As the automotive industry continues to move towards e-mobility, the manufacturing world is adapting to the respective requirements. Large gear ratios are necessary to reduce the high input speeds of electric motors to the required speed of the drive wheels. At the same time, masking noise of combustion engines is now missing, posing challenges to the noise level of transmissions. Principally, two main transmission concepts have become established for e-drive applications: two-stage layshaft transmissions with four gears, and planetary transmissions.
Gear honing is a highly productive process for the production of small and
medium sized gears and is used mainly in the serial production of the automotive
industry. The low robustness of the process is a particular challenge in gear
honing. The consequences range from an inadequate gear quality to an early breakage of the honing tool. In order to describe the processmachine interaction, the machining forces must be known.
Hard finishing technology, e.g. — honing — is used to manufacture high-performance gears. Gear honing is primarily used to hard finish small- and medium-sized automotive gears. And yet trials have shown that gears with a module larger than mn = 4 mm can also be honed efficiently, but problems often occur due to unstable process design. In this paper a model to improve the process design is described.
The honing of gears - by definition
- facilitates ease of operation, low noise and smoother performance in a transmission. Honing also contributes to
reduced friction in the powertrain. Both the intense cutting (roughing process) as well as the functionally fine- finishing of transmission gears can be performed in one setup, on one machine.
A high-performance, 11-axis CNC system
from NUM has enabled machine tool
manufacturer Sicmat to create a gear honing machine that sets a new industry standard for post-hardening fine finishing.
Gear tooth wear and micropitting are very difficult phenomena to predict
analytically. The failure mode of micropitting is closely correlated to the lambda ratio. Micropitting can be the limiting design parameter
for long-term durability. Also, the failure mode of micropitting can progress to wear or macropitting, and then go on to manifest more severe failure modes, such as bending. The results of a gearbox test and manufacturing process development program will be presented to evaluate super-finishing and its impact on micropitting.
Stringent NVH requirements, higher
loads and the trend towards miniaturization to save weight and space are forcing transmission gear designers to increasingly tighten the surface finish, bore size and bore-to-face perpendicularity
tolerances on the bores of transmission
gears.