Brake Assist System (Vacuum Assist)

Brake Assist System Description and Operation (Vacuum Assist)

System Component Description

The brake assist system consists of the following:
Brake Pedal
- Receives, multiplies and transfers brake system input force from driver.

Brake Pedal Pushrod
- Transfers multiplied input force received from brake pedal to brake booster.

Vacuum Brake Booster
- Uses source vacuum to decrease effort required by driver when applying brake system input force.
When brake system input force is applied, air at atmospheric pressure is admitted to the rear of both vacuum diaphragms, providing a decrease in brake pedal effort required. When input force is removed, vacuum replaces atmospheric pressure within the booster.

Vacuum Source
- Supplies force used by vacuum brake booster to decrease brake pedal effort.

Vacuum Source Delivery System
- Enables delivery and retention of source vacuum for vacuum brake booster.

System Operation

Brake system input force is multiplied by the brake pedal and transferred by the pedal pushrod to the hydraulic brake master cylinder. Effort required to apply the brake system is reduced by the vacuum brake booster.

Active Brake Booster

Incorporated into the vacuum brake booster, is an electric solenoid actuator. This actuator can be used to apply the brake booster and thus the master cylinder as commanded by the electronic brake control module (EBCM). During stability events, the EBCM can command the solenoid actuator in the brake booster to apply the booster. This quickly provides a large volume of pressurized brake fluid to the brake pressure modulator valve (BPMV). The BPMV will then control the flow of fluid to the brake corners to obtain the appropriate response for the vehicle.