Motor Vehicle Level 3 Electronics and Electronic Components Resource 1

Motor Vehicle Level Resource 1 Aims Electronics and Electronic Components To recognize the role of electronics within an ABS system

Objectives By the end of the session you will be able to: 1.Identify Electronic ABS components 2.Recognize the inputs and outputs of an ABS system 3.Describe the operation of ABS electrical components. Motor Vehicle Level 3 Resource 1 Electronics and Electronic Components

ABS ECU Block Diagram Motor Vehicle Level 3 Resource 1 Electronics and Electronic Components

Location of Components (Electrical) Motor Vehicle Level 3 Resource 1 Electronics and Electronic Components

Electronic ABS Components An ABS system will include the following electronic components Wheel Speed Sensors Wiring Relays ABS ECU Actuators Motor Vehicle Level 3 Resource 1 Electronics and Electronic Components

Location of ABS Electronic Components Motor Vehicle Level 3 Resource 1 Electronics and Electronic Components

Wheel Speed Sensors A wheel speed sensor mounted on each wheel is utilised within an ABS system in order to determine the rotational speed of the vehicles wheels (to determine if a wheel is skidding or de-accelerating), this is then sent to the ABS ECU. Front wheel speed sensors are mounted onto the steering knuckle. Rear wheel speed sensors can be mounted to the rear axle carrier or mounted to the suspension arm depending on set up. Motor Vehicle Level 3 Resource 1 Electronics and Electronic Components

Wheel Speed Sensors Motor Vehicle Level 3 Resource 1 Electronics and Electronic Components

Wheel Speed Sensor Operation As the teeth of the sensor rotor pass the iron core, the magnetic lines of force cut through the coil windings This causes a voltage to be induced into the coil When the tooth is centered on the iron core the magnetic field does not move and 0v is produced. As the tooth moves away from the iron core the magnetic field expands causing a negative voltage The faster the rotor increases the signal increases indicating a high wheel speed which is then sent to the ECU. Motor Vehicle Level 3 Resource 1 Electronics and Electronic Components

Wheel Speed Sensor Operation Voltage is induced to the coil when the magnetic field is altered each time the sensor passes the iron core Motor Vehicle Level 3 Resource 1 Electronics and Electronic Components

ABS relays Supplies power to the solenoids in order to prevent wheel lock up but only when the following conditions are met:- The IGN is on The self diagnostic check performed by the vehicle on start up was completed OK If any of these conditions are not met, the ECU will switch the solenoids off. Motor Vehicle Level 3 Resource 1 Electronics and Electronic Components

Circuit Diagram showing ABS relays Motor Vehicle Level 3 Resource 1 Electronics and Electronic Components

Relays The motor relay will switch the voltage to the pump motor The solenoid relay switches the voltage to the actuator solenoids Motor Vehicle Level 3 Resource 1 Electronics and Electronic Components

Actuators The actuators on an ABS system will control the amount of brake pressure that the wheel is subjected to, depending on information received from wheel speed sensors etc. It controls this via three solenoids:- Pressure holding Pressure increase Pressure Reduction These solenoids will be discussed further in the next session. Motor Vehicle Level 3 Resource 1 Electronics and Electronic Components

Actuators Motor Vehicle Level 3 Resource 1 Electronics and Electronic Components

ABS ECU The ECU (Electronic control unit) is the vehicles on board computer that will ensure that all systems are performing correctly. The ECU will collect data from sensors, battery and brake light switch in order to determine how the ABS system is performing. If a wheel speed sensor is measuring as de-accelerating (lock up) the ECU will react by sending a signal to the actuators to reduce that pressure at the offending wheel. Motor Vehicle Level 3 Resource 1 Electronics and Electronic Components

Block Diagram ABS ECU Motor Vehicle Level 3 Resource 1 Electronics and Electronic Components

Circuit Diagram ECU Motor Vehicle Level 3 Resource 1 Electronics and Electronic Components

Summary Aim: To recognize the role of electronics within an ABS system Objectives: At the end of the session, students should be able to: Identify Electronic ABS components Recognize the inputs and outputs of an ABS system Describe the operation of ABS electrical components. Motor Vehicle Level 3 Resource 1 Electronics and Electronic Components