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Development History of Low Fuel Consumption Automotive Bearings

Release time:

2023-01-13

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Due to the simple structure of automotive bearings, the appearance differences are often not significant. However, looking at the process of bearing technology characteristics from the 1980s to the present, it can be found that the basic performance of bearings continues to develop under market demand expectations. This article introduces the new development of automotive bearings (deep groove ball bearings, tapered roller bearings) technology in low fuel consumption (low torque).

1. Development History of Automobile Bearings

1.1 Deep groove ball bearings

In order to meet the market demand for multi-level automatic transmissions and continuously variable transmissions, the functions of deep groove ball bearings mainly used in transmissions have been improved, including applications with high speed and low torque. In addition to the requirements of compactness, lightweight, and long service life, the drive motor bearings of electric vehicles also face similar technical requirements.

Through changes in materials, heat treatment, internal design parameters, and improvements such as seals, retainers, and lubricants (Figure 1), low torque requirements and compact, lightweight designs are achieved.

Deep groove ball bearings for transmissions are usually open bearings without dust covers or seals. However, contact seals (LU/LH seals) are currently used to prevent hard foreign objects from invading the lubricating oil, resulting in a decrease in bearing service life.

Due to the influence of sealing sliding characteristics, contact sealed bearings have higher torque compared to open bearings. Therefore, open bearings are typically used in situations where low torque is a critical requirement. The improvement of materials and heat treatment technology enables bearings to have a longer service life under environmental conditions where foreign objects invade.

The newly developed LE seal improves the sealing material and sealing lip structure, ensuring low torque while ensuring sealing performance. These improvements make the torque of LE seals under oil lubrication conditions as low as that of non-contact seals.

1.2 Tapered roller bearings

Tapered roller bearings for transmissions or differentials have more design elements than deep groove ball bearings. Therefore, explore the various characteristics of these design parameters. In addition to low torque, improvements in materials and heat treatment have also achieved a long service life.

This section discusses the transition from improved internal design and material/heat treatment to lower torque. In order to improve the internal design, the ST series was established to reduce torque by improving the roller sliding characteristics. This is mainly achieved through the special shape and processing of the inner ring edge guard. In terms of material/heat treatment improvement, special heat treatment was carried out using carburized steel as the substrate. Due to this special heat treatment technology, residual austenite on the surface of the raceway is increased, which helps to extend its service life.

With the improvement of the micro curvature (convexity) of the inner/outer ring raceway and the combination of this technology with other materials/heat treatment technologies for product development, the ECO-Top series has been obtained. In addition, changing the design of the steel cage can significantly reduce the stirring resistance of the lubricating oil. In the new series, ULTAGE tapered roller bearings for automobiles have been improved through convex design and established batch processing technology, meeting the application requirements of modern hybrid/electric vehicles (HEV/EV) for lightweight and compactness. ULTAGE ® NTN combines "ultimate" and "stage" to name the bearings. In addition, ULTAGE ® Also