It can be roughly divided into direct acting vacuum assist and hydraulic vacuum assist. Because the direct-acting vacuum boost directly assists the pedaling force, and the brake operation feeling is good, it is widely used in cars and small-sized cargo vehicles. However, because the toe-down force is directly used as a booster, it is restricted by the installation space. The hydraulic vacuum assist is to use the master cylinder to generate hydraulic pressure to assist, so it can be installed anywhere between the master cylinder and the wheel cylinder, but the brake operation feeling is generally worse than the direct action vacuum boost.
The power source of the booster device uses the negative pressure of the engine intake manifold (gasoline engine vehicle) or the negative pressure of the vacuum pump (mainly diesel engine vehicle).
The check valve between the booster and the negative pressure source must be fitted with a check valve. The check valve can maintain a high vacuum while reducing negative pressure variation in the booster. In addition, in gasoline engine vehicles, in order to prevent gasoline from flowing into the booster, a check valve is generally installed between the engine intake manifold and the booster. To prevent the gasoline in the hose from flowing into the booster device, the check valve is installed at the highest point of the hose, or it is installed near the highest point by a section of the engine.
The brakes for general vehicles are classified into hydraulic brakes and pneumatic brakes according to the transmission medium. Both the hydraulic boosting mechanism and the pneumatic boosting mechanism can be used as the assisting mechanism of the hydraulic brake. The hydraulic booster brake pressurizes the hydraulic oil output by the hydraulic pump through the hydraulic booster, and the boosted hydraulic fluid passes through the master cylinder to make each wheel wheel cylinder work.
A full-pressure brake uses the air generated by the compressor as a transmission medium, and a full-power brake is a device that applies this idea to a hydraulic brake. That is, the hydraulic oil pressurized by the hydraulic pump is temporarily stored in the oil reservoir, and the hydraulic pressure matching the pedaling effort is transmitted to the wheel cylinders by the control of the control valve during braking. Now, full-power brakes are rare.
The pneumatic pressure assist mechanism is a mechanism that uses compressed air as a power source to generate assist force in a hydraulic brake that uses hydraulic oil as a transmission medium. The so-called air brake booster, when the brake pedal is depressed, the brake fluid output from the master cylinder flows into the hydraulic air assist assembly, and while pushing the hydraulic piston, the control piston is pushed to deliver the compressed air stored in the cylinder into the shell. The body makes the power piston work. This increases the oil pressure delivered to the wheel cylinders and provides a powerful boosting effect.