Brakes and Traction Control: Description and Operation

Brake System - Hybrid
The hybrid brake system consists of the following components:
^ Brake pedal travel sensor
^ Diagonal split hydraulic system
^ Fixed position foot pedal
^ Four-wheel anti-lock brake system (4WABS)
^ Front brake discs utilizing a single piston floating brake caliper
^ Longitudinal accelerometer
^ Master cylinder
^ Mechanical parking brake system utilizing a drum-in-hat type brake within the rear brake discs
^ Rear brake discs utilizing a single piston floating brake caliper

Regenerative Braking System
Instead of just using the brakes to stop the vehicle, the electric motor that drives the hybrid electric vehicle can also slow the vehicle. In this mode, the electric motor acts as a generator and charges the batteries while the vehicle is slowing down. To achieve this, the ABS module calculates the amount of speed reduction requested by the driver through the accelerator pedal position and brake pedal travel sensor located on the master cylinder. The ABS module measures the inertia of the vehicle through the longitudinal accelerometer located in the stability control sensor cluster and determines if the required deceleration has been achieved. During deceleration/braking, the PCM partially engages the electronically controlled continuously variable transmission (eCVT) to be turned by the vehicle's wheels and slow it down. The ABS module requests the powertrain more or less dependent upon the driver request through the pedals. If the desired deceleration is not achieved through regenerative braking, the ABS module applies the friction brake pads to accommodate the driver request. The driver does not, under normal circumstances, have direct control over the amount of brake pressure that is applied to the rotors. In the event that the ABS module detects a fault which requires the deactivation of this system, the ABS module relinquishes control of braking and the driver will still have the use of manual hydraulic brakes. The hydraulic control unit (HCU) will still provide power assisted braking even if the ABS system is disabled.

Since the regenerative braking uses the electric motor to slow the vehicle's front wheels, front brake pad wear is reduced. The rear brake pads, because of the regenerative braking, wear at approximately twice the rate of the front brake pads.