The steering rack is a critical feature in all Automotive vehicles. The most common type of steering rack is one that incorporates a rack and pinion system that is driven by the steering wheel from the user. As the user turns the steering wheel the pinion drives the rack left and right, resulting in the wheels changing angle. Maintaining consistent contact between the rack and pinion gears is safety critical as disengagement of the gears would stop the driver having control over the direction of the vehicle.
To maintain a consistent engagement between the rack and pinion, a steering yoke (guide bearing) is employed. This device, in combination with a spring feature, is pressed onto the rack, pushing it against the pinion. The steering rack has to move through the steering yoke during steering operation meaning that friction at this interface significantly affects the steering feel. A low friction bearing will provide a smooth on-centre steering feel for the user, which should last for the lifetime of the vehicle.
NORGLIDE® steering yoke bearings are custom made to conform to the steering rack of any steering system. It is the unique laminate design that enables this innovation, as the thick PTFE layer allows low friction and smooth steering, drive after drive.
Saint-Gobain engineers have designed the shape of the steering rack yoke laminate to allow for high rack conformity of the bearing (Figure 1). This results--compared to traditional design--in a higher contact area of the yoke onto the rack, reducing the pressure of the system, which leads to less wear over the lifetime of the vehicle. This is only achievable using our unique material due to the thick layer of PTFE used in NORGLIDE® Bearings (Figure 2).
Figure 1: The offset between the steering yoke and the rack shaft is an order of magnitude less than competitor yokes. Here the NORGLIDE® steering yoke has an offset value of 0.03, compared to the competitor yoke with a 0.55 mm offset. This allows the NORGLIDE® steering yoke to be brought closer to the rack, ensuring more contact, resulting in reduced pressure and wear.
Figure 2: Cross-section through the unique NORGLIDE® materials (left - SMTL, right - PRO) that will perform consistently throughout the lifetime of the part due to the thick PTFE layer.
Saint-Gobain NORGLIDE® Bearings offer convenient and cost-effective solutions for a wide range of automotive applications. These maintenance free and wear resistant bearings are capable of handling direct torque transfer, torque slip, axial retention, controlled collapse and radial loading between the mating components.