Low temperature environment poses multiple challenges to the normal operation of vehicle gear box, among which the performance of lubrication system and mechanical response of gearbox are the core issues. Low temperature will significantly change the physical properties of lubricating oil, resulting in a decrease in its flow performance, which in turn affects the lubrication effect of various components inside the gearbox, causing a series of mechanical wear and functional abnormalities, which requires a comprehensive analysis from the two dimensions of lubrication mechanism and mechanical operation.
Under low temperature environment, the viscosity of vehicle gear box lubricating oil will increase significantly as the temperature decreases, showing a state similar to solidification. This change directly leads to a significant decrease in the fluidity of lubricating oil inside the gearbox, making it difficult to quickly reach the friction surfaces of various moving parts. For example, key lubrication points such as gear meshing surfaces and bearing rotating parts may produce dry friction at the beginning of startup due to lack of sufficient oil film protection, aggravating the wear of metal parts. At the same time, lubricating oil with increased viscosity will increase the workload of the oil pump, resulting in a delay in the establishment of oil pressure, further delaying the normal working process of the lubrication system, and making the gearbox face a higher risk of wear during the low temperature startup stage.
The deterioration of lubricating oil fluidity will also affect the heat dissipation performance of the gearbox. Under normal working conditions, lubricating oil not only performs the lubrication function, but also removes the heat generated by the friction of components through circulation. However, in a low-temperature environment, the circulation speed of the viscous lubricating oil slows down, and the heat transfer efficiency decreases, which may cause uneven temperature distribution inside the gearbox. In particular, during vehicle driving, gears and other components continue to generate heat due to friction. If the heat cannot be dissipated in time, the temperature may be too high in some areas, which will accelerate the oxidation and deterioration of the lubricating oil. At the same time, the seals will lose their elasticity due to high-temperature aging, causing oil leakage problems, further weakening the lubrication effect, and forming a vicious cycle.
For manual transmissions, low-temperature environments will make their shifting operations more difficult. This is because manual transmissions rely on the lubrication and cooling of gear oil. At low temperatures, the viscosity of gear oil increases, which will increase the meshing resistance between gears. The driver needs to apply more force when shifting gears, and the gear switching process may be stuck, affecting the driving experience. In addition, the working efficiency of the synchronizer will also decrease due to insufficient fluidity of the lubricating oil, resulting in difficulty in gear synchronization during gear shifting and the generation of gear-smacking sounds. This will seriously wear the synchronizer and gear tooth surfaces for a long time, reducing the service life of the transmission.
Automatic transmissions also face severe challenges in low-temperature environments. As the core component of the automatic transmission, the torque converter has an increased viscosity of the transmission fluid at low temperatures, which will lead to a decrease in power transmission efficiency. Power hysteresis may occur when the vehicle starts. After the driver steps on the accelerator, the engine speed increases but the vehicle speed increases slowly, affecting driving responsiveness. At the same time, the hydraulic control system of the automatic transmission relies on the flow of transmission fluid to transmit pressure signals. Insufficient transmission fluid fluidity at low temperatures will cause the shift solenoid valve to delay action, inaccurate shift timing, and shift setbacks or shocks, which will not only affect ride comfort, but may also cause additional impact loads on the clutch, brake and other actuators inside the transmission.
Low temperature environments may also cause hardening and shrinkage problems of vehicle gear box seals. Most transmission seals are made of rubber, and low temperatures will reduce their elasticity, making them hard, brittle and easy to break. For example, the oil seals at the input shaft, output shaft, etc. may shrink at low temperatures and create gaps between the shaft necks, resulting in lubricating oil leakage. The failure of seals will not only reduce the amount of lubricating oil, aggravating the problem of poor lubrication, but also allow external impurities such as moisture and dust to enter the gearbox, contaminate the lubricating oil, further damage the normal operation of the lubrication system, and even cause serious faults such as gear rust and bearing jamming.
For the gearbox of new energy vehicles (such as reducers or electronic control drive systems), the impact of low temperature environment is more complicated. This type of gearbox usually integrates motors and electronic control units and is more sensitive to temperature. The increase in lubricating oil viscosity at low temperatures may cause insufficient lubrication of motor bearings, abnormal noise and vibration, and increase the running resistance of the motor, affecting energy transfer efficiency and reducing the vehicle's cruising range. In addition, the sensors and actuators of the electronic control system may experience signal transmission delays or malfunctions at low temperatures, resulting in failure of the gearbox's shifting logic or power distribution strategy, affecting the vehicle's power performance and driving safety.
In order to cope with the adverse effects of low temperature environments on gearboxes, vehicle manufacturers usually take a series of technical measures. For example, synthetic lubricants with better low-temperature fluidity are selected, and the freezing point of lubricants is reduced through chemical formula optimization; heating devices are installed inside the gearbox, such as electric heating elements or using engine waste heat to preheat the lubricant to improve the lubrication effect during low-temperature startup; seal materials are improved, and low-temperature resistant rubber or composite materials are used to reduce the risk of seal failure at low temperatures. At the same time, when using the vehicle in a low-temperature environment, the driver should pay attention to preheating the gearbox and avoid high-load driving immediately after a cold start, so as to reduce mechanical wear caused by poor lubrication and extend the service life of the vehicle gear box.
