Pressurized telescopic front fork leg, front fork and vehicle

Abstract

A front fork for a vehicle comprises a telescopic fork leg having an outer tube and an inner tube telescopically arranged relative each other. A main piston arrangement in the inner tube regulates a damping fluid for damping movements between two parts of the vehicle. The telescopic fork leg comprises a pressurizing piston arranged in the inner tube and configured to pressurize the damping fluid. The pressurizing piston comprises an axial first end portion facing the main piston arrangement an axial opposite second end portion facing a pressurized volume. A fluid reservoir for holding a pressurized fluid is fluidly coupled to the pressurized volume. The pressurizing piston is coaxially arranged with the main piston arrangement, inside the inner tube. The fluid reservoir is at least partly arranged on an outside of the inner tube. Also, a front fork and a vehicle having fork legs according to above are described.

Claims

1. A front fork for a vehicle, comprising a telescopic fork leg, said telescopic fork leg comprising; an outer tube and an inner tube being telescopically arranged relative each other, a main piston arrangement arranged in said inner tube configured to regulate a damping fluid for damping movements between two parts of said vehicle when in use, wherein the telescopic fork leg further comprises, a pressurizing piston arranged in said inner tube and configured to pressurize the damping fluid, said pressurizing piston comprising an axial first end portion facing said main piston arrangement, and further comprising an axial opposite second end portion facing a pressurized volume, a fluid reservoir for holding a pressurized fluid, said fluid reservoir being fluidly coupled to said pressurized volume, and a fluid coupling between the damping fluid and an ambient volume, wherein said pressurizing piston is coaxially arranged with said main piston arrangement, inside said inner tube and said fluid reservoir is at least partly arranged on an outside of said inner tube.

2. The front fork according to claim 1, wherein said fluid reservoir is arranged in a fork leg bottom body.

3. The front fork according to claim 1, wherein said pressurizing piston comprises a first sealing means configured to seal against the damping fluid, and a second sealing means configured to seal against the pressurized fluid, wherein said first and second sealing means are axially displaced along an axial extension of the pressurizing piston.

4. The front fork according to claim 3, further comprising a cylinder case arranged inside said inner tube, wherein said pressurizing piston is arranged inside said cylinder case, and wherein said fluid coupling between the damping fluid and the ambient volume is enabled by an aperture in said cylinder case axially located between said first sealing means and said second sealing means.

5. The front fork according to claim 4, wherein the first sealing of said pressurizing piston is configured interact with the aperture in the cylinder case so that said fluid coupling between the damping fluid and the ambient volume is only opened when the pressurizing piston is in a predetermined axial position.

6. The front fork according to claim 1, wherein said damping fluid is a liquid, and said pressurized fluid is a gas.

7. The front fork according to claim 6, wherein the gas is selected from the group consisting of air, nitrogen, and CO.sub.2.

8. The front fork according to claim 1, further comprising a cylinder case arranged inside said inner tube, wherein said pressurizing piston arranged inside said cylinder case.

9. The front fork according to claim 1, further comprising an intermediate restriction means arranged between the main piston and the pressurizing piston, and configured to restrict the axial movement of the pressurizing piston.

10. The front fork according to claim 9, wherein the restriction means is further configured to restrict the fluid flow at high stroke speeds.

11. The front fork according to claim 1, wherein said telescopic fork leg is one of a compression leg and a rebound leg, configured to mainly damp movements in a compression stroke or a rebound stroke, respectively.

12. The front fork according to claim 1, wherein said main piston arrangement comprises an electrically controlled valve for controlling the flow of damping medium.

13. The front fork according to claim 1, comprising two telescopic fork legs.

14. The front fork according to claim 13, wherein one of said two telescopic fork legs is a compression leg configured to mainly damp movements in a compression stroke, and the other one of said two telescopic fork legs is a rebound leg configured to mainly damp movements in a rebound stroke.

15. A vehicle comprising a telescopic front fork according to claim 1 for damping movements between a vehicle wheel and vehicle chassis.

16. The front fork according to claim 1, wherein said damping fluid is a damping oil, and said pressurized fluid is a gas.

17. The front fork according to claim 16, wherein the gas is selected from the group consisting of air, nitrogen, and CO.sub.2.

Description

SHORT DESCRIPTION OF THE APPENDED DRAWINGS

(1) The invention will be understood through the following illustrative and non-limiting detailed description of preferred embodiments, with reference to the appended drawing, on which:

(2) FIG. 1a shows a front fork leg from an outside view,

(3) FIG. 1b shows a cross-section along B-B of the same fork leg, being a compression leg,

(4) FIG. 1c shows a close-up of FIG. 1b, disclosing more details of the fork leg components,

(5) FIG. 2 shows a close-up of a rebound-leg,

(6) FIG. 3 shows a front fork having two fork legs,

(7) FIG. 4a shows a left-side view of a motorcycle having a front fork, and

(8) FIG. 4b shows a right-side view of a motorcycle having a front fork.

DETAILED DESCRIPTION

(9) All figures are schematic, not necessarily to scale, and generally only show parts which are necessary in order to elucidate the invention, wherein other parts may be omitted or merely suggested. Throughout the figures the same reference signs designate the same, or essentially the same features.

(10) Although the fork legs in the illustration are illustrated as having a first leg for compression damping and a second leg for rebound damping, the invention is equally applicable when the legs are designed to damp both rebound and compression movements in a single leg.

(11) Further, although the figures all include an inner cylinder 103, it would be possible to carry out the invention without said inner cylinder. That is, the pressurizing piston may be arranged directly in the inner tube 102 or indirectly by being arranged inside one (or several) other components located inside the inner tube 102. The embodiment where the pressurizing piston is arranged directly in the inner tube would be a monotube fork leg. In such an embodiment the ambient volume 170 could be on the outside of the inner tube.

(12) FIG. 1a and 1b are included to illustrate an overview of a front fork leg 100a from an outside view, and in a cross-section along the line “B-B” in FIG. 1a. The front fork leg 100a is a compression leg, and is illustrated in further detail in FIG. 1c. The compression front fork leg 100a comprise a main piston arrangement 120 for regulating the damping fluid. Further, it comprises the pressurizing piston 130, which at a first end face that damping fluid (upwards in the figure) and at the other ends face a pressurizing gas which is fluidly connected to a fluid reservoir 150. The fluid reservoir is arranged in the fork leg bottom body 160.

(13) The compression front fork leg 100a, is now further discussed in relation to the close-up in FIG. 1c. Here, all the components as discussed above in relation to FIG. 1b are also present, and in addition more details are illustrated. Moreover, the components in the rebound front fork 100b illustrated in FIG. 2 comprise most of the components described in relation to FIG. 1c.

(14) Starting from the bottom of the figure, the fork leg bottom comprises an aperture 161 for fitting a wheel axle of a front wheel of a vehicle. The front wheel axle may be fastened by a fastening arrangement 162.

(15) Further the fluid reservoir 150 arranged in the fork leg bottom body 160, comprise a fluid connection 151 to the inside of the inner tube 102. In the illustrated embodiment, the fluid connection 151 connects the fluid reservoir with the cylinder case (103). The fluid connection may be achieved in any way but is illustrated as two bores, drilled from two directions, one from the cylinder case side and one from the fluid reservoir side. Further. The fluid reservoir 150 comprises an end cap 152 and in the end cap there is a valve 153 for filling the fluid reservoir to a desired pressure. In the illustrated embodiment, the fluid reservoir is a bore into the fork leg bottom body 160. Hereby, a simple and cost efficient fluid reservoir is achieved.

(16) Moving on upwards, the pressurizing piston 130, it is arranged in a cylinder case 103 which in turn is arranged in an inner tube 102. The pressurizing piston is configured to pressurize the damping fluid, whereby it comprises an axial first end portion 131 facing the main piston arrangement 120 (upwards in the figure), and further comprising an axial opposite second end portion 132 which is facing the pressurized volume being fluidly connected to the fluid reservoir 150.

(17) Further, the pressurizing piston 130 comprise a first sealing means 133 which is configured to seal against the damping fluid. It also comprises a second sealing means 134 which is configured to seal against the pressurized fluid. Further, the first and second sealing means are axially displaced along the axial extension of the pressurizing piston 130, so that the first sealing means 133 is arranged on/close to the first end portion 131, and the second sealing means 134 is arranged on/close to the second end portion 132.

(18) The cylinder case 103 comprises an aperture 104 being axially located between said first sealing means 133 and said second sealing means 134 under normal use. The aperture allows a fluid coupling between the damping fluid and an ambient volume 170.

(19) The first sealing 133 of the pressurizing piston is further sized and adapted to interact with the aperture 104 in the cylinder case 103 so that the fluid coupling between the damping fluid and an ambient volume 170 is only open when the pressurizing piston 130 is in a predetermined axial position. The predetermined axial position being closer to the fork leg bottom 160 than under normal use. Hereby, the damping medium may escape into the ambient volume 170 instead of pushing the pressurized piston further towards the fork leg bottom. This makes the system self-adjusting in terms of oil/damping medium levels.

(20) Hereby, the aperture may be closed by means of the first sealing means 133 during ordinary use, but when the volume with damping fluid is increased so much that the axial position of the preloading piston reaches the predetermined axial position, the damping fluid is let out through the aperture 104 in the cylinder case 103 to the ambient volume 170.

(21) Moving further upwards, the fork leg comprise an intermediate restriction means 140 arranged between the main piston and the pressurizing piston. Moreover, the compression leg comprises an additional tube to which the end lock portion 123 is attached forming an end so that pressure in compression stroke is built up between the main piston 121 and the end-lock 123. Damping medium will be transported back and forth between the space above the pressurizing piston 130 and the space above the main piston 121 This occurs in the gap between the two tubes and through an opening in an upper region of the inner pipe. This opening is adapted to throttle the flow to a suitable extent, namely to avoid that the pressurizing piston 130 moves due to pressure build up during a compression stroke in same manner as restriction means 140 does in a rebound leg. It could be preferable to use unthrottled openings in the upper regions of the inner tube and use throttle plates instead. This since it would be possible to obtain more suitable flow dynamics. Such solution would, however, be costlier.

(22) Finally, the fork leg comprises a main piston arrangement 120 as discussed above. The piston arrangement comprises a main piston 121 having a shim stack and a check valve for controlling the flow a damping fluid. Moreover, the piston arrangement is connected to a piston rod 122.

(23) Moving on the rebound fork leg 100b, as illustrated in FIG. 2, most of the components are identical with (or at least corresponding to) the components as has been discussed in relation to the compression for leg 100a. This is especially true for the lower part of the fork leg including the fork leg bottom body 160 the fluid reservoir 150 and the pressurizing piston 130 arrangement.

(24) One illustrated difference is that the fork leg's intermediate restriction means 140, being arranged between the main piston 121 and the pressurizing piston 130 comprise a valve arrangement 141 being configured to restrict fluid flow of the damping medium at high stroke speeds (as discussed above, high stroke speed may be about 2-6 m/s in this context).

(25) Further, the main piston arrangement 120 differs to some extent compared to the piston arrangement as illustrated in the compression fork leg 100a. Also in the rebound leg, the piston arrangement comprises a main piston 121 having a shim stack and a check valve for controlling the flow a damping fluid.

(26) Moving on, FIG. 3 shows a front fork having two fork legs, one being illustrated as the compression fork leg 100a, and the other one being the rebound fork leg 100b. The fork legs are sized and adapted to be mounted on a respective side of a vehicle wheel, and to damp movements between the wheel and a vehicle chassis.

(27) Further, FIG. 4a shows a left-side view of a motorcycle (vehicle) 1 having a front fork 10, and FIG. 4b shows a right-side view of the same motorcycle 1 with the front fork 10. When looking from the left-hand view in FIG. 4a the compression front fork leg 100a is visible, and when looking from the right-hand view in FIG. 4b the rebound front fork leg 100b is visible.

(28) While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. The skilled person understands that many modifications, variations and alterations are conceivable within the scope as defined in the appended claims.

(29) Additionally, variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

(30) In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to obtain an advantage. Any reference signs in the claims should not be construed as limiting the scope of the claims.