Arc gear elastohydrodynamic lubrication theory: Involute gear meshing is equivalent to two cylinders, and the direction of motion is on the normal plane of the gear teeth. The meshing of the circular arc gear is equivalent to the rolling of the two circular arc cylinders, and the mutual motion and geometric relationship are relatively complicated. The pitch circle radius of the two gears is R01 and R02, the end face pressure angle As, and the contact point shift distance is l. Since the arc radius of the convex tooth profile on the end face is slightly smaller than the arc radius of the concave tooth profile, the two teeth should theoretically be in point contact. However, after the running-in, the contact portion rapidly expands, occupying the entire tooth height. 60 to 80 or more. Therefore, the meshing of the circular arc gear can be regarded as the line contact of the two circular arc cylinders, and the radius thereof is RK1 and RK2, the width is 2L, and the radius of the arc is l.
According to the meshing geometry of the arc gear, the normal curvature of the two conjugate tooth faces tangent to the contact trace can be derived. Thus, the geometry, movement speed and load of a pair of two arcuate cylinders that are engaged with each other can be obtained. Then according to the Dowson-Higginson formula, the diesel flowmeter can be simplified by considering the influence of the arc surface and the arc gear, and the minimum oil film thickness hmin of the arc gear elastohydrodynamic lubrication can be obtained.
After calculating the minimum thickness of the oil film, the lubricant investment must check the extent of the thickness of the oil film covering the entire working surface to determine the lubrication state between the moving pairs and whether it plays a role in preventing wear. The ratio K of the oil film thickness to the root mean square deviation of the machined surface roughness is usually quoted as a measure of the film thickness ratio, that is, K = hminH2jf1 H2jf2.
When K≤1, the two tooth surfaces are in the boundary lubrication state, and the tooth surface is prone to wear, abrasion and gluing;
At 13 o'clock, the two tooth surfaces are in full elastohydrodynamic lubrication state, and the tooth surface does not wear and glue.
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