Diesel filter is one of the main components of the fuel supply system, its function is diesel engine with rust, dirt, dust, wax crystal and water pollutants to the fuel pump, including oil pump and fuel injection pump gear pump, injector and other precision components reduce wear to a minimum. In addition to the impact of the filter performance of the engine emissions and life, the impact of its leakage on the engine and even the vehicle's safety and environmental impact, but also more and more people's attention.
Filter seat is one of the key components of the diesel oil filter, which is generally used in aluminum die casting.
Aluminum die casting is a kind of pressure casting parts, using installed pressure die casting machine die casting machine casting, heating liquid aluminum or aluminum alloy poured into the die casting machine enters the material mouth, by die casting, casting a restrict mold shape and size of the aluminum parts or aluminum alloy parts, such parts is usually called aluminum die casting. Aluminum die casting has the advantages of high strength, good surface quality, high production efficiency and low cost, and is suitable for mass production. But at the same time due to the die casting process is completed in the cavity, the cavity of the gas to be discharged, so often the internal pores smaller, dense only in the surface form 0.2-0.9mm. Sincerely, dense layer have sealing effect. Because after the completion of the filter base of die casting machine, or die casting mould to after a certain number of adhesion phenomenon, the inevitable emergence of stomatal exposure and the small pores to only 0.1-0.3mm, with naked eye is extremely difficult to find, which is may lead to products in use process appear leakage phenomenon. Because the air hole is the inevitable defects of die casting process, so to improve the reliability of the product can only start from the prevention and inspection.
In prevention, the measures to increase the follow-up process using microporous sealing technology, by vacuum infiltration, sol thermosetting closed pores, improve the product qualified rate. The process is now very mature, a pass rate of infiltration can reach more than 98%, the effect on the 0.1-0.3mm of the micro hole is particularly evident. But the sealing effect of the pores above 0.5mm was obviously weakened. In the detection, aluminum die casting touch the water, if not timely drying, exposed to air after very susceptible to mildew, and aluminum die casting internal hole caused by leakage is very small. If the wet test, bubble small and discontinuous, visual inspection is not easy to distinguish, it is prone to omissions, so at the time of detection generally use dry-type test method.
Dry test generally use the leak detector, is on the verge of specimen placed in the air, under the constant temperature environment, to a certain pressure on specimen of inflation and stabilizing and pressure sensors will monitor inside the cavity pressure changes. In leak detection stage, the tester call stored without leakage parts (standard parts) pressure losses characteristic curve, and measured the characteristic curve of parts compared to determine the product leak or not. The method has the advantages of high efficiency and no damage to the tested parts. The disadvantage is due to gas expansion and contraction characteristics significantly, thus influence by environmental temperature transformation is relatively large.