This invention relates to suspension systems capable of maintaining a stable squat response magnitude under powered vehicle acceleration.
Automobiles, bicycles, motorcycles, all terrain vehicles, and other wheel driven vehicles are used for various purposes, including transportation and leisure. These vehicles are designed to use a power source to drive, through a power transmission system, a wheel or wheels, which transfers rotary motion to the ground via tractive force between a wheel or wheels and the ground. Vehicles are also used to traverse even terrain like paved streets, and uneven terrain like off-road dirt trails. Off road trails are generally bumpier and allow for less wheel traction than paved roads. A bumpier terrain is best navigated with a vehicle that has a suspension system. A suspension system in a vehicle is aimed to provide a smoother ride for an operator or rider, and increase wheel traction over varied terrain. Vehicle suspension systems may be employed on forward and on rearward wheels.
One undesirable effect of suspension systems is the loss of energy in the way of suspension compression or extension during powered acceleration. Such energy loss is particularly notable in vehicles that are driven by low energy power sources, for example, bicycles and solar vehicles. For example, the average rider of a bicycle can exert only a limited amount of power or energy for a short period of time and an even lesser amount for an extended period of time. Therefore, even a very small power loss can have a significant effect on rider performance and comfort. Common vehicle tires require high suspension stiffness for optimal traction and bump absorption, and common human physiology requires low suspension stiffness for bearable human comfort levels. Because of the differing requirements for operator comfort, tire traction, and bump compliance, other undesirable effects of suspension systems can include loss of vehicle operator comfort due to a suspension being too stiff for comfort, or loss of traction and bump absorption due to a suspension being too soft for traction and bump absorption. Suspension travel is the distance a suspended wheel travels when the suspension is moved from a fully extended state to a fully compressed state. Suspension systems can exhibit wide variations in squat magnitude as a suspension is compressed. Generally, due to suspension kinematics, the further a typical suspension is compressed, the wider the variation in squat magnitude becomes over the duration of the suspension compression from a fully extended to a fully compressed state. This variation in squat magnitude means that the suspension cannot operate at a point of peak efficiency, or lowest amount of suspension movement, over its entire travel. This variation is squat can further compress or extend the suspension due to acceleration forces at different points in the suspension travel. A suspension must be configured to attain ideal bump apportion, comfort, or performance efficiency traits at a finite point in its suspension travel distance. All other points in the suspension travel distance will exhibit some performance traits that may be undesirable to the vehicle operator. In bicycles, suspension travel has been increased for many designs and with these increases in suspension travel; the aforementioned energy loss has become even more apparent to riders. But even for a vehicle with a high power energy source, any loss in energy reduces the vehicle's efficiency, for example its fuel efficiency. Where vehicles are used in a manner that requires frequent accelerations and deceleration (or positive and negative accelerations), the safety and comfort of the vehicle operator and the efficiency of the vehicle are particularly affected by excess chassis movement resulting from the vehicles geometry, including the geometry and design of its suspension systems.
A suspension system for a vehicle should be designed to minimize the variance in suspension movement due to acceleration forces, and to minimize energy loss, comfort loss, and loss of ability to absorb bumps. Ultimately, the environmental impact of the vehicle is reduced. The need for a suspension system that can better preserve a vehicles efficiency and energy has therefore become more pressing. The present invention provides suspension system designs for vehicles that reduce these energy losses and additionally provided improved operator comfort or improved tire traction.