Leaf spring

Abstract

To control a broken portion of a leaf to prevent the leaf from falling from a vehicle and thereby improve safety when the leaf is broken in a leaf spring including multiple leaves.SOLUTION: In a leaf spring 1, multiple leaves 10 are connected to an axle 3 in a laminated state. The multiple leaves 10 include a first leaf 23 bound by a clip 41. The first leaf 23 is provided between a connection part 4 connected to the axle 3 and the clip 41 and includes a limit detection part S in which durability against stress is reduced compared to the other leaves 10, excluding the first leaf 23, of the multiple leaves 10.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] This case relates to a leaf spring in which multiple leaves are stacked and connected to an axle. [Background technology]

[0002] Conventionally, leaf springs using multiple leaf-shaped leaf springs (leaf portions) have been used as vehicle suspension devices (for example, Patent Document 1). Suspension devices using such leaf springs have a simple structure, are inexpensive, have high strength and durability, and are capable of positioning the axle even if one of the leaves breaks, and therefore are widely used in vehicles such as trucks and buses. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-214177 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, in the above-mentioned leaf spring, in the unlikely event that one of the leaves breaks, it is also required that the broken leaf does not fall off the vehicle. The present invention has been devised in consideration of the above-mentioned problems, and one of its objectives is to prevent the leaves from falling off the vehicle and improve safety in the event of leaf breakage in a leaf spring having multiple leaves by controlling the location at which the leaves break. [Means for solving the problem]

[0005] The present invention has been made to solve at least some of the problems described above, and can be realized in the following aspects or application examples.

[0006] (1) The leaf spring in this application example is a leaf spring in which a plurality of leaves are stacked and connected to an axle, the plurality of leaves including a first leaf that is fastened by a clip, the first leaf being provided between a connection portion with the axle and the clip, and including a limit detection portion that has reduced durability against stress compared to the other leaves of the plurality of leaves except for the first leaf.

[0007] In this way, the durability of the limit detector of the first leaf against stress is suppressed, so that the first leaf can be made to break more easily than the other leaves. As a result, when the leaf spring reaches its limit, the limit detector provided on the first leaf breaks first, so the leaf does not break at other positions, and the location where the leaf breaks can be controlled.

[0008] In addition, the first leaf is bound by a clip, and the limit detection portion is provided between the connection portion with the axle and the clip. Therefore, even if the first leaf breaks at the limit detection portion, the end portion of the first leaf is supported by the clip and prevented from falling off. In this way, even if the leaf spring reaches its limit and breaks, the leaf's breakage location can be controlled so that the supporting force of the clip is applied to the broken leaf, thereby preventing the leaf from falling off and improving safety.

[0009] (2) The first leaf may be fixed to the clip. Because the first leaf is fixed to the clip, when the end portion of the first leaf breaks at the limit detection portion, it will not fall out of the clip but can catch on the other leaves via the clip.

[0010] (3) The other leaves may include a second leaf that abuts against a lower side of the first leaf in the vehicle vertical direction. In this case, the limit detection portion may be provided at a position overlapping the second leaf as viewed in the vehicle vertical direction. According to such a leaf spring, if the first leaf breaks at the limit detection portion, the first leaf is supported by the second leaf located below, thereby making it possible to more effectively prevent the leaves from falling off.

[0011] (4) The other leaves may include a third leaf having attachment portions at front and rear ends for attachment to a vehicle body. Since the state of the third leaf, which has the function of positioning the leaf spring relative to the vehicle body, is likely to affect driving performance and ride comfort, by not providing a limit detection part on the third leaf, which has an attachment part, it is possible to prevent the leaf from falling off while also ensuring driving performance and preventing a decrease in ride comfort.

[0012] (5) In a case where the first leaf is subjected to shot peening, the limit detection portion may be formed by not subjecting the first leaf to shot peening. By forming the limit detection portion depending on whether or not shot peening is performed, the durability of the limit detection portion against stress can be easily controlled.

[0013] (6) In a case where the first leaf has been subjected to shot peening, the limit detection portion may be formed by shot peening in such a way that the durability is reduced compared to a portion of the first leaf other than the limit detection portion. By forming the limit detection portion by controlling whether or not the effect of shot peening is controlled (controlling whether or not durability is controlled), it is possible to easily control the durability of the limit detection portion against stress.

[0014] (7) In the above case of (5) or (6), the shot peening may be performed on one of the upper and lower surfaces of the first leaf on which tension acts. In this case, the limit detection portion may be provided on the surface on which tension acts. By subjecting the upper and lower surfaces of the first leaf to shot peening, whichever is subjected to tension, it is possible to efficiently increase the durability against stress of the portions other than the limit detection portion.

[0015] (8) The above 1R In the case where the first leaf has been heat-treated, the heat treatment applied to the limit detection portion may be different from the heat treatment applied to the portion of the first leaf excluding the limit detection portion. Heat treatment makes it possible to adjust the stress durability of the limit detection portion and other portions as desired, thereby more appropriately controlling the location of leaf breakage.

[0016] (9) In a case where the first leaf is formed from a composite material, the limit detection portion may be formed from a material different from a material other than the limit detection portion of the first leaf. By changing the constituent materials of the composite material, it is possible to adjust the stress durability of the limit detection section and other sections as desired, thereby more appropriately controlling the location of leaf breakage.

[0017] (10) The limit detection portion may be formed by making the plate thickness of the first leaf thinner than a portion of the first leaf excluding the limit detection portion. In this case, the durability of the first leaf against stress can be adjusted by a simple method.

[0018] (11) The limit detection portion may be formed by making the plate width of the first leaf narrower than a portion of the first leaf excluding the limit detection portion. In this case, the durability of the first leaf against stress can be adjusted by a simple method. Effect of the Invention

[0019] According to the disclosed leaf spring, in a leaf spring having multiple leaves, by controlling the location at which the leaves break, it is possible to prevent the leaves from falling off the vehicle and improve safety in the event of a leaf breakage. [Brief description of the drawings]

[0020] [Figure 1]1 is a left side view illustrating a portion of a vehicle to which a leaf spring according to an embodiment of the present invention is applied; [Diagram 2] FIG. 2 is a perspective view of a portion X in FIG. 1, showing a clip provided in the leaf spring according to the embodiment, a first leaf fixed to the clip, and a second leaf abutting the underside of the first leaf. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The embodiments of the present invention will be described with reference to the drawings. The following embodiments are merely examples, and are not intended to exclude the application of various modifications and techniques not specified in the embodiments. The configurations of the following embodiments can be modified in various ways without departing from the spirit of the embodiments. In addition, they can be selected or combined as necessary.

[0022] [1. Configuration] Fig. 1 illustrates an example of a main part of a vehicle to which a leaf spring 1 of this embodiment is applied. Hereinafter, the forward movement direction of the vehicle is referred to as the front, and the opposite direction (the backward movement direction of the vehicle) is referred to as the rear. In addition, left and right are defined based on the state in which the vehicle faces forward, and the left and right direction is also referred to as the vehicle width direction. Furthermore, the direction perpendicular to both the front-rear direction and the vehicle width direction is referred to as the up-down direction.

[0023] The leaf springs 1 are attached to a pair of left and right side rails 2 extending in the front-rear direction of the vehicle, and function as suspension devices that support (suspend) the axles 3 of the vehicle. The side rails 2 are a body frame that forms the skeleton of the vehicle together with a cross member (not shown) that extends in the vehicle width direction. The axles 3 are shafts that extend in the vehicle width direction and support wheels (not shown) at both ends in the vehicle width direction. Note that while FIG. 1 shows the leaf spring 1 attached to the left side rail 2, the leaf spring 1 attached to the right side rail 2 is configured in the same way (symmetrically).

[0024] The leaf spring 1 is formed by stacking multiple leaves 10 vertically when attached to a vehicle (hereinafter referred to as the "mounted state"). Each of the multiple leaves 10 is a long, narrow leaf spring piece of different length, and when attached, each has a curved shape (arch shape) with the central portion in the longitudinal direction bulging downward. Below, the configuration of the leaf spring 1 will be described based on the mounted state.

[0025] The longitudinal direction of each leaf 10 is arranged along the front-rear direction. The leaf spring 1 is connected to the axle 3 via a pair of U-bolts 4 that are hung on all of the leaves 10. Each leaf 10 has a hole at the longitudinal center through which a center bolt 5 passes, and the leaves 10 are fastened together by the center bolt 5 without being glued or welded to each other.

[0026] In this embodiment, a two-stage leaf spring 1 is exemplified that has a total of eight leaves 10, consisting of five main leaves 20 and three helper leaves 30 stacked on the upper sides. The two-stage leaf spring 1 has a characteristic that, when a large load is applied to the vehicle, the main leaves 20 bend upward, causing the helper leaves 30 to rise and come into contact with stoppers 6 fixed to the side rails 2, changing the spring constant to one appropriate for the load.

[0027] The five main leaves 20 are set so that the higher they are, the longer their longitudinal lengths become. Moreover, all of the five main leaves 20 in this embodiment are formed to have uniform cross sections with the same thickness. In contrast, the three helper leaves 30 are formed in a tapered shape with a thickness that decreases toward the longitudinal end. In this embodiment, the lowest of the three helper leaves 30 has a shorter longitudinal length than the other two.

[0028] Of the five main leaves 20, the uppermost main leaf 20 (third leaf) has eye portions 21a (mounting portions) at both ends in the longitudinal direction for mounting the leaf spring 1 to the side rail 2. As described above, since the leaves 10 are arranged such that the longitudinal direction is along the front-rear direction, it can be said that the eye portions 21a are provided at the front and rear ends of the uppermost main leaf 20. The eye portions 21a are formed by winding a leaf spring piece in a spiral shape. The main leaf 20 having the eye portions 21a is pivotally attached to a bracket 7 fixed to the side rail 2, so that the main leaf 20 is attached so as to be swingable via a shackle pin (not shown), thereby positioning the leaf spring 1 relative to the vehicle body.

[0029] The leaf spring 1 further includes clips 40 for preventing lateral slippage (shift in the vehicle width direction) of each leaf 10. In this embodiment, a leaf spring 1 including one main clip 41 for preventing lateral slippage of the main leaf 20 and one helper clip 42 for preventing lateral slippage of the helper leaf 30 is exemplified. Note that a compressive force acts on the five main leaves 20 in the vertical direction such that they come into close contact with each other, and a compressive force also acts on the three helper leaves 30 in the vertical direction such that they come into close contact with each other.

[0030] As shown in FIG. 2, the main clip 41 is a U-shaped plate-like member formed by bending a rectangular thin plate so as to open upward, and includes a bottom surface portion 41a extending in the vehicle width direction, and a pair of side surfaces 41b extending upward from both the left and right ends of the bottom surface portion 41a. The main leaf 20 is inserted between the pair of side surfaces 41b to regulate its position in the vehicle width direction. In this embodiment, as shown in FIG. 1, the first three main leaves 20 from the top out of the five main leaves 20 (i.e., three main leaves 20) are inserted into the main clip 41 and bound together. The main clip 41 in this embodiment is fixed to the lower surface side of the main leaf 20 (first leaf) located third from the top by a rivet (not shown).

[0031] The main clip 41 includes a bolt 41c penetrating the upper part of the pair of side portions 41b in the vehicle width direction. The bolt 41c is disposed with a gap between the bolt 41c and the main leaf 20 bound by the main clip 41. When the main leaf 20 bound by the main clip 41 is broken, the bolt 41c has a function of catching the broken main leaf 20. That is, the main clip 41 of this embodiment has both a function of preventing lateral displacement and a function of preventing the leaf from falling off. Note that the main clip 41 of this embodiment is disposed rearward of the U-bolt 4 and the center bolt 5, but may be disposed forward of the U-bolt 4 and the center bolt 5, or may be disposed one each in front of and behind the U-bolt 4 and the center bolt 5.

[0032] Like the main clip 41, the helper clip 42 is a U-shaped plate member formed by bending a rectangular thin plate so as to open upward. The helper clip 42 is fixed to the lowest helper leaf 30 among the three helper leaves 30, and binds all the helper leaves 30 together. The helper clip 42 of this embodiment is located forward of the U-bolt 4 and the center bolt 5, but may be located rearward of these, or one each may be located forward and rearward. The helper clip 42 of this embodiment does not have a bolt like the main clip 41, and mainly has a function of preventing lateral displacement.

[0033] Hereinafter, when distinguishing between the five main leaves 20, they will be referred to as the No. 1 main leaf 21, the No. 2 main leaf 22, the No. 3 main leaf 23, the No. 4 main leaf 24, and the No. 5 main leaf 25, starting from the top. The above-mentioned eye portion 21a is provided on the No. 1 main leaf 21. The main clip 41 is fixed to the vicinity of the rear end of the No. 3 main leaf 23 to bind the No. 1 main leaf 21, the No. 2 main leaf 22, and the No. 3 main leaf 23 together. In other words, the main clip 41 is located rearward of the rear end of the No. 4 main leaf 24, and does not overlap with the No. 4 main leaf 24 and the No. 5 main leaf 25 when viewed in the up-down direction.

[0034] The leaf spring 1 may break one of the leaves 10 due to long-term use, the action of a load exceeding the allowable stress, or a combination of these. If the leaf 10 breaks, the spring function is reduced and the vehicle body tilts, so that the passengers can easily notice the abnormality of the leaf spring 1.

[0035] At this time, the leaf spring 1 is required not to allow fragments of the broken leaf 10 to fall off. In particular, if the leaf 10 breaks while the vehicle is running, it is important that the broken leaf 10 not fall off until the vehicle stops. If the leaf spring 1 breaks while the vehicle is stopped, it is required that the broken leaf 10 not fall off when the vehicle starts to run, and even if the vehicle has already started to run, it is desirable that the broken leaf 10 not fall off until the vehicle stops.

[0036] Therefore, in the leaf spring 1 of this embodiment, the leaf 10 that is less likely to fall off among the multiple leaves 10 is provided with a limit detection part S that has reduced durability against stress compared to the other leaves 10, thereby controlling the breakage location of the leaf 10 and preventing the leaf 10 from falling off when broken. In Fig. 1 and Fig. 2, the limit detection part S is shown with a dot pattern for ease of understanding.

[0037] Here, "durability against stress" refers to the performance indicating how long the leaf spring 10 can resist stress acting on it, and can also be interpreted as "strength" including tensile strength and fatigue strength. In other words, the limit detection part S is the part of all the leaves 10 that breaks first (the part that detects the limit) when stress (bending stress, repeated stress, etc.) continues to act on the leaf spring 1 and the leaf spring 1 reaches its limit. The fact that the limit detection part S breaks first means, in other words, that no part other than the limit detection part S will break first. Also, as described above, the occupant can notice something unusual about the leaf spring 1 when a leaf breaks, so the limit detection part S can also be said to be a part that functions as a sensor that detects the limit of the leaf spring 1.

[0038] In this embodiment, the limit detection unit S is provided on the No. 3 main leaf 23, which is fixed to the main clip 41, among the No. 1 main leaf 21, the No. 2 main leaf 22, and the No. 3 main leaf 23 that are bound by the main clip 41. In this case, the above-mentioned "other leaves 10" refers to the four main leaves 20 excluding the No. 3 main leaf 23 and the three helper leaves 30.

[0039] The limit detection portion S is provided in the longitudinal direction of the No. 3 main leaf 23, between the U-bolt 4, which is a connecting portion with the axle 3, and the main clip 41. As shown in FIG. 2, the limit detection portion S in this embodiment is provided at a position overlapping with the No. 4 main leaf 24 (second leaf) that abuts against the lower side of the No. 3 main leaf 23 when viewed in the vertical direction. Although not shown in FIG. 2, the No. 2 main leaf 22 is present above the limit detection portion S, so that the limit detection portion S in this embodiment is provided at a position sandwiched between the other leaves 22, 24 in the vertical direction. Moreover, the limit detection portion S in this embodiment extends in the width direction of the No. 3 main leaf 23.

[0040] An example of a method for providing the limit detection portion S is a method using shot peening. For example, when the No. 3 main leaf 23 is subjected to shot peening, the No. 3 main leaf 23 is not subjected to shot peening at a portion where the limit detection portion S is to be provided. Specifically, when the No. 3 main leaf 23 is subjected to shot peening, the position where the limit detection portion S is to be provided is masked with a cover that does not provide the effect of the shot peening.

[0041] In this manner, the limit detection part S is formed by not performing shot peening. Since the surface subjected to shot peening has increased surface hardness and fatigue strength, not performing shot peening at the position where the limit detection part S is to be provided results in suppressing the durability of the limit detection part S against stress.

[0042] As another example of a method of providing the limit detection portion S using shot peening, there is a method of performing shot peening that suppresses durability at the portion where the limit detection portion S is to be provided, instead of performing shot peening on the No. 3 main leaf 23. In this manner, the limit detection portion S is formed by performing shot peening that suppresses durability.

[0043] For example, when the No. 3 main leaf 23 is shot peened, the portion where the limit detection portion S is provided may be subjected to a peening method that suppresses the effect of the shot peening, which is different from the portion of the No. 3 main leaf 23 other than the limit detection portion S (hereinafter also referred to as "other portions"). Alternatively, the amount of peening steel balls may be reduced in the portion where the limit detection portion S is provided, compared to other portions. Since the surface that has been subjected to shot peening increases in surface hardness and fatigue strength in accordance with the shot peening applied, by performing shot peening with suppressed effect in the portion where the limit detection portion S is provided, the durability of the limit detection portion S against stress is suppressed as a result.

[0044] The shot peening may be performed on both the upper and lower surfaces of the No. 3 main leaf 23, or on one of the upper and lower surfaces of the No. 3 main leaf 23 on which tension acts (the surface on the tension side). As described above, in the leaf spring 1 of this embodiment, the leaves 10 are stacked in the vertical direction and bend upward due to the load applied to the vehicle, so that the shot peening is performed on the upper surface of the No. 3 main leaf 23. The shot peening may be performed on all or part of the other leaves 10. In addition, when the shot peening is performed on all or part of the other leaves 10, the shot peening may be performed on one of the upper and lower surfaces of the leaf 10 on which tension acts. In addition, when the other leaves 10 have higher durability against stress than the No. 3 main leaf 23 even without the shot peening, the other leaves 10 do not need to be shot peened.

[0045] Other methods of providing the limit detection portion S include, for example, a method using heat treatment or a method of changing the material itself. For example, when the No. 3 main leaf 23 is subjected to heat treatment, the limit detection portion S may be formed by subjecting a portion of the No. 3 main leaf 23 where the limit detection portion S is provided and the other portions (other parts) to different heat treatments. For example, only the portion where the limit detection portion S is provided may be subjected to heat treatment that reduces its strength, or the portions other than the limit detection portion S may be subjected to heat treatment that increases its strength, or these may be combined.

[0046] Furthermore, when the No. 3 main leaf 23 is made of a composite material, the limit detection portion S may be formed by constructing the portion of the No. 3 main leaf 23 where the limit detection portion S is provided and the other portions (other parts) of the No. 3 main leaf 23 from different materials. For example, a material that reduces the strength of only the portion where the limit detection portion S is provided may be used, or a material that increases the strength of the portion other than the limit detection portion S may be used, or a combination of these may be used.

[0047] [2. Actions and Effects] (1) According to the leaf spring 1, the durability of the limit detection part S of the No. 3 main leaf 23 (first leaf) against stress is suppressed, so that the No. 3 main leaf 23 can be made to break more easily than the other leaves 10. As a result, when the leaf 10 of the leaf spring 1 reaches its limit, the limit detection part S provided on the No. 3 main leaf 23 breaks first, so that the leaf 10 does not break at other positions, and the location where the leaf 10 breaks can be controlled.

[0048] The No. 3 main leaf 23 is bound by the main clip 41, and the limit detection portion S is provided between the U-bolt 4, which is a connection portion with the axle 3, and the main clip 41. Therefore, even if the No. 3 main leaf 23 breaks at the limit detection portion S, one side of the No. 3 main leaf 23 (the part on the axle 3 side) is supported by the U-bolt 4 and the center bolt 5, and the other side (the part on the rear end side) is supported by the main clip 41, preventing it from falling off. In this way, even if the leaf spring 1 reaches its limit and breaks, by controlling the broken part of the leaf 10 so that the supporting force of the main clip 41 acts on the broken leaf 10, it is possible to prevent the leaf 10 (here, the No. 3 main leaf 23) from falling off, thereby improving safety.

[0049] (2) In the leaf spring 1 described above, since the No. 3 main leaf 23 is fixed to the main clip 41, when the No. 3 main leaf 23 breaks at the limit detection portion S, the end portion of the No. 3 main leaf 23 does not fall off from the main clip 41. Furthermore, when the No. 3 main leaf 23 breaks, the main clip 41 catches the other leaves (the No. 1 main leaf 21 and the No. 2 main leaf 22) that are bundled together. Therefore, the No. 3 main leaf 23 fixed to the main clip 41 can also be caught by the other main leaves 21, 22 via the main clip 41. This makes it possible to better prevent the leaf 10 from falling off when the limit of the leaf spring 1 is reached, thereby further improving safety.

[0050] (3) The limit detection portion S is provided at a position overlapping the No. 4 main leaf 24 (second leaf) that abuts the underside of the No. 3 main leaf 23 when viewed in the up-down direction. Therefore, if the No. 3 main leaf 23 breaks at the limit detection portion S, the No. 3 main leaf 23 is supported by the compressive force from the No. 4 main leaf 24 located below, which further prevents the broken leaf 10 from falling off.

[0051] (4) The leaves 10 other than the No. 3 main leaf 23 having the limit detection part S include the No. 1 main leaf 21 (third leaf) having the eye part 21a for mounting to the vehicle body. As described above, the No. 1 main leaf 21 has the function of positioning the leaf spring 1 relative to the vehicle body. Therefore, by not providing the No. 1 main leaf 21 with the limit detection part S, it is possible to prevent the leaf 10 from falling off, ensure driving performance, and prevent a decrease in ride comfort.

[0052] (5) When the limit detection portion S is formed by not subjecting the No. 3 main leaf 23 to shot peening, the strength of the No. 3 main leaf 23 can be adjusted by a simple method. (6) When the limit detection portion S is formed by subjecting the No. 3 main leaf 23 to shot peening, which reduces durability compared to other portions, the strength of the No. 3 main leaf 23 can be adjusted by a simple method. (7) In particular, by subjecting the No. 3 main leaf 23 to shot peening on the upper and lower surfaces thereof where tension acts, the durability against stress of the portions other than the limit detection portion S can be efficiently improved.

[0053] (8) Furthermore, when the limit detection portion S is formed by subjecting the limit detection portion S and the portion of the No. 3 main leaf 23 other than the limit detection portion S (the entire portion other than the limit detection portion S) to different heat treatments, the durability against stress of the limit detection portion S and the other portions can be adjusted as desired, thereby making it possible to more appropriately control the breakage point of the leaf 10.

[0054] (9) Also, even if the No. 3 main leaf 23 is formed of a composite material and the limit detection portion S is formed of a material different from that of the portion of the No. 3 main leaf 23 other than the limit detection portion S, the durability against stress of the limit detection portion S and the other portions can be adjusted as desired, so that the breakage point of the leaf 10 can be more appropriately controlled.

[0055] [3. Modifications] The above-described configuration of the leaf spring 1 is an example. The limit detection portion S does not have to extend in the vehicle width direction, and may be provided, for example, in a portion of the vehicle width direction. Also, the limit detection portion S is preferably provided in one location of the first leaf (the No. 3 main leaf 23 in the above embodiment) on which the limit detection portion S is provided, but multiple limit detection portions may be provided.

[0056] The limit detection portion S only needs to be provided between at least the connection portion with the axle 3 (the U-bolt 4 in the above embodiment) and the main clip 41, and does not need to overlap with the second leaf (the No. 4 main leaf 24 in the above embodiment) that abuts the underside of the first leaf when viewed in the up-down direction. Furthermore, the leaf on which the limit detection portion S is provided is not limited to the No. 3 main leaf 23, but may be provided on another main leaf 20 that is fastened to the main clip 41. In this case, the other main leaf 20 corresponds to the "first leaf" as defined in the claims.

[0057] The thickness of the main leaf 20 may vary in the longitudinal direction. In this case, the limit detection portion S may be formed by making the thickness thinner than the portion of the first leaf (No. 3 main leaf 23 in the above embodiment) excluding the limit detection portion S. The width of the main leaf 20 may also vary in the longitudinal direction. In this case, the limit detection portion S may be formed by making the width narrower than the portion of the first leaf (No. 3 main leaf 23 in the above embodiment) excluding the limit detection portion S. In either case, the durability of the first leaf against stress can be adjusted by a simple method. Six methods for providing the limit detection portion S have been given as examples, but the limit detection portion S may be formed by any one of the methods, or the limit detection portion S may be formed by a combination of these methods.

[0058] A plurality of main clips 41 may be provided in front of and / or behind the U-bolt 4, which is a connecting portion with the axle 3. The main clip 41 in the above embodiment fastens the top three main leaves 20, but the number of main leaves 20 fastened by the main clip 41 is not limited to this. For example, all five main leaves 20 may be fastened, or the second to fourth main leaves 21 and 22 or the fourth to fourth main leaves 21 to 24 may be fastened. That is, the position of the main clip 41 is not limited to the vicinity of the rear end of the No. 3 main leaf 23. The position of the main clip 41 may be at least a position where the limit detection portion S can apply a supporting force to the end portion of the broken leaf 10. In other words, the limit detection portion S may be provided at a position where the supporting force of the clip applies to the end portion of the broken leaf 10.

[0059] The clip 40 does not have to be fixed to the leaf 10, and may simply engage with the leaf 10 through surface contact. At least a plurality of leaves 10 are subjected to a compressive force in the vertical direction relative to each other, so even if the clip 40 and the leaf 10 are not fixed to each other, the engaging force of the clip 40 and the compressive force between the leaves 10 can prevent a broken leaf 10 from falling off. In this case, it is better that another leaf 10 is present vertically below the limit detection portion S.

[0060] The leaf spring has at least two leaves (first 1R The number of main leaves 20 is not limited to five as long as the leaf spring has a helper leaf 30 (a main leaf 20 and other leaves excluding the main leaf 20). The above-mentioned configuration does not require a helper leaf 30, and the above-mentioned configuration (limit detection unit S) may be applied to a leaf spring that does not have a helper leaf. The above-mentioned configuration may also be applied to a leaf spring that has a leaf whose longitudinal center portion bulges upward. [Explanation of symbols]

[0061] 1 Leaf spring 2 Side rails 3 Axle 4 U-bolts 5 Center Bolt 6 Stopper 7 Bracket 10 Leaf 20 Main Reef 21 No.1 Main Reef (Third Reef) 21a Eye part (attachment part) 22 No.2 Main Reef 23 No.3 Main Reef (1st Reef) 24 No.4 Main Reef (2nd Reef) 25 No.5 Main Reef 30 Helper Reef 40 clips 41 Main Clip 41a Bottom part 41b Side part 41c Bolt 42 Helper Clip S Limit detection section

Claims

1. A leaf spring in which a plurality of leaves are stacked and connected to an axle, The plurality of leaves includes a first leaf that is bound by a clip; The first leaf is provided between a connection portion with the axle and the clip, and includes a limit detection portion having a lower durability against stress than other leaves among the plurality of leaves except for the first leaf. A leaf spring characterized by:

2. The first leaf is fixed to the clip. A leaf spring according to claim 1 , characterized in that

3. the other leaves include a second leaf that abuts against a lower side of the first leaf in the vehicle up-down direction, The limit detection portion is provided at a position overlapping the second leaf when viewed in the vertical direction of the vehicle. A leaf spring according to claim 1 or 2, characterized in that

4. The other leaves include a third leaf having attachment parts at the front and rear ends for attachment to the vehicle body. A leaf spring according to any one of claims 1 to 3.

5. The first leaf is shot peened, The limit detection portion is formed by not performing shot peening on the first leaf. A leaf spring according to any one of claims 1 to 4.

6. The first leaf is shot peened, The limit detection portion is formed by performing shot peening so that the durability of the first leaf is reduced compared to the portion other than the limit detection portion. A leaf spring according to any one of claims 1 to 4.

7. the shot peening is performed on one of the upper and lower surfaces of the first leaf to which tension acts, The limit detection portion is provided on a surface on which the tension acts. A leaf spring according to claim 5 or 6, characterized in that

8. the first leaf has been heat treated; The heat treatment applied to the limit detection portion is different from the heat treatment applied to the portion of the first leaf other than the limit detection portion. A leaf spring according to any one of claims 1 to 7, characterized in that

9. the first leaf is formed of a composite material; The limit detection portion is formed of a material different from that of the portion of the first leaf other than the limit detection portion. A leaf spring according to any one of claims 1 to 8.

10. The limit detection portion is formed by making the plate thickness of the first leaf thinner than that of the portion other than the limit detection portion. A leaf spring according to any one of claims 1 to 9.

11. The limit detection portion is formed by making the plate width of the first leaf narrower than that of the portion other than the limit detection portion. A leaf spring according to any one of claims 1 to 10, characterized in that

Images