Push spring device

Abstract

A pressing spring device (1, 2) is provided with a first plate spring (11) and a second plate spring (12) which extend in the longitudinal direction (X), both ends of the first plate spring in the longitudinal direction serve as fixed sections (21) which are laminated and joined to the second plate spring in the plate thickness direction (Z), and intermediate sections (23, 24) of the first plate spring and the second plate spring in the longitudinal direction face each other while being separated from each other in the plate thickness direction. An intermediate portion of the first leaf spring is provided with: a pair of first vertical wall portions (25) extending from a fixed portion of the first leaf spring in a plate thickness direction in a direction away from the second leaf spring; and a first flat section (26) that connects the pair of first vertical wall sections in the longitudinal direction, the length of the intermediate section of the second leaf spring along the surface of the second leaf spring as viewed from the plate width direction (Y) being shorter than the length of the intermediate section of the first leaf spring along the surface of the first leaf spring as viewed from the plate width direction.

Description

Technical Field

[0001] The present invention relates to a pressing spring device.

[0002] This application claims priority based on Japanese Patent Application No. 2022-190366 filed in Japan on November 29, 2022, and incorporates its content herein. Background Art

[0003] Conventionally, a pressing spring device is known. For example, as shown in Patent Document 1 below, the top portions of a bent first leaf spring and a second leaf spring are used to clamp and press a body to be pressed in the plate thickness direction.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent No. 5040228 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] In the conventional pressing spring device, it is difficult to output a high load with a low stroke.

[0009] An object of the present invention is to provide a pressing spring device capable of outputting a high load with a low stroke.

[0010] Means for Solving the Problems

[0011] A pressing spring device according to one aspect of the present invention includes a first leaf spring and a second leaf spring extending in the length direction. Both end portions of the first leaf spring in the length direction are fixed portions that are laminated and joined to the second leaf spring in the plate thickness direction. The middle portions of the first leaf spring and the second leaf spring in their respective length directions face each other in a state of being separated from each other in the plate thickness direction. The middle portion of the first leaf spring includes: a pair of first longitudinal wall portions that extend from the fixed portion of the first leaf spring in the plate thickness direction toward a direction away from the second leaf spring; and a first flat portion that connects the pair of first longitudinal wall portions to each other in the length direction. The length of the middle portion of the second leaf spring along the surface of the second leaf spring as observed in the plate width direction is shorter than the length of the middle portion of the first leaf spring along the surface of the first leaf spring as observed in the plate width direction.

[0012] Since the first leaf spring and the second leaf spring are provided, if the pressing spring device is clamped between a pair of bodies to be pressed in the plate thickness direction, and a pressing load is applied to the first flat portion of the first leaf spring in the plate thickness direction toward the second leaf spring, a tensile force in the length direction is applied to the second leaf spring via the first longitudinal wall portions and the fixed portion of the first leaf spring.

[0013] At this time, since the length of the middle portion of the second leaf spring along the surface of the second leaf spring as observed from the plate width direction is shorter than the length of the middle portion of the first leaf spring along the surface of the first leaf spring as observed from the plate width direction, the second leaf spring suppresses the deformation of the first leaf spring regardless of the material of the second leaf spring or the like, can increase the spring constant of the push spring device that appears, and can output a high load with a low stroke.

[0014] In one aspect of the present invention, the first flat portion may also be formed to be elastically deformable in a manner of bulging toward the second leaf spring along the plate thickness direction when a press-fitting load toward the second leaf spring is applied along the plate thickness direction.

[0015] If the press-fitting load applied to the first flat portion of the first leaf spring increases and the deformation in the length direction of the second leaf spring is restricted, the first flat portion elastically deforms in a manner of bulging toward the second leaf spring along the plate thickness direction, and the spring constant of the push spring device that appears can be reduced. Thus, during the process of increasing the press-fitting load in the plate thickness direction applied, the spring constant that appears can be made to be high at a small displacement and low at a large displacement.

[0016] In one aspect of the present invention, the length of the first flat portion along the surface of the first flat portion as observed from the plate width direction may also be made longer than the length of the first longitudinal wall portion along the surface of the first longitudinal wall portion as observed from the plate width direction.

[0017] Since the length of the first flat portion along the surface of the first flat portion as observed from the plate width direction is longer than the length of the first longitudinal wall portion along the surface of the first longitudinal wall portion as observed from the plate width direction, during the process of increasing the press-fitting load applied to the first flat portion, when the deformation in the length direction of the second leaf spring is restricted, the first flat portion can be easily deformed in a manner of bulging toward the second leaf spring along the plate thickness direction.

[0018] The push spring device according to one aspect of the present invention may also include a third leaf spring having a middle portion, the middle portion being provided on the opposite side of the first leaf spring across the middle portion of the second leaf spring in the plate thickness direction as observed from the plate width direction, and the middle portions of the second leaf spring and the third leaf spring being separated from each other in the plate thickness direction as observed from the plate width direction.

[0019] Since, when viewed in the plate width direction, the middle part of the third leaf spring is provided on the opposite side of the first leaf spring across the middle part of the second leaf spring in the plate thickness direction, and when viewed in the plate width direction, the middle parts of the second leaf spring and the third leaf spring are separated from each other in the plate thickness direction, the first flat part of the first leaf spring and the middle part of the third leaf spring are clamped in the plate thickness direction by a pair of pressed bodies, and a less deviated press-fitting load can be applied to the first leaf spring and the third leaf spring from the pair of pressed bodies, and the attitude of the press spring device can be kept stable between the pair of pressed bodies, etc.

[0020] A press spring device according to one aspect of the present invention may also include a pair of third leaf springs provided on both sides in the plate width direction of the first leaf spring. The end parts in the length direction of the third leaf spring are projecting parts that project in the plate width direction from the fixed part of the first leaf spring. The middle part in the length direction of the third leaf spring includes: a pair of third longitudinal wall parts that, when viewed in the plate width direction, extend from the projecting part of the third leaf spring in the plate thickness direction toward a direction away from the middle part of the first leaf spring; and a third flat part that connects the pair of third longitudinal wall parts to each other in the length direction. When viewed in the plate width direction, the third flat part is located on the opposite side of the first flat part across the middle part of the second leaf spring in the plate thickness direction.

[0021] Since the third leaf spring having a projecting part, a pair of third longitudinal wall parts, and a third flat part is provided, the first flat part of the first leaf spring and the third flat part of the third leaf spring are clamped in the plate thickness direction by a pair of pressed bodies, and a less deviated press-fitting load can be applied to the first leaf spring and the third leaf spring from the pair of pressed bodies, and the attitude of the press spring device can be kept stable between the pair of pressed bodies, etc.

[0022] Advantages of the Invention

[0023] According to the above aspect of the present invention, a high load can be output with a low stroke. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a perspective view of the press spring device of the first embodiment.

[0025] Figure 2 is when viewed in the plate width direction Figure 1 of the press spring device.

[0026] Figure 3 is showing the Figure 2 state where a press-fitting load in the plate thickness direction is applied to the press spring device.

[0027] Figure 4 is a perspective view of the press spring device of the second embodiment.

[0028] Figure 5 Viewed from the plate width direction Figure 4 of the pressing spring device.

[0029] Figure 6 It is Figure 5 a VI-VI line view sectional view. Specific embodiments

[0030] Hereinafter, with reference to Figures 1 to 3 an embodiment of the pressing spring device will be described.

[0031] As Figure 1 and Figure 2 shown, the pressing spring device 1 of the present embodiment includes a first leaf spring 11 and a second leaf spring 12 extending in the length direction X, and is used while being sandwiched between a pair of pressed bodies in the plate thickness direction Z.

[0032] The end portions of the first leaf spring 11 and the second leaf spring 12 in the length direction X are laminated and joined in the plate thickness direction Z.

[0033] Hereinafter, the end portions of the first leaf spring 11 in the length direction X will be referred to as first fixing portions (fixing portions) 21, and the end portions of the second leaf spring 12 in the length direction X will be referred to as second fixing portions (fixing portions) 22.

[0034] The middle portions 23 and 24 of the first leaf spring 11 and the second leaf spring 12 face each other in a state of being separated from each other in the plate thickness direction Z.

[0035] Viewed from the plate width direction Y, the middle portion 24 of the second leaf spring 12 is bent so as to extend in the direction away from the middle portion 23 of the first leaf spring 11 along the plate thickness direction Z, presenting a convex curve shape.

[0036] The middle portion 23 of the first leaf spring 11 includes a pair of first longitudinal wall portions 25 and a first flat portion 26, and presents a trapezoidal shape when viewed from the plate width direction Y.

[0037] The first longitudinal wall portion 25 extends from the first fixing portion 21 in the direction away from the second fixing portion 22 (that is, the second leaf spring 12) along the plate thickness direction Z. The pair of first longitudinal wall portions 25 are opposed to each other in the length direction X. The pair of first longitudinal wall portions 25 extend in the direction approaching each other in the length direction X as they are away from the first fixing portion 21 in the plate thickness direction Z. In other words, as the first longitudinal wall portion 25 is away from the second leaf spring 12, it extends from the first fixing portion 21 toward the central position in the length direction X of the middle portion 23.

[0038] The first flat portion 26 connects a pair of first longitudinal wall portions 25 to each other in the length direction X. The first flat portion 26 is formed in a flat plate shape with the front and back facing the plate thickness direction Z. The connecting portion 23a of the first flat portion 26 and the first longitudinal wall portion 25 is curved into a convex curve shape facing the outside in the length direction X when viewed from the plate width direction Y.

[0039] The first flat portion 26 is formed such that when a press-fitting load toward the second leaf spring 12 is applied along the plate thickness direction Z, as Figure 3 shown, it can elastically deform in a manner of bulging toward the second leaf spring 12 along the plate thickness direction Z.

[0040] In the illustrated example, the length of the first flat portion 26 along the surface of the first flat portion 26 when viewed from the plate width direction Y is longer than the length of the first longitudinal wall portion 25 along the surface of the first longitudinal wall portion 25 when viewed from the plate width direction Y. The first flat portion 26 is formed such that when the above-mentioned press-fitting load is applied, when viewed from the plate width direction Y, the first flat portion 26 and the pair of first longitudinal wall portions 25 present an M shape, and the central portion in the length direction X can elastically deform in a manner of bulging toward the second leaf spring 12 along the plate thickness direction Z.

[0041] The protruding amount of the middle portion 23 of the first leaf spring 11 in the plate thickness direction Z with respect to the first fixing portion 21 is larger than the protruding amount of the middle portion 24 of the second leaf spring 12 in the plate thickness direction Z with respect to the second fixing portion 22.

[0042] The length of the middle portion 24 of the second leaf spring 12 along the surface of the second leaf spring 12 when viewed from the plate width direction Y is shorter than the length of the middle portion 23 of the first leaf spring 11 along the surface of the first leaf spring 11 when viewed from the plate width direction Y.

[0043] The pressing spring device 1 of the present embodiment includes a third leaf spring 13 having a middle portion 28 which, when viewed from the plate width direction Y, is provided on the opposite side of the middle portion 23 of the first leaf spring 11 with the middle portion 24 of the second leaf spring 12 interposed therebetween in the plate thickness direction Z. When viewed from the plate width direction Y, the middle portions 24 and 28 of the second leaf spring 12 and the third leaf spring 13 are separated from each other in the plate thickness direction Z.

[0044] In the illustrated example, third leaf springs 13 are individually provided on both sides of the first leaf spring 11 in the plate width direction Y. Both end portions in the length direction X of the third leaf spring 13 are integrally formed with the first fixing portion 21 of the first leaf spring 11 and extend 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 throughout the region.

[0045] Hereinafter, both end portions in the length direction X of the third leaf spring 13 will be referred to as protruding portions 27.

[0046] The intermediate portion 28 of the third leaf spring 13 in the longitudinal direction X includes a pair of third vertical wall portions 31 and a third flat portion 32 .

[0047] The pair of third longitudinal wall portions 31 extend from the extension portion 27 of the third leaf spring 13 in the plate thickness direction Z in a direction away from the middle portion 23 of the first leaf spring 11 as viewed in the plate width direction Y. The pair of third longitudinal wall portions 31 extend in a direction approaching each other in the length direction X as they move away from the extension portion 27 in the plate thickness direction Z. In other words, the third longitudinal wall portions 31 extend toward the center position of the middle portion 28 in the length direction X as they move away from the extension portion 27 in the plate thickness direction Z.

[0048] The third flat portion 32 connects the pair of third vertical wall portions 31 to each other in the longitudinal direction X. The connecting portion 28a of the third flat portion 32 and the third vertical wall portion 31 is curved in a convex curve toward the outside in the longitudinal direction X when viewed from the plate width direction Y. The third flat portion 32 is located on the opposite side of the first flat portion 26 across the middle portion 24 of the second leaf spring 12 in the plate thickness direction Z when viewed from the plate width direction Y.

[0049] The middle portion 28 of the third leaf spring 13 is trapezoidal in the opposite direction to the middle portion 23 of the first leaf spring 11 when viewed from the plate width direction Y. The middle portions 28 and 23 of the third leaf spring 13 and the first leaf spring 11 are symmetrical with respect to a straight line passing through the center of the first fixing portion 21 and the extension portion 27 in the plate thickness direction Z and extending in the length direction X when viewed from the plate width direction Y. The dimensions of the third vertical wall portion 31 and the third flat portion 32 of the third leaf spring 13, including the plate width, are all the same as the dimensions of the first vertical wall portion 25 and the first flat portion 26 of the first leaf spring 11.

[0050] As described above, according to the push spring device 1 of the present embodiment, since it includes the first leaf spring 11 and the second leaf spring 12, if the push spring device 1 is clamped by a pair of pushed bodies along the plate thickness direction Z, and a pressing load toward the second leaf spring 12 is applied to the first flat portion 26 of the first leaf spring 11 along the plate thickness direction Z, a tensile force in the length direction X is applied to the second leaf spring 12 via the first longitudinal wall portion 25 and the first fixed portion 21 of the first leaf spring 11.

[0051] At this time, since the length of the middle portion 24 of the second leaf spring 12 along the surface of the second leaf spring 12 observed from the leaf width direction Y is shorter than the length of the middle portion 23 of the first leaf spring 11 along the surface of the first leaf spring 11 observed from the leaf width direction Y, regardless of the material of the second leaf spring 12, the second leaf spring 12 suppresses the deformation of the first leaf spring 11, can increase the spring constant of the apparent push spring device 1, and can output high loads with a low stroke.

[0052] If the press-fitting load applied to the first flat portion 26 of the first leaf spring 11 increases and the deformation of the second leaf spring 12 in the longitudinal direction X is restricted, then as Figure 3 shown, the first flat portion 26 elastically deforms so as to bulge toward the second leaf spring 12 along the plate thickness direction Z, and the spring constant of the pressing spring device 1 that appears can be reduced. Thus, in the process in which the press-fitting load in the plate thickness direction X applied increases, the spring constant that appears can be made to be higher at a smaller displacement and lower at a larger displacement.

[0053] Since the length of the first flat portion 26 along the surface of the first flat portion 26 as viewed from the plate width direction Y is longer than the length of the first longitudinal wall portion 25 along the surface of the first longitudinal wall portion 25 as viewed from the plate width direction Y, when the deformation of the second leaf spring 12 in the longitudinal direction X is restricted in the process in which the press-fitting load applied to the first flat portion 26 increases, the first flat portion 26 can be easily deformed so as to bulge toward the second leaf spring 12 along the plate thickness direction Z.

[0054] Since the intermediate portion 28 of the third leaf spring 13 is provided on the opposite side of the intermediate portion 23 of the first leaf spring 11 across the second leaf spring 12 in the plate thickness direction Z as viewed from the plate width direction Y, and the intermediate portions 24 and 28 of the second leaf spring 12 and the third leaf spring 13 are separated from each other in the plate thickness direction Y as viewed from the plate width direction Y, the first flat portion 26 of the first leaf spring 11 and the intermediate portion 28 of the third leaf spring 13 are clamped by a pair of pressed bodies in the plate thickness direction Z, and a press-fitting load with less deviation can be applied to the first leaf spring 11 and the third leaf spring 13 from the pair of pressed bodies, and the attitude of the pressing spring device 1 can be kept stable between the pair of pressed bodies, etc.

[0055] Since the third leaf spring 13 having the protruding portion 27, a pair of third longitudinal wall portions 31, and the third flat portion 32 is provided, the first flat portion 26 of the first leaf spring 11 and the third flat portion 32 of the third leaf spring 13 are clamped by a pair of pressed bodies in the plate thickness direction Z, and a press-fitting load with less deviation can be applied to the first leaf spring 11 and the third leaf spring 13 from the pair of pressed bodies, and the attitude of the pressing spring device 1 can be kept stable between the pair of pressed bodies, etc.

[0056] In addition, in the present embodiment, when the first flat portion 26 is applied with a press-fitting load toward the second leaf spring 12 in the plate thickness direction Z, it may not bulge toward the second leaf spring 12 in the plate thickness direction Z, or may maintain the shape before the press-fitting load is applied. The length of the first flat portion 26 along the surface of the first flat portion 26 as viewed from the plate width direction Y may also be shorter than the length of the first longitudinal wall portion 25 along the surface of the first longitudinal wall portion 25 as viewed from the plate width direction Y.

[0057] Next, referring toFigures 4 to 6 The pressing spring device 2 of the second embodiment of the present invention will be described.

[0058] In addition, in this second embodiment, the same reference numerals are assigned to the parts that are the same as the structural elements of the first embodiment, and the description thereof is omitted, and only the differences will be described.

[0059] In the pressing spring device 2 of the present embodiment, the middle portion 24 of the second leaf spring 12 is formed in a flat plate shape with the front and back facing the plate thickness direction Z. In the second leaf spring 12, the second fixing portion 22 extends more to both sides in the plate width direction Y than the middle portion 24, and is laminated and joined at the extending portions 27 of the pair of third leaf springs 13. The plate width of the first leaf spring 11 is wider than the plate width of the third leaf spring 13. The plate width of the second leaf spring 12 is wider than the plate width of the following fourth leaf spring 14. The plate widths of the second leaf spring 12 and the fourth leaf spring 14 are each sized so as not to interfere with the deformation of the third leaf spring 13 and the first leaf spring 11 in the plate thickness direction Z.

[0060] In addition, in the present embodiment, the second fixing portion 22 may not extend to both sides in the plate width direction Y compared to the middle portion 24.

[0061] A fourth leaf spring 14 is provided with both end portions in the length direction X laminated and joined at the extending portions 27 of the third leaf spring 13.

[0062] Hereinafter, both end portions in the length direction X of the fourth leaf spring 14 will be referred to as fourth fixing portions 29.

[0063] The middle portions 33 and 28 in the length direction X of the fourth leaf spring 14 and the third leaf spring 13 face each other in a state of being separated in the plate thickness direction Z. Two fourth leaf springs 14 are provided and are individually provided on the pair of third leaf springs 13. The fourth leaf spring 14 is formed in a flat plate shape with the front and back facing the plate thickness direction Z over the entire length in the length direction X. When viewed from the plate width direction Y, the middle portion 23 of the first leaf spring 11 and the middle portion 28 of the third leaf spring 13 are individually located on both sides in the plate thickness direction Z of the fourth leaf spring 14. The fourth fixing portions 29 of the two fourth leaf springs 14 are connected to each other in the plate width direction Y, and this connecting portion is laminated and joined at the first fixing portion 21 of the first leaf spring 11. The length of the middle portion 33 of the fourth leaf spring 14 along the surface of the fourth leaf spring 14 when viewed from the plate width direction Y is shorter than the length of the middle portion 28 of the third leaf spring 13 along the surface of the third leaf spring 13 when viewed from the plate width direction Y.

[0064] In addition, in the present embodiment, the fourth fixing portions 29 of the two fourth leaf springs 14 may not be connected to each other in the plate width direction Y.

[0065] As described above, in the pressing spring device 2 according to the present embodiment, in addition to the above-described effects of the pressing spring device 1 of the first embodiment, since the fourth leaf spring 14 is provided, when a pressing load is applied to the third flat portion 32 of the third leaf spring 13 in the plate thickness direction Z toward the first leaf spring 11, a tensile force in the length direction X is applied to the fourth leaf spring 14, and the fourth leaf spring 14 suppresses the deformation of the third leaf spring 13, and the spring constant of the pressing spring device 2 that appears can be effectively improved.

[0066] In addition, 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.

[0067] For example, each intermediate portion 24, 33 of the second leaf spring 12 and the fourth leaf spring 14 may be bent in a convex curve shape toward the intermediate portion 23 of the first leaf spring 11 in the plate thickness direction Z when viewed from the plate width direction Y, or may extend in a wave shape along the length direction X when viewed from the plate width direction Y.

[0068] When viewed from the plate width direction Y, the intermediate portion 33 of the fourth leaf spring 14 may also be bent in a convex curve shape in a direction away from the intermediate portion 23 of the first leaf spring 11 in the plate thickness direction Z.

[0069] The third leaf spring 13 and the fourth leaf spring 14 may not be provided in the pressing spring device of the above-described embodiment.

[0070] The second fixing portion (fixing portion) 22 may also be provided at a portion other than the both ends in the length direction X of the second leaf spring 12.

[0071] The second leaf spring 12 and the third leaf spring 13 may be located at the same position in the plate width direction Y, and the intermediate portions 24, 28 of the second leaf spring 12 and the third leaf spring 13 may be opposed to each other in the plate thickness direction Z.

[0072] In addition, within the scope not departing from the spirit of the present invention, the structural elements of the above-described embodiment can be appropriately replaced with known structural elements, and the above-described embodiment and modification examples can also be appropriately combined.

[0073] Description of Reference Numerals

[0074] 1, 2: Pressing spring device

[0075] 11: First leaf spring

[0076] 12: Second leaf spring

[0077] 13: Third leaf spring

[0078] 21: First fixing portion (fixing portion)

[0079] 22: Second fixing part (fixing part)

[0080] 23: Middle part of the first leaf spring

[0081] 24: Middle part of the second leaf spring

[0082] 25: First longitudinal wall part

[0083] 26: First flat part

[0084] 27: Protruding part

[0085] 28: Middle part of the third leaf spring

[0086] 31: Third longitudinal wall part

[0087] 32: Third flat part

[0088] X: Length direction

[0089] Y: Plate width direction

[0090] Z: Plate thickness direction

Claims

1. A pressing spring device, characterized in that: The pressing spring device includes a first leaf spring and a second leaf spring extending in the length direction; Both end portions in the length direction of the first leaf spring become fixed portions that are laminated and joined to the second leaf spring in the plate thickness direction; The middle portions in the length direction of the first leaf spring and the second leaf spring are opposed to each other in a state of being separated in the plate thickness direction; The middle portion of the first leaf spring includes: A pair of first longitudinal wall portions extending from the fixed portion of the first leaf spring in the plate thickness direction toward a direction away from the second leaf spring; and A first flat portion connecting the pair of first longitudinal wall portions to each other in the length direction; The length of the middle portion of the second leaf spring along the surface of the second leaf spring as viewed from the plate width direction is shorter than the length of the middle portion of the first leaf spring along the surface of the first leaf spring as viewed from the plate width direction.

2. The pressing spring device according to claim 1, characterized in that: The first flat portion is formed to be elastically deformable in a manner of bulging toward the second leaf spring in the plate thickness direction when a pressing load toward the second leaf spring is applied in the plate thickness direction.

3. The pressing spring device according to claim 2, characterized in that: The length of the first flat portion along the surface of the first flat portion as viewed from the plate width direction is longer than the length of the first longitudinal wall portion along the surface of the first longitudinal wall portion as viewed from the plate width direction.

4. The pressing spring device according to any one of claims 1 to 3, characterized in that: The pressing spring device includes a third leaf spring having a middle portion, and the middle portion is provided on the opposite side of the first leaf spring across the middle portion of the second leaf spring in the plate thickness direction as viewed from the plate width direction; As viewed from the plate width direction, the middle portions of the second leaf spring and the third leaf spring are separated from each other in the plate thickness direction.

5. The pressing spring device according to any one of claims 1 to 3, characterized in that: The pressing spring device includes a pair of third leaf springs provided on both sides in the plate width direction of the first leaf spring; Both end portions in the length direction of the third leaf spring become protruding portions extending in the plate width direction from the fixed portion of the first leaf spring; The middle portion in the length direction of the third leaf spring includes: A pair of third longitudinal wall portions extending from the protruding portion of the third leaf spring in the plate thickness direction toward a direction away from the middle portion of the first leaf spring as viewed from the plate width direction; And A third flat portion connecting the pair of third longitudinal wall portions to each other in the length direction; As viewed from the plate width direction, the third flat portion is located on the opposite side of the first flat portion across the middle portion of the second leaf spring in the plate thickness direction.

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