Coil spring
torsion bar
leaf spring
2012年9月27日星期四
2012年9月25日星期二
SUSPENSION & Principles of suspension
Suspension is the term given to the system of springs, shock absorbers and linkages that connects a vehicle to its wheels and allows relative motion between the two. Suspension systems serve a dual purpose — contributing to the vehicle's roadholding/handling and braking for good active safety and driving pleasure, and keeping vehicle occupants comfortable and reasonably well isolated from road noise, bumps, and vibrations,etc. These goals are generally at odds, so the tuning of suspensions involves finding the right compromise. It is important for the suspension to keep the road wheel in contact with the road surface as much as possible, because all the forces acting on the vehicle do so through the contact patches of the tires. The suspension also protects the vehicle itself and any cargo or luggage from damage and wear. The design of front and rear suspension of a car may be different.
in the beam axle setup both of the front wheels are connected to each other by a solid axle.
Swing alxe
the axles pivot about a location somewhere near the center of the car and allow the wheels to travel up and down through their respective arcs.
trailing link suspension
uses a set of arms located ahead of the wheels to support the unsprung mass
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 as 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.
Types of Suspension
solid beam axle:in the beam axle setup both of the front wheels are connected to each other by a solid axle.
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| beam alxe suspension |
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| Solid-axle coil spring suspension |
the axles pivot about a location somewhere near the center of the car and allow the wheels to travel up and down through their respective arcs.
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| swing alxe |
uses a set of arms located ahead of the wheels to support the unsprung mass
MacPherson
This strut based system, where the spring/shock directly connects the steering knuckle to the chassis and acts as a link in the suspension, offers a simple and compact suspension package
equal length A-arm & unequal length double A-arm
Principles of suspension
The suspension system isolates 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 as 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.
2012年8月29日星期三
STEERING SYSTEMS-- Steering Rack
Steering Rack
Steering racks are a component in rack-and-pinion steering controls. They are the metal part on which gears, or pinions, slide back and forth, determining how far a corresponding wheel turns.
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| steering rack |
Disassemble & Reassemble
special service tools:
1.adjuster nut spanner
2.gland nut spanner
3.tube nut spanner
4.DTI(dial test indicater)
5.V blocks
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| pinion and rack |
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| tie rod end & tie rod |
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| rack body & pinion assembly |
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| pinion housing |
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| pinion housing |
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| pinion count the number of teeth on the pinion :8 |
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| rack
count the number of teech on the rack:27
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| the magnetic base of the DTI requires a metal bench to work correctly. rack run-out reading:0.05mm |
2012年8月21日星期二
ABS
An anti-lock braking system (ABS) is an automobile safety system that allows the wheels on a motor vehicle to continue interacting tractively with the road surface as directed by driver steering inputs while braking, preventing the wheels from locking up (that is, ceasing rotation) and therefore avoiding skidding. It is an automated system that uses the principles of threshold braking and cadence braking, that was practised by skilful drivers with previous generation non-ABS braking systems.
Vehicles with ABS are equipped with a pedal-actuated, dual-brake system. The basic hydraulic braking system consists of the following:
•ABS hydraulic control valves and electronic control unit
•Brake master cylinder
•Necessary brake tubes and hoses
The anti-lock brake system consists of the following components:
•Hydraulic Control Unit (HCU).
•Anti-lock brake control module.
•Front anti-lock brake sensors / rear anti-lock brake sensors.
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 hydraulic 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 constant.
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 repeats 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 applied. These changes in position may cause rapid pulsations to be felt through the brake pedal.
Vehicles with ABS are equipped with a pedal-actuated, dual-brake system. The basic hydraulic braking system consists of the following:
•ABS hydraulic control valves and electronic control unit
•Brake master cylinder
•Necessary brake tubes and hoses
The anti-lock brake system consists of the following components:
•Hydraulic Control Unit (HCU).
•Anti-lock brake control module.
•Front anti-lock brake sensors / rear anti-lock brake sensors.
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 hydraulic 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 constant.
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 repeats 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 applied. These changes in position may cause rapid pulsations to be felt through the brake pedal.
Brake roller testing
Some of the main systems that are tested include:
Brakes and ABS
Transmission
Parking PAWL and Parking Brake
Speed Control
Traction Control and Electronic Stability Programs (ESP)
Vibration Analysis
Speedometer Accuracy
Body / Chassis / Electrical Controllers
Vehicle Electronic Control Unit (ECU)
Tire Pressure
Brakes and ABS
Transmission
Parking PAWL and Parking Brake
Speed Control
Traction Control and Electronic Stability Programs (ESP)
Vibration Analysis
Speedometer Accuracy
Body / Chassis / Electrical Controllers
Vehicle Electronic Control Unit (ECU)
Tire Pressure
2012年8月18日星期六
repair the master cylinder
when the master cylinder fails,the master cylinder may be the seals around the pistons.the pisten should be removed and the cylinder need to check for corrosion, cause brake fluid deaws in water and if the vehicle is parked for too big ,it can cause the master cylindto corrode.
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If it is a steel cylinder it can be honed using methalated spirits or kerosene with a honing tool and then it should be cleaned out with brake cleaner. 
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Master Cylinder & Brake calliper
Master Cylinder:
the master cylinder is a control device that converts non-hydraulic pressure into hydraulic pressure. This device controls slave cylinders located at the other end of the hydraulic system.
As piston move along the bore of the master cylinder, this movement is transferred through the hydraulic fluid, to result in a movement of the slave cylinder. The hydraulic pressure created by moving a piston toward the slave cylinder compresses the fluid evenly, but by varying the comparative surface-area of the master cylinder and/or each slave cylinder, one can vary the amount of force and displacement applied to each slave cylinder, relative to the amount of force and displacement applied to the master cylinder.
The most common vehicle uses of master cylinders are in brake and clutch systems. In brake systems, the operated devices are cylinders inside of brake calipers and/or drum brakes; these cylinders may be called wheel cylinders or slave cylinders, and they push the brake pads towards a surface that rotates with the wheel until the stationary brake pad create friction against that rotating surface.
Brake Caliper:
A brake caliper is a device used to push the brake pads against the surface of the brake rotor to slow the car down.
The brake caliper works with hydraulic pressure, every time you push the brake pedal, the brake fluid travels from the brake master cylinder to the brake proportioning valve ( when the car is not equipped with ABS ), if the car has ABS, the brake fluid travels through the ABS Hydraulic control unit, and from there the brake fluid travels inside the brake lines all the way to the brake calipers, this hydraulic pressure pushes one or more cylinders inside the brake caliper against the brake pads, this pressure forces the brake pads to make contact with the brake rotor, the force will ve relatively equal to the force applied by the driver to the brake pedal.
- The bad brake caliper are the following:
1- Brake fluid is leaking past the seals in the caliper pistons.
2- The car always pulls to one side when the brakes are applied ( signs of a sticking brake caliper )
3- Premature brake pads wear. ( Also caused by sticking brake calipers )
1- Brake fluid is leaking past the seals in the caliper pistons.
2- The car always pulls to one side when the brakes are applied ( signs of a sticking brake caliper )
3- Premature brake pads wear. ( Also caused by sticking brake calipers )
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