The quality level of the gear oil is selected according to the severity of the working conditions. The severity of the working condition can be measured by the product pv value of the contact pressure p of the gear and the sliding speed v. The magnitude of the dramatic changes in pressure and speed can also reflect the harshness of gear operating conditions.
In recent years, the gears of the main reducer of imported and Sino-foreign joint venture cars and some trucks have a contact pressure of more than 3000 MPa and a sliding speed of more than 10 m/s; the oil temperature is as high as 120-130 ° C, and the working conditions are very demanding. CLE grade gear oil (GL-5 grade) must be used. The main reducer adopts gears, but the contact pressure of the tooth surface is below 3000MPa, the sliding speed is between 1.5~8m/s, and the working conditions are not too harsh. CLD gear oil (GL-4 grade) can be selected. Domestic Dongfeng EQ1090, BJ1040, BJ2022 and Shanghai SH760A are all selected GL-4 gear oil. Some old vehicles, such as the liberation CA10B (10C), Yuejin NJ130, Yellow River JN150 and other vehicles, the rear axle final drive, the use of ordinary spiral bevel gear, optional CLC gear (GL-3). One point to note here is that although some rear-loading mains reducers use ordinary spiral bevel gears, their load is heavier and the working conditions of the gears are harsh. It also requires the use of GL-4 class vehicle gear oil, such as liberating CA30. , Dongfanghong 665, Hongyan 261, Mercedes-Benz 2026 and so on. In this type of car, there have been instances of damage to the early wear of the gear caused by the replacement of ordinary gear oil.
In general, the gearbox and the steering gear are lightly loaded. Therefore, in order to simplify the use of oil, and to facilitate the use and management, the correct selection of a gear oil in China is recommended by Tianjin Automobile as the same type of gear oil as the rear axle. However, in foreign countries, the rear axle of the car generally uses GL-4 or GL-5 gear oil, while the manual transmission uses GL-3 and GL-1 gear oil, and some use automatic transmission fluid or engine oil. If the transmission contains copper parts, diesel oil is required. This is because the automotive gear oil contains extreme pressure anti-wear additives that corrode copper.
Selecting the viscosity grade of automotive gear oil according to operating environmental conditions The low temperature viscosity of automotive gear oil determines the operating performance of the gear transmission at low temperatures. Generally, the highest temperature at which the apparent viscosity of the gear oil reaches 150 Pas is taken as the lowest temperature to be applied (see Table 3), and is selected according to the local minimum temperature. The minimum applicable temperature for multi-grade oil is shown in Table 4. In addition, in order to avoid excessive wear of the gear, the temperature at which the kinematic viscosity of the gear oil is not lower than 10 to 15 mm 2 /s is taken as the maximum operating temperature of the automobile gear oil. Investigations show that in the hot season in southern China, the rear axle oil temperature is higher than the ambient temperature of 60 °C, that is, the oil temperature will not exceed 100 °C. Therefore, from the perspective of lubrication, the general vehicle No. 90 oil can fully meet the requirements of its use, and only the No. 140 oil is used in vehicles with particularly hot weather or heavy load.
In view of the fact that most of the cars used in China in the past are residual oils, the oil change period is short. For example, the liberation CA10B type rear axle and transmission oil change mileage manufacturing factory is 5,000-7000km, Dongfeng EQ1040 is stipulated as two first-class maintenance cycles, and Beijing BJ1040 stipulates seasonal oil change. In actual work, the automobile transportation unit often replaces the gear oil during the advanced maintenance (3 to 40,000 km) or changes the oil in combination with the seasonal maintenance. China's current use of fractional gear oil, its oxidation safety and wear resistance are better than the residue type, oil change period should not be shorter than before. For example, if the operating vehicle is driven 4 to 50,000 km per year, and the social vehicle is calculated to be less than 20,000 km per year, in order to avoid the waste caused by the seasonal oil change, the viscosity grade of the gear oil used in each place is best to ensure the winter and summer.
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