Tham khảo tài liệu 'advanced vehicle technology episode 2 part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Inflation pressure fbar Fig. Effect of tyre inflation pressure on cornering force reaction force at ground level known as the cornering force. As the cornering force centre of pressure is to the rear of the geometric centre of the wheel and the side force acts perpendicularly through the centre of the wheel hub the offset between the these two forces known as the pneumatic trail causes a moment couple about the geometric wheel centre which endeavours to turn both steering wheels towards the straight ahead position. This self-generating torque attempts to restore the plane of the wheels with the direction of motion and it is known as the self-aligning torque Fig. . It is this inherent tyre property which helps steered tyres to return to the original position after negotiating a turn in the road. The self-aligning torque SAT may be defined as the product of the cornering force and the pneumatic trail. . Tsat Fc X tp Nm Higher tyre loads increase deflection and accordingly enlarge the contact patch so that the pneumatic trail is extended. Correspondingly this causes a rise in self-aligning torque. On the other hand increasing the inflation pressure for a given tyre load will shorten the pneumatic trail and reduce the self-aligning torque. Other factors which influence self-aligning torque are load transfer during braking accelerating and cornering which alter the contact patch area. As a general rule anything which increases or decreases the contact patch length raises or reduces the self-aligning torque respectively. The self-aligning torque is little affected with small slip angles when braking or accelerating but with larger slip angles braking decreases the aligning torque and acceleration increases it Fig. . Fig. Illustration of self-aligning torque 292 Self-aligning toíque Nmt Fig. Variation of self-aligning torque with cornering force Static steering torque that is the torque needed to rotate the steering when the wheels are not .
