2.2 Valve seat
(1) The floating design is adopted for the valve seat to reduce the processing difficulty and ensure that the center line of the valve seat coincides with the center point of the spherical surface of the hemisphere, thus improving the sealing performance. There is a gap between the valve seat and the valve body. During assembly, the use of hemispherical positioning can automatically align the center line, ensuring full contact between the sealing surface of the valve seat and the spherical surface of the hemispherical body, solving the leakage caused by machining accuracy errors, and improving the service performance and life of the pneumatic ball valve.

In recent years, with the rapid development of pneumatic butterfly valve industry. As a component of the exhaust assembly of commercial vehicles that does not directly affect the quality and application of the whole vehicle - pneumatic butterfly valve and its similar products, in the past decades, domestic commercial vehicle manufacturers and users have not attracted the satisfactory attention and application. The exhaust pipe of the starter and the muffler are directly connected with hard pipes, resulting in large vibration, high noise, low life and heavy pollution of commercial vehicles. As people put forward higher requirements for the appearance, safety and warmth of commercial vehicles, car enterprises began to pay attention to the use of exhaust pneumatic butterfly valves. This paper analyzes the functional advantages of the exhaust pneumatic butterfly valve and its application in cars.
As usual, with the strengthening of environmental protection and the introduction of foreign advanced commercial vehicle technologies, many domestic commercial vehicle manufacturers have successively adopted corrugated pipes to connect exhaust pipes and silencers. Although the bellows can play a certain role in azimuth compensation and vibration reduction, it still has limitations in many indicators such as falling metal fatigue, noise reduction and bearing circumferential shear load; Therefore, some domestic commercial vehicle manufacturers and commercial vehicle manufacturers in prosperous countries in Europe and America have adopted flexible pneumatic butterfly valves with inner buckle and structure to replace bellows. Pneumatic butterfly valve exchange bellows is the trend of future expansion.
1 Type of pneumatic butterfly valve
The soft joint of commercial vehicles generally includes three types: active joint, bellows, and pneumatic butterfly valve. The ability to reduce vibration and compensate displacement is in descending order: pneumatic butterfly valve, bellows, and active joint. Pneumatic butterfly valves are widely used in the exhaust system of new freight cars around the world as exchange products because of their common inner buckle structure, which makes the axial direction flexible (also known as elastic joints). Now the commonly used pneumatic butterfly valves at home and abroad are of double-layer buckle structure. Since the end face is polygonal in shape, there are edges on the circumference from the surface. Now there are many manufacturers at home and abroad, but there is still a certain gap between domestic products and foreign products in terms of functional indicators, such as sealing, elongation, application of materials, and appearance.