The precautions for repairing the camshaft of the diesel engine are as follows:
The damage of the camshaft of diesel engine, such as shaft bending, shaft neck and bearing and high wear of cam outline, is mainly due to its long structure, small contact area of cam and tappet, high unit pressure and high relative sliding speed in the work.
Various kinds of damage to the camshaft of diesel engine often affect each other. For example, the shaft neck and the bearing fit loose and loose, and the axis bending will aggravate the wear of the camshaft gear teeth and the journal bearing. Even the gear will produce noise or break the tooth when the gear works. This will accelerate the wear of the cam and the journal. Some damage will not only affect the accuracy of the valve train, but also bring difficulty to the adjustment of the valve clearance, so attention should be paid to the maintenance work.
3 important matters of attention when repairing the camshaft of a diesel engine:
(1) the appearance of the early wear of the valve cam surface of the valve cam is basically the same, which is mainly concentrated in the vicinity of the top, especially the highest position. The cam wear will reduce the height of the cam and make the valve opening insufficient.
The main cause of early wear is due to poor lubrication. This is because there are two kinds of lubrication for the cam and tappet bottom of the diesel engine camshaft: one is spatter lubrication, the other is the oil entering the oil channel, and the oil channel on the bearing seat of the convex axle is flowing into the rocker arm through the rocker shaft seat, and the rocker arm shaft, rocker arm, and the push rod ball are lubricated. Head, then from the push rod into the tappet, and then out of the lower oil hole, lubricate the cam and the tappet bottom. If the oil surface is too low or the tappet, the cylinder body bearing hole gap is too small, the oil can not flow in the tappet. That is, the cam and the tappet bottom are not lubricated. The wear is serious.
In addition, the valve tappet can not operate normally, it is also a reason for the early wear of the valve cam surface. When working normally, the tappet should have a rotating movement in order to wear evenly and prevent the occlusion. If the tappet is bonded with the shaft hole, the push rod is bent and the bottom sphere of the tappet is incompatible with the slope of the convex wheel and so on, so that the tappet is at work. Not dead rotation, that is, will cause aggravation of wear.
The inspection of cam wear can be used to measure the distance between the center line of the cam to the base circle (i.e. the cam lift) by the spiral micrometer. For example, the intake cam lift of Sofim 8140 diesel engine is 9.5mm, and the exhaust cam lift is 10.5mm. if the cam lift is more than 0.5mm, it is necessary to wear or replace the new parts.
The cam grinding mill should be carried out on the camshaft grinder. If the cam is worn out, the cam working section is sunken, or has more corrosion spots, it can also be worn against the cam template with the file and the oil stone. However, it is necessary to keep the outline shape line and the surface roughness of the cam and meet the standard. Otherwise, the new camshaft should be replaced.
(2) check and adjust the axial clearance and allow the axial clearance of camshaft to exceed the allowable value, which will make the valve timing dish change greatly, resulting in insufficient intake of diesel engine and poor exhaust.
A common method for detecting the axial clearance of the camshaft is to pry the camshaft forward and check it between the timing gear and the thrust flange with a tape gauge. The clearance is generally required to be different from the other diesel engine for the 0.07~0.25mm.WD615 diesel engine camshaft, and the camshaft can be pried forward in the first shaft neck slot and convex. The wheelset limit plate is measured with feeler gauge. The standard value should be 0.1~0.4mm..
When changing clearance, it can be adjusted by replacing thrust plates, limiting plates or adjusting rings with different thickness.
(3) the inspection method of bending of the camshaft for the maintenance of the bending deformation is similar to the crankshaft inspection method. First, the camshaft is placed on the two V shaped iron frame parallel to each other, or the camshaft is fixed to the two thimble of the lathe. The dial gauge is used to measure the pulsation of the middle axle neck. The 1/2 of the dial readings, that is, the cam shaft. If the half axle neck beat exceeds 0.025mm, the cold pressing method should be used to correct or replace the new parts.
The roundness and cylindricity of the camshaft journal worn should generally be less than 0.015mm.. When the wear degree of the camshaft is beyond the specified value, the journal should be grinded or replaced.
The grinding axle neck can be carried out on the outer grinding machine, requiring the uniform repair of the camshaft neck. The normal maintenance size of the journal is divided into 6 grades according to the GB/T3808-1983 standard, and the size of the camshaft neck of the diesel engine repair mill is divided into 4 levels, that is, -0.25mm, -0.50mm, -0.75mm and -1.OOmm., and should be based on the grinding before grinding. The bearing is selected for bearing wear and then the grade of maintenance dimensions is determined.
