If the engine is the heart of the car, then the filter is the lungs of the car. As one of the three filters, the oil filter is of great significance to the realization of engine performance and durability.
In addition to the filtration effect, the indicators for assessing the performance of the oil filter are also crucial to the pressure loss of the system.
A bypass valve must be installed on the full-flow oil filter, and the performance of the bypass valve has a great impact on the filtration effect of the oil filter and the pressure loss of the system.
If the structural design and manufacturing of the bypass valve are unreasonable, the specific manifestations are that the opening pressure of the bypass valve is too small and the sealing of the bypass valve is not good, resulting in poor filtration effect of the filter element and even failure of the filter element; the size of the bypass valve port is too small and the design If the opening pressure is too high, the system pressure loss will be too large, which will eventually affect the engine performance. The fundamental reason for this problem is that there is no reasonable design and calculation.
The oil filter bypass valve is normally closed.
When the pressure drop of the filter element is too high, enough engine oil (even if this part of the engine oil is unfiltered) is supplied to each friction pair of the engine in the form of transportation or splashing to lubricate and cool the friction pairs, and take away heat and The role of iron filings and impurities.
When the engine is started in a cold state (the oil viscosity is high) or the filter element is blocked and the flow rate is difficult to meet the engine requirements, the bypass valve opens to meet the work needs.
1. The bypass valve is connected in parallel with the filter in the lubrication system. There are two forms of arrangement: one is inside the filter and is glued together with the filter element to form a closed surface. The valve body is spot welded on this surface and opens when the pressure difference between the inside and outside of the valve core exceeds the design pressure; the other is inside the filter. On the assembly, it is located on an interface connected with the oil inlet, and the oil discharge port is connected with the oil outlet.
2. The opening pressure of the bypass valve should be determined according to needs or requirements of the supporting factory, and should meet the filter life pressure requirements. The opening pressure of the bypass valve cannot be too small. If the opening pressure is too small, more unfiltered engine oil will enter the main oil passage, and impurities will most likely enter the friction pair with the oil, accelerating the wear of moving parts. The original resistance of the filter is generally a few KPa~25KPa, and some are relaxed to 30kPa, while the filter life pressure drop is 70KPa. When the pressure drop is lower than the life pressure drop, the bypass valve should generally not be opened unless the cold start motor viscosity It is allowed to be turned on temporarily when it is too large. Therefore, the design opening of the bypass valve cannot be lower than the service life pressure of 70kPa.
However, the opening pressure of the bypass valve cannot be too high.
First, the opening pressure drop is based on not damaging the filter elements. The strength of the filter element is determined by the filter paper material, folding structure, etc. Generally, it can withstand a pressure drop of no more than 300KPa~400KPa. If the pressure exceeds the pressure, the filter element will be crushed or even blocked.
Second, the opening pressure drop should not cause the oil supply pressure in the main oil channel to be too low. During a cold start or when the filter element is clogged with impurities, if the opening pressure is too high, the oil cannot be sent to the friction pairs of the moving parts of the diesel engine in time for lubrication. The pressure in the main oil passage will drop, and the oil supply pressure in the oil passage will continue to be too low, causing serious problems. Serious accidents such as burning tiles and holding the crankshaft may occur. In order to ensure the normal operation of the lubrication system, the resistance should not be greater than about 200KPa when passing the rated flow rate.
Third, does the quality of the oil filter affect the use effect of lubricating oil? The quality of the oil filter directly affects the performance of the lubricating oil. If the quality of the machine filter element is poor, the paint film, carbon deposit, sludge and other sediments and metal debris generated during the lubrication process will be filtered out and enter the cycle again, causing wear and tear on the lubricating parts; on the other hand, the dirt will enter again Circulation will promote the continuous increase of oil deposits, and may also cause filter element clogging and poor oil supply.
Fourth, why are there several filters installed in the engine lubrication system? The more times the oil passes through the filter before it reaches the friction surface, the smaller the gap through which it passes, and the cleaner the oil is. But in turn, the resistance to oil flow will be greater, and the oil supply in the oil circuit will not be smooth, affecting normal lubrication.
In order to solve the contradiction between filtration and smooth oil passage, it is necessary to install several filters with different filtration capabilities in the oil passage of the lubrication system - a collector filter and a coarse filter. If there is no problem with the car, it does not mean that the machine filter has not reached the end of its service life. I forgot that an important design of the engine filter is the bypass valve. Even if the filter paper of the engine filter is blocked, the engine oil can still flow through to lubricate the car. However, the engine oil is not filtered, so you will feel that the engine oil is attenuated. In fact, it is The engine oil is dirty. Remember
