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Reasons for early damage of bearing gas distribution structure and matters needing attention
Source: China Bearing Network Time: 2013-11-25
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First, the primary cause of early damage of gas distribution tissue . Poor repair quality The outstanding problem in repair work is that the processing quality of the valve and valve seat working surface is not up to the demand; the ablation, collapse and early damage of the working surface are formed, and the cooperation gap, touch area and each of the camshaft bearing in the scraping process Bearing concentricity does not meet demand; accelerate wear and tear; present abnormal noise to form early damage, valve guide when replacing new parts; reaming quality does not meet regulatory requirements; directly affect valve and valve seat service life.
2. Inappropriate use of repair data: Scientific selection of repair data during repair is an important reason for the early damage of the machine. For example, the width of the touch surface of the valve and the valve seat; the regular intake valve is 1 to 2. 2 mm; the exhaust valve is 1. 5~2. 5mm. But in the repair; everyone tends to think that the width is narrower than the narrow one; the upper limit of the habit is used or the upper limit is close to the upper limit; therefore, the width of the newly-operated valve door is already close to the limit. Void; general car rules are 0. 2 ~ 0. 25mm; but in the protection adjustment also mistakenly think that the gap is a little larger than the smaller; thus; the upper limit is applied. In practice, the gap is too large; not only reduces the engine power; Will present a percussion sound (valve from the valve) and early damage.
Second, the matters that should be paid attention to during the repair<br> The gas distribution organization has more manual work in the repair; because of the technical differences and understanding errors of the repair personnel; the repair quality is difficult to reach the rule requirements, so it should be uniquely emphasized in the repair The quality of the repair of the gas distribution organization; and the adoption of useful methods to improve the quality of repair; to extend its life.
1. Light grinding of the valve: in the repair operation; if the valve exhibits ablation, pitting and depression; all should be light-grinded (replace the valve when severe). Generally, it is carried out on the valve light grinder; Difficulty: First, make sure that the valve head is concentric with the rod; otherwise, it should be straightened first. Second, the amount of light grinding should be as small as possible on the premise that the cone can be polished. Third, try to improve the surface finish. Fourth, the valve stem The end of the depression should be smoothed.
2. Reaming of valve seat: valve seat reaming is generally a craft operation; it should pay special attention to three problems: one is to eliminate the depression and mottled; the hinge can be hinged out; the smaller the reaming, the better. It is the force to be even when reaming; the knife is lighter; the less hinge is more investigated; to ensure less reaming and higher finish, the third is to match the valve; to determine the orientation and width of the work surface. It should be adjusted to the middle and lower part of the valve cone; the upper and lower reamer can be adjusted upwards or downwards. The width of the working surface; the intake valve can be grasped at 0.9 mm (rule is 1-2. 2 mm); The door can be grasped at 1. 4mm (rules are 1. 5 ~ 2. 5mm). Practice has proved that the above width is after the valve and valve seat grinding; the intake valve can reach 1mm; the exhaust valve can reach 1. 5mm; The lower limit of the width; can greatly improve the life of its application.
3. Grinding of the valve: The grinding of the valve is divided into two conditions; one is that the valve and the seat need only fine pitting; the grinding is not required for light grinding and reaming, and the second is that the valve and the seat have been passed through the light grinding and reaming. Grinding. The former is first ground with rented sand; after grinding the pittings; grinding with fine diamonds; finally applying oil to the grinding; until the seal meets the requirements; the width is in accordance with the rules. The latter only needs sealing to meet the demand. Grinding; but must pay attention to the operation; do not use too much force; do not hit the valve up and down; otherwise it will show concave sand marks; affect the quality of repair.
4. Reaming of the valve guide: the cooperation gap between the valve stem and the valve guide is the key to determining the life of the valve guide; therefore, when replacing the new valve guide; the cooperation gap should be strictly grasped during the reaming; the lower limit of the regular gap of each model can be used; Useful extensions to extend the life.
5. Scratch of camshaft bearings: The scraping of camshaft bearings is attributed to the craft work; ensuring the quality is inevitable. It is convenient for scraping; it is generally processed outside the cylinder; therefore, it should pay special attention to four problems: First, it is necessary to determine the inner hole after the bearing is scraped. The diameter is expressed by the formula: inner hole diameter = measured value of journal diameter + lower limit of cooperative gap + measured value of bearing and seat hole interference). Second, it is necessary to pay attention to the inner hole and outer circle of the bearing during scraping. Coaxiality, the third is the side scraping edge and the journal test (the gap is the interference + cooperation gap); and ensure that the touch marks are evenly distributed, the fourth is to press the bearing into the seat hole; should pay attention to the positive oil hole. After loading the camshaft; change the number of turns; properly trim as appropriate; the touch area should reach more than 75% and spread evenly; the gap meets rule 6. Adjusting the clearance of the valve foot: the parts of the gas distribution structure are in normal operation; following the wear of the parts; the clearance of the valve foot will change. If the cam, the valve rod end face and the touch surface of the tappet are worn, the gap will become larger; After the valve seat wears, the gap changes again. 虼 诘髡 诘髡 诘髡 θ 湎 湎 湎 闹 闹 渲 渲 . . . . . . . . . . . . . . . . . 如 如 如 如 如 如 如 如 如 如 如 如 如 如 如 如 如The situation; also considered the measurement error problem; can fully ensure the completion of the valve foot gap effect.
In addition; the repair of other components and parts of the gas distribution organization; the first is to strengthen the removal and inspection of the parts; and correct adjustment and installation according to the rules; to complete its harmonious operation.
In practice operations; only need to protect according to the above matters; that is, it can be useful to extend the life of the valve organization.
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