Analysis of the application and development of nonlinear spring suspension

In comparison, semi-active suspensions require much less energy and will be more commercially promising today as fuel prices continue to rise. The nonlinear suspension is a passive suspension. It does not need to input additional energy to meet the comfort of the car during the working process. Therefore, the nonlinear suspension has been widely used in recent years. This article will focus on the principle of nonlinear spring suspension and its implementation. What kind of nonlinear spring characteristics are most beneficial to the comfort and safety of the car should first start with the design of the linear suspension. The suspension is a device that connects the body to the wheel.

It transmits the driving force of the wheel on the one hand and absorbs the impact from the ground on the other hand to improve the ride comfort. The key to the suspension design process is to coordinate the relationship between the suspension parameters, namely the spring stiffness and damping coefficient. The soft spring with less stiffness can improve the ride comfort, and it also increases the dynamic displacement and dynamic load of the tire. It needs more design space, which increases the roll and acceleration and deceleration of the car during cornering. The car's pitching, which reduces the steering stability of the car. If a more rigid spring is used to improve the steering stability of the car, the comfort of the car will be greatly reduced. How to adjust the relationship between them? In the linear suspension, it is impossible to satisfy both at the same time, usually according to the specific car type under the premise of compromise, for example, some cars emphasize comfort, while others emphasize power. Such a design inevitably has its drawbacks. Since the linear suspension is the product of the compromise between vehicle handling stability and comfort, the optimized linear suspension appears to be too stiff (too stiff) at no load and too soft (too little stiffness) at full load. In this case, a nonlinear suspension with variable spring stiffness occurs. In addition, the nonlinear spring should be soft under small excitation, improve the comfort of the car, and the spring hardens under the excitation of large vibration, avoiding excessive wheel dynamic load and wheel dynamic displacement, thus ensuring steering stability. Different ways and approaches have emerged in the implementation of nonlinear suspensions. The following describes the principle of nonlinearity for different types of springs.

Coil springs with different pitches. Since the diameters of the springs are the same, when the springs are in operation, the moments on the cross-sections of the spring wires are equal, so that the deformation of the parts in the axial direction is the same, and the springs are linear in nature. However, when the force F reaches a certain size, the portion of the spring wire having a small pitch starts to be temporarily depressed, and the effective number of coils is temporarily reduced, and the rigidity of the spring becomes large. This type of spring is now used in many suspensions of motorcycles in China (springs with different springs. The diameter of this spring wire varies, which leads to different inertia G of different sections of the spring. When subjected to the axial force F, a part of the spring wire with a small inertia will cause greater axial deformation. When the working pressure reaches a certain level, the thinner part of the wire will temporarily compress and fail, and the effective number of springs is reduced. The stiffness increases.

Nowadays, people are expecting air springs to be used in cars. Some manufacturers are also trying to equip some of their own products with air springs. The elastic medium of the air spring is air, which has near-ideal spring characteristics. It not only can form ideal nonlinear characteristics, but also can maintain the height of the body by changing the pressure inside the air spring according to the load. This provides favorable conditions for the car to be equipped with a less rigid spring. General steel spring air springs Air springs are generally divided into two types: capsule type and membrane type. The capsule spring is mainly composed of a rubber bag, a waist ring, an upper and lower pressure ring and two upper and lower cover plates. The advantage is that the life is long and the manufacturing process is relatively simple. However, the stiffness is large, and if a relatively soft characteristic is to be obtained, a larger additional air chamber is required. Membrane springs can be further divided into confined membrane type, free membrane type, reel type, double membrane type and combined capsule type. The membrane spring is composed of a rubber bladder, an inner cylinder and an outer cylinder (constrained and combined bladder).