Hydraulic brake is a braking mechanism that uses brake fluids, normally containing glycol ethers or diethylene glycol, to transfer pressure from the control mechanism to the braking mechanism.
It is one of the most useful brake systems. Most cars today use hydraulically controlled foot brakes on all four wheels and have a mechanically operated handbrake on the rear wheel.
This type of brake is more trusted compared to other types of brake and easier to handle. Today, almost all passenger cars use this type of brake system.
Table of Contents
How it Works?
In a hydraulic brake system, when the brake pedal is depressed, a push rod exerts force on a piston in the master cylinder, causing fluid to flow from the brake fluid reservoir through the equalization port and into the pressure chamber. This increases the pressure in the entire hydraulic system, causing the fluid to flow through the hydraulic line to one or more calipers, where it acts on one or more caliper pistons.
Check out the below figure to know how hydraulic brake works.
The caliper piston then exerts force on the brake pads, pushing them against the spinning brake disc. Friction between the brake pads and brake discs creates braking torque and slows the vehicle. The heat generated by this friction is either dissipated through rotor vents and ducts or conducted through linings made of special heat-resistant materials such as Kevlar or sintered glass.
Instead, in drum brakes, the fluid enters the wheel cylinder and one or two brake shoes are pressed against the inside of the rotating drum. The brake shoes use the same heat-resistant friction material as disc brake pads.
When the brake pedal/lever is then released, the spring in the master cylinder assembly will return the master piston back into place. This action first releases hydraulic pressure in the caliper, then applies suction to the brake piston in the caliper assembly back into the housing, allowing the pads to push the rotor away.
The hydraulic brake system is designed as a closed system.
If the system is leak-free, no brake fluid will flow in or out and no fluid will be consumed by use. However, leaks can occur through cracks in o-rings or holes in brake lines. Cracks can occur when two types of brake fluid are mixed, or when brake fluid is mixed with various liquids such as water, alcohol, and antifreeze.
Parts of Hydraulic Brake System
A key component of the hydraulic brake system is the master cylinder, which contains the brake fluid reservoir.
Various parts of hydraulic brake system are shown in the below figure.
The master cylinder is actuated by the brake pedal and is connected to each wheel’s wheel cylinder by a steel tube. The system is designed to maintain a slight pressure of 50 kPa in the piping to keep the wheel cylinder shell inflated even when the brake is in the released position.
Advantages of Hydraulic Brake
The main advantage of hydraulic brake is that this types of brakes have a larger contact area, which helps dissipate heat and therefore provides more stopping power. They also rarely fail, so they are more reliable at high speeds and perform better in wet and muddy conditions compared to mechanical brakes.