How to maintenance metric cam follower bearing?

Metric cam follower bearing is a component of piston engine. Its function is to control the opening and closing of the valve. Although the rotational speed of camshaft in four-stroke engine is half that of crankshaft (the rotational speed of camshaft is the same as that of crankshaft in two-stroke engine), it is still very high and needs to bear a lot of torque. Therefore, in the design, the requirements for strength and support of metric cam follower bearing are very high, and the metric cam follower bearing material is usually special cast iron, and occasionally forgings are used. Because the law of valve movement is related to the power and operation characteristics of an engine, the design of camshaft occupies a very important position in the design process of the engine.

Structural characteristics of metric cam follower bearing

1. Thick outer ring needle roller bearing and bolt combination structure

2. There are metric cam follower bearing and inch cam follower bearing in size.

3. The bearing bolts are provided with lubricating oil passages.

4. For the convenience of installation, the big end of the bearing is designed with "straight" and "hexagonal hole" wrench assembly methods.

5. The outer surface of the outer ring has cylindrical shape and spherical shape, which can be selected according to practical applications.

6. Full-roller type is suitable for occasions with heavy load and low rotating speed.

7. The eccentric type can conveniently and accurately adjust the axial position of the bolt when installing the bearing.

 

Maintenance of metric cam follower bearing

(1) Check the curvature of camshaft. With the journal at both ends as the fulcrum, the radial runout shall not exceed 0.03mm If it exceeds 0.1Omm, it can be corrected by cold pressure correction method.

(2) When the lift of the cam is not less than 5% of the specified value, it is allowed not to grind the cam, but the cam base circle and the radial circle runout tolerance of the cam base circle to the camshaft axis should be checked; The overhaul standard is 0.03mm, and the allowable overhaul is no more than 0.05mm.

(3) The surface of the cam is rough, damaged and pitted, which should be polished. When the wear of the top of the cam exceeds 1.00mm, the top of the cam should be grinded after surfacing to restore its original size and shape, or replaced.

(4) If the tooth surface of the oil pump drive gear on the camshaft is rough or worn more than 0.50mm, it should be repaired. Individual gear teeth are damaged, and it is allowed to continue to be used after grinding off acute angles without affecting the use. The surface roughness of the eccentric wheel driving the oil transfer pump shall not exceed O.80μm m. When the eccentric wear exceeds 2.00mm, the camshaft should be repaired or replaced by surfacing welding.

(5) Cylindricity tolerance of each journal of camshaft: overhaul standard is 5μm, overhaul allowable is no more than 15μm, and service limit is 25 μ m.

(6) The radial runout tolerance of the journal and the end face runout error of the axial thrust end face of the camshaft with timing gear are not more than 35 μ m.

 

Adjustment of axial clearance of camshaft

The axial clearance of camshaft shall comply with relevant regulations, and the thickness difference between thrust flange and spacer can also be measured directly by thickness gauge. When the axial clearance exceeds the specified value due to wear of thrust flange, the thrust flange with standard thickness should be replaced, and the thickness of spacer ring should not be arbitrarily reduced, otherwise, the axial position of cam will be changed and the accuracy of valve timing will be affected.

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