What Is Master Cylinder?
The master cylinder in a car stopping mechanism is a water-powered gadget in which the chambers and some cylinders are arranged in such a way that the mechanical power attached to the brake pedal in the auto by the driver of the vehicle or the brake switch in bicycles is converted to a water-driven load, which is thus used for braking by the brake caliper.
In a hydraulic braking system, an ace chamber is a gadget that delivers the required weight or braking power to the final braking segment after duplication of mechanical power attached by the driver via the brake pedal or brake switch. The master cylinder is an equally important part of a disc brake assembly, just like the brake disc/rotor.
Generally, it is made of aluminum or casts iron. It works like a throttle system in any motorcycle. As the throttle supplies fuel to the engine, a master cylinder supplies brake fluid to the caliper assembly.
Types of Master Cylinders:
#1. Open System
An open system master cylinder assembly consists of a bladder inside the reservoir tanks. These bladders help to adjusts the level of brake fluid in the master’s cylinders. As one side of the bladders is exposed to the environment, it expands or contracts according to changes in heat.
Advantages:- Automatic adjustment of brake fluid level in the master cylinder assembly, Disc brake system protection from overheating, Since the level of brake fluid is automatically adjusted by the expansion or contraction of the bladder, and it does not affect the performance of braking. You do not need to apply the brakes as it is an open system.
Disadvantages:- A disadvantage is that it adjusts automatically. When the brake pads malfunction, the open system supplies an additional amount of fluid to the caliper, bore so that the piston can be adjusted according to the malfunctioning pad.
If this condition persists for a long time, it can guarantee a change in the disc and caliper assembly, which is a very expensive affair. Apart from this, it creates brake noise & affects the braking performance.
Underfilled bladder under vacuum or overfilled bladders under pressures brake fluid in an open system master cylinder can significantly affect braking performance. It is considered old technology.
#2. Closed System
The closed system master cylinder does not have a bladder in a reservoir tank. Therefore the system needs manual adjustment.
Advantages:- It is widely used in all kinds of automobiles; you can check the brake fluid level through the reservoir tank and change whether it is dark or not between recommended levels. If brake pads are worn out, they can be easily detected in such systems.
Disadvantages:- It can cause overheating problems; If the level of brake fluid is not at the required levels, then it can affect the performance of braking. If air remains anywhere throughout the system, it can affect braking performance; You will need to bleed oil change if there is any air in the system.
#3. Single Cylinder
Single-cylinder is the most basic type of master cylinder and is intrinsically similar to a plastic medical syringe. The brake pedal lever pushes the plunger pistons inside the cylinders, which flows fluid through the lines and into the slave cylinder. When the brake pedals are released, springs inside the cylinder push the plunger back to its original position.
Negative pressure draws the brake fluid from the lines and the brake fluid from the reservoir into the cylinder. Automakers longs ago switched to more redundant tandems master cylinders, but many race car manufacturers prefer to use a pair of singles cylinders instead of a singles tandems cylinder to control front/rear brake pressure bias.
#4. Ported Tandem Cylinder
A tandem cylinder consists of two pistons in one. The primary pistons are connected to the brake pedal. When the brake pedals are pressed, the piston exerts pressure on a spring attached to the rear of the secondary piston. Once that spring is fully compressed, the secondary piston begins to push the fluid through its own dedicated systems.
The reservoir inlets port allows fluid to flow past the piston to maintain even pressure on both sides. When the brake pedals are released, the pressure of the spring pushes the piston back, and a small compensation port from the brake fluid reservoir introduces excess fluid into the chamber.
The compensating port is necessary to accelerate brake release, which would otherwise be hindered by the movement of fluid movings backward through the lines.
#5. Portless Master Cylinder
First introduced on the Toyotas MR2, portless masters cylinders offer a faster brake release than standard designs that use a compensating port. Portless cylinders use a valve assembly in the piston that opens to equalize pressure when the brake is released.
This allows the brake cylinders to do without a compensating port, which is more restricted to fluid flow and reduces pressure from the brake system under the initial application.
The fast-reacting portless cylinder works better with the anti-lock braking (ABS) system, which uses rapid pressure modulation to adjust the braking force.
Working Principle of Master Cylinders:
Single Circuit Master Cylinder In Single Circuit Ace Barrel, when the brake pedal is not squeezed, i.e., in a nonactivation state, the cylinder remains in its unique position, thus closing the bay valve of the repository, causing no contact with brake liquid. The center of the store is for the pressure chamber. When the brake pedal is squeezed, i.e., the energized position, the cylinder is connected with the brake pedal through the interfacing pole, which thus opens the gulf valve, allowing the brake fluid to flow from the store to the pressure chamber.
This brake liquid inside the pressure chamber is packed due to the growth of the cylinder inside the barrel like a medicated syringe. After pressurizing to a specific load, the outlet valve opens, and this exceptionally compressed brake fluid is diverted to the brake lines for additional brake activation.
A couple of master cylinders, the working of the double ace barrel is 70% the same as single circuit mc, but in this type 2, autonomous circuits of braking are used; let’s see how it works. When the brake pedals are not actuated, the cylinder remains in its unique position, closing the delta valves of both pressure chambers, thus cutting off the supply or arrival of brake fluid between both repository chambers.
When the brake pedal is prodded, the necessary cylinder moves first, which opens the required bay valve. Pressures of the brake fluid inside the required chamber are initially due to the development of the required cylinder. After the pressure in the required chamber is met, the required outlet valve opens, and this packed brake fluid is additionally sent through the brake lines to the brake calipers and activation of the required circuit brake.
After the development of the required cylinder, i.e., at its exceptional end, the auxiliary cylinder starts running due to the power attached to the spring of the required cylinder, which thus opens the alternator valve and approaches the brake fluid in the alternator pressure chamber from the auxiliary supply.
This brake liquid is then packed, and after full pressure, the auxiliary outlet is opened, and this deeply compacted liquid is sent through the brake lines to the brake calipers and activation of the alternating circuit break.
Also, Read: What Are Pliers Used? | 34 Types of Pliers
Parts of Master Cylinders:
A master cylinder assembly consists of various parts such as a reservoir tank, bore, piston assembly, lever or pedal, hosepipe, and so on. Let us look at these parts separately.
#1. Lever or Pedal
This is the part of the master cylinder assembly from which you instruct the master cylinder.
A piston or MC pistons is connected to a push rod and a return spring. When the brake lever or pedals is pressed to push the brake fluid, it slides inside the bore.
#3. Spring Return
This is what we have seen in drum brake and disc brake assemblies. This helps the piston to return to its original position when the brake lever or pedal is released.
The pushrod is attached to a lever and a piston. When the brake lever is pressed, it pushes the piston to slide inside the bore.
As we have seen in caliper assembly, master cylinder assemblies also have a bore below which the piston moves.
#6. Piston Assembly
A piston assembly consists of a piston, a series of O rings/gaskets are also known as cup / O rings, circle p, primary cup, and secondary cup, and return spring. A piston assembly is placed inside the bore of the master cylinders.
It is made of aluminum or casts iron. It contains brake fluid. It has a window so you can check the oil level and the color of the oil. Generally, the shape is rectangular or square-shaped, but sometimes round-shaped reservoirs are used for rear disc brakes.
#8. Brake Fluid
Brake fluids are a type of hydraulics fluid. This is as important as oil for an engine. It transfers force under pressure. Like engine oil, brake fluid is also graded like DOT 3, DOT 4, etc. DOT stands for Transport Department. Click here for more information about Brake Fluid.
The bladder is found in the open system master cylinder. It is made of thin-walled rubber, which allows it to deform through expansion and contraction. It has liquid on one side and an atmosphere on the other.
A tube-type pipe that transfers brake fluid from the master cylinder assembly to the caliper assembly.
#11. O ring/Series of gaskets
This includes the cup or o ring, primary cup, secondary cup, and circle p. A cup and circle P (also called a lock ring) act as a retainer for the piston. They are located between the pushrod and piston. A primary seal can be a cups styles or an O ring style seal. This cup allows brake fluid from the reservoir to flow over it into the brake hose pipe when the brake lever or pedal is pressed. On the other hand, the secondary seal keeps the reservoir brake fluid sealed and prevents it from moving to the others side of the cylinder when the brake lever or pedals is pressed. It also acts as a spring retainer.
Contains the entire master cylinder assembly. When the brake lever or pedals are pressed, the pushrod that is attached to the lever or pedal and the pistons push the piston. This movement allows the pistons to slide and push the return spring inside the bore of the master cylinder, which generates pressure in the reservoir tank. At this time, a primary seal allows the brake fluid of the reservoir tank to flow from the top of it into the brake hosepipe.
A secondary seal ensures that brake fluid does not flow to the other side. When brake levers are released, the return spring pushes the piston back to its original position & allows fluid to returns to the reservoir via the hosepipe and cylinder bore.