3. Airtightness for rotary fitness
In the sealing of rotary fitness movement, skeleton seal mechanical seal are generally selected. However, the working pressure of the skeleton seal is lower, compared with the O-ring, it looks too complicated the process performance is poor. Although mechanical seal can be used for high pressure (40MPa), high speed (50m / s) high temperature (400 ℃), its structure is more complicated huge, its cost is increased. It is only applicable to some heavy machinery equipment with crude oil, chemical plant other functions.
Joule thermoelectric effect is the key problem in the use of O-ring to rotate fitness exercise. The Joule thermoelectric effect causes friction heat at the contact between the high-speed rotating shaft the O-ring, the transformed heat makes the temperature of the contact position rise continuously. The elastomer material is seriously deformed when exposed to heat, the shrinkage extension change. The burning of automobile plane pressure bearing also accelerates the embrittlement of rubber seal, reduces the service life of O-ring, destroys the sealing floating oil, thus causing oil cut-off speeding up the sealing damage.
According to the above-mentioned situation, in recent years, many countries in the world have carried out extensive deep-seated scientific research on the use of O-ring for rotary fitness. In order to prevent Joule thermoelectric effect, the key point is to the design scheme properly according to the characteristics of vulcanized rubber. The main structural parameters of O-ring are mainly drawing amount compression coefficient of O-ring. According to the experiment, the design scheme of O-ring for rotary fitness exercise is that the inner diameter of O-ring is the same as slightly larger than the diameter of rotating shaft, which is generally 3% ~ 5%. When installing the O-ring, it should be reduced the inner axis, the reduction of cross-section should be smaller, generally about 5%. Moreover, the rubber seals with less heat damage should be selected as far as possible, considering the heat removal problem of the O-ring installation. In this way, the working condition of O-ring is greatly improved, which can be used for the sealing of rotating shaft with high speed ratio up to 2m / s.
In recent years, high temperature resistant fluororubber wear-resistant polyurethane rubber, automobile shock absorber bearings, have a deeper understanding of the Joule thermoelectric effect in the work of vulcanized rubber components, for this problem, scientific research solutions, design a new O-ring sealing structure, so that the O-ring can be more used high-speed, high-pressure rotary fitness exercise.
Because of its small size, simple structure, low cost, good performance wide application, O-ring is widely used in rotary fitness sports sealing equipment.