Method for leaf springs made of fiber-reinforced plastic with integrated eye bushings, and leaf spring made of fiber-reinforced plastic

Abstract

A fiber-reinforced plastic leaf spring and a method for producing the fiber-reinforced plastic leaf spring are provided, which is suitable in particular for use in a motor vehicle. It has an elongate leaf spring main body which comprises a first eye bushing at a first end and a second eye bushing at a second end. The leaf spring main body and the first and second eye bushings are formed using at least a first layer and a second layer of a composite material. Each of the layers is guided along a centerline of the leaf spring main body to form the leaf spring main body and, to form the first and second eye bushings, is respectively wrapped around a bushing element having a first center axis and around a bushing element having a second center axis.

Claims

1. A method for producing a fiber-reinforced leaf spring for use in a motor vehicle, the method comprising: forming an elongate leaf spring main body with a first eye bushing at a first end and a second eye bushing at a second end using at least a first layer and a second layer of a plastic and/or composite material; guiding each of the layers along a centerline of the leaf spring main body to form the leaf spring main body and to form the first and second eye bushings; wrapping the first layer around a first bushing element having a first center axis in a first circumferential direction and around a second bushing element having a second center axis in the same, first circumferential direction such that a first end region of the first layer terminates adjacent to the first bushing, a second end region of the first layer terminates adjacent to the second bushing and is spaced apart from the first end region of the first layer, and a central region of the first layer between the first and second end regions is guided along only a first side of a curved spring centerline; and wrapping the second layer in a second circumferential direction, counter to the first circumferential direction, around the first bushing element and in the same, second circumferential direction around the second bushing element such that a first end region of the second layer terminates adjacent to the first bushing, a second end region of the second layer terminates adjacent to the second bushing and is spaced apart from the first end region of the second layer, and a central region of the second layer between the first and second end regions is guided along only a second side of the curved spring centerline, the second side of the spring centerline opposite to the first side of the spring centerline.

2. The method of claim 1 further comprising: wrapping a third layer in the first circumferential direction around the first bushing element and, in the same, first circumferential direction, around the second bushing element.

3. The method of claim 2, wherein each of the first, second, and third layers is in one piece.

4. The method of claim 2, wherein the first, second, and third layers are arranged one on top of another at least in a region adjacent to the first and second eye bushing, wherein each of the layers completely surrounds the respective underlying layer, at least in the region adjacent to the first and second eye bushing.

5. The method of claim 2, wherein the centerline forms a curve and the first and third layers are arranged on a first side of the centerline with a first radius of curvature, and the second layer is arranged on a second side of the centerline having a second radius of curvature, the second radius of curvature being greater than the first radius of curvature.

6. The method of claim 1 further comprising wrapping a plurality of additional layers around the first and second bushing elements, wherein the plurality of additional layers are wrapped in alternating first and second circumferential directions around the first and the second bushing element.

7. The method of claim 6, wherein the first layer, the second layer and the plurality of additional layers total an odd number of layers.

8. The method of claim 1, wherein the first layer is wrapped prior to the second layer being wrapped.

9. The method of claim 1, wherein each of the first and second layers are guided only in one ply along the centerline.

10. The method of claim 1, wherein the first and/or the second bushing element has an outer metal sleeve, an inner metal sleeve, and a rubber-like insert positioned therebetween.

11. The method of claim 1, wherein the composite material further comprises prepreg.

12. A fiber-reinforced leaf spring for use in a motor vehicle, the leaf spring comprising: first and second bushing elements; and an elongate leaf spring main body formed by the method of claim 1, the main body with first and second eye bushings extending around the first and second bushing elements, respectively.

13. The method of claim 1, wherein the first layer is wrapped in the first circumferential direction such that the first layer does not cross the curved spring centerline between the first and second bushings; and wherein the second layer is wrapped in the second circumferential direction such that the second layer does not cross the curved spring centerline between the first and second bushings.

14. A leaf spring comprising: a first bushing and a second bushing; a first fiber-reinforced composite layer having a central region extending between opposite first and second end regions; and a second second fiber-reinforced composite layer layer having a central region extending between opposite first and second end regions; wherein the first and second end regions of each layer are wrapped about first and second bushings, respectively, such that the first end region of each layer terminates adjacent to the first bushing, and the second end region of the each layer terminates adjacent to the second bushing; wherein each end region of the first layer is positioned between an associated bushing and an associated end region of the second layer; wherein the central region of the first layer extends along only a first side of a curved spring centerline; and wherein the central region of the second layer extends along only a second side of the curved spring centerline.

15. The leaf spring of claim 14, wherein each end region of the first layer terminates on the second side of the spring centerline adjacent to an associated bushing; and wherein each end region of the second layer terminates on the first side of the spring centerline adjacent to an associated bushing.

16. The leaf spring of claim 15, wherein the central regions of each of the first and second layers extend as a single ply between the first and second bushings.

17. The leaf spring of claim 16 further comprising a third fiber-reinforced layer having a central region extending between opposite end regions wrapped about the first and second bushings, respectively, the central region of the third layer extending along only the first side of the spring centerline and in contact with the central region of the first layer; wherein each end region of the second layer is positioned between an associated end region of the first layer and an associated end region of the third layer.

18. The leaf spring of claim 17 further comprising first and second bushings, each bushing having a metal outer wall and a metal inner wall, wherein the leaf spring has a constant wall thickness at the bushings and along the centerline of the spring.

19. A fiber-reinforced leaf spring for use in a motor vehicle, the leaf spring comprising: a first bushing element having a first center axis; a second bushing element having a second center axis; and an elongate leaf spring main body with a first eye bushing at a first end and a second eye bushing at a second end, wherein the leaf spring main body and the first and second eye bushings are formed using at least a first layer and a second layer of a plastic and/or composite material, wherein each of the layers runs along a centerline of the leaf spring main body to form the leaf spring main body and, to form the first and second eye bushings, is respectively wrapped around the first bushing element and around the second bushing element; wherein each of the layers runs in only one ply along the centerline; wherein the first layer is wrapped in a first circumferential direction around the first bushing element and in the same first circumferential direction around the second bushing element, such that a first end region of the first layer terminates adjacent to the first bushing element, a second end region of the first layer terminates adjacent to the second bushing element, and a central region of the first layer between the first and second end regions only runs along a first side of the centerline between the first and second bushing elements; wherein the second layer is wrapped in a second circumferential direction, counter to the first circumferential direction, around the first bushing element and in the same second circumferential direction around the second bushing element, such that a first end region of the second layer terminates adjacent to the first bushing element, a second end region of the second layer terminates adjacent to the second bushing element, and a central region of the second layer between the first and second end regions runs only along a second side, opposite the first side, of the centerline between the first and second bushing elements; and wherein the leaf spring main body and the first and the second eye bushing all have a uniform wall thickness.

20. The leaf spring of claim 19, wherein the composite material further comprises prepreg.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic side view of an exemplary embodiment of a leaf spring according to the invention, with integrated eye bushings,

(2) FIG. 2 is a schematic side view of a first eye bushing of the exemplary embodiment of FIG. 1, and

(3) FIG. 3 is a schematic side view of a second eye bushing of the exemplary embodiment of FIG. 1.

DETAILED DESCRIPTION

(4) As required, detailed embodiments of the present disclosure are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary and may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present disclosure.

(5) In the different figures, identical parts are always provided with the same reference signs, and so said parts are generally also described only once.

(6) FIG. 1 shows an exemplary embodiment of a leaf spring 1 according to the invention, made of fiber-reinforced plastic or composite material, which has a leaf spring main body 2 with a first and a second integrated bushing element 3, 4 for mounting and/or securing the leaf spring 1, for example in a spring system of a vehicle shock damping arrangement. The first bushing element 3 comprises an outer metal sleeve 5, an inner metal sleeve 7 and a rubber insert 9. The second bushing element 4 also comprises an outer metal sleeve 6, an inner metal sleeve 8 and a rubber insert 10. The bushing elements 3, 4 are positioned at opposite ends of the leaf spring 1. The depicted leaf spring 1 is axisymmetric and has an arcuate or curved profile. The dashed centerline 18 is an imaginary line connecting a center axis z3 of the first bushing element 3 and a center axis z4 of the second bushing element 4. The centerline 18 replicates the curvature profile of the leaf spring 1. If the leaf spring 1 experiences a mechanical load, the curvature decreases. When the load is removed, the curvature returns to its original profile.

(7) The wrapping sequence of an embodiment of a production method according to the present disclosure is illustrated in the same manner by the schematic side views for the first eye bushing 11 and the second eye bushing 12 in FIGS. 2 and 3. Various layers of fiber-reinforced composite material 13, 14, 15, 16 and 17, for example layers of resin mats, are wrapped according to the following method sequence:

(8) In a first step, a first layer 13 is wrapped in a first circumferential direction 1, as indicated by the arrow directions shown, clockwise around the first bushing element 3 (FIG. 2). Then, the first layer 13 is guided along the centerline 18 of the leaf spring 1 and finally wrapped around the second bushing element 4 clockwise in the first circumferential direction 1 (FIG. 3).

(9) In a second step, a second layer 14 is wrapped in a second circumferential direction 2, as indicated by the arrow directions shown, counter-clockwise around the first bushing element 3 (FIG. 2). Then, the second layer 14 is guided along the centerline 18 of the leaf spring 1 and finally wrapped around the second bushing element 4 counter-clockwise in the second circumferential direction 2 (FIG. 3).

(10) In a third step, a third layer 15 is wrapped in the first circumferential direction 1, as indicated by the arrow directions shown, clockwise around the first bushing element 3 (FIG. 2). Then, the third layer 15 is guided along the centerline 18 of the leaf spring 1 and finally wrapped around the second bushing element 4 clockwise in the first circumferential direction 1 (FIG. 3).

(11) In a fourth step, a fourth layer 16 is wrapped in the second circumferential direction 2, as indicated by the arrow directions shown, counter-clockwise around the first bushing element 3 (FIG. 2). Then, the fourth layer 16 is guided along the centerline 18 of the leaf spring 1 and finally wrapped around the second bushing element 4 counter-clockwise in the second circumferential direction 2 (FIG. 3).

(12) In a fifth step, a fifth layer 17 is wrapped in the first circumferential direction 1, as indicated by the arrow directions shown, clockwise around the first bushing element 3 (FIG. 2). Then, the fifth layer 17 is guided along the centerline 18 of the leaf spring 1 and finally wrapped around the second bushing element 4 clockwise in the first circumferential direction 1 (FIG. 3).

(13) Depending on the desired thickness of the leaf spring 1, as many layers as desired can be wrapped in further steps according to the above sequence. In each successive step, the start and end points of the respective layers 13, 14, 15, 16 and 17, and of further layers, are offset in the direction of the leaf spring main body 2, or the respective distance with respect to the corresponding center axis z1 or z2 is increased.

(14) This layer-by-layer construction permits a constant wall thickness in all regions, both along the leaf spring main body 2 and in the regions of the eye bushings 3, 4. If the first layer 13 is first wrapped counter-clockwise, the overlying layers alternate accordingly. As the wall thickness of the fiber-reinforced plastic increases, the start and end points of a respective layer become ever further from the center axes z3, z4 of the bushing elements.

(15) As shown in FIGS. 2-3, each layer has a central region 20 extending between a first end region 22 and a second end region 24. Each layer terminates at their respective first and second end regions 22, 24. The first end region 22 of each layer wraps about the first bushing element or bushing 3. The second end region 24 of each layer wraps around the second bushing element or bushing 4.

(16) As shown in the Figures, the central regions 20 of the first and second layers 13, 14 extend along and are positioned on only first and second sides 26, 28 of a curved spring centerline 18, respectively. The central regions 20 of each of the layers extend as a single ply between the first and second bushings 3, 4.

(17) With reference to FIGS. 2-3, odd layers, e.g. the first, third, and fifth layers 13, 15, 17, overlay and are in contact with one another on a first side 26 of the centerline 18 of the spring between the first and second bushings. Even layers, e.g. the second and fourth layers 14, 16, overlay and are in contact with one another on the second opposite side 28 of the centerline 18 of the spring between the first and second bushings. The layers 13, 14, 15, 16, 17 may be sequentially numbered, and either odd or even, starting with the first layer 13 in contact with and closest to the bushings 3, 4.

(18) With further reference to FIGS. 2-3, the layers 13, 14, 15, 16, 17 are sequentially wound and overlaid around each of the first and second bushings 3, 4. Each end region 22, 24 of the first layer 13, or another odd layer, terminates on the second side 28 of the spring centerline 18 adjacent to an associated bushing 3, 4. Each end region 22, 24 of the second layer 14, or another even layer, terminates on the first side 26 of the spring centerline 18 adjacent to an associated bushing 3, 4. For example, each end region 22, 24 of the first layer 13 is positioned between an associated bushing 3, 4 and end region 22, 24 of the second layer 14. Each end region 22, 24 of the second layer 14 is positioned between an associated end region 22, 24 of the first layer 13 and an associated end region 22, 24 of the third layer 15.

(19) While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the disclosure. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.