For the vacuum source of the vacuum power-assisted system, the vehicle equipped with gasoline engine can generate high vacuum pressure in the intake manifold because the engine adopts ignition type, which can provide sufficient vacuum source for the vacuum power-assisted braking system. For vehicles driven by diesel engine, because the engine adopts CI (compression ignition cycle), it cannot provide the same level of vacuum pressure at the intake manifold, so it is necessary to install a vacuum pump to provide vacuum source. In addition, for GDI (gasoline direct injection) designed to meet higher emission and environmental protection requirements, the intake manifold can not provide the same level of vacuum pressure to meet the requirements of vacuum braking power system, so a vacuum pump is needed to provide vacuum source. Vacuum pump is mainly composed of pump body, rotor, blades, air inlet and air outlet. As shown in fig. 4, taking a single-blade vacuum pump as an example, when the driving torque rotates the rotor through the engine camshaft and the vacuum pump joint, the plastic single blade is driven to rotate along the contour of the vacuum pump cavity and is in an eccentric position of the cavity. In fig. 4, the upper side of a single blade is divided into two cavities, and the left side is a vacuum cavity. With the rotation of a single blade, the volume of the cavity becomes larger and larger. So as to generate a vacuum degree, and at the same time, the vacuum booster can increase the vacuum degree through an air inlet with a one-way valve connected with the vacuum booster; The right cavity is a compression cavity. With the rotation of a single blade, the volume of the cavity becomes smaller and smaller, thus compressing the lubricating oil and air pumped from the vacuum booster into the engine.
Lubricating oil from the engine enters from the center of the rotor, lubricates the vacuum pump cavity and corresponding components, and plays a sealing role between the floating terminal on a single blade and the cavity contour. The function of vacuum pump is to generate negative pressure, thus increasing the braking force. The vacuum pump of automobile generator is generally an oil pump, that is, the vacuum pump core rotates with the shaft of generator. Through continuous oil absorption and pumping, negative pressure, that is, vacuum, is generated in the shell of vacuum pump. Vacuum pump refers to a device or equipment that uses mechanical, physical, chemical or physico-chemical methods to pump the pumped container to obtain vacuum. Generally speaking, a vacuum pump is a device for improving, generating and maintaining vacuum in a closed space by various methods. According to the working principle of vacuum pump, vacuum pump can be basically divided into two types, namely gas capture pump and gas transmission pump. Widely used in metallurgy, chemical industry, food, electronic coatings and other industries.