Vehicle Braking Systems: Types, Troubleshooting, and ABS Technology
Vehicle Braking Systems
Topic 12: Correctors of Vehicle Braking Systems
Correctors adapt the operation of braking systems to different vehicle weights and load distributions. They compensate for variations in braking circumstances.
Limit Fixed Compensator Output
Hydraulic pressure toward the axis with less support is limited.
Integrated Compensators
These compensating brakes are located directly on the brake calipers and do not rely on external parameters.
Deceleration-Based Compensators
These compensators base their operation on the vehicle’s deceleration. As the vehicle decelerates, the load on the front axle increases, and the compensator adjusts accordingly.
Load-Based Compensators
The operation of this type is based on vehicle load, performing various flow adjustments.
Types of Servo Systems
There are two main types of servo systems:
- Mastervac System: The most commonly used system in vehicles. The servo is inserted in series between the brake pedal and the hydraulic pump.
- Hidrovac System: Operates on the same principle as the Mastervac system, but it is not integrated in series between the pedal and the pump. It can be placed in any part of the system.
Common Servo System Breakdowns
- Perforation of the control membrane
- Breaking of the vacuum tube driver
- Valve malfunction
- Slack in the actuation of the brake pedal
- Appearance of brake fluid in the brake booster
Troubleshooting Braking Systems
Uneven Braking
Possible causes include warped brake discs, stiff brake calipers, brake fluid loss, or poor performance in the brake corrector.
No Pedal Response
This could be due to fluid loss, presence of air in the hydraulic circuit, brake fluid leakage, or a ruptured seal in the brake calipers.
Topic 13: Constitution of Pneumatic Brake Systems
Components of a pneumatic brake system include:
- Air compressor
- Dehydrator
- Air tank/accumulator
- Pressure regulator
- Pump antifreeze
- Air decanter
- Pneumatic valves
- Brake cylinder and braking elements
Verification During Slowdown
- Exhaust-free movement of the control linkage to close the butterfly valve
- Feeding compressed air to the cylinder drive
- Elimination of the electric current
Hydraulic Slowdown Check
- State and level of the system’s oil
- Electric and electronic control of valves
- Mechanical state of the overall slowdown system
Topic 14: Anti-Lock Braking System (ABS)
An anti-lock braking system is an electronically managed system designed to prevent wheel lockup during braking, thereby maintaining vehicle control and stability.
Phases of ABS Operation
- No Braking Action: The solenoid is open, and the entry and exit valves remain closed.
- Braking Without Wheel Lockup: When the brake pedal is pressed, a switch informs the electronic control unit (ECU). The ECU detects the deceleration of the wheels and, since they are not locked, the ABS does not activate.
- Wheel Lockup: If a wheel tends to lock up, the inlet solenoid closes, and the outlet solenoid of the affected wheel opens. This releases brake fluid into the accumulator, reducing braking force and unlocking the wheel.
- Pressure Degradation: The pressure decrease reduces braking force, preventing the wheel from locking up again.
ABS System Constitution
- Hydraulic circuit
- Pressure sensor
- Brake pedal travel sensor
- Acceleration sensor
- Steering angle sensor
- Stability control system
Dynamic Factors Used by ESP (Electronic Stability Program)
- Transverse Acceleration: Force applied when making a turn, pushing the vehicle outwards.
- Yaw Moment: The sum of the centrifugal forces applied to each wheel when turning.
- Vehicle Turning Radius: The radius of the circle traced by the inner rear wheel during a turn.
Topic 15: Ceramic Brakes
Advantages of Ceramic Brakes
- Reduced stopping distance
- Improved braking stability
- Extended lifespan of the discs
- Nonexistent oxidation and corrosion
- Savings in braking assistance systems
Working Temperature of Carbon Brakes
Carbon brakes must operate above 400°C for optimal performance. The ideal temperature range is between 600°C and 750°C. Performance drops significantly below this range.
Disadvantages of Carbon Brakes
- High cost due to the high friction coefficient and larger friction surface compared to conventional brakes.
- Susceptibility to oxidation due to environmental oxygen and high operating temperatures.
Perforated Discs
Perforated discs allow for heat dissipation as air flows through the holes generated by the motion of the disc.
Beveled Discs
Beveled discs are designed to evacuate the wear products created during braking.
Advantages of Ceramic Bearings
, high wear resistance / less friction in rolling the vehicle / reduction of between 20% and 30% of the total weight / better dissipation of heat from the bearing / lower internal dilatation to work at temperatures high / higher corrosion resistance wing