รายละเอียด:
Structure and Features
IKO Needle Roller Cages for Engine Connecting Rods are bearings for use in engine connecting rods. These bearings have superior performance proven in high performance engines of racing motor cycles, and are widely used in small motor vehicles, motor cycles, outboard marines, snow mobiles, high-speed com- pressors, etc. and also in general-purpose engines. Bearings for engine connecting rods are used under extremely severe and complex operating conditions such as heavy shock loads, high speeds, high tem- peratures and stringent lubrication.
Needle Roller Cages for Engine Connecting Rods are lightweight, and have high load ratings and high rigidi- ty as well as superior wear resistance to withstand these severe conditions.
Accuracy
The diameter tolerances of needle rollers of Needle Roller Cages for Engine Connecting Rods are classi- fied When the classification symbol is not indicated in the identification number, the classification symbol "B2" is applied.
The tolerance of the cage width Bc is ? 0.2 ?? 0.4 mm. But cages with marks in the Bc column in the dimension tables are manufactured with the following width tolerances.
?:0 ?? 0.2 mm ?:? 0.1 ?? 0.3 mm
Clearance
Radial internal clearances are selected according to the type of engine and the operating conditions (rota- tional speed, load, lubricating conditions, etc.). If a bearing is used with an inadequate clearance, bearing troubles such as seizure, early flaking and noise increase may occur, leading to an engine failure. Therefore, it is necessary to select the clearance carefully according to test results and experience Recommended radial internal clearances are shown in Table 3. When operating at high speeds, it is rec- ommended to select the upper limit of the clearance.
Fit
To obtain the recommended clearance , it is general practice to match a connecting rod, crank pin or piston pin and needle roller cage of suitable tolerances for assembly.
Precautions for Use
When designing a connecting rod, crank pin and pis-
ton pin, the following precautions should be taken, because the raceways are subjected to loads under extremely severe conditions.
1 Material
It is recommended to use carburizing steel because the raceways are subjected to fluctuating loads with frequent and heavy shock loads. Generally, chromi- um molybdenum steel is used. Nickel chromium molybdenum steel is also used.
2 Hardness
The recommended surface hardness of the raceway is 697?800HV (60?64HRC). While the effective hardening depth differs depending on the applica- tions, the general value is 0.6?1.2 mm.
3 Surface roughness
To minimize initial wear and to extend life, it is recom-
mended that the surface roughness of the crank pin
and piston pin be 0.1?mR or less, and the surface a
roughness of the connecting rod large end and small end bores be 0.2?mRa or less.
4 Accuracy
Circularity and cylindricity of connecting rod, piston pin and crank pin.
5 Parallelism and torsional accuracy of connect- ing rod bores.
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