LEAF SPRING FOR A VEHICLE

Abstract

A leaf spring for a vehicle suspension system, the leaf spring comprising a middle leaf plate located between an upper leaf plate and a lower leaf plate and a center bolt extending through an aperture of each of the leaf plates at a central region of the leaf spring, wherein the middle leaf plate has a wavy structure in the longitudinal direction where troughs and crests of waves of the wavy structure form longitudinally distributed contact points for transfer of load between the middle leaf plate and the upper and lower leaf plates, wherein the center bolt aperture of the middle leaf plate has an elongation in the longitudinal direction that is greater than that of the center bolt aperture of the upper and lower leaf plates so as to allow the middle leaf plate to move in the longitudinal direction relative to the upper and lower leaf plates.

Claims

1. A leaf spring for a vehicle suspension system, the leaf spring comprising: a plurality of elongated leaf plates extending along each other in a longitudinal direction of the leaf spring; and a connection arrangement for holding the plurality of leaf plates together, wherein the connection arrangement comprises a center bolt extending through an aperture of each of the leaf plates at a central region of the leaf spring; wherein the plurality of leaf plates comprises a middle leaf plate located between an upper leaf plate and a lower leaf plate; wherein the middle leaf plate has a wavy structure in the longitudinal direction where troughs and crests of waves of the wavy structure form longitudinally distributed contact points for transfer of load between the middle leaf plate and the upper and lower leaf plates; wherein the center bolt aperture of the middle leaf plate has an elongation in the longitudinal direction that is greater than that of the center bolt aperture of the upper and lower leaf plates so as to allow the middle leaf plate to move in the longitudinal direction relative to the upper and lower leaf plates; and wherein the middle leaf plate is slidably arranged relative to the upper and lower leaf plates in the longitudinal direction such that when a load is transferred between the middle leaf plate and the upper or lower leaf plate via one or more of the contact points and the waves of the middle leaf plate thereby are stretched, the middle leaf is allowed to i) expand in the longitudinal direction as a result of the stretching of the waves and to ii) slide as a whole along and relative to the upper and lower leaf plates in the longitudinal direction.

2. The leaf spring of claim 1, wherein the leaf spring is provided with a slide friction reducer arranged between the middle leaf plate and an adjacent leaf plate.

3. The leaf spring of claim 2, wherein the slide friction reducer comprises roller bearings.

4. The leaf spring of claim 1, wherein the leaf spring comprises a guiding arrangement configured to guide the relative movement of the middle leaf plate in the longitudinal direction.

5. The leaf spring of claim 4, wherein the guiding arrangement comprises first and second interactive guiding members, wherein the first guiding member is arranged on the middle leaf plate and the second guiding member is arranged on an adjacent leaf plate and facing the first guiding member.

6. The leaf spring of claim 5, wherein one of the first and second interactive guiding members is a ridge or other elongated protrusion extending in a longitudinal direction, and wherein the other of the first and second interactive guiding members is a longitudinally directed groove adapted to receive the ridge.

7. The leaf spring of claim 2, wherein the guiding arrangement is provided with a slide friction reducer so as to form a combined guiding and friction reducing structure.

8. The leaf spring of claim 3, wherein the guiding arrangement is provided with a slide friction reducer so as to form a combined guiding and friction reducing structure.

9. The leaf spring of claim 5, wherein the guiding arrangement is provided with a slide friction reducer so as to form a combined guiding and friction reducing structure.

10. The leaf spring of claim 6, wherein the guiding arrangement is provided with a slide friction reducer so as to form a combined guiding and friction reducing structure.

11. The leaf spring of claim 3, wherein the ridge or other elongated protrusion is provided with roller bearings so as to form a combined guiding and friction reducing structure.

12. The leaf spring of claim 4, wherein the ridge or other elongated protrusion is provided with roller bearings so as to form a combined guiding and friction reducing structure.

13. The leaf spring of claim 5, wherein the ridge or other elongated protrusion is provided with roller bearings so as to form a combined guiding and friction reducing structure.

14. The leaf spring of claim 6, wherein the ridge or other elongated protrusion is provided with roller bearings so as to form a combined guiding and friction reducing structure.

15. The leaf spring of claim 1, wherein each of the waves of the wavy structure has a shape such that compression of the middle leaf plate between the upper and lower leaf plates leads to stretching and at least partly flattening of the wave.

16. A vehicle comprising: a chassis; a pair of left and right wheels; a wheel axle that extends transversely across the vehicle and that is connected at the end portions thereof to the left and right wheels; and at least one left or right leaf spring connected to the wheel axle in association with a corresponding wheel, wherein the at least one leaf spring of claim 1 is connected also to the chassis so as to, while deflecting, allow relative vertical movement between the chassis and the wheel axle and thereby also between the chassis and the corresponding wheel.

17. The vehicle of claim 16, wherein the at least one leaf spring has an elongated shape and extends in a direction substantially in parallel with a longitudinal roll axis of the vehicle.

18. The vehicle of claim 16, wherein the at least one leaf spring is connected to the chassis at a first point in front of the corresponding wheel and at a second point behind the corresponding wheel with reference to a front and rear of the vehicle.

19. The vehicle of claim 16, wherein the at least one leaf spring is connected to the second point of the chassis via a pivoted shackle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Examples are described in more detail below with reference to the appended drawings.

[0025] FIG. 1 shows an example of a vehicle in the form of a truck provided with an example of a pair of leaf springs according to this disclosure.

[0026] FIG. 2 shows one of the leaf springs of FIG. 1.

[0027] FIGS. 3A and 3B show a central region of the leaf spring of FIG. 2 in an exploded view (FIG. 3A) and when put together (FIG. 3B).

[0028] FIG. 4 shows a part of an example of a combined guiding and friction reducing arrangement.

[0029] FIG. 5 shows, in a sectional view, an example of a leaf spring provided with an arrangement according to FIG. 4.

DETAILED DESCRIPTION

[0030] The detailed description set forth below provides information and examples of the disclosed technology with sufficient detail to enable those skilled in the art to practice the disclosure.

[0031] The exemplified vehicle 10 of FIG. 1 comprises a chassis 11, a pair of left and right wheels 12, 13, a wheel axle 14 that extends transversely across the vehicle 10 and that is connected at the end portions thereof to the left and right wheels 12, 13. As part of a vehicle suspension system, the vehicle further comprises a pair of left and right leaf springs 1, 2 (which in this example are in principle identical) connected to the wheel axle 14 in association with the corresponding wheel 12, 13. The suspension system may further comprise e.g. separate shock absorbers (not shown).

[0032] Each leaf spring 1, 2 is connected also to the chassis 11 so as to, while deflecting, allow relative vertical movement between the chassis 11 and the wheel axle 14 and thereby also between the chassis 11 and the wheels 12, 13. Each leaf spring 1, 2 has an elongated shape and extends in a direction substantially in parallel with a longitudinal roll axis 15 of the vehicle 10.

[0033] Each leaf spring 1, 2 is connected to the chassis 11 at a first point 11a in front of the corresponding wheel 12, 13 and at a second point 11b behind the corresponding wheel 12, 13 with reference to a front and rear of the vehicle 10. Further, each leaf spring 1, 2 is connected to the second point 11b of the chassis via a pivoted shackle 16 (see FIG. 2).

[0034] As shown in FIGS. 2-5, each leaf spring 1, 2 comprises a plurality of elongated leaf plates 3, 4, 5 extending along each other in a longitudinal direction of the leaf spring 1, 2 and a connection arrangement for holding the plurality of leaf plates 3, 4, 5 together. The connection arrangement comprises a center bolt 6 extending through an aperture 8a, 8b, 8c of each of the leaf plates 3, 4, 5 at a central region 9 of the leaf spring 1, 2. The connection arrangement also comprises a nut 7 screwed onto the center bolt 6 and a plurality of clips (not shown) arranged to hold the leaf plates (3, 4, 5) in place laterally.

[0035] As shown in e.g. FIG. 2, the plurality of leaf plates comprises a middle leaf plate 4 located between and adjacent to an upper leaf plate 5 and a lower leaf plate 3, where upper and lower refers to the relative position when the leaf spring 1, 2 is mounted in a typical orientation onto a vehicle. A bent end part of the upper leaf plate 5 forms an eye 25 for connection to the chassis 11. A bent end part of the middle leaf plate 4 forms in this example a part of the eye 25.

[0036] The middle leaf plate 4 has a wavy structure in the longitudinal direction where troughs and crests of waves 20 of the wavy structure form longitudinally distributed contact points 21 for transfer of load between the middle leaf plate 4 and the upper and lower leaf plates 3, 5.

[0037] As shown in FIGS. 3A and 3B, the center bolt aperture 8b of the middle leaf plate 4 has an elongation in the longitudinal direction that is greater than that of the circular center bolt aperture 8a, 8c of the upper and lower leaf plates 3, 5 so as to allow the middle leaf plate 4 to move in the longitudinal direction relative to the upper and lower leaf plates 3, 5. Shim plates 29 are arranged between the leaf plates 3, 4, 5 at the center bolt 6.

[0038] The middle leaf plate 4 is slidably arranged relative to the upper and lower leaf plates 3, 5 in the longitudinal direction such that when a wheel 12, 13 hits a bump when the vehicle 10 moves and a load is transferred from the lower leaf plate 3 to the middle leaf plate 4 via one or more of the contact points 21 and the waves 20 of the middle leaf plate 4 thereby are stretched, the middle leaf 4 is allowed to i) expand in the longitudinal direction as a result of the stretching of the waves 20 as well as to ii) slide as a whole along and relative to the upper and lower leaf plates 3, 5 in the longitudinal direction. The latter is of primary importance in case the load is asymmetric, such as when the vehicle 10 brakes or is located in a steep slope. As mentioned already further above, this longitudinal repositioning of the middle leaf plate 4 improves load distribution within the leaf spring 1, 2 and reduces stress concentration, which in turn increases durability of the leaf spring 1, 2. It also provides reduction in vertical movement of the leaf spring 1, 2 and in the amount of load transferred to the chassis 11 of the vehicle 10, which in turn reduces risk of damage to the chassis 11.

[0039] As shown in FIGS. 4-5, the leaf spring 1, 2 is provided with a slide friction reducer in the form of roller bearings 22 in this example arranged on an upper side of the middle leaf plate 4 so as to be located between the middle leaf plate 4 and a lower side of the adjacent upper leaf plate 5. The roller bearings 22 reduces the friction and facilitates relative sliding of the middle leaf plate 4.

[0040] Cylindrical roller bearings 22 are placed sideways into cutouts 28 provided in a ridge 23a as shown in FIG. 4. An upper with of the cutouts 28 is smaller than the diameter of the roller bearings 22 so as to keep the roller bearings 22 in place vertically. Pins 27 placed on coil springs 26 keep the roller bearings 22 in place in the lateral direction of the middle leaf spring 4 (i.e. in the longitudinal direction of the roller bearings 22). The pins 27 are pressed down to insert the roller bearings 22. The pins 27 are placed in holes (not shown) in the middle leaf plate 4.

[0041] The leaf spring 1, 2 further comprises a guiding arrangement 23, 24 configured to guide the relative sliding movement of the middle leaf plate 4 in the longitudinal direction. In this example the guiding arrangement comprises first and second interactive guiding members in the form of a ridge 23 extending in the longitudinal direction and a groove 24 adapted to receive the ridge 23. As shown in FIG. 5, one ridge 23b is formed on the upper side of the lower leaf plate 3 with a corresponding groove 24b provided on the lower side of the middle leaf plate 4, and another ridge 23a is formed on the upper side of the middle leaf plate 4 with a corresponding groove 24a provided on the lower side of the upper leaf plate 5. When the middle leaf plate 4 slides/moves in relation to the upper and lower leaf plates 3, 5, the ridges 23a, 23b are guided by their corresponding groove 24a, 24b so as to keep the leaf plates 3, 4, 5 aligned in the longitudinal direction.

[0042] As further shown in FIGS. 4 and 5, the roller bearings 22 are in this example arranged in the ridge 23a that also forms part of the guiding arrangement. The leaf spring 1, 2 shown in the figures is thus provided with a combined guiding and friction reducing structure.

[0043] As to the waves 20 of the wavy middle leaf plate 4, their exact shape and number can be adapted depending on the particular dimension, design and intended use of the leaf spring 1, 2. Also the stiffness of the middle leaf plate 4 may be varied. In this case there are around three contact points 21 at each of the adjacent leaf plates 3, 5, at each side of the central region 9. Along the central region 9 the middle leaf plate may be substantially flat. As shown in FIG. 2, each of the waves 20 has a shape such that compression of the middle leaf plate 4 between the upper and lower leaf plates 3, 5 leads to stretching and at least partly flattening of the wave 20. This means there no extreme bends/waves where the middle leaf plate 4 at some point extends in a direction that is parallel to a normal to the surface of the adjacent leaf plates 3, 5 (i.e. the middle leaf plate never extends in a vertical direction if the surface of adjacent leaf plates is horizontal).

[0044] The terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting of the disclosure. As used herein, the singular forms a, an, and the are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the term and/or includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms comprises, comprising, includes, and/or including when used herein specify the presence of stated features, integers, actions, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, actions, steps, operations, elements, components, and/or groups thereof.

[0045] It will be understood that, although the terms first, second, etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element without departing from the scope of the present disclosure.

[0046] Relative terms such as below or above or upper or lower or horizontal or vertical may be used herein to describe a relationship of one element to another element as illustrated in the Figures. It will be understood that these terms and those discussed above are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures. It will be understood that when an element is referred to as being connected or coupled to another element, it can be directly connected or coupled to the other element, or intervening elements may be present. In contrast, when an element is referred to as being directly connected or directly coupled to another element, there are no intervening elements present.

[0047] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0048] It is to be understood that the present disclosure is not limited to the aspects described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the present disclosure and appended claims. In the drawings and specification, there have been disclosed aspects for purposes of illustration only and not for purposes of limitation, the scope of the disclosure being set forth in the following claims.