Explain the operation of an integral drum brake
parking brake.
The correct answer and explanation is :
An integral drum brake parking brake is a type of parking brake system commonly used in automotive applications. It is integrated into the rear drum brake mechanism and serves the function of holding the vehicle stationary when it is parked.
Correct Answer:
An integral drum brake parking brake operates by using a mechanical linkage that applies pressure to the brake shoes, forcing them against the drum to create friction, which prevents the vehicle from rolling.
Explanation:
The integral drum brake parking brake operates within the existing drum brake system, which is typically used for rear brakes in vehicles. Here’s how it functions:
- Drum Brake Components: A drum brake consists of several key components: the brake drum, brake shoes, springs, and a wheel cylinder. When the vehicle’s regular brakes are applied, hydraulic pressure from the master cylinder forces the brake shoes outward, pressing them against the inside of the drum to slow down or stop the vehicle.
- Parking Brake Mechanism: The integral parking brake is designed to work off of this same drum brake assembly. However, rather than relying on hydraulic pressure, the parking brake is operated mechanically. This is typically achieved via a lever or pedal in the cabin, which is connected to a cable.
- Engagement of the Parking Brake: When the parking brake is engaged, pulling the lever or pressing the pedal pulls the cable, which in turn pushes a mechanism (often a star wheel or pawl) inside the brake assembly. This mechanism forces the brake shoes further out against the drum.
- Holding the Vehicle in Place: The increased friction between the brake shoes and drum prevents the wheel from turning. The force applied by the parking brake is enough to hold the vehicle stationary when it is parked, even on inclines.
- Self-Adjusting Mechanism: Many integral drum brake systems feature a self-adjusting mechanism. This ensures that the parking brake maintains proper shoe-to-drum contact as the brake shoes wear down over time, thereby maintaining consistent parking brake performance.
This design integrates the parking brake directly into the primary brake system, allowing for a simpler, more space-efficient setup while providing effective holding power.