Shock absorber with variable bypass damping

Details Shock absorber with variable bypass damping Shock absorber with variable bypass damping

1998-09-09

2001-06-12

Oberleitner, Robert J. (Department: 3613)

Brakes

Internal-resistance motion retarder

Having a thrust member with a variable volume chamber

C188S282500

Reexamination Certificate

active

06244398

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to shock absorbers for vehicles, such as bicycles and motorcycles, and more particularly, to a dampener for a shock absorber to regulate the flow of damping fluid depending upon velocity and displacement of the shock absorber piston relative to the shock absorber body.
BACKGROUND OF THE INVENTION
Front and rear suspensions have improved the performance and comfort of mountain bicycles. Over rough terrain the suspension system can improve traction and handling by keeping the wheels on the ground. A rider can more easily maintain control at higher speeds and with less effort when the suspension absorbs some of the shock encountered when riding. Ideally, the suspension should react well to both (1) low amplitude, high frequency bumps and (2) high amplitude, low frequency bumps. However, these can be competing requirements for the damping systems in conventional shock absorbers.
Higher rebound damping is desirable for high amplitude, low frequency bumps than for low amplitude, high frequency bumps. With high frequency, low amplitude bumps, such as may be encountered on a washboard gravel fire road, minimal damping may be preferable so the spring can quickly recover from a minor impact before the next is encountered. However, with a large bump (such as the size of a curb), increased rebound damping aids the rider by keeping the bike from forcefully springing back too quickly, causing loss of traction and control on the rebound. Compression damping will also stop the bike from bottoming out with large bumps and make for a smoother absorption of the bumps.
Some current shock absorbers that include springs and dampeners allow the rider to adjust rebound and/or compression damping before a ride. Other air shock absorbers include an on/off switch to disable the shock absorber all together. However, such preadjustment is at best a compromise; the rider must select better damping in one scenario at the expense of the other. A typical off-road mountain bike ride will include small bumps, medium, and large bumps, as well as possibly jumps, drop-offs, and tight descending to ascending transitions. If the rider significantly reduces the damping to ride smoothly over high frequency, low amplitude bumps, then the bike may lose traction and control when a large bump is encountered or may “bottom out” the shock absorber. If the rider increases the damping force of the shock absorber, then the system will not recover fast enough to quickly absorb high frequency bumps, the rider will be rattled, and the bike will lose traction.
Another limitation of current shock absorbers is evidenced by rider-induced bobbing: suspension movement caused by rider movement during pedaling. Related to this is pedal-induced suspension action: the cyclic forces on the chain pulling the rear swing arm up or down relative to the frame. If the damping in the shock absorber is greater, these influences will not be felt as much by the rider. However, a stiff suspension, especially at the beginning of the stroke of the shock absorber, can decrease the ability of the suspension to absorb small bumps well.
Attempts to overcome the current limitations in suspension systems have focused on swing arm linkages and pivot arrangements. At a significant cost, some amelioration of rider- or pedal-induced suspension action has resulted, but much less progress has been made on the dilemma of large and small bump absorption.
SUMMARY OF THE INVENTION
The present invention addresses the suspension challenges of both high frequency/low amplitude and low frequency/high amplitude shock absorption while also reducing rider- and pedal-induced suspension action. The present invention can be applied to most suspension configurations as it addresses these challenges with a unique, active damping shock absorber. The shock absorber is soft over small bumps and stiffens when encountering large shocks after the shock travels to a certain extent. The shock absorber stiffens further under extreme shock to avoid harsh bottoming out. Rebound damping may also be tuned independent of compression damping. The shock absorber changes damping during compression and rebound according to the speed and displacement of the shaft and piston assembly relative to the housing during the suspension action.
The present invention includes a dampener for a shock absorber. The dampener of one embodiment includes a fluid chamber, a piston, a fluid bypass assembly, and a valve. The fluid chamber contains fluid for damping action of the shock absorber. The piston is disposed at least partially within the fluid chamber. The piston is forced at least partially through the reservoir under the force of a shock acting on the shock absorber. The fluid bypass assembly has a bypass channel with an outlet portion, a first port, and a second port in fluid communication with the fluid chamber. The bypass channel permits fluid to flow through the outlet portion and operably bypass the piston within the fluid chamber. The valve is in the bypass channel and controls the flow of the fluid therethrough. The valve is in fluid communication with the second port and is movable toward a closed position for restricting flow of the fluid through the bypass channel. The valve is movable from an open position toward the closed position in response to the extent of piston displacement or the velocity of piston displacement within the fluid chamber.
In one embodiment of the invention, the piston is movable in the fluid chamber between first and second piston positions. In the first piston position, the first port and an outlet port of the outlet position are on the piston's first side. In a second position, the first port is on the piston's first side and the outlet port is on the piston's second side, thereby allowing the fluid to bypass the piston. The piston is also movable to a third piston position, wherein the piston blocks the first port and blocks the fluid from flowing into the bypass channel.
In this embodiment, the fluid chamber has first and second chamber portions. The first chamber portion contains a non-compressible first fluid and the second chamber portion contains a compressible second fluid, such as a gas. A chamber seal in the fluid chamber separates the first and second fluids. The chamber seal is movable axially within the fluid chamber between first and second positions. In the first position, the chamber seal at least partially blocks the second port. In the second position, the chamber seal is spaced apart from the second port, thereby allowing the first fluid to move into the second port. The valve is positioned so the fluid moving into the second port moves the valve toward the closed position. Thus, the valve is positioned to move toward the closed position in response to the extent or velocity of piston displacement in the fluid chamber, which controls the fluid moving from the fluid chamber into the second port. In the closed position, the valve closes the bypass channel and prevents the fluid from bypassing the piston via the bypass assembly.
In another embodiment, the fluid bypass assembly includes a bypass body with an inlet channel and an outlet channel each in fluid communication with the fluid chamber. The inlet and outlet channels are in fluid communication with each other through first and second ports. The first port is between the second port and an inlet aperture of the inlet channel. The valve is positioned adjacent to the second port and is movable toward the closed position to restrict the fluid flow through the second port and into the outlet channel. This fluid flow restriction is in direct response to the extent of piston displacement or the velocity of piston displacement.
In one aspect of this alternate embodiment, a bypass member connected to the piston is in fluid communication with the outlet channel and is positioned to carry fluid out of the outlet channel to the piston's opposite side, thereby bypassing the piston. The bypass member is a rigid hollow tube having a first end c

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