Linsheng said: In order to ensure reliable and effective braking, the car with air brake must strictly control the oil content in the compressed air. Excessive amount of oil in the compressed air causes pollution of the brake system, causing the brake to malfunction and causing a traffic accident, resulting in serious loss of life and property. The oil in the compressed air is mainly due to the smashing of the lubricating oil in the crankcase of the air compressor, so it must be solved.
The oil contained in the compressed air is mainly due to the simmering of the lubricating oil in the crankcase of the air compressor. Therefore, the problem of simmering oil must be solved.
A. Oil supply of piston ring and its improvement
1. The process of lubricating oil
After the piston ring of rectangular cross section is inserted into the piston ring groove, there is generally a gap of 0.04 mm to 0.08 mm in the height direction. When the air compressor is in operation, the ring is swayed up and down in the ring groove, and the gap between them constitutes a periodically varying sealed volume. When the piston descends, the ring is pressed against the upper side of the ring groove, and the lubricating oil scraped on the surface of the cylinder wall is injected into the lower portion and the bottom gap of the ring groove; when the piston is ascending, the ring is pressed against the lower side of the ring groove. The lubricating oil is squeezed into the upper gap of the ring groove. Repeatedly, the lubricating oil is continuously scraped into the cylinder and discharged with the compressed air, resulting in an increase in the oil content of the compressed air.
2. Application of twisted ring
In order to resist the passage of lubricating oil through the gap of the ring groove, the twisted ring has been widely used in vehicle air compressors, and its structural form is more twisted and reverse twisted.
The positive twist ring is a groove or chamfer at the inner or outer edge of the rectangular cross-section ring. When installing, the inner edge is cut or chamfered upward and the outer edge is grooved or chamfered downward. During the movement of the twisted ring, a significant dish-like deformation occurs, and the edge of the ring is in linear contact with the side wall of the ring groove and the wall of the cylinder. This not only reduces the pumping action of the piston ring, but also improves the airtight performance of the piston ring. The wedge-shaped annulus formed by the tangential or chamfered positive twist ring and the cylinder wall surface can oil up and down, not only the lubrication between the cylinder wall and the piston (piston ring) group, but also Reduced the upper jaw of the lubricant. Since the first sealing ring is subjected to greater gas pressure and is prone to early wear, it is preferable to use a positively twisted ring with an inner edge grooving or chamfering.
The structure of the anti-twist ring is similar to that of the positive twist ring, except that the ring is mounted in the opposite way, ie the inner edge is slotted or chamfered downwards and the outer edge is slotted or chamfered upwards. Therefore, the twisted ring can generate a dish-shaped deformation opposite to the positive twisted ring under the action of the gas pressure, and can better suppress the flaw on the lubricating oil. However, due to the inverted wedge formed by the outer edge of the ring and the cylinder wall, the squeegee is caused by scraping into the cylinder. Therefore, it is not suitable for the first sealing ring.
3. Improvement of piston ring groove
The improvement of the piston ring groove is mainly to control the assembly gap between the piston ring and the ring groove, and improve the surface roughness and shape tolerance of the ring groove. The assembly side clearance of piston ring and ring groove of Rudong Windmill air compressor is changed from 0.04mm~0.08mm to 0.04mm~0.065mm, and the verticality error of the control ring groove side to the piston center line is not more than 0.01mm per 100mm sampling length. The surface roughness Ra=1.6, in order to ensure a good fit of the ring and the ring groove, improve the airtightness of the cylinder and reduce the upper limit of the lubricating oil.
B. Other reasons for the sputum on the lubricant
1. The influence of the piston ring on the intercept and lateral forces
The forward interception of the piston ring to the cylinder wall includes the initial spring force of the piston ring and the gas pressure in the operation of the air compressor. It is the main cause of the wear of the piston ring and the cylinder wall, especially the first air ring wears more. Piston rings and cylinder wall squeegees increase as wear increases. In order to reduce the amount of lubricant, it is necessary to control the wear of the piston ring. To this end, the material of the piston ring should be made of materials with high wear resistance, hardness and toughness, and the matching clearance between the piston and the cylinder wall should be strictly controlled.
2. Influence of oil return cross section at the bottom of oil ring groove
The lubrication of the cylinder wall of the air compressor of the vehicle is usually based on splash lubrication. However, when the pressure of the lubricating oil in the crankcase is high, the amount of splash increases. If the oil ring is poorly scraped, it will cause oil. Therefore, increasing the oil return hole cross section can resist the simmering oil.
3. The effect of temperature
When the air compressor is working, due to the compression of the gas and the friction of the moving parts, the temperature of the body is raised to lower the viscosity of the lubricating oil, thereby increasing the enthalpy of the lubricating oil. To this end, the specifications of the oil should be selected according to the region and season.
4. The effect of blockage and excessive pressure
The air compressor oil return pipe is blocked. Because the engine air pump is supplied with oil from the main oil passage of the engine, if the oil return oil pipe of the air compressor is blocked, the oil cannot return to the oil sump of the engine, causing the crankcase of the air compressor to be filled with oil, the oil level rises, and the oil Forced to break into the cylinder and cause simmering oil, and at the same time, it will cause serious oil leakage at both ends of the pump.
The air filter core on the air compressor is clogged, the air intake resistance of the air pump is increased, the air intake amount is reduced, and the air in the cylinder becomes thin, thereby increasing the oil absorption effect of the cylinder and causing the air compressor to simmer oil.
The engine oil pressure is too high, and sometimes the air compressor is smashed.
C. Air compressor oil hazard
(1) After the air compressor is simmered, the oil will enter the car air reservoir. When the car brakes, the oil enters the brake valve. After a long time, the rubber seal in the valve expands and relaxes, causing the judgment. The motion control work failed. At the same time, the oil will also cause early corrosion damage to the brake hose and brake cup, which will affect the safety of driving.
(2) After the oil is blown into the cylinder head of the air compressor, the exhaust valve and the valve spring on the cylinder head of the air compressor are prone to cementation due to the high pressure, which affects the normal operation of the air compressor and finally causes air pressure. The machine does not work.
(3) After the air compressor is simmered, the engine oil consumption will increase, which will affect the lubrication of the engine, increase the transportation cost of the vehicle, and cause the engine to exceed the standard, causing environmental pollution.
linsheng concluded that through the improvement of the piston ring groove, the surface roughness and the precision of the assembly are improved, and the airtightness of the ring and the ring groove in the cylinder is ensured. Use the improved piston ring groove, reasonably select and correctly assemble the piston ring, and consider factors such as material and working temperature; often check whether the return line and intake air are unblocked, and replace the engine oil and oil filter according to the standard, which can effectively control the air pressure. Better control and resolution of the harm of the machine oil