With the understanding of the braking system in automobiles, discussing the hydraulic type is very necessary as it’s widely used. The braking system uses hydraulic fluid to transmit the brake pedal or level force to the final drum shoes or disc caliper for the braking to prevail.
In a hydraulic braking system, the mechanical force from the brake pedal is transmitted and converted into hydraulic pressure with the help of the master cylinder. The hydraulic brake system works with the principle of Pascal’s law. The laws state that whenever pressure is applied to the fluid, it travels uniformly in all directions.
In this reading, we’ll explore what a hydraulic braking system is, its functions, diagram, components, and how it works.
Let’s get started!
What Is A Hydraulic Braking System?
A hydraulic braking system is a mechanism that uses brake fluid to transmit force, transferring pressure from the control mechanism to the brakes. The hydraulic brake system is widely used in low-speed four-wheelers.
It works with the drum type, while the disc type is used in almost all cars. It’s also used on some bikes. Single-acting hydraulic brakes are used in the front-wheel brakes of some pulsars, while dual-acting hydraulic brakes are used in almost all conditions mentioned above.
Functions Of A Hydraulic Braking System
A hydraulic braking system serves several important functions in a vehicle, ensuring effective, safe, and reliable braking. Here are the key functions:
- The hydraulic brake generates a very high force compared to mechanical braking.
- The final braking is quick and effective; that’s why it’s used on high-performance vehicles.
- Frictional wear and tear that occurs in the mechanical braking system are much reduced to an optimum level in the hydraulic braking system.
- Chances of brake failure are reduced in the hydraulic braking system compared to the mechanical types because of the direct connection between the actuator (brake pedal or lever) and the brake disc or drum.
- The hydraulic braking system is very easy to fix due to its lower complexity compared to mechanical brakes.
Construction
The construction of a hydraulic braking system contains reinforced hydraulic lines, and the brake caliper assembly consists of one or two hollow aluminum or chrome-plated steel pistons. It’s known as caliper pistons.
There is a set of thermally conductive brake pads and a rotor, which is also known as a brake disc or drum attached to an axle. A glycol-ether-based brake fluid filled the system to transmit force to four wheels. Though other fluids can also be employed.
Suddenly, manufacturers begin to design passenger vehicles with drum brakes on the four wheels. Conventionally, a disc brake is used in the front wheel, while drum brakes are employed for the rear wheel.
The disc brakes have better heat dissipation and greater resistance to fading and are well safer than drum brakes. This is why four-wheel disc brakes have vastly increased over the years. Also, hydraulic brakes offer faster and more consistent pad withdrawal upon the pedal release.
Applications
Vehicles are the primary application for hydraulic brakes, which contributes to their popularity. The system is widely used due to its great advantages. Various types of transportation and rolling stock industries like aerospace, heavy transport, marine, and off-highway systems also make great use of the hydraulic braking system.
The system is also designed for industrial equipment such as machine tools, pumps, conveyors, motors, robotics, and automation. The vast usage is because the mechanical braking system can’t offer better as it does and it’s significantly easier to modulate.
Related: What Is A Braking System? Its Parts, Types, And How It Works
Hydraulic Braking System Diagram
Components Of Hydraulic Braking System
A hydraulic braking system consists of several key components that work together to ensure effective braking. Here’s an overview of the main components:
Drum Brake
Drum brakes are small round drums designed with a set of brake shoes in them. The brake shoes are supported on a back plate that is attached to the axle casing with bolts. It rotates along with wheels and it resists the rotation of the wheel when the brake pedal is pressed. The shoes move toward the drum for the braking to take place.
Disk Brake
Disk brakes are designed with a disc-shaped metal rotor bolted to the wheel hub. The metal rotor spins within the wheel. As the brake pedal is pressed, the brake pads are pressed against the disk, causing the vehicle or device to slow down.
Brake Pedal
Just as it’s common for automobiles to have brake pedals to apply brakes, the hydraulic braking system also uses such. The pedal is connected to the master of the cylinder using a mechanical cord or linking rod.
Master Cylinder
The master cylinder is the part that converts the applied force from the pedal to hydraulic pressure. The function of the part is to develop pressure, equalize the required pressure for braking, and also prevent contaminants such as water and air. Components of the master cylinder include housing, reservoir, piston, rubber cup, pressure, check valve, etc.
Wheel Cylinder
A wheel cylinder in the hydraulic brake system helps convert hydraulic pressure to mechanical pressure. In its working, it pushes the brake shoes toward the drum. The wheel cylinder is categorized into two, which include a stepped wheel cylinder and a single-piston wheel cylinder.
Brake Lines or Hoses
Brake lines or hoses help in transferring high-pressure fluid between different components. The difference between the two is that brake lines are rigid in construction and made with double-wall steel tubes. These brake hoses are flexible and can be moved. Hydraulic fluids pass the component as the brake pedal is pressed.
Brake Fluid
Brake fluids are the means through which pressure is transferred to the wheel cylinders. Hydraulic brake fluids must have a low freezing point, water tolerance, lubrication, non-corrosiveness, proper viscosity, and a high boiling point.
Specifications Of An Hydraulic Braking System
The following are the performance specifications to be considered while choosing a hydraulic brake system:
- Torque rating: the maximum torque rating for the brake should equal or exceed the application requirement.
- Power: the maximum capacity or power rating for the brake.
- Speed: This specification applies only to rotary brakes, which is the maximum rotary speed rating.
- Maximum pressure—the maximum pressure limit for hydraulic brakes.
- Shaft configuration: how the brake will be mounted (in-line, parallel, or right angle).
How An Hydraulic Braking System Works
Because there are various types of hydraulic braking systems, we’ll be explaining the working since they vary. Starting from the drum and disc brake to the single and dual-acting hydraulic brakes.
Working Of Drum Hydraulic Brake System Work
In the case of hydraulic brakes, a connecting rod connects the piston of a master cylinder to the brake pedal. This in turn pushes the master cylinder’s piston inside the master cylinder, working just like an injection system or medical syringe.
The piston inside the master cylinder compresses the brake fluid, which then offers the conversion of mechanical energy into hydraulic pressure. This highly compressed brake fluid moves inside the brake, which then transfers the hydraulic pressure from the master cylinder to the brake drum.
As soon as the high-pressure brake fluid enters the drum cylinder or wheel cylinder, the movement of the cylinder piston occurs due to the high pressure. This in turn expands the stationary brake shoes attached to it.
The expansion of the brake shoes causes the frictional contact between the shoes and drum lining (the rotating drum part) to convert the kinetic energy of the vehicle into heat energy, which makes the braking happen.
Working Of Disc Hydraulic Brake
The disc hydraulic brake working principle is similar to the drum hydraulic types but with a slight difference. The difference begins from where the high-pressure brake fluid enters the brake lines. High-pressure brake fluids enter the disc caliper from the brake lines, which then cause the movement in the caliper cylinder’s piston.
The caliper cylinder piston causes the movement of the brake pad, which is attached to the piston inside the caliper. The movement of brake pads causes them to clamp with the rotating disc rotor. These components come into frictional contact with each other. So it causes the conversion of the vehicle’s kinetic energy into heat energy to occur, which causes the vehicle to stop or decelerate.
Single & Double-Acting Drum And Disc Brake Working
The components of the single-acting and double-acting hydraulic brakes are the same. Whether it’s the drum-type single-acting brake or disc-type single-acting brake, there’s no difference. Well, differences may occur in the master cylinder used to decide the brake force distribution. For instance, in bikes, single-wheel braking or double-wheel braking; in vehicles, two-wheel braking or all-wheel braking.
The working single-acting drum type of braking system is exactly as the above-mentioned principle. That’s for the drum hydraulic braking system. In its working, single wheel or single pf wheels get the braking force. In the double-acting hydraulic brake, the high-pressure brake fluid from the master cylinder supplies in two directions. i.e. in the bike, both wheels and cars are all-wheel due to the tandem master cylinder.
A single-acting disc hydraulic brake also works just as the disc type of brake, which is explained above. The wheel or single pair of wheels gets the braking force. Whereas, the double-acting disc hydraulic brake distributes the high-pressure fluid from the master cylinder in two directions. For instance, in bikes, both wheels and cars are all-wheel due to the tandem master cylinder.