Mixed Lubrication State Research Articles

Effects of tooth profile on scoring behavior in spur gears.

To find out a fundamental tooth profile design policy for the scoring of spur gears, the effects of tooth profiles on scoring behavior were examined taking account of the two-cylinder test results. The tip interference on the approach side markedly affects the scoring phenomena. Both the reduction of the maximum specific sliding on the geometrical working flanks and the avoidance of tip interference on the approach side are the essential conditions to obtain spur gears having superior scoring load capacity. In the mixed lubrication state, where the scoring occurrence has an intimate relation with the working flank bulk temperature, the scoring bulk temperature of a spur gear pair with no tip interference on the approach side can be estimated well by the bulk temperature on the outer surface of the cylinder immediately before seizure in two-cylinder tests.

Effects of tooth profile on scoring behavior in spur gears.

To elicit a fundamental tooth profile design policy for the scoring of spur gears, the effects of tooth profiles on scoring behavior were examined taking into account the two-cylinder test results. The tip interference on the approach side markedly affects the scoring phenomena. Both the reduction of the maximum specific sliding on the geometrical working flanks and the avoidance of tip interference on the approach side are essential conditions when attempting to obtain spur gears having superior scoring load capacity. In the mixed lubrication state, where the scoring occurrence has an intimate relation with the working flank bulk temperature, the scoring bulk temperature of a spur gear pair with no tip interference on the approach side can be estimated accurately by the bulk temperature on the outer surface of the cylinder immediately before seizure in two-cylinder tests.

Scoring in spur gear pairs. (3rd report Increase in scoring load capacity due to tooth profile wear on the approach side)

The influence of tip interference on scoring load capacity was studied using gears having tooth profile wear due to scoring on the approach side. The results were compared with those obtained with gears having no profile wear from viewpoints of scoring load and scoring temperature, taking the lubrication state on the working flank into consideration. The tip interference on the approach side should be reduced because, unlike on the recess side, it diminishes the scoring load capacity. In the mixed lubrication state, the bulk temperature on the working flank is suitable for an index in calculating the scoring load capacity of a spur gear pair. The scoring temperature on the recess side can be estimated well by the bulk temperature on the outer surface of the cylinder just before seizure in two-cylinder tests, provided that the specific sliding and the sliding velocity at the end of gear meshing are taken into account.

Effects of load distribution on the anti-seizure capacity of lubricating oil. (1st report Effects of contact width under uniform bearing)

As a basic study for making clear the effects of load distribution in the tooth trace direction on the anti-seizure capacity of lubricating oil, the effects of contact width on asperity interaction and the anti-seizure capacity under uniform bearing have been studied for a gear base oil with a two-cylinder test rig at a high specific sliding. The seizure took place from the mixed lubrication state. Though the asperity interaction is high at a small contact width, the effects of contact width on the asperity interaction diminishes as the contact width is enlarged. At a small surface roughness, the seizure load and the outer surface bulk temperature just before seizure increase as the contact width is enlarged. On the other hand, at a large surface roughness, in the higher sliding velocity range, the seizure load diminishes as the contact width is enlarged over a certain value, and the outer surface bulk temperature just before seizure is lower than that at the small one.

Effects of load intensity fluctuation on anti-seizure capacities of lubricating oils. 4th report Influence of contact width in heavy load intensity sector.

As a basis for making clear the treatment of the dynamic load in the calculation of the scoring load capacity of a spur gear pair, the influence of the contact width in a heavy load intensity sector on the anti-seizure capacity of a gear base oil was examined by two-cylinder tests in which the load intensity was fluctuated during rotation from the viewpoints of load and temperature. Experiments were carried out at a high specific sliding. The contact width little affects the anti-seizure capacity as the sliding velocity is increased. The anti-seizure capacity under the fluctuating load intensity is not less than that under the constant load intensity. Particularly, the difference between both capacities increases as the sliding velocity is increased when the frictional surfaces are finished finely and the contact width is small. Independent of whether the load intensity is fluctuated or not, the seizure occurrence in the mixed lubrication state has an intimate relation with the outer surface bulk temperature rather than with the maximum contact surface temperature.

Scoring in Spur Gear Pair : 1st Report, Scoring Temperature in Case of Gear Base Oil

The relation of the scoring occurrence to the temperature and the correlation between the gear test results and the two-cylinder test results were examined with a gear base oil using an IAE type high-speed spur gear test rig. In the mixed lubrication state, a scoring occurrence has intimate relation to the working flank bulk temperature which is not affected markedly by the sliding velocity and the oil-jet direction unlike the maximum contact surface temperature and the integral temperature. The scoring temperature of a spur gear pair can be estimated from the bulk temperatures just before seizures in two-cylinder tests taking the specific slidings and the sliding velocities at the beginning or the end of gear meshing into consideration.