Excavator lubrication system oil radiator and cooler components

1. Oil radiator and cooler

When the engine is running, because the oil viscosity becomes thinner with the increase of temperature, the lubricating ability is reduced. Therefore, some engines are equipped with oil coolers. There are two types of oil coolers: air-cooled and water-cooled. The air-cooled type is usually called an oil radiator. Its function is to reduce the temperature of the engine oil and maintain a certain viscosity of the lubricating oil.


(1) Oil radiator

The oil radiator is composed of radiator pipe, pressure limiting valve, switch, oil inlet and outlet pipes, etc. Its structure is similar to the cooling water radiator. The oil radiator is generally installed in front of the cooling water radiator, in parallel with the main oil passage. When the oil pump is working, on the one hand, the oil is supplied to the main oil passage, and on the other hand, the oil inlet pipe enters the oil radiator through the pressure limiting valve and the oil radiator switch, and after cooling, it flows back to the oil pan from the oil outlet pipe, and then circulates.


(2) Oil cooler 

The oil cooler is placed in the cooling water circuit, and the temperature of the cooling water is used to control the temperature of the lubricating oil. When the temperature of the lubricating oil is high, it is cooled by the cooling water. When the engine starts, it absorbs heat from the cooling water to increase the temperature of the lubricating oil quickly. The oil cooler is composed of a shell made of aluminum alloy, a front cover, a rear cover and a copper core tube. In order to enhance cooling, heat sinks are fitted outside the tube. Cooling water flows outside the pipe, while lubricating oil flows inside the pipe for heat exchange. There is also a structure in which oil flows outside the pipe and water flows inside the pipe.


2. Valve

There are several pressure limiting valves and bypass valves in the lubrication system to ensure the lubrication system works normally.


(1) Pressure limiting valve

The oil supply pressure increases with the increase of engine speed, and when the oil passage in the lubrication system is blocked, the bearing clearance is too small or the oil viscosity is too high, the oil supply pressure will also increase. Therefore, a pressure limiting valve is installed in the oil pump and the main oil passage of the lubrication system to limit the maximum pressure of the oil to ensure safety. When the oil pressure on the oil pump and the main oil passage exceeds the predetermined pressure, it overcomes the spring force of the pressure limiting valve, opens the valve, and a part of the oil flows into the oil pan from the side passage, so that the oil pressure in the oil passage drops to the set normal After the value, the valve closes.


(2) Bypass valve

The bypass valve is used to ensure the smooth flow of the oil passage in the lubrication system. When the oil filter is blocked, the oil directly enters the main oil passage of the lubrication system through the bypass valve connected in parallel to prevent the main oil passage from being cut off. The structure of the bypass valve and the pressure limiting valve is basically the same, but its installation position, control pressure, and overflow direction are different. Usually the spring stiffness of the bypass valve is much smaller than that of the pressure limiting valve.


3. Dipstick and oil pressure gauge

The dipstick is used to check the amount of oil in the oil pan and the level of the oil level. It is a piece of metal rod with a flat bottom end and engraved lines. The oil level must be between the upper and lower engraved lines on the oil dipstick. The oil pressure gauge is used to indicate the size of the oil pressure in the lubricating system when the engine is working. Generally, an electric oil pressure gauge is used. It consists of an oil pressure gauge and a sensor, and the middle is connected by a wire. The sensor is installed on the strainer or the main oil passage, and it transmits the oil pressure felt to the oil pressure gauge. The oil pressure gauge is installed on the dashboard in the cab to display the value of the oil pressure.



4. Crankcase ventilation

When the engine is working, part of the combustible mixture and exhaust gas leak into the crankcase through the piston ring. After the gasoline vapor leaking into the crankcase condenses, the lubricating oil will become thinner. At the same time, the high temperature of the exhaust gas and the acidic substances and water vapor in the exhaust gas will corrode the parts and deteriorate the performance of the lubricant. In addition, because the mixed gas and exhaust gas enter the crankcase, the pressure in the crankcase increases and the temperature rises, which easily causes the oil to leak from the oil seals, gaskets, etc. For this reason, the general automobile engine has a crankcase ventilation device, so that the mixed gas and exhaust gas entering the crankcase can be drawn out in time, so that the fresh gas enters the crankcase and continuously convection. There are generally two ways of crankcase ventilation: one is natural ventilation and the other is forced ventilation.


(1). Natural ventilation

The ventilation method in which the gas extracted from the crankcase is directly introduced into the atmosphere is called natural ventilation. Diesel engines often use this natural crankcase ventilation method. A drooping air outlet pipe is connected to the valve chamber cover or the lubricating oil filling port connected with the crankcase, and the pipe mouth is cut into an oblique mouth, and the direction of the cut is opposite to the driving direction of the car. Utilize the air flow of the car and the cooling fan to form a certain degree of vacuum at the air outlet to extract the gas from the crankcase.


(2). Forced ventilation

The gas extracted from the crankcase is introduced into the intake pipe' of the engine and sucked into the cylinder for combustion. This type of ventilation is called a forced-ventilation gasoline engine—generally, this kind of crankcase is used.


In this way, the mixed gas escaping into the crankcase can be recycled and used, which is beneficial to improve the economy of the engine. Forced ventilation can recycle the mixed gas and reduce environmental pollution. Gasoline engines are generally used more often, and diesel engines used in construction machinery generally use natural ventilation. Ventilation is located in the oil


The chamber cover is equipped with a filter device to prevent dust and impurities from entering the crankcase.