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Brake Master Cylinder

The brake master cylinder is a component in a vehicle’s braking system that converts the force applied to the brake pedal into hydraulic pressure, which is then used to apply the brakes at each wheel. It is typically located near the brake pedal and connected to the brake pedal via a pushrod. When the brake pedal is pressed, a piston inside the brake master cylinder pushes fluid through the brake lines to the brake calipers or wheel cylinders, which in turn apply the brakes. A malfunctioning brake master cylinder can cause a loss of braking power or complete brake failure.

What is Brake Master Cylinder and What Does It Do?

Brake master cylinder (brake center pump) is the part that converts the force applied by the driver to the brake pedal into hydraulic pressure and sends it to the wheel brake mechanisms. The hydraulic pressure created in the brake master cylinder is applied to the calipers in disc brakes; in drum brakes, it is sent to the wheel brake cylinder. The brake center pump (cylinder) is located just in front of the brake booster (hydraulic), and the brake fluid reservoir box is located above it. Brake master cylinder takes the brake fluid it needs from here and the hydraulic coming back from the brake line returns to this reservoir.

Parts and Structure of Brake Master Cylinder

There are two pistons (tandem cylinder) inside the brake master cylinder (brake center pump), thanks to these two pistons, two separate brake line outputs are obtained from the brake center. The brake hydraulic oil tank is mounted on the brake master cylinder, the brake hydraulic oil tank meets the hydraulic oil requirement in the system, and the brake oil returns to this tank when braking is finished. The brake fluid reservoir is also divided into two separate compartments inside, so that in case of a leak in one of the brake lines, it can continue to supply oil for the other brake line. There is also an oil level sensor in the brake fluid reservoir.

The parts of the brake master cylinder are:

*Primary piston and piston return spring

*Second piston and piston return spring

*Piston gaskets – seals (sealing elements)

*Brake hydraulic oil reservoir tank

*Brake hydraulic oil level sensor

Working Principle of Brake Master Center (How Does Brake Master Cylinder Work?)

Normal Position (No Brake Pedal):

In this case, the passage channels from the brake fluid reservoir tank to the brake master cylinder are open. Two return springs inside the cylinder have pushed the pistons back.

Two passage channels are connected from the brake fluid reservoir to both chambers in the cylinder. The larger channel is called “inlet channel – inlet hole”, it provides oil reinforcement from the hydraulic tank into the cylinder.

The second and narrower channel is called “balancing channel – balancing hole”. According to the pressure change in the brake line, brake oil is sent from the reservoir tank or brake oil returns.

When a liquid in a closed container is compressed by a piston (liquids are incompressible), pressure is created in the liquid and this pressure is applied equally to every surface in the container. In the brake master cylinder, the driver presses the brake pedal, the pedal push rod is transferred to the brake servo, and this thrust force is increased in the brake servo.

Operating Position (Brake Pedal Depressed):

The push rod at the output of the brake booster pushes the first piston in the brake master cylinder forward, while the piston moves forward, it creates pressure in the brake oil in the chamber in front of it, this pressure both pushes the second piston in front of it forward and creates the hydraulic pressure sent to the 1st brake line.

The second piston pushed forward by the first piston also moves forward, creating pressure in the brake fluid in the chamber in front of it. This pressure is sent to the 2nd brake line. Thus, hydraulic oil pressure is sent to the caliper piston in the wheels or the brake cylinder in the drum and braking is done.

When Brake Pedal Released:

The driver takes his foot off the brake pedal and the thrust applied to the brake master cylinder piston is eliminated. Pressurized hydraulic brake oil is no longer sent to the brake system. The return springs in the brake master cylinder push the pistons back (to their previous position). Pressurized brake oil in the brake line returns to the reservoir tank.

  When the brake pedal is released, the balancing channel performs an important function. When the brake pedal is released, the pistons retract quickly, but the pressurized brake oil in the system cannot return as quickly. In this case, vacuum (low pressure) is formed in the master cylinder as a result of the rapid volume increase in the chambers in front of the pistons. This channel balances the vacuum created in the chamber as a result of the return springs pushing the piston back when the brake pedal is released, by sending hydraulic oil to it. When the piston returns to its normal position, the pressurized hydraulic oil still present in the brake line returns to the reservoir tank through this channel.

   In addition, when the brake hydraulic oil, whose volume changes with temperature, expands, it flows back to the reservoir box from the balancing channel, and spontaneous pressure build-up in the cylinder due to the temperature effect is prevented.

    We have also alternative good quality brand Sampierana. This is an also Italian brand and dealer of Berco in Italy. They are manufacturing undercarriage parts since 1980. We have been working with them since 2013. We trust their high quality spare parts.

    We also start to manufacture some of the spare parts for undercarriage under OHP brand. But it is pretty new so we have limited options. Please check out OHP Brand section what we have for now. If you don’t find it, send us an inquiery so we can check whether we can produce it or not.

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