tài liệu anh văn chuyên nghành trường spkt Rack And Pinion Streering System The most common steering system the rack and pinion gets its name trom the two gears it use the rack (the linear gear) and the pinion (circular gear). This system is used in most of the cars and is usually not employed in heavyduty vehicles. Its working may appear complex but uses quite simple physics. The steering wheel has a shaft attached to it and on the other end of the shaft in the pinion. The pinion is positioned on top of the rack and moves when the steering wheel is moved. The end of the rack has something called a tie rod. The tie rods connect to the steering arm which in tum is connected to the wheel hub. Orwards to the working of rack and pinion. When you rotate the steering wheel the shaft rotates along with it. This in turn rotates the pinion which is on top of the rack. The rotation of the pinion makes the rack move linearly moving the tie rod. The tie rod connected to the steering arm then causes the wheel to turn. The size of the pinion affects how much turning you get. If the pinion is large in size it means that you’ll be getting more tum from less streering wheel rotaion which will make it harder to control. On the other hand, a smaller pinion means it’ll be easier to control but you will need multiple streering
Rack And Pinion Streering System The most common steering system the rack and pinion gets its name trom the two gears it use the rack (the linear gear) and the pinion (circular gear) This system is used in most of the cars and is usually not employed in heavy-duty vehicles Its working may appear complex but uses quite simple physics The steering wheel has a shaft attached to it and on the other end of the shaft in the pinion The pinion is positioned on top of the rack and moves when the steering wheel is moved The end of the rack has something called a tie rod The tie rods connect to the steering arm which in tum is connected to the wheel hub Orwards to the working of rack and pinion When you rotate the steering wheel the shaft rotates along with it This in turn rotates the pinion which is on top of the rack The rotation of the pinion makes the rack move linearly moving the tie rod The tie rod connected to the steering arm then causes the wheel to turn The size of the pinion affects how much turning you get If the pinion is large in size it means that you’ll be getting more tum from less streering wheel rotaion which will make it harder to control On the other hand, a smaller pinion means it’ll be easier to control but you will need multiple streering wheel turns to make the car corner Recirculating Ball Steering System The recirculating ball steering system has two gears, the worm gear and the sector gear The steering wheel is connected to a threaded shaft which is connected to a block The worm gear is quite big and goes through the block which is threaded in such a way it allows the worm gear inside This block has gear teeth outside of it to which the sector gear is connected This sector gear is then connected to the pitman arm while the pitman arm is attached to the tie rod There are ball bearings inside the block that fill the thread of the worm gear The working is simple just like rack and pinion When the steering wheel rotated the shaft connected to the steering rotates as well The gear is bolted to not move up and down This makes the block and the worm gear rotate The rotation makes the block move as is not held down by anything The moving block then moves the sector gear which in turn moves the pitman arm The thread of the worm gear is filled with ball bearings which reduce friction and prevent the slop in gear Power-assisted rack and pinion The power steering adds some more parts to the rack and pinion system which makes it easier to use, mainly the pump, pressiure tubes, rotary control valve, fluid lines and a hydraulic piston The job of the pump is to as you might have guessed, pump the fluid around when needed The rotary control valve ensures that the movement of fluid is only perfomed when the driver is actually steering the car The hydraulic piston moves around depending on which fluid line brings the high-presisure fluid This piston movement on the rack makes it easier for the driver as it is applying most of the force necessary to steer the car This concludes the brief discussion on how a hydraulic power steering system works Sprung mass Sprung mass refers to vehicle part supported on the springs, such as the body, frame and engine Unsprung mass includes parts of the steering and suspension not supported by spring, such as wheels, tires and brake assemblies The suspension system …isloates the body from road shocks and vibrations which would otherwise be transferred to the passengers and load It also must keep the tires in contact… with the road When a tire hits an obstruction, there is a reaction force The size of this …reaction force depends on the unsprung mass at each wheel assembly… The sprung mass is that part of the vehicle Supported… by the springs - such as the body, the frame, the engine and associated parts Unsprung mass includes the components that follow the road contours, such as wheels, tires, brake assemblies and any part of the steering and suspension not supported by the springs Vehicle ride and handling can be improved… by keeping unsprung mass low as possible When large and heavy wheel assemblies encounter a bump or pothole, they experience a larger reaction force, sometimes large enough to make the tire lose contact… with the road surface Wheel and brake units that are small and light, follow road contours without a large effect on the rest of the vehicle At the same time, a suspension system must be strong enough… to withstand loads imposed by vehicle mass during cornering, accelerating…, braking and uneven road surfaces Accelerating / contact / isolates / enough / in contact / wheel assembly / supported / improved / reaction force / wheel / steering / performance ABS 1, the antilock braking system controls braking force by controlling the hydraulic pressure of the braking system, so that the wheels not lock during braking Braking force and the tendency of the wheels to lock up are affected by a combination of factors such as the friction coefficient of the road surface, and the difference between the vehicle speed and the road wheel speed The ABS prevents the road wheels from locking up during heavy braking by controlling the vehicle's brake system hydraulic pressure During normal braking, as the rotational speed of the wheel falls, no electric current flows from the ECU to the solenoid unit The solenoid valve is not energized The brake master cylinder hydraulic pressure is applied to the brake unit, and the ABS is not involved However, even though the ABS is passive during normal braking, its control module is constantly monitoring for rapid …deceleration of any of the wheels If a wheel-speed sensor signals severe wheel deceleration-which means the wheel is likely to lock up-the ECU sends a current to the hydraulic unit This energizes the solenoid valve The action of the valve isolates the brake circuit from the master cylinder This stops the braking pressure at that wheel from rising, and keeps it locking If the sensors signal the wheel is still decelerating too rapidly, the ECU sends a larger current to the hydraulic unit The armature moves even further and opens the valve It opens a passage from the brake circuit Brake fluid is sent from the brake circuit back to the master cylinder Pressure in the brake caliper circuit is reduced so that the wheel is braked less heavily If the wheel sensors indicate that lowering the brake pressure is letting the wheel accelerate again, the ECU stops sending current to the hydraulic unit and de-energizes the solenoid valve This lets the pressure increase, so that the wheel is again decelerated This cycle signal itself about four to six times per second It is normal in an ABS for the valves in the hydraulic control unit to keep changing position as they change the brake pressure that’s being increased These changes in position may cause rapid pulsations to be felt through the brake pedal Hydraulic / decelerated Suspension System The purpose of the suspension system is to isolate the vehicle body from road bumps and vibrations, while keeping the wheels in contact with the road The purpose of the complete suspension system is to isolate the vehicle body from road shocks and vibrations which would otherwise be transferred to the passengers and load It must also keep the tires in contact with the road, regardless of road surface A Basic suspension System…consists of… springs, axles, shock absorbers, arms, rods, and ball joints The spring is the…flexible component of the suspension Basic types are leaf springs, coil springs, and torsion bars Modern passenger vehicles usually use light coil springs Light commercial vehicles have…Heavier….springs than passenger vehicles, and can have coil springs at the front and…leaf springs at the rear Heavy commercial vehicles usually use leaf springs, or air suspension Solid, or beam, axles connect the wheels on each side of the vehicle This means the movement of a wheel on one side of the vehicle is transferred to the wheel on the… other….side With independent suspension, the wheels can move…independently……of each other, which reduces body movement This prevents the other wheel being affected by movement or the wheel on the opposite side, and this reduces …body movement… When a wheel strikes a bump, there is a…reaction force……., and energy is transferred to the spring which makes it oscillate Oscillations left uncontrolled can cause loss of traction between the wheel and the…road surface……