Fork shaft, telescopic fork, and motorcycle

Abstract

The invention relates to a fork shaft for a telescopic fork which extends along a longitudinal axis, wherein the fork shaft has an upper bearing region and a lower bearing region. The fork shaft is designed such that the area moment of inertia thereof in the travel direction differs at least in some regions from the area moment of inertia transversely thereto, and each of the area moments of inertia has a minimum in the central region of the fork shaft.

Description

[0001] Fork shaft, telescopic fork and motorcycle

[0002] The present invention relates to a fork shaft for a fork of a motorcycle, in particular a motorcycle, a telescopic fork and a motorcycle.

[0003] Fork stems of two-wheeled vehicles, such as bicycles or motorcycles, are typically cylindrical tubes with a circular outer cross-section. It is also known to design the outer cross-section to be non-circular, which can provide different mechanical properties in different spatial directions (see, for example, BE 10 27 93 7 A1). However, it has been shown that such an approach, especially with telescopic forks, is often insufficient to enable targeted control of the deformation of the lower fork bridge and also targeted deformation of the fork legs.

[0004] It is therefore an object of the present invention to provide a fork stem for a telescopic fork, a telescopic fork and a motorcycle, wherein the fork stem is intended in particular to enable a targeted influencing of the deformation of the lower to the upper fork bridge and also a targeted deformation of the fork legs.

[0005] This object is achieved by a fork stem according to claim 1, a telescopic fork according to claim 12 and a motorcycle according to claim 13. Further advantages and features emerge from the subclaims as well as the description and the attached figures.

[0006] According to the invention, a fork stem for a telescopic fork extends along a longitudinal axis, wherein the fork stem has an upper bearing region and a lower bearing region, and wherein the fork stem is designed such that its area moment of inertia in the direction of travel is at least partially different from its area moment of inertia transverse thereto, and wherein the area moments of inertia each have their minimum in a central region of the fork stem. It has surprisingly been found that this enables a targeted influence on the deformation of the lower to the upper fork bridge and also a targeted deformation of the fork legs, which are fastened in the fork bridges. A telescopic fork comprises two fork bridges and two fork legs or fork tubes. The two fork legs usually consist of a stanchion and a lower fork tube. The fork bridges are connected by the fork stem.The geometry of the fork tube can be used to influence the deformation behavior of the entire fork.

[0007] It has been found that the area moment of inertia of the fork stem, particularly in the central region, is advantageously greater in the direction of travel than the area moment of inertia perpendicular to it. "In the direction of travel" refers to the area moment of inertia about the y-axis, while "perpendicular to it" refers to the area moment of inertia about the x-axis, with the x-axis oriented along the direction of travel, the z-axis along the longitudinal axis of the fork stem, and the y-axis perpendicular to it. According to one embodiment, the above applies over the entire length or essentially over the entire length of the fork stem (between the bearing areas).

[0008] The bearing areas serve, on the one hand, to support the fork stem within the respective vehicle's frame. The fork bridges are also attached there. Typically, the bearing areas have a round, especially circular, outer cross-section.

[0009] According to one embodiment, the fork tube is designed such that the area moments of inertia decrease toward the center region of the fork tube. Accordingly, according to one embodiment, they are at their minimum there. The center region is the area or section of the fork tube that is positioned centrally or essentially centrally between the bearing areas. There, the area moment of inertia is expediently minimal both in the direction of travel and transversely to it.

[0010] Forging has proven to be a particularly suitable manufacturing process for providing the desired mechanical properties of the fork stem. The fork stem is therefore expediently forged at least partially or entirely, in other words, manufactured or machined using a forging process. The fork stem can also be referred to as a forged part. Forging enables, in particular, working with very thin walls. According to a preferred embodiment, the fork stem comprises a web-shaped central region which widens towards the bearing areas. The cross-section of the web-shaped central region is preferably approximately quadrangular, preferably particularly rectangular. The longer side of the rectangle is preferably oriented along the direction of travel. This ensures that the area moment of inertia is greater in the direction of travel than transverse to it.According to a preferred embodiment, a ratio between a longer side and a shorter side of the web-shaped central region is between approximately 2 and 1, preferably in particular in a range from approximately 1.1 to 1.5, very particularly preferably in a range from approximately 1.2 to 1.4. It has been found that this can have particularly advantageous effects on the handling of the respective motorcycle.

[0011] Regarding the beneficial effects on the motorcycle's handling, it should be noted that this depends heavily on the individual case. Such a fork stem can have a beneficial effect on the response of the spring / damper elements. Such a fork stem can have a beneficial effect on smoothness. Such a fork stem can have a beneficial effect on steering behavior. Such a fork stem can have a beneficial effect on driving stability, etc.

[0012] According to a preferred embodiment, the preferably web-shaped central region widens toward the bearing areas. In other words, the very thin or delicate central region becomes wider toward the bearing areas.

[0013] According to a preferred embodiment, the fork steerer tube has a plate-shaped or approximately plate-shaped structure in the transition areas between the central region and the bearing areas. This can also be easily manufactured, for example, using the forging process.

[0014] Subsequently, the plate-shaped structures advantageously transition into the preferably cylindrical bearing areas. The bearing areas are preferably solid or initially solid.

[0015] According to one embodiment, the bearing areas are hollow, in particular drilled hollow. Corresponding holes or openings can be mechanically created after forging. According to one embodiment, the fork tube comprises at least one recess oriented transversely to the direction of travel. This allows the mechanical properties of the fork tube to be further adjusted.

[0016] According to a preferred embodiment, recesses or holes are formed adjacent to the web-shaped central region.

[0017] According to one embodiment, recesses are formed in the transition areas to the bearing areas. In addition to influencing the mechanical properties of the fork tube, such recesses can also further reduce the weight of the fork tube.

[0018] The invention also relates to a telescopic fork or a double-crown fork comprising a fork stem according to the invention. As already mentioned, such a telescopic fork comprises two fork bridges and two fork legs or fork tubes. The two fork legs typically comprise a stanchion and a fork leg. The fork bridges are connected by the fork stem. The geometry of the fork stem can advantageously influence the deformation behavior of the entire telescopic fork.

[0019] The invention also relates to a motor cycle, in particular a motorcycle, comprising a telescopic fork according to the invention. The fork shaft allows for different deformations in the individual spatial directions of the front wheel guide system, whereby the driving dynamics characteristics of the respective vehicle can be specifically modified. Certain independently adjustable deformations can thus be conveniently implemented in a targeted manner.

[0020] Motorcycles of the type in question can be single- or multi-track, such as trikes or LMW (Leaning Multi Wheel) vehicles. Such a fork stem can also be used on bicycles. These, too, increasingly feature telescopic forks or double-bridge forks. Bicycles of the type in question can incorporate an auxiliary motor, for example, an electric one, or can be powered purely by muscle power. Further advantages and features will become apparent from the following description of an embodiment of a fork stem with reference to the attached figures.

[0021] They show:

[0022] Fig. 1: a sectional view of an embodiment of a fork shaft according to the invention and several cross sections thereof;

[0023] Fig. 2: a perspective view of the embodiment known from Fig. 1.

[0024] The left half of Fig. 1 shows a fork stem 10 which extends along a longitudinal axis L. For orientation, a Cartesian coordinate system is shown, the x-axis of which extends along a direction of travel F. This direction is predominantly oriented to the left. The fork stem 10 has an upper bearing area 12 and a lower bearing area 14. Fork bridges (not shown here) can be arranged on the bearing areas 12, 14. In addition, the fork stem 10 is mounted in a frame (likewise not shown), in particular in a steering tube or steering head area, of a corresponding motorcycle, via the bearing areas 12, 14. It can be seen that the fork stem 10 has a very slim and delicate central area 20. This can also be referred to as web-shaped, whereby the cross-sectional shape of this "web" can be taken, for example, from cross section Q4.It can also be seen there that the shape of the cross-section of the central region 20 can be essentially described as rectangular, with a length l20 extending along a direction of travel F and a width b20 correspondingly transverse thereto. The web-shaped central region 20 widens towards the bearing regions 12 and 14, respectively, and merges into an approximately plate-shaped structure 22. Recesses 26 are formed adjacent to the central region 20, which can further optimize the mechanical properties of the fork stem 10 and reduce its weight. The regions between the central region 20 and the upper bearing region 12 and the lower bearing region 14, respectively, are also referred to as transition regions 24. This is where the plate-shaped structures 22 begin to merge into the cylindrical bearing regions 12 and 14. The outer cross-section of the bearing regions 12 and 14 is expediently round, in particular circular, since this is where the bearing seats are formed.Preferably, openings or bores 16 extending along the longitudinal axis L are provided in the bearing areas 12 and 14. The bearing areas 12 and 14 are therefore expediently drilled hollow. The fork stem 10 as such is preferably a forged part. The cross-sections sketched in the left half of the image are shown in the right half of the image. Cross-section Q4 has already been discussed. Adjacent to this, the fork stem 10 has cross-sections Q3 and Q4. In particular, the approximately or essentially plate-shaped structure 22 of the fork stem 10 can be seen there. In the sketched cross-sections Q3 and Q5, this is also provided with recesses 26. Adjacent to this, i.e. towards the bearing areas 12 and 14, the essentially plate-shaped structure 22 merges into the cylindrical shape of the bearing areas 12 and 14, compare in particular cross-sections Q2 and Q6.In cross sections Q1 and Q7 the fork tube has already reached an almost circular outer cross section.

[0025] Fig. 2 shows a perspective view of the embodiment known from Fig. 1. For orientation, the x-axis of the Cartesian coordinate system is indicated; see also Fig. 1 in this regard. This extends along the direction of travel F. The upper bearing area 12 and the lower bearing area 14 can be seen. The very thin central area 20 of the fork tube 10 is also particularly clear. In the transition areas 24, the central area 20 has an approximately plate-like structure, which transitions into a cylindrical shape towards the bearing areas 12 and 14. The initially solid bearing areas 12 and 14 are, as already mentioned, preferably hollow; see reference numeral 16.

[0026] List of reference symbols

[0027] 10 Fork tube

[0028] 12 upper storage area

[0029] 14 lower storage area

[0030] 16 Opening, hole

[0031] 20 Middle range

[0032] 22 plate-shaped structure

[0033] 24 Transition area

[0034] 26 Recess

[0035] I20 length b20 width

[0036] L Longitudinal axis x, y, z Cartesian coordinate system

[0037] F Direction of travel

[0038] Q1 ... Q7 cross sections

Claims

Claims 1. Fork stem (10) for a telescopic fork, which extends along a longitudinal axis (L), wherein the fork stem (10) has an upper bearing region (12) and a lower bearing region (14), and wherein the fork stem (10) is designed such that its area moment of inertia in the direction of travel (F) is at least partially different from its area moment of inertia transverse thereto, and wherein the area moments of inertia each have their minimum in a central region (20) of the fork stem (10).

2. Fork stem (10) according to claim 1, wherein the fork stem (10) is designed such that the area moment of inertia in the direction of travel (F), in particular in the central region, is greater than the area moment of inertia transverse thereto.

3. Fork stem (10) according to claim 1 or 2, wherein the fork stem (10) is designed such that the area moments of inertia decrease towards the central region (20) of the fork stem (10).

4. Fork stem (10) according to one of the preceding claims, wherein the fork stem (10) is forged or at least partially forged.

5. Fork stem (10) according to one of the preceding claims, comprising a web-shaped central region (20) which widens towards the bearing regions (12, 14).

6. Fork stem (10) according to one of the preceding claims, wherein the fork stem (10) has a plate-shaped structure (22) in the transition regions (24) between the central region (20) and the bearing regions (12, 14).

7. Fork stem (10) according to claim 6, wherein the plate-shaped structures (22) merge into cylindrical bearing areas (12, 14).

8. Fork stem (10) according to one of the preceding claims, wherein the bearing areas (12, 14) are hollow, in particular hollow-drilled.

9. Fork stem (10) according to one of the preceding claims, comprising at least one recess (26) oriented transversely to the direction of travel (F).

10. Fork stem (10) according to one of the preceding claims, wherein recesses (26) are formed adjacent to the web-shaped central region (20).

11. Fork stem (10) according to one of the preceding claims, wherein recesses (26) are formed in the transition regions (24) to the bearing regions (12, 14).

12. Telescopic fork comprising a fork stem (10) according to one of the preceding claims.

13. Motor cycle, in particular a motorcycle, comprising a telescopic fork according to claim 12.

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