A car’s driveline is normally considered to include everything from the clutch through to the driven wheels.

The gearbox can be considered as a translator working between the engine and the wheels of a vehicle. Or put it another way, it is the gearbox, that enables the engine to answer the driver's request for power in any driving condition, whether the need is for high torque at low speed in hill climbing or for high speed at low torque on the motorway. It is the gearbox, that allows the engine to run in a balanced state and at an appropriate level.

As old as the car industry, there is a strong need for continuous development and innovation in gearbox designs. There are two gearbox designs currently common in car production: one are manual transmission, and the other is automatic transmission. The demands are coming from the market, such as reduction of fuel consumption and noise, improvements in drivability and, last but not least, the “fun-to-drive” factor. HCH contributes to meeting these targets by offering high quality anti-friction bearings.

Bearing carrier
In a car gearbox, the accuracy and stability of the gear wheels' relative position on the main shaft and the layshaft is vital for the correct functioning of the gear mesh. Directly linked to this is the noise and friction behavior of the gearbox. In order to have a stable condition, it is important to have a rigid support of the mainshaft and layshaft. In transmissions with a high power density, this requirement can be enhanced by bearing carrier unit consisting of a sheet metal carrier, and two bearings (typically either deep groove ball bearings) pressed into the carrier. The bearing carrier offers potential for cost saving on the gearbox assembly line. Pre-assembling the gear shafts in the bearing carrier and then mounting this complete assembly in the casing can be a significantly simplify to the assembly process.

HCH bearings for gearbox
HCH high efficiency tapered roller bearings and ball bearings are used primarily on the pinion and differential shafts in the final drives of rear-wheel drive or all-wheel drive cars. This new improved level of efficiency is possible through the detailed application of HCH’s comprehensive theoretical knowledge and specialized manufacturing know-how. HCH high efficiency tapered roller bearings offer reduction of bearing power loss and increased service life by optimized bearing design which adapts to the external loading conditions. HCH deep groove ball bearings in the gear box usually appear as a pair with located position in the pre-assembled unit bolts onto the gearbox housing. With high quality bearing material and optimized seal construction, we meet our customers’ demand with their satisfaction.

Transmission & Gearbox bearings and HCH solution
Bearings used in transmission or differential gears are usually lubricated by oil containing foreign particles such as swarf, burrs produced when parts are machined, worn powders of gears, and debris from the case. Particularly, the failure mode of bearings under lubricating conditions including hard foreign particles is surface flaking originated at the edges of dents due to roll-over of foreign particles or surface layer peeling caused by abrasive ear. With ordinary bearings, life is shortened to one of several parts to one of several tens of parts of that in clean oil. Therefore this problem is solved either by the material/heat treatment or the sealing technology improvement as indicated below:

Material/heat treatment technology solution
With tapered roller bearings, life is extended by applying HCH’s original carburizing steel materials and heat treatment technology. In order to reduce crack propagation and cracking and at the same time for early elimination of dent edges due to foreign particle, a special heat treatment to raise surface hardness and optimize the amount of retained austenite was developed, which extremely extended the bearing service life.

Seal design solution
Regarding sealed ball bearings in transmissions, entry of foreign particles in the oil into bearings is drastically reduced and running torque is also lowered by the HCH optimized seal lip design to minimize the amount of interference change relative to misalignment and axial gear load. The rubber material of the seal is selected considering heat resistance and compatibility with oil. The bearing is filled with grease and sealed to improve initial lubricating performance.

Coping with high load and high moment
Along with making units like transmissions more compact and lightweight, more compact bearings are demanded. On the other hand, engine torque increase and weight reduction of casing bring increase in bearing load and in shaft deflection, resulting a harsh condition for the bearing. As a result, particularly with tapered roller bearings have line contact; life is often shortened due to the edge stress. Based on the results of rigidity analysis of case and shaft systems using the latest computer technology, HCH has developed a special crowning shape in the axial direction that makes contact stress distribution of the area where the rollers contact with the raceway uniformly based on the results of rigidity analysis of case and shaft system, and is now mass producing the bearing with such technology. The life is around 3 times longer compared with an ordinary bearing.

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