support 21 and the second support 22 move closer to each other axially, causing the limiting portion 25 of the first support 21 to abut against the shaft portion 26 of the second support 22 axially. This causes the spring body 1e to elastically deform by a predetermined amount in the direction of axial compression, thereby generating tensile stress on the inner circumferential surface 1b of the spring body 1e.

[0125] Furthermore, with an axial compressive force applied to the spring body 1e using the first support 21 and the second support 22, the first support 21 is rotated in one direction around the central axis O, and the second support 22 is rotated in the other direction around the central axis O. Since the anti-rotation member 28 restricts the rotational movement of the spring body 1e relative to the second support 22 around the central axis O, the spring body 1e also rotates in the other direction around the central axis O as the second support 22 rotates. Consequently, the pressing member 24 slides circumferentially on the inner circumferential surface 1b of the spring body 1e.

[0126] According to the disc spring manufacturing method of this embodiment, when the spring body 1e is subjected to an axial compressive force by a first support 21 that supports at least the radially outer end of the inner peripheral surface 1b of the spring body 1e, a compressive residual stress is applied to at least the radially outer end of the inner peripheral surface 1b of the spring body 1e by making the first support 21 and the spring body 1e slide into contact with each other while rotating relative to each other around the central axis O.

[0127] Therefore, a disc spring 1 can be reliably obtained such that a compressive residual stress is applied over the entire circumferential length of the radially outer end of the spring body 1e, with the maximum tensile stress occurring at the inner circumferential surface 1b when using the disc spring 1, and decreasing towards the outer circumferential surface 1a.

[0128] Furthermore, according to the method for manufacturing disc springs in this embodiment, since the compressive residual stress is applied to multiple disc springs 1 simultaneously, it is possible to efficiently obtain multiple disc springs 1 with the compressive residual stress applied as described above over the entire circumferential length of the outer radial end of the spring body 1e.

[0129] (Third Implementation)

[0130] Next, refer to Figure 6 A third embodiment of the method for manufacturing the disc spring of the present invention will be described. Furthermore, in the description of this embodiment, structures identical to those in the second embodiment described above are labeled with the same reference numerals and their descriptions are omitted; only the differences are described.

[0131] In this embodiment, similar to the second embodiment described above, the compressive residual stress is applied simultaneously to the multiple disc springs 1 when they are connected in series along the axial direction. Furthermore, in this embodiment, the multiple disc springs 1 are arranged with their axial directions facing opposite directions.

[0132] The manufacturing apparatus 30 used for the manufacturing method of the disc spring in this embodiment will be described.

[0133] like Figure 6 As shown, in the manufacturing apparatus 30, the pressing member 24A of the plurality of pressing members 24 of the first support body 21, except for the pressing member 24 located on the side closest to the bottom 23b, is configured to support two disc springs 1. Specifically, two disc springs 1 with axial orientations opposite to each other are configured to sandwich the pressing member 24A axially. At this time, the two disc springs 1 are configured such that the inner peripheral surface 1b of the spring body 1e faces the pressing member 24A. The pressing member 24A supports at least the radially outer end of the inner peripheral surface 1b of the spring body 1e of the two disc springs 1 on both sides of the pressing member 24A.

[0134] Of the multiple flat plates 27 of the second support 22, the flat plate 27A, excluding the one furthest from the bottom 23b, is configured to support two disc springs 1. Specifically, two disc springs 1 with axial orientations opposite to each other are configured to sandwich the flat plate 27A axially. In this configuration, the outer peripheral surface 1a of the spring body 1e faces the flat plate 27A. The flat plate 27A supports at least the radially inner ends of the outer peripheral surface 1a of the spring body 1e of the two disc springs 1 on both sides of the flat plate 27A. Furthermore, anti-rotation members 28 are provided on both sides of the flat plate 27A.

[0135] The manufacturing method of the disc spring using the manufacturing apparatus 30 is the same as in the second embodiment. That is, while the spring body 1e is subjected to an axial compressive force by means of the first support member 21 and the second support member 22, the first support member 21 and the spring body 1e are slidably contacted to each other while being rotated relative to each other around the central axis O. As a result, compressive residual stress is applied to at least the radially outer end of the inner circumferential surface 1b of the spring body 1e over its entire circumferential length.

[0136] According to the manufacturing method of the disc spring of this embodiment, the same effect as that of the second embodiment can be achieved. That is, a disc spring 1 can be reliably obtained in which a compressive residual stress is applied along the entire circumferential length of the radially outer end of the spring body 1e, with the maximum stress at the inner circumferential surface 1b where the highest tensile stress is generated when using the disc spring 1, and decreasing towards the outer circumferential surface 1a. In addition, since the compressive residual stress is applied to multiple disc springs 1 simultaneously, multiple disc springs 1 with the compressive residual stress applied as described above along the entire circumferential length of the radially outer end of the spring body 1e can be efficiently obtained.

[0137] Furthermore, according to this embodiment, since the two disc springs 1 are supported by a pressing member 24 (24A) and a flat plate portion 27 (27A), the number of components of the pressing member 24 and the flat plate portion 27 can be reduced. Therefore, the configuration of the first support body 21 and the second support body 22 can be simplified. In addition, the axial dimension of the manufacturing apparatus 30 can be shortened.

[0138] (Fourth Implementation)

[0139] Reference Figure 7 A fourth embodiment of the method for manufacturing the disc spring of the present invention will be described. Furthermore, in the description of this embodiment, configurations identical to those in the first to third embodiments described above are labeled with the same reference numerals and their descriptions are omitted; only the differences are described.

[0140] In this embodiment, the compressive residual stress is applied to the multiple disc springs 1 simultaneously while they are oriented in the same direction as the axial direction and arranged on the same plane.

[0141] The manufacturing apparatus 40 used in the method for manufacturing the disc spring according to this embodiment will be described.

[0142] like Figure 7 As shown, in the manufacturing apparatus 40, the main body 23 of the first support 21 is coaxially arranged with a rotation axis Og that is different from the central axis O of the spring body 1e. Multiple disc springs 1 are arranged at intervals around the rotation axis Og, in a state where they are arranged on the same plane. Each of the multiple disc springs 1 is provided with a shaft portion 26, a flat plate portion 27, and a pressing member 24. The shaft portion 26, the flat plate portion 27, and the pressing member 24 are coaxially arranged with the central axis O of their respective disc springs 1.

[0143] Furthermore, in this embodiment, a pressing member 24 is provided for each of the disc springs 1, but a pressing member 24 may also be provided on the entire plurality of disc springs 1.

[0144] The second support 22 also includes a rotating shaft 42 coaxially arranged with the rotation axis Og. A drive gear 41A is provided at the upper end of the rotating shaft 42. Additionally, a driven gear 41B meshing with the drive gear 41A is provided at the upper end of the shaft 26. Thus, when the rotating shaft 42 is rotated in one direction around the rotation axis Og, the shaft 26 rotates in another direction around the central axis O. Furthermore, as the shaft 26 rotates, the flat plate 27 and the spring body 1e also rotate in the other direction around the central axis O. Therefore, by rotating the rotating shaft 42, multiple spring bodies 1e can be rotated simultaneously around the central axis O.

[0145] In this embodiment, the first support 21 does not rotate. The pressing member 24 is fixed to the bottom 23b of the main body 23 in a non-rotatable manner. In addition, the limiting part 25 is arranged coaxially with the rotation axis Og. The limiting part 25 is configured to protrude from the radial center of the bottom 23b toward the rotation axis 42.

[0146] Next, the manufacturing method of the disc spring using manufacturing apparatus 40 will be described.

[0147] First, the disc spring 1 is shot-peened for hardening. Then, with an axial compressive force applied to the spring body 1e using the first support 21 and the second support 22, the first support 21 and the spring body 1e are made to slide into contact with each other while rotating relative to each other around the central axis O. This applies compressive residual stress to at least the radially outer end of the inner circumferential surface 1b of the spring body 1e over its entire circumferential length.

[0148] In the illustrated example, when an axial compressive force is applied to the spring body 1e, the first support 21 and the second support 22 move closer to each other axially, causing the limiting portion 25 of the first support 21 to abut against the rotating shaft portion 42 of the second support 22 axially. This causes the spring body 1e to elastically deform by a predetermined amount in the direction of axial compression, thereby generating tensile stress on the inner circumferential surface 1b of the spring body 1e.

[0149] Furthermore, with the first support 21 and the second support 22 applying an axial compressive force to the spring body 1e, the rotating shaft 42 is rotated in one direction around the rotation axis Og. At this time, the shaft 26 rotates in the other direction around the central axis O. As the shaft 26 rotates, the spring body 1e also rotates in the other direction around the central axis O. By rotating the spring body 1e around the central axis O without rotating the first support 21 (pressing member 24), the inner circumferential surface 1b of the spring body 1e causes the pressing member 24 to slide circumferentially.

[0150] According to the disc spring manufacturing method of this embodiment, when the spring body 1e is subjected to an axial compressive force by a first support 21 that supports at least the radially outer end of the inner peripheral surface 1b of the spring body 1e, a compressive residual stress is applied to at least the radially outer end of the inner peripheral surface 1b of the spring body 1e by making the first support 21 and the spring body 1e slide into contact with each other while rotating relative to each other around the central axis O.

[0151] Therefore, a disc spring 1 can be reliably obtained such that a compressive residual stress is applied over the entire circumferential length of the radially outer end of the spring body 1e, with the maximum tensile stress occurring at the inner circumferential surface 1b when using the disc spring 1, and decreasing towards the outer circumferential surface 1a.

[0152] Furthermore, according to the manufacturing method of the disc spring of this embodiment, since the compressive residual stress is applied to multiple disc springs 1 simultaneously, it is possible to efficiently obtain multiple disc springs 1 with the compressive residual stress applied as described above over the entire circumferential length of the outer radial end of the spring body 1e.

[0153] Furthermore, although a driven gear 41B is provided on the shaft 26, a driven gear can also be provided on the side of the pressing member 24, so that the shaft 26 (spring body 1e) does not rotate, but the pressing member 24 rotates. Even in this case, the first support 21 and the spring body 1e can slide in contact with each other while rotating relative to each other around the central axis O.

[0154] Furthermore, the technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

[0155] For example, an outer claw protruding radially outward may be provided on the outer periphery 1c of the spring body 1e, and if the outer peripheral surface 1a and the inner peripheral surface 1b of the spring body 1e are coplanar with the outer and back surfaces of the outer claw, a limiting portion abutting against the radially outer end of the outer claw may be provided on the first support 11. In this case, compressive residual stress can be easily applied to at least the radially outer end of the inner peripheral surface 1b of the spring body 1e.

[0156] In the first embodiment, an anti-rotation component may also be provided on the second support 12 to restrict the rotational movement of the spring body 1e relative to the second support 12 about the central axis O.

[0157] For example, if multiple inner claws are provided at circumferential intervals on the inner periphery 1d of the spring body 1e, the anti-rotation member can be located between the inner claws that are adjacent to each other in the circumferential direction. If no inner claws are provided on the spring body 1e, the anti-rotation member can clamp the radial inner end of the spring body 1e from both sides in the axial direction.

[0158] In the first to fourth embodiments, when the first supports 11 and 21 apply an axial compressive force to the spring body 1e, the spring body 1e may not be elastically deformed along the axial direction. In this case, the second supports 12 and 22 may also support the outer peripheral surface 1a of the spring body 1e.

[0159] In the first embodiment, at least one of the first support member 11 and the second support member 12 may be configured to be able to rotate relative to the other about the central axis O.

[0160] For example, when both the first support 11 and the second support 12 are configured to rotate around the central axis O, while the first support 11 and the spring body 1e are in sliding contact with each other, the first support 11 can rotate in one direction around the central axis O, while the second support 12 rotates in another direction around the central axis O. Alternatively, the first support 11 and the second support 12 can rotate in the same direction around the central axis O with a speed difference.

[0161] Alternatively, when the first support 11 and the spring body 1e are in sliding contact with each other, the first support 11 can be made not to rotate around the central axis O, but only the second support 12 can be made to rotate around the central axis O.

[0162] In the second and third embodiments, at least one of the first support body 21 and the second support body 22 may be configured to rotate relative to the other about the central axis O. That is, when the first support body 21 and the spring body 1e are in sliding contact with each other, the first support body 21 may not rotate about the central axis O, but only the second support body 22 may rotate about the central axis O, or the second support body 22 may not rotate about the central axis O, but only the first support body 21 may rotate about the central axis O.

[0163] Alternatively, the first support 21 and the second support 22 can be rotated with a speed difference in the same direction around the central axis O.

[0164] In the second to fourth embodiments, the multiple pressing protrusions 13 of the first embodiment may be provided instead of the circular pressing member 24.

[0165] Furthermore, without departing from the spirit of the present invention, the constituent elements in the above embodiments may be appropriately replaced with known constituent elements, and the above embodiments and variations may also be appropriately combined.

[0166] Industrial availability

[0167] According to the present invention, a disc spring can be obtained in which a compressive residual stress is applied over the entire circumferential length of the radially outer end of the spring body, with the maximum tensile stress occurring at the inner circumferential surface when using the disc spring, and decreasing towards the outer circumferential surface.

[0168] Explanation of reference numerals in the attached figures:

[0169] 1: Disc spring

[0170] 1a: outer peripheral surface

[0171] 1b: Inner circumferential surface

[0172] 1c: peripheral edge

[0173] 1d: Inner periphery

[0174] 1e: Spring body

[0175] 11, 21: First support structure (support body)

[0176] 13: Press the protrusion

[0177] 13a: Pressing surface

[0178] O: Central axis

Claims

1. A method for manufacturing a disc spring, wherein, The disc spring has a spring body formed in a ring shape. The spring body has: The outer peripheral surface, which faces outward in a radial direction; The inner circumferential surface, which faces radially inward; The outer periphery, which is the radially outer end face; and The inner periphery is the radially inner end face. When a support body, which supports at least the radially outer end of the inner circumferential surface at the entire circumferential region or multiple locations, applies an axial compressive force along the central axis of the spring body to the spring body, the spring body is subjected to such a force. By causing the support and the spring body to slide into contact with each other while rotating relative to each other around the central axis. This applies compressive residual stress to at least the radially outer end of the inner circumferential surface. When the support body is used to apply the axial compressive force to the spring body, the spring body is elastically deformed along the axial direction.

2. The method for manufacturing a disc spring according to claim 1, wherein, The support body has a plurality of pressing protrusions spaced apart in the circumferential direction. At least the radially outer end of the inner circumferential surface is supported by a plurality of the pressing protrusions.

3. The method for manufacturing a disc spring according to claim 2, wherein, In a longitudinal sectional view along the said axial direction and through the said central axis, The inner circumferential surfaces that are opposite each other in the axial direction and the pressing surfaces of the pressing protrusions are inclined in the same direction relative to the horizontal surface orthogonal to the central axis.

4. The method for manufacturing a disc spring according to claim 3, wherein, With the axial gap provided between the portion of the inner circumferential surface located closer to the radial side than the radial outer end and the pressing surface, the axial compressive force is applied to the spring body.

5. The method for manufacturing a disc spring according to any one of claims 2 to 4, wherein, The pressing surface of the pressing protrusion, which faces the inner circumferential surface in the axial direction, appears as a curved shape protruding in the axial direction when viewed radially.

6. A method for manufacturing a disc spring according to any one of claims 1 to 4, wherein, With multiple disc springs connected in series along the axial direction, the compressive residual stress is applied to the multiple disc springs simultaneously.

7. A method for manufacturing a disc spring according to any one of claims 1 to 4, wherein, With multiple disc springs oriented in the same direction as the axial direction and arranged on the same plane, the compressive residual stress is simultaneously applied to the multiple disc springs.

8. A disc spring, wherein, The disc spring has a spring body formed in a ring shape. The spring body has: The outer peripheral surface, which faces outward in a radial direction; The inner circumferential surface, which faces radially inward; The outer periphery, which is the radially outer end face; and The inner periphery is the radially inner end face. By causing the support body supporting at least the radially outer end of the inner circumferential surface and the spring body to slide into contact with each other while rotating relative to each other about the central axis of the spring body, a compressive residual stress is applied to at least the radially outer end of the inner circumferential surface along its entire circumferential length about the central axis. The compressive residual stress is greatest on the inner circumferential surface and decreases towards the outer circumferential surface. The surface roughness of the portion of the inner circumferential surface to which the compressive residual stress is applied is less than the surface roughness of the portion located closer to the radial side.

9. A disc spring, wherein, The disc spring has a spring body formed in a ring shape. The spring body has: The outer peripheral surface, which faces outward in a radial direction; The inner circumferential surface, which faces radially inward; The outer periphery, which is the radially outer end face; and The inner periphery is the radially inner end face. By causing the support body supporting at least the radially outer end of the inner circumferential surface and the spring body to slide into contact with each other while rotating relative to each other about the central axis of the spring body, a compressive residual stress is applied to at least the radially outer end of the inner circumferential surface along its entire circumferential length about the central axis. The compressive residual stress is greatest on the inner circumferential surface and decreases towards the outer circumferential surface. The portion of the inner circumferential surface to which the compressive residual stress is applied has a higher hardness than the portion located on the inner side closer to the radial direction.

10. The disc spring according to claim 9, wherein, The surface roughness of the portion of the inner circumferential surface to which the compressive residual stress is applied is less than the surface roughness of the portion located closer to the radial side.

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