As an indispensable and standard technology in modern automobiles, mechatronic steering systems not only reduce energy consumption but also enhance the driving experience. With the development of electrification, this technology is gradually being applied to the field of electric vehicles.
Because electric vehicles produce relatively little noise, the gears used in mechatronic steering technology can generate significant noise, which somewhat detracts from the driving experience. To address this, Schaeffler recently introduced a new type of bearing, the "new pendulum bearing," to solve the noise problem.
Currently, there are four commonly used steering systems in automobiles:
Rack and pinion electric power steering system: Due to the weight of SUVs, light trucks and heavy vehicles, in order to obtain the maximum steering torque assistance, the motor shaft and rack shaft are designed to be parallel.
This parallel structure design allows the spindle of the ball screw drive unit to be directly connected to the rack. The series of ball screw drive products used in this type of steering system are developed and manufactured by Schaeffler.
Column-type electric power steering (EPSC): Commonly used in small and light vehicles, its electric power steering is achieved through the steering column, hence the name column-type electric power steering (EPSC).
Electric Power Steering (EPSsp): Power steering for medium and heavy vehicles. Its electric power steering is achieved through the power steering system on the rack, which acts directly on the pinion of the mechanical steering mechanism, hence the name Electric Power Steering (EPSsp).
Dual pinion electric power steering (EPSdp): Based on the pinion electric power steering system, an electric gear device is added to the rack. The steering torque is transmitted to the rack through the two pinions. This type of steering system is called dual pinion electric power steering (EPSdp).
In general, the power assist provided by the electric motor transmits the steering torque to the steering shaft (EPSc) on the steering column or to the steering rack (EPSsp and ESPdp) through a worm gear mechanism.
Detailed solutions for electric vehicles
For steering systems employing worm gear mechanisms, the steering bearings must simultaneously meet several specific requirements. As they function as positioning bearings and support the worm, they must be able to withstand loads from both the axial and radial directions. Due to gear design considerations, conventional ball bearings experience increased torque friction, leading to noise and impacting the performance of the gear unit.
To address the issue of bearing tilting and excessive noise caused by the vertical movement of the worm gear, NewSwivel Bearing employs a specially curved self-aligning outer ring. This new design allows the bearing inner ring to automatically tilt, compensating for the worm gear's rotation angle and thus preventing increased frictional torque and noise.
Another advantage of this design is that the worm can be preloaded radially, eliminating backlash between the worm and the turbine and reducing noise that often occurs during steering when the gear teeth mesh in the opposite direction. Simultaneously, the rotational motion of the new pendulum bearing can compensate for installation errors in the bearing housing.
As automotive products continue to improve, consumers have become accustomed to enjoying a quiet and comfortable in-car environment. In this context, the noise generated by power steering significantly diminishes the consumer experience. This is especially true for electric vehicles, where the relatively low noise of the electric motor makes it difficult to mask other noises, thus exacerbating the problem. The development of this new bearing further demonstrates that achieving widespread acceptance of electric vehicles requires not only large-scale solutions such as electric drive systems but also attention to detail.
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