TYPES AND HOW TO WORK BRAKE BOOSTER ON CARS

Modern vehicles are equipped with a booster to assist the driver when applying the brake pedal. Most of the common types of the booster are vacuum types. The vacuum is a condition in which the pressure of a specific area is lower than the pressure of the surrounding atmosphere. The pressure difference can be manipulated using a diaphragm, which is a flexible membrane that reacts to different pressures. The vacuum booster system uses the difference between engine manifold vacuum (negative pressure in the intake manifold) and atmospheric pressure (which is approximately 14.7 pounds per square inch (psi).

1. Types of booster

* Vacuum booster

There are two types of vacuum boosters used in modern vehicles: single-diaphragm and tandem-diaphragm (dual-diaphragm). Both types of boosters operate the same but the tandem boosters have a smaller diaphragm diameter.

The boost is installed between the brake pedal pushrod and the master cylinder and receives vacuum via the hose and valve (one-way valve). The valve maintains the vacuum pressure during engine shutdown and ensures that the booster will have a spare vacuum for 2-3 brakes.

* Boster hydraulic (pressure)

This booster is used in vehicles that do not allow the use of a vacuum booster, such as:

* Very narrow space (not enough available for placement of the vacuum booster.

* There is no constant vacuum in the intake manifold (diesel engine with turbo charger).

* Vehicles that require a large braking force, so the use of a vacuum booster is not possible.

The way this type of hydraulic pressure booster works takes advantage of the hydraulic pressure from the power steering system. The power steering pump pressure is used to operate this type of brake booster.

2. How the booster works

* Vacuum booster

a. Single diaphragm

~ Conditions have not worked

When the brake pedal is in the free position, the internal vacuum port opens

allows vacuum to flow from the space in front of the piston (chamber

vacuum) to the space behind the piston (variable space). Therefore

on both sides of the diaphragm becomes vacuum.

The diaphragm spring presses the piston towards the base, so that the pushrod does not

pressing the master cylinder piston.

~ Working conditions

When the brake pedal is depressed, the pushrod moves forward and closes

vacuum port and open the water inlet valve. Thus the space in sections

the back of the diaphragm is cut off with the space in front of the diaphragm and on

the same time allowing atmospheric air pressure to pass through

the air inlet valve enters the space behind the diaphragm. This moves the piston forward and the pushrod presses the master cylinder piston so that the brakes work.

b. Double diaphragm

~ Conditions have not worked

The unit has two constant pressure and two variable pressure chambers. The piston separates each variable pressure chamber and the constant pressure chamber. When the brake is not applied, the air valve is applied and the rod operating valve is pushed to the right by the piston return spring, arriving at the valve stopper key. Because the Air Valve Control Valve pushes back to the right, this section closes the atmospheric air channel into the booster, and causes the vacuum valve and control valve not to touch each other (open vacuum channel), the pressure of the vacuum chamber (A) and the variable space (B). ) the same. So that a vacuum is applied to both the constant chamber and the variable pressure chambers, hence, there is no pressure difference between the two piston side chambers.

~ Working conditions

When the brake pedal is depressed, both the operating alve rod and the air valve are pushed to the left together. As a result, the control alve and the vacuum valve coincide with each other, the variable space (B) against the constant pressure chamber (A). Furthermore, the air valve moves away from the control valve, allowing atmospheric air to enter. This results in a pressure difference between the variable chamber and constant pressure chamber, and the piston moves to the left. Pressure is transmitted to the Reaction Disc through the Valve Body, then transmitted to the Booster Push Rod, becoming the output power of the booster. This is the sum of the surface area of ​​the piston No. 1 and No. 2, multiplied by the pressure difference between the constant chamber and the variable pressure chamber, equal to the output power of the booster.

* Hydraulic pressure booster

Power steering pump pressure is used to assist braking and also to fill the accumulator, which is a space that holds fluid pressure. This pressure is used when the engine is off (off). When hydraulic pressure fills the accumulator, it pushes the rubber seal against the piston and compresses the spring. If the power steering pump stops (the engine stops), the spring will squeeze and push fluid into the booster to aid in braking. The accumulator can provide sufficient hydraulic pressure for two or three (2 or 3) conditions (emergency) for brake application if power steering pressure is lost.