Automobile Air Conditioning System (A/C) is an important comfort subsystem in automobile comfort/cycle system, which consists of refrigeration system, heating system, air supply system, purification system and electric control system. The refrigeration system is actually a pipeline system, consisting of compressor, condenser, liquid storage filter dryer (or collecting dryer), expansion valve (or orifice tube), evaporator, high and low pressure pipe, etc. The refrigeration system uses refrigerant such as R134a as working medium and evaporative refrigeration. When working, the pressure on the high pressure side can reach about 3400 kPa and the temperature can reach about 80 C. The sealing of refrigeration pipeline is the basis of normal operation of refrigeration system.
According to the working principle, the forming packing seal can be divided into extrusion (or compression) seal ring and lip seal ring. O-ring belongs to extrusion sealing ring. The quality of O-ring, such as design, material and manufacture, has great influence on the normal operation, working efficiency and performance, service life, energy saving, emission reduction, consumption reduction and environmental protection of the equipment. Therefore, great attention should be paid to the design, manufacture, use and maintenance of O-ring.
Formula design plays an important role in the processing of rubber products. Reasonable formula design can ensure excellent performance of rubber seals, good processing performance of rubber materials and low production cost. In order to solve the quality and service life of O-ring, the design of the formula of waste material is the key.
The purpose of formulation design is to find out the proportion combination of various formulations, so as to obtain good comprehensive performance. Formula design should be based on the requirements of product use, in accordance with the principle of economic and practical, reasonable selection of various raw materials and the benefits of their dosage:
The processing performance of O-ring compound is good. On the basis of satisfying the service performance of the product, the processing performance of the compound is considered. Good processing performance facilitates the manufacture of rubber and sealing rings to meet the needs of mass production.On the premise of guaranteeing the quality of O-ring, raw materials with low price, abundant sources, low toxicity and stable performance are selected to achieve the goal of reducing costs, improving economic benefits, not polluting the environment and safety in production. The results show that the properties of the finished O-ring depend on the properties of the vulcanizate.
In the refrigeration system of automobile air conditioning, O-ring plays an important role in static sealing. Its application mainly includes three aspects: one is as an auxiliary sealing element for mechanical seal or lip seal of rotary shaft of refrigeration compressor; the other is as a sealing element between the body and end cover of refrigeration compressor; and the third is as a sealing element for joint of refrigeration pipeline. Compared with other sealing rings, O-ring is widely used in automotive, power, machinery, petrochemical and other fields because of its following advantages. (1) Simple structure, small size, light weight, compact installation; (2) Pre-sealing and self-sealing, without periodic adjustment; (3) Static and dynamic seals can be used, and there is almost no leakage when used as static seals; (4) Single-piece use has two-way sealing effect; (5) small friction coefficient, small dynamic friction resistance; (6) wide range of use. If the material is selected properly, the temperature range is - 60 ~220 ; (7) It is easy to manufacture, low cost and easy to disassemble and assemble.
However, O-ring also has some limitations. For example, when used for dynamic seal, the relative speed between workpiece and O-ring should not be too high (linear speed is not higher than 15m/s), and leakage is easy to occur when the speed is too high; the friction resistance of starting dynamic seal is larger, about 3-4 times of the dynamic friction resistance; O-ring should not be used in low temperature and high temperature environment, etc.