Air suspension fork with linearized spring characteristic through a multi-chamber system

Abstract

Pneumatic suspension element (for example for bicycles or motorcycles), consisting of at least one suspension unit and one damping unit, characterized in that the suspension element consists of two telescopically movable tubes [4,5].

Description

Technical area

[0001] The invention relates to a pneumatic suspension system, particularly for bicycles and motorcycles, with an optimized spring characteristic. More specifically, the invention relates to a suspension fork with a multi-chamber pressure system for linearizing the spring travel in the initial and middle ranges while simultaneously maintaining final progression. The system is particularly suitable for use in two-wheeled vehicles where low weight and individually adjustable suspension characteristics are important. Furthermore, the suspension system is also conceivable for other applications in the fields of automotive engineering, mechanical engineering, or medical technology where controlled spring characteristics are required. State of the art

[0002] Suspension forks are an essential component of modern mountain bikes and represent a key quality feature. In practice, two systems are predominantly used: mechanical suspension forks with steel or titanium springs as well as pneumatic systems in which compressed air in sealed chambers serves as the suspension medium.

[0003] Pneumatic suspension systems offer significant advantages in terms of weight and adjustability. The air pressure can be adjusted to suit the user's weight and intended use. However, a major problem lies in the typical, non-linear characteristics of such systems: the force curve is hyperbolic. In the main part of the suspension travel, the stiffness is comparatively low, leading to inefficient shock absorption and excessive compression over small bumps. In the end range, however, the spring rate increases exponentially, which prevents bottoming out but can also lead to an abrupt ride.

[0004] Mechanical suspension systems, on the other hand, offer an approximately linear spring characteristic – the applied force is proportional to the travel. This results in predictable damping behavior throughout the entire travel. However, these systems lack the desirable end-of-stroke progression, increasing the risk of bottoming out. In addition, there is a significant weight disadvantage compared to air suspension forks.

[0005] Various approaches have already been tested to improve pneumatic systems. Some designs incorporate solid-state friction elements or hydraulic / fluid-acting damping components to influence the behavior in the initial range. However, these measures usually only lead to a limited linearization of the characteristic curve and simultaneously increase the complexity and weight of the device.

[0006] Another well-known approach is to influence the spring characteristic by changing the air volume. This is achieved, for example, by using movable separating elements that reduce or expand the usable air volume, thus adjusting the spring characteristics. These systems also offer certain advantages, but often do not achieve a sufficiently linear spring characteristic across the entire travel range.

[0007] A frequently used solution is to use two air chambers, one as a positive chamber and the other as a negative chamber. The negative chamber improves the response by reducing the breakaway torque. However, this does not achieve a targeted linearization of the middle spring range.

[0008] In summary, existing systems offer either a linear characteristic curve with insufficient final progression (mechanical springs) or a pronounced final progression with uneven response (air springs). A solution that combines the advantages of both approaches has so far been inadequately implemented. Description of the invention

[0009] The invention is based on the object of providing a pneumatic suspension system which, despite the use of air as the suspension medium, has a largely linear spring characteristic in the initial and middle range and at the same time enables a progressive characteristic in the final range in order to avoid bottoming out. The system should be easy to adjust, user-friendly and particularly suitable for applications in vehicles, preferably two-wheelers.

[0010] To solve this problem, a pneumatic suspension system is proposed that comprises a multi-chamber pressure system with several independently fillable pressure chambers arranged in series. The individual chambers are separated from each other by movable sealing elements and are designed in such a way that the respective initial pressures are not exceeded and complete pressure equalization between the chambers in the initial state is avoided. Each chamber has a defined initial pressure that differs from the pressures of the other chambers.

[0011] As the load increases, only the chamber with the lowest pressure is compressed initially. As soon as the pressure in this chamber equals the pressure in the adjacent chamber, the next chamber is automatically "activated," so that its volume also contributes to the suspension. The successive activation of the chambers creates a nearly linear force curve over a large portion of the suspension travel. In the final progression—when all chambers are active—the compressed air acts with exponentially increasing force, preventing bottoming out.

[0012] The pressure chambers can be filled using various devices: individually using switching mechanisms or jointly using pressure-controlled valve systems. This allows for user-specific preconfiguration. The system is suitable for a wide range of applications, particularly bicycle and motorcycle suspension, but can also be used in other technical areas requiring lightweight, adaptable suspension.

[0013] The central features of the invention can be summarized as follows: • Pneumatic multi-chamber suspension system with gradually activating pressure chambers • separate chambers with different initial pressures and movable sealing elements, • linearized force curve in the initial and middle range of the spring travel, • progressive final characteristic curve to avoid breakdown, • High flexibility thanks to adaptable filling mechanisms for individual configuration. Description of the invention

[0014] The idea of ​​the present invention is a suspension fork system that does not use just one positive pressure chamber [7] filled with gas, but rather a system of several positively filled air chambers [21, 22, 23] that are cleverly coupled to one another. The key factor here is that the initial pressures exhibited by the chambers [7] differ before the compression process. This is achieved by movable seals [8] between the chambers, which have an upper stop so that expansion beyond this maximum is prevented. The preferred embodiment uses different pressures in the chambers, whereby these are separated from one another and kept pressure-tight by the aforementioned spatial limitations [9], so that the pressures cannot equalize in the initial state.

[0015] As the force applied increases, the chamber with the lowest initial pressure

[21] is compressed first. If its pressure reaches the initial pressure of the adjacent chamber

[22] , this chamber is also activated. The process is repeated with the third chamber

[23] , so that several chambers are activated gradually as the load increases. This principle of sequential activation results in a significantly linearized force-displacement characteristic curve in the middle range. Only in the end range does the remaining air volume create a desired progressive characteristic curve that prevents bottoming out. The effectiveness of this principle has been proven both mathematically and experimentally.

[0016] In the Fig. 1 and Fig. Figure 3 shows an exemplary implementation of the system in a front suspension fork for bicycles or motorcycles. The fork comprises a fork stem [2] mounted on the steering head [1], a fork crown [3], and two fork legs [4], each of which terminates in a fork leg [5] to which the wheel

[18] is attached.

[0017] Fig. Figure 2 shows the integration of the system in a rear shock absorber

[20] , consisting of a spar [4] and a support leg [5] with attachment points on the frame and rear swing arm

[19] .

[0018] Fig. Figure 4 illustrates the core concept of the invention with the coupling of the chambers for linearizing the spring characteristic. Only one side of the fork is shown, as one side typically contains the suspension and the other the damping. The system consists of a fork leg [4] that moves into the supporting leg [5]. A fork guide

[13] and a dust wiper

[14] serve for guidance and sealing.

[0019] The three positively filled chambers [21-23] are filled with specific pressures by means of a pressure relief valve

[16] via an internal filling tube

[24] . A rotating mechanism with a wheel

[26] , shown in Fig. 7, allows for targeted connection to the individual chambers. Alternatively, filling can also be achieved via an external filling pipe

[25] with integrated filling valves

[17] (cf. Fig. 5). In a simplified embodiment ( Fig. 6), only the uppermost chamber

[23] is filled via the pressure relief valve

[16] , while the chambers below [21, 22] are automatically filled with adjusted lower pressures via differential pressure valves

[15] . This variant is particularly user-friendly and cost-effective.

[0020] The movable seals [8] are spatially fixed by limits [9] to prevent unwanted pressure equalization between the chambers. In addition, there is a negative chamber

[12] in the lower area, which automatically fills with ambient air when the spring is released. This helps reduce the breakaway force during compression.

[0021] During the compression process, the fork leg [5] remains stationary, and thus also the piston

[11] . The fork leg [4] moves relative to it, causing the compression of the chambers one after the other: first chamber 1

[21] , then chamber 2

[22] , and finally chamber 3

[23] . This gradual activation results in the desired, optimized spring characteristic.

[0022] Three versions are provided for individual or serial filling of the pressure chambers [7]: • In a first embodiment (cf. Fig. 4 and Fig. 7) filling takes place via a central tube

[10] , which can be selectively connected to individual chambers [7] via a rotating mechanism

[11] . • In a second embodiment (cf. Fig. 5) filling is carried out externally via an external trachea

[16] , in which individual chambers [7] are controlled via valve circuits or another rotary mechanism

[11] . • In a third, particularly simple embodiment (cf. Fig. 6) only the top chamber [7] is filled with the highest pressure, while the downstream chambers [7] are automatically filled proportionally via differential pressure valves. Figure reference:

[0023] Fig. 1 and Fig. 3 show the application of the system according to the invention in a front suspension fork. This fork has classic features such as a fork stem [2] for attachment to the steering head [1], a fork crown [3], two fork legs [4], and two support legs [5] for supporting the wheel

[18] . Fig. 2 represents a rear wheel suspension

[20] with a stanchion [5], a bar [4] and a swing arm

[19] . Fig. Figure 4 shows the chamber coupling system in cross section. Fig. 5-7 show different filling variants. AppendixGlossary No. Description 1 steering head 2 fork steerer 3 Fork head 4 fork leg 5 fork leg 6 Filling device 7 air chamber 8 Seal 9 Limitation 10 center pipe 11 pistons 12 negative chamber 13 Bar guide 14 dust wipers 15 Differential pressure valve 16 Schrader valve 17 filling flaps 18. Wheel 19 Rear swing arm 20 rear wheel dampers 21 Chamber 1, positive 22 Chamber 2, positive (p o : K1 < K2 < K3) 23 Chamber 3, positive 24 Inner filling pipe 25 Outer filling pipe 26 cogs 27 Circular seal with recess. Short description of the drawings Fig. 1 shows a front suspension fork according to the invention in an isometric view. Fig. 2 shows the application of the system according to the invention in a rear wheel damper connected to a rear swing arm. Fig. 3 shows the front fork according to Fig. 1 in side view. Fig. 4 shows a schematic longitudinal section through an embodiment of the suspension fork with three coupled air chambers. Fig. 5 shows an alternative filling variant with an external filling system. Fig. 6 shows a simplified embodiment with automatic pressure distribution via differential pressure valves. Fig. 7 shows a detailed view of the filling rotary mechanism with connection to individual chambers.

Claims

[1] Pneumatic suspension element (for example for bicycles or motorcycles), consisting of at least one suspension unit and one damping unit, characterized by that the suspension element consists of two telescopically movable tubes [4,5]. [2] Suspension element according to claim 1 characterized by that it functions as a front fork for a bicycle and thus has a fork head [3] and a fork stem [2] to allow attachment to the steering head [1] of the bicycle, and has two fork tubes to allow attachment of the front wheel [18] on both sides. [3] Front fork according to claim 1 characterized by that the individual chambers can be connected via an inner tube through which the individual air chambers can be filled using a special mechanism, such as a rotating mechanism [see appendix]. [4] Front wheel fork according to claim 1 characterized bythat individual chambers can be filled by filling the top chamber with the highest desired pressure and the remaining chambers are also filled proportionally due to differential pressure valves [15]. [5] Front fork according to claim 1 characterized by that the air filling takes place through one or more air tubes running along the outside, which fill individual chambers with the help of a special mechanism. [6] Suspension element according to claim 1 characterized by that it acts as a rear wheel damper for a bicycle and therefore has mounting brackets at the ends to enable attachment to the frame and rear swing arm [19]. [7] Suspension element according to claim 1 characterized bythat it has more than two individual pneumatic suspension units, for example air chambers [21,22,23,12], which exert different forces on the seals, for example through different pressures. [8] Suspension element according to claim 1 characterized by that hydraulic, metal spring coupling and solid friction systems can serve as a supplement to claim 2 [9] Suspension element according to claim 1 characterized by that it has several suspension units (for example an air chamber), each of which has a spatial limitation [9] so that the pressure cannot fall below a certain preset value (initial pressure). [10] Suspension element according to claim 1 characterized by that it has several suspension units which are coupled (for example with movable sealing elements [8]) in such a way that no mass exchange is possible during compression, but pressures can be equalized.

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