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Abstract: Planetary gear wheels are generally equipped with straddle-mounted planetary idlers, which are supported by the pin of the carrier. These planets have an integral or two-piece design. Traditionally, many planetary gear systems with higher rated power use cylindrical roller bearings. It is intended herein to demonstrate that the use of preloaded tapered roller bearings in an integrated component should be a priority for such applications. It can increase the bearing capacity, improve power density, extend fatigue life. According to DIN 281-4, the overall integrated patented technology [1] has a bearing life of up to six times that of non-integrated technology and 1.5 times more than semi-integrated technology without changing the space size of the planetary gear.

            Preface - Design Challenges for Planetary Gear Trains
The planetary gear train is particularly suitable for achieving a higher gear ratio in a compact space. Figure 1 shows the use of cylindrical roller bearings in a typical straddle planetary idler. Due to the high power density, the planetary gear train is widely used by designers to integrate into various types of equipment, including automotive gearbox, roadside equipment main reducer, wind turbine gearbox and cement vertical mill gearbox and so on.
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        As with any other form of powertrain, engineers are faced with a number of analytical challenges in order to ensure high reliability at the design stage. If it is a planetary gear train, because of the revolution and rotation of parts transmission power when there are complex interactions, will make this problem more complex and more challenging.
    However, for all equipment, for economic considerations, increasing power density and reliability is an eternal topic. The use of the PLANE TPAC integrated planetary roller bearing assembly enhances device reliability on the basis of further use of existing designs to minimize the cost of design changes. On the other hand, its higher power density can make the design more compact, thus reducing the cost and weight.
    What is the integrated planetary roller bearing assembly (PLANET PAC)?
The traditional high power planetary gear set consists of a gear, two outer rings, two inner rings, two rows of rolling elements, two retainers and one carrier pin. In some cases, but also with a cage or open ring. In most cases, the life of the gear is calculated using 99% reliability or L1 fatigue life, while the bearings that support the gears are calculated using 90% reliability and L10 fatigue life.
Some gearbox manufacturers have half integrated bearings in their planetary gears. Figure 2 shows a semi-integrated solution that combines the outer and gears of the bearing. The guiding principle of the design is to define the recommended gear rim thickness as a proportion of the gear modulus, for example, three times the gear modulus. By changing this ratio value, you can increase the bearing pitch diameter and roller diameter, thereby enhancing the bearing capacity and fatigue life.
    With the advantages of modern bearing technology and the integration of further components, it is possible to achieve extremely high power density design. As shown in Figure 3, this integration includes the integration of the gear-bearing outer ring and the integration of the planetary carrier pin with the bearing inner ring. The full complement of the roller uses a patented coated ES300 to prevent the metal from bonding between the rollers. This is the integrated planetary wheel bearing assembly. In this particular design, the carrier must be two-piece, bolted together to complete the system assembly. This design eliminates the need for two bearing inner and outer rings, a spacer and four contact surfaces. Without these contact surfaces, the potential friction corrosion and the impact on bearing clearance settings are avoided, and this effect can lead to premature failure of the bearing. The design also integrates an additional retaining ring into the assembly to control the bearing clearance settings. In addition, the assembly can also add additional features such as forced oil lubrication.
    Some gearbox manufacturers may use a monolithic carrier. The sidewalls used in this design are similar to the two-piece, but they are inseparable. The gears can only slide between two fixed side walls. A pin is passed through the inner ring of the bearing to hold the bearing and gear in place. As shown in Figure 4, in this case, Planet Pac can not make the pin and the inner ring into one. However, a retainer can be integrated to set the bearing clearance and full of rollers with an ES300 coating to increase the power density of the bearing assembly.


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