Leaf spring

Abstract

To provide a leaf spring that can reduce the number of components.SOLUTION: A leaf spring includes: a main spring part 3 to which a load is input; a sub-spring part 5 connected to the main spring part 3 in series; opposite parts 15 and 17 included in the sub-spring part 5; and a clearance C between the opposite parts 15 and 17. The main spring part 3 transfers load to the sub-spring part 5 in accordance with the load input thereto, the sub-spring part 5 deforms, and the opposite parts 15 and 17 come into contact with each other when the clearance C disappears.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a leaf spring used as a leaf spring for a vehicle, and having a variable spring constant. [Background technology]

[0002] A conventional leaf spring with a variable spring constant is the leaf spring suspension described in Patent Document 1. This leaf spring suspension supports a leaf spring with a swingable shackle. When a load is applied to the leaf spring, the effective length of the leaf spring shortens in response to the swing of the shackle, changing the spring constant.

[0003] However, in such a conventional leaf spring suspension, the leaf spring must be supported on the vehicle body via a shackle, which makes the structure complicated. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Utility Model Application Publication No. 6-43380 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved is that the structure becomes complicated in order to change the spring constant. [Means for solving the problem]

[0006] The present invention comprises a main spring portion to which a load is input, a sub-spring portion connected in series to the main spring portion, an opposing portion of the sub-spring portion, and a clearance between the opposing portions, and in response to the input of a load from the main spring portion, the load is transmitted to the sub-spring portion, causing the sub-spring portion to deform, and the opposing portion comes into contact, eliminating the clearance. Effect of the Invention

[0007] In the present invention, deformation occurs due to the spring constant when the auxiliary spring section and the main spring section are connected in series until there is no clearance, and once there is no clearance, deformation occurs mainly due to the spring constant of the main spring section, making it possible to change the spring constant with a simple structure. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic side view of a leaf spring according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic side view showing an enlarged view of the auxiliary spring portion of FIG. [Diagram 3] FIG. 3 is a schematic side view showing a state in which a load is input to a main spring portion of the leaf spring of FIG. [Figure 4] FIG. 4(A) is a schematic side view with a portion of the leaf spring omitted before the opposing portions come into contact, and FIG. 4(B) is a schematic side view showing an enlarged view of the auxiliary spring portion. [Diagram 5] FIG. 5(A) is a schematic side view with a portion of the leaf spring omitted when the opposing portions come into contact, and FIG. 5(B) is a schematic side view showing an enlarged view of the auxiliary spring portion. [Figure 6] FIG. 6(A) is a schematic side view with a portion of the leaf spring omitted, showing deformation after the opposing portions come into contact, and FIG. 6(B) is a schematic side view showing an enlarged view of the sub-spring portion. [Figure 7] FIG. 7 is a graph showing the relationship between the load and the displacement according to the embodiment. [Figure 8] FIG. 8 is a schematic side view of a leaf spring according to a modified example, with a portion thereof omitted. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The present invention achieves the object of making it possible to change the spring constant with a simple structure by using a leaf spring in which a main spring portion and a sub-spring portion are joined together.

[0010] That is, the leaf spring 1 comprises a main spring portion 3, a secondary spring portion 5, opposing portions 15 and 17, and a clearance C. The main spring portion 3 is a portion to which a load is input. The secondary spring portion 5 is a portion connected in series to the main spring portion 3. The secondary spring portion 5 has the opposing portions 15 and 17, and the clearance C is provided between the opposing portions 15 and 17. In response to a load being input to the main spring portion 3, the leaf spring 1 transmits the load to the secondary spring portion 5, causing the secondary spring portion 5 to deform, and the opposing portions 15 and 17 come into contact with each other without the clearance C.

[0011] The main spring portion 3 may be set to have a lower spring constant than the sub-spring portion 5 .

[0012] The secondary spring portion 5 may include a support portion 7 for rotatably supporting the secondary spring portion 5 on the other side to which it is attached.

[0013] The leaf spring 1 may comprise a curved connecting portion 11 connecting the secondary spring portion 5 to the primary spring portion 3 .

[0014] The secondary spring portion 5 may include a hook portion 9 that is curved continuously to the opposing portions 15 and 17 .

[0015] The main spring portion 3 may be curved with a constant curvature, and the hook portion 9 may be curved with a curvature larger than that of the main spring portion 3 .

[0016] The hook portion 9 may have a convex shape facing the inside of the curved portion of the main spring portion 3 . EXAMPLES

[0017] [Leaf spring configuration] Fig. 1 is a schematic side view of a leaf spring according to an embodiment of the present invention, Fig. 2 is a schematic side view showing an enlarged view of a sub-spring portion of Fig. 1.

[0018] The leaf spring 1 is configured as, for example, a leaf spring for a vehicle, and is made of metal such as carbon steel or stainless steel, or resin such as FRP (Fiber Reinforced Plastics). The material of the leaf spring 1 can be appropriately changed depending on the intended use of the leaf spring 1.

[0019] This leaf spring 1 includes a main spring portion 3 and a sub-spring portion 5, and has support portions 7 at both ends.

[0020] The main spring portion 3 is formed long with a constant plate thickness and plate width, and is curved in an arc when viewed from the side. However, the plate thickness and plate width may be partially increased or decreased. Also, the main spring portion 3 is made of a single plate, but may be made of multiple plates overlapping each other, or may be made of multiple plates in some parts.

[0021] The curvature of the main spring portion 3 is a constant curvature with a single center of curvature, but may have multiple centers of curvature. The main spring portion 3 may also be linear with no curvature. Alternatively, the main spring portion 3 may be an arc shape as a whole formed by combining an arc shape with a linear shape, or a combination of multiple short linear shapes, or may be a mountain shape, a valley shape, a wave shape, or the like.

[0022] The main spring portion 3 has a relatively low spring constant and is the portion to which a load is input.

[0023] The sub-spring portions 5 are connected in series to the main spring portion 3 and have a relatively high spring constant. The sub-spring portions 5 in this embodiment are connected to both ends of the main spring portion 3, and are connected in series between the main spring portion 3 and the support portions 7 at the ends of the leaf spring 1. These sub-spring portions 5 are symmetrical, but can also be asymmetrical.

[0024] The connection of the auxiliary spring portion 5 to the main spring portion 3 and the support portion 7 is integral or one-piece, and is realized by one-piece molding in this embodiment. "In series" refers to the connection state of the main spring portion 3 and the auxiliary spring portion 5 in terms of spring action, and corresponds to the state in which two springs are connected in series.

[0025] The number and positions of the secondary spring portions 5 can be set arbitrarily. For example, the secondary spring portion 5 can be provided only at one end of the main spring portion 3, only at the middle portion of the main spring portion 3, or at one end or both ends and the middle portion of the main spring portion 3. When multiple secondary spring portions 5 are provided, the shapes of any one, some, or all of the secondary spring portions 5 may be different.

[0026] The auxiliary spring portion 5 of this embodiment is formed with the same plate thickness and plate width as the main spring portion 3, and includes a hook portion 9, a first curved joint portion 11, and a second curved joint portion 13. Note that the auxiliary spring portion 5 may be different from the main spring portion 3 in either or both of the plate thickness and plate width.

[0027] The hook portion 9 integrally has a straight portion 9a, a first curved portion 9b, and a second curved portion 9c in a side view. The hook portion 9 can also be realized in a simple U-shape or V-shape.

[0028] One end of the straight portion 9a of the hook portion 9 is connected to one end of the first curved connecting portion 11. The first curved connecting portion 11 may be replaced with a corner portion. The other end of the straight portion 9a is connected to one end of the first curved portion 9b. This makes the straight portion 9a continuous in the tangential direction of one end of the first curved portion 9b.

[0029] By setting the straight portion 9a in this manner, when a load is transmitted from the main spring portion 3 to the straight portion 9a via the first curved connecting portion 11, the bending load can be reliably transmitted by the straight portion 9a to the first curved portion 9b.

[0030] The first curved portion 9b is curved with a curvature larger than that of the main spring portion 3. The other end of the first curved portion 9b is connected to one end of the second curved portion 9c. The first and second curved portions 9b and 9c are continuous with each other at an inflection point, and the curved direction is reversed. The other end of the second curved portion 9c is connected to one end of a second curved connecting portion 13. The second curved connecting portion 13 may be replaced with a corner portion.

[0031] The second curved portion 9c and the second curved joint portion 13 are formed continuously with the same curvature. The curvatures of the second curved portion 9c and the second curved joint portion 13 are smaller than the curvature of the first curved joint portion 11. However, the curvatures of the second curved portion 9c and the second curved joint portion 13 may be the same as or larger than the curvature of the first curved joint portion 11. The curvatures of the second curved portion 9c and the second curved joint portion 13 may also be different.

[0032] The other end of the first curved joint portion 11 is joined to an end of the main spring portion 3. The other end of the second curved joint portion 13 is joined to the support portion .

[0033] The support portion 7 is formed of a cylindrical member separate from the leaf spring 1, and is connected to the other end of the second curved joint portion 13. However, the support portion 7 may be configured by winding the other end of the second curved joint portion 13 into a cylindrical shape.

[0034] The support portion 7 is a portion that is rotatably supported by the other side to which it is attached. By attaching this support portion 7, the end of the leaf spring 1 is rotatably supported by the other side, resulting in an attachment configuration that does not move in the plate thickness direction of the main spring portion 3 and in the longitudinal direction of the main spring portion 3. Note that the support portion 7 may be configured to be supported so as not to rotate.

[0035] The hook portion 9 has a convex shape facing the inside of the curve of the main spring portion 3. However, the hook portion 9 may have a convex shape facing the outside of the curve of the main spring portion 3 as long as it can deform the sub-spring portion 5.

[0036] The orientation of the convex shape can be changed in various ways depending on the required characteristics of the leaf spring 1. For example, the first curved portions 9b of the hook portions 9 at both ends can be oriented so that their symmetrical lines overlap, or the first curved portions 9b can be oriented in the vertical direction. Although the term "vertical" refers to the direction of gravity, it may refer to a direction other than the direction of gravity depending on the mounting state of the leaf spring 1.

[0037] The hook portion 9 does not need to open when a load is transmitted from the main spring portion 3 to the sub-spring portion 5, and the angle θ can be set to approximately 90°. The angle θ is the angle between the vertical direction and an imaginary line passing through the first and second opposing portions 15 and 17 described below.

[0038] The auxiliary spring portion 5 has a first opposing portion 15 and a second opposing portion 17 .

[0039] The first opposing portion 15 is formed between the first curved joint portion 11 and the straight portion 9a of the hook portion 9. The second opposing portion 17 is formed between the second curved joint portion 13 and the second curved portion 9c.

[0040] A clearance C is formed between the first and second opposing portions 15 and 17. The first and second opposing portions 15 and 17 face each other and come into contact with each other at this clearance C. The clearance C can be set to a large or small value, and the change characteristics of the spring constant of the leaf spring 1 can be determined.

[0041] For example, by changing the size of the clearance C at both ends, it is possible to make the first and second opposing portions 15 and 17 come into contact at one clearance C first, and then make the first and second opposing portions 15 and 17 come into contact at the other clearance C.

[0042] [Function of leaf spring] Fig. 3 is a schematic side view showing a state in which a load is input to the main spring portion 3. Fig. 4(A) is a schematic side view, with part of the leaf spring omitted, before the opposing portions come into contact, and Fig. 4(B) is a schematic side view showing an enlarged view of the sub-spring portion. Fig. 5(A) is a schematic side view, with part of the leaf spring omitted, at the time when the opposing portions come into contact, and Fig. 5(B) is a schematic side view showing an enlarged view of the sub-spring portion. Fig. 6(A) is a schematic side view, with part of the leaf spring omitted, showing deformation after the opposing portions come into contact, and Fig. 6(B) is a schematic side view showing an enlarged view of the sub-spring portion.

[0043] 3, when the main spring portion 3 receives a load F, the leaf spring 1 deforms from the state shown by the two-dot chain line to the state shown by the solid line. At this time, the end of the leaf spring 1 is rotatably supported by the support portion 7 on the vehicle body or the like, and receives the load.

[0044] The relationship between the load on the leaf spring 1 and the deformation of the leaf spring 1 is as shown in FIG. 4(A) to FIG. 6(B).

[0045] As shown in FIGS. 4(A) and 4(B), when no load acts on the main spring portion 3, the clearance C of the sub-spring portion 5 is maintained.

[0046] When a downward load F in the thickness direction is input to the center of the main spring portion 3, the leaf spring 1 deforms so that the main spring portion 3 is displaced downward. The deformation here is due to the spring constant of the leaf spring 1 when the sub-spring portion 5 and the main spring portion 3 are connected in series.

[0047] That is, the load F received by the main spring portion 3 is received by the support portion 7 via the first curved joint portion 11, the hook portion 9, and the second curved joint portion 13 in this order, causing the main spring portion 3 and the sub-spring portion 5 to deform.

[0048] In this deformation, the first opposing portion 15 of the auxiliary spring portion 5 is displaced within the clearance C toward the second opposing portion 17.

[0049] Thus, at the beginning of the input of the load F, both the main spring portion 3 and the sub-spring portion 5 deform and exhibit spring properties. This is similar to when two springs are connected in series. Therefore, until the clearance C disappears, the leaf spring 1 has spring properties similar to when the main spring portion 3 and the sub-spring portion 5 are connected in series.

[0050] 5(A) and 5(B), as deformation of the leaf spring 1 progresses due to the load F, the clearance C between the first and second opposing portions 15 and 17 disappears, and the first and second opposing portions 15 and 17 come into contact with each other.

[0051] 6(A) and 6(B), when the deformation of the leaf spring 1 progresses further after the first and second opposing portions 15 and 17 come into contact, the secondary spring portion 5 becomes difficult or impossible to deform, and the spring constant of the secondary spring portion 5 increases. As a result, the leaf spring 1 is mainly deformed by the main spring portion 3, and exerts its spring properties. In other words, the leaf spring 1 has spring characteristics with a spring constant that depends on the main spring portion 3.

[0052] Fig. 7 is a graph showing the relationship between load and displacement. In Fig. 7, the vertical axis shows the magnitude of the load (N), and the horizontal axis shows the displacement (mm) of the main spring portion 3 according to the load. In Fig. 7, modified example 1 is a leaf spring 1 in which the spring constant of the sub-spring portion 5 is made larger than that of the embodiment, and modified example 2 is a leaf spring 1 in which the spring constant of the sub-spring portion 5 is made lower than the spring constant of the main spring portion 3. Fig. 8 is a schematic side view of the leaf spring according to modified example 2 with a portion omitted.

[0053] The leaf spring 1 of the modified example 1 is fixed at its end to the other side so that it cannot rotate or move, but otherwise is the same as the leaf spring 1 of the embodiment 1. As shown in Fig. 8, the leaf spring 1 of the modified example 2 is configured such that the curvature of the auxiliary spring portion 5 is smaller than that of the embodiment 1, and the auxiliary spring portion 5 is thinner than the main spring portion 3. The spring constants of the main spring portion 3 and the auxiliary spring portion 5 can be set arbitrarily depending on the shape, etc.

[0054] 7, in the load-displacement characteristics of the leaf spring 1 of the embodiment, the spring constant changes at point C when the first and second opposing portions 15 and 17 come into contact, and the spring constant before contact B is lower than after contact A. In the modified examples 1 and 2, the same characteristics as those of the embodiment are obtained.

[0055] Therefore, leaf spring 1 deforms with a spring constant close to that when main spring portion 3 and sub-spring portion 5 are connected in series until clearance C is eliminated due to contact between first and second opposing portions 15 and 17 in response to load, and once clearance C is eliminated, it deforms mainly due to the spring constant of main spring portion 3, making it possible to change the spring constant with a simple structure. Also, because leaf spring 1 has a simple structure, the number of parts does not increase, making assembly and parts management easy.

[0056] Furthermore, the characteristics of the leaf spring 1 can be easily changed by adjusting the settings of the hook portion 9 of the sub-spring portion 5. For example, the timing at which the spring constant of the leaf spring 1 changes can be easily set by adjusting the size of the clearance C and the protruding length of the hook portion 9. Furthermore, by changing the size of the clearance C at both ends, multi-stage characteristics can be obtained.

[0057] The leaf spring 1 has a support portion 7 at its end for rotatably supporting the other side to which it is attached, and natural deformation is possible without moving the position of the support portion 7, and no bushing or the like is required for the support portion 7.

[0058] Since the leaf spring 1 has a first curved connecting portion 11 that connects the secondary spring portion 5 to the main spring portion 3, the first curved connecting portion 11 reliably transmits the load from the main spring portion 3 to the straight portion 9a of the hook portion 9, and the load is transmitted from the straight portion 9a to the first hook curved portion 9b, thereby enabling the first and second opposing portions 15 and 17 to contact each other smoothly and reliably.

[0059] Furthermore, since the main spring portion 3 is curved with a constant curvature and the hook portion 9 is curved with a curvature larger than that of the main spring portion 3, when a load is transmitted from the main spring portion 3 to the auxiliary spring portion 5, stress is easily concentrated in the auxiliary spring portion 5, and the clearance C can be easily eliminated.

[0060] Since the hook portion 9 has a convex shape facing the inside of the curve of the main spring portion 3, the shape of the leaf spring 1 including the sub-spring portion 5 can be easily made compact, and it can be easily disposed on the other side to which it is attached.

[0061] In addition, since the same characteristics as those of the embodiment can be obtained in the modified examples 1 and 2, the same effects as those of the embodiment can be obtained even when the spring constant of the main spring portion 3 or the auxiliary spring portion 5 is changed or when the fixing method of the end of the leaf spring 1 is changed. When changing the spring constant of the main spring portion 3 or the auxiliary spring portion 5, the main spring portion 3 and the auxiliary spring portion 5 may have the same spring constant. [Explanation of symbols]

[0062] 1 Leaf spring 3 Main spring section 5 Secondary spring section 7 Support part 9 Hook part a Straight section b First curved section c Second curved section 11 First curved section 13 Second curved section 15 First opposing part 17 Second opposing part C. Clearance

Claims

1. a main spring portion to which a load is input; A secondary spring portion connected in series to the primary spring portion; An opposing portion of the auxiliary spring portion; a clearance between the opposing portions, When a load is input to the main spring portion, the load is transmitted to the auxiliary spring portion, causing the auxiliary spring portion to deform, and the opposing portions come into contact with each other without the clearance. Leaf spring.

2. 2. The leaf spring of claim 1, The main spring portion has a lower spring constant than the sub-spring portion. Leaf spring.

3. The leaf spring of claim 1 or 2, The end portion is provided with a support portion that allows the attachment partner to rotatably support the attachment partner. Leaf spring.

4. The leaf spring according to any one of claims 1 to 3, A curved connecting portion is provided to connect the secondary spring portion to the primary spring portion. Leaf spring.

5. The leaf spring according to any one of claims 1 to 4, The auxiliary spring portion includes a hook portion curved continuously with the opposing portion. Leaf spring.

6. The leaf spring of claim 5, The main spring portion is curved with a constant curvature, The hook portion is curved with a curvature larger than the curvature of the main spring portion. Leaf spring.

7. The leaf spring of claim 5 or 6, The hook portion has a convex shape facing toward the inside of the curve of the main spring portion. Leaf spring.

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