Anti-friction bearing, strut mount, and a combined strut mount and bearing. These components work together to provide effective damping, which is crucial for vehicle handling, comfort, and safety. Damping components control the energy dissipation in suspension systems, ensuring wheels maintain contact with the road while providing a comfortable ride.
Fundamental Damping Components and Their Functions
Shock Absorbers and Dampers
Dampers, often incorrectly called "shocks," are the primary components responsible for controlling the suspension movement in vehicles. Their main function is to dissipate kinetic energy generated when wheels encounter road irregularities, converting it into heat through hydraulic resistance. Without proper damping, a vehicle would continue to bounce after hitting a bump, reducing stability and control.
Dampers work by regulating the flow of hydraulic fluid through precisely designed pathways. When a suspension compresses or rebounds, the damper's piston moves through oil-filled chambers, creating resistance that controls the rate of suspension movement. This resistance is what provides the damping effect.
Two critical aspects of damping control include:
1. Compression damping: Controls the resistance during upward suspension movement when encountering bumps or uneven surfaces. It prevents the suspension from rapidly bottoming out and helps maintain tire contact with the road.
2. Rebound damping: Regulates the return of the suspension to its original position after compression. Proper rebound damping prevents excessive oscillation and bouncing.
Modern dampers often feature separate high-speed and low-speed damping adjustments. High-speed damping manages sudden, aggressive suspension movements (like hitting a large bump), while low-speed damping controls more gradual movements during normal driving conditions such as cornering, braking, and accelerating.
Types of Automotive Dampers
Several types of dampers are used in modern vehicles, each with unique characteristics:
1. Monotube Dampers
Found in vehicles like the Audi A4 and Mazda MX-5 Miata, monotube dampers use a single cylinder divided by a floating divider into oil and gas chambers. Damping force is created when the shaft pushes the piston in the cylinder, with shim stacks controlling oil flow during compression and rebound.
2. Twin-Tube Dampers
Common in vehicles like the Cadillac CT6 and Ram 1500, twin-tube dampers employ two concentric tubes. The inner tube contains oil, the shaft, and piston, while an additional base valve directs oil flow into the outer tube (reservoir) during compression. Damping force is determined by shim stacks on the piston and the contribution from the base valve.
3. Internal-Bypass Dampers
Used in off-road vehicles like the Ford F-150 Raptor, these advanced dampers provide position-sensitive damping through multiple bypass circuits. This design allows for progressive damping rates that increase as the suspension compresses or rebounds further, providing both comfort during normal driving and control during extreme conditions.
4. Magnetorheological Dampers
Featured in performance vehicles like the Cadillac CTS-V and Ferrari 488GTB, these innovative dampers control damping rates by changing the viscosity of the hydraulic fluid. They contain iron particles that align when exposed to a magnetic field, increasing resistance to flow. By varying the magnetic field strength through electrical current, these dampers can instantly adjust damping characteristics.
5. Spool-Valve Dampers
Found in performance-oriented vehicles like the Chevrolet Camaro ZL1 1LE, spool-valve dampers use spring-loaded discs to precisely control oil flow through shaped ports. This design allows engineers to achieve exact force/velocity curves without the trial and error typically associated with passive damper tuning.
6. Electronically Controlled Dampers
Present in vehicles like the Ford Focus RS and Volvo S90, these adaptive dampers use a combination of electronically controlled valves and passive shim-stack valves to adjust damping force in real-time. Available in both monotube and twin-tube configurations, they can vary damping characteristics to suit changing road conditions and driving styles.
Strut Mounts and Bearings
Strut mounts and bearings are critical components that connect the suspension strut to the vehicle's chassis and allow for steering movement.
Strut Mounts
The strut mount is a bonded rubber bush mounted to the top of the damper and fixed to the vehicle's chassis. It serves multiple essential functions:
1. Acts as a cushion between the strut and the vehicle, absorbing shocks and vibrations from the road.
2. Provides a connection point between the strut assembly and the car body, maintaining suspension system integrity.
3. Reduces noise, vibration, and harshness transmitted from the road to the cabin.
4. Allows for low-friction and distortion-free movement of the shock absorber spring during steering and deflection.
Strut mounts are designed with different stiffness characteristics in different directions. In the lateral direction, they are typically stiffer to improve driving dynamics and steering response, while still providing adequate damping in other directions.
Anti-Friction Bearings
Anti-friction bearings are essential components in the suspension system, particularly for front-wheel struts that must rotate during steering. These bearings:
1. Allow the strut to rotate smoothly when steering, functioning as the steering pivot.
2. Support the weight of the vehicle while permitting rotational movement.
3. Reduce friction in the suspension system, improving steering feel and responsiveness.
The suspension strut bearing is an integral part of the chassis in vehicles using MacPherson front axle strut-type suspension. It decouples the spring from the vehicle body, enabling the suspension strut to pivot when steering. As such, these bearings play a significant role in determining a vehicle's handling characteristics.
Conclusion
Damping components play a crucial role in vehicle suspension systems, affecting everything from ride comfort and noise levels to handling dynamics and safety. The evolution of damping technology from simple mechanical devices to sophisticated electronically controlled systems represents a significant advancement in automotive engineering.
