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How to Fix Diesel Generator Camshaft Damage

Oct. 25, 2018


Common damage characteristics of diesel generator set camshaft


The diesel generator set camshaft has a valve train camshaft and a fuel injection pump camshaft. The damage of the fuel pump camshaft in use is similar to that of the camshaft in the valve train, mainly including cam profile wear and camshaft bending. These damages will directly affect the timing of the gas distribution of the diesel generator set and the timing of fuel supply, affecting the normal working quality of the diesel generator set, resulting in overloading of other cylinders and seriously damaging the safety of the diesel generator set. Therefore, it is particularly urgent to timely repair and repair the damage of the cam surface of the diesel generator set and reduce the failure rate. The following is a brief introduction to the main damage characteristics of the diesel generator set camshaft.


How to Fix Diesel Generator Camshaft Damage.jpg


1. Diesel generator set cam face wear

 

When the camshaft is at rated speed, the linear speed is up to 1.3 m/s. During the oil supply process of driving the plunger upward, the friction and pressure of the cam surface are quite large due to the compression pressure of the fuel and the spring pressure. When the point of death is turned, the back side of the cam is subjected to the impact of the elastic force. Therefore, there are different degrees of wear on both sides of the cam, especially on the side of the cam lift, in addition to the wear, and a little fatigue pit. When the cam wears up to 0.3 mm, it will obviously affect the accuracy of the oil supply time and the fuel injection continuous angle, resulting in poor engine fire, power and economy. When there is a pit in the surface of the genset cam, the surface roughness will decrease, and if it continues to be used, it will accelerate the wear.

 

2. Diesel generator set camshaft neck wear

 

The journal and the inner ring of the ball bearing are tightly fitted and generally do not wear. After the individual shafts wear out, the radial clearance is increased, which affects the speed regulation performance of the engine.

 

3. Diesel generator set cam keyway wear

 

Generally, it is not common. In some cases, the installation of the transmission bushing is loose, so that the impact occurs during operation and wear. After wear, the oil supply time will lag behind.

 

4. Diesel generator set camshaft broken


The broken part is mostly on the tapered cylinder of the shaft head. This is because a small number of camshafts have inherent defects during manufacture, fatigue wear during operation, and finally lead to breakage or jamming or breaking of the plunger, causing the camshaft transmission torque to rise significantly, exceeding the permissible stress of the camshaft, due to the conical head taper. The section of the part is small and it is easy to break here.

 

Common damage causes and maintenance methods for camshafts of diesel generator sets

 

Damage to the camshaft of the diesel generator set will directly affect the timing of the valve timing and fuel supply timing of the diesel generator set, and damage the normal operation of the generator set in severe cases. Therefore, it is very important to eliminate the cause of the damage of the cam surface of the diesel generator set and reduce the failure rate. The reasons for the damage of the diesel generator set are analyzed, and the maintenance method of the camshaft is discussed to improve the maintenance quality of the camshaft of the fuel injection pump of the diesel generator set.

 

Common causes of damage to camshafts of diesel generator sets

 

1. When the oil pump is assembled, if the axis of the push rod is deflected during the assembly process, the roller and the camshaft cam are not in line contact, but a point contact occurs, resulting in uneven force, causing the roller to roll poorly, resulting in the roller and the cam. Work surface wear is intensified.

 

2. The lower body of the fuel injection pump and the cam are pressure-lubricated, and the oil is supplied to the lower body of the pump through the hollow bolt, the small copper pipe for supplying oil, and the joint body, and the cam and the roller are lubricated, which is often caused by the blockage of the hollow bolt, the small copper pipe and the joint body. The oil is not smooth, the heat generated by the cam and the roller can not be lost in time, initially causing the cam and the roller to be injured. The roller copper sleeve is worn out of excess, and the roller rolling on the cam causes the impact on the roller, which aggravates the wear of the copper sleeve and the positioning pin, sometimes Causes the copper sleeve to lock on the pin. Sliding friction occurs between the roller and the cam, as the roller forms an irregular ellipse and the top of the cam is severely damaged.

 

3. The clearance between the valve body and the push rod is too large. Due to improper fitting of the push rod, the clearance between the valve body and the push rod is too large, and the clearance between the push rod and the roller pin is too large, which can cause the guide pin to be poorly guided, and the roller axis and the cam axis are deviated, resulting in deviation The gas distribution roller is indexed at a small angle to injure the camshaft valve cam.

 

Diesel generator set camshaft inspection method

 

1. Check the axial clearance of the camshaft, press the camshaft end, tilt the cam axial side, adjust the hands to "0", and then move the cam shaft to the other side. The indication value of the hands is the axial direction. The gap (0. 05~0. 15 mm is normal). If the axial clearance exceeds the specified value, it can be adjusted by replacing the adjustment spacers of different thicknesses. If the axial clearance is too large, replace the thinner gasket; if the axial clearance is too small, replace the thicker gasket. If the camshaft is left at 0. 05 mm, the right gasket (thickness is also 0. 05 mm) is taken out and placed on the left.

 

2. Check the camshaft curvature. If the degree of curvature exceeds 0.05 mm, the method of cold pressing should be used for repeated straightening. It is not advisable to use a hammer (hand hammer) to hard-hit. There are only two cases of camshaft bending: one is the bending of the central part of the camshaft; the other is the bending of the end of the camshaft (the end connected to the automatic oil feeder), which is equipped with a gear-driven type of oil supply. When the automatic advancer is used, the front end of the camshaft is most often bent. This kind of bending makes the tapered roller bearing set at the front end of the camshaft the most powerful, which makes the bearing race "out of the circle", the bearing cover loose and outward, the camshaft turbulence increases, the cam, the tappet ball The wear of the timing gears that mesh with each other in the gearbox is accelerated. In severe cases, the bearing roller support frame may be broken, the lubricating oil in the pump may leak from the loose bearing cover edge, the timing gear may be cracked, etc., therefore, the cam The bending of the shaft must be straightened in time.

 

3. Check the journal at the oil seal of the camshaft. If the depth of the groove is more than 0. 10 mm, repair repair is required. Check the cooperation of the camshaft keyway and the semicircle key. Check the camshaft taper and threads. If it is rough or damaged, use a stone to grind or replace the camshaft. Check the cam on the camshaft and replace the camshaft if it is damaged, deformed or severely worn. The amount of cam wear should not exceed 0.5 mm. Check the radial runout of the camshaft. If it exceeds 0.5 mm, it should be cold-pressed. Check the camshaft axial clearance. If it exceeds 0.15 mm, adjust or replace the camshaft.

 

4. Grinding the cam profile and roller, the roller and cam profile ensure uniform contact during assembly; the pusher body and the pump lower body should be carefully cleaned before inspection and check whether the roller surface is pocked or scratched, and its rotation and roller axle whether the up and down movement is flexible and whether the gap is too large.

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