Pivot-Pendulum Bearing Assembly for Low-Noise Power Steering
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Solution Overview
Problem
Electromechanical power steering systems face challenges in reducing noise and play in worm gear components due to asymmetric loads and wear, which increase over time, leading to acoustic problems and excessive wear.
Innovation Solution
An electromechanical power steering system with a helical gear and a bearing arrangement that includes a roller bearing and a prestressing device, where a movable bearing element is resiliently preloaded against the gear housing, and an eccentric cam adjusts the clearance between the helical gear and shaft, providing a two-point support to minimize play and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the backlash is set to zero during assembly, then acoustic problems such as deflection knocking or rattling are reduced, but the increasing backlash due to wear over time cannot be compensated
Solution Approach 1:
The bearing support is designed to be movable relative to the gearbox housing, allowing dynamic adjustment of the bearing position. This enables the system to adapt to wear over time by compensating for increasing backlash through the movable bearing support's ability to shift position while maintaining contact through the two-point support mechanism
Solution Approach 2:
The preload force on the worm shaft is made adjustable through the movable bearing support design. By changing the position of the bearing support relative to the housing, the preload force can be optimized to maintain backlash-free operation while accommodating wear, thus controlling noise without sacrificing reliability
2Object-generated harmful factors
If a spring is used to preload the worm shaft into a backlash-free mesh, then acoustic problems are reduced, but the preload force may become excessive causing excessive torque and wear
Solution Approach 1:
The spring preload force is optimized by designing the bearing support with specific geometric parameters (lever arm length, contact surface positions) that distribute the preload forces appropriately. This allows achieving backlash-free operation without excessive preload that would cause excessive wear or torque
Solution Approach 2:
The two-point support system uses asymmetric contact surface positioning to distribute loads more evenly. The first contact surface provides primary support while the second contact surface provides additional stabilization, creating a balanced force distribution that reduces wear while maintaining noise reduction
3Device complexity
If the bearing is fixed in the gearbox housing, then the structure is simple, but the bearing cannot compensate for wear and increasing backlash over time
Solution Approach 1:
The bearing support is designed to be movable relative to the gearbox housing, transforming the static bearing structure into a dynamic one. This mobility allows the bearing to self-adjust and compensate for wear and backlash accumulation over time, improving reliability without requiring complex adjustment mechanisms
Solution Approach 2:
The movable bearing support automatically compensates for wear and backlash through its inherent design. The two-point support system with lever arm geometry enables the bearing to self-adjust its position in response to load changes and wear, eliminating the need for external adjustment mechanisms or complex control systems
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces noise and play in the worm gear, ensuring long-term performance and minimizing wear, thereby enhancing the service life and reducing acoustic issues.
Implementation Method 1
a preloading device is included which spring-elastically preloads a movable bearing element of the bearing arrangement against the gearbox housing to adjust the clearance of the engagement between the helical gear and the shaft
Implementation Method 2
The bearing support further comprises an eccentric cam on its base body, which bears against the first contact surface on the housing in a first contact area
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
The invention relates to an electromechanical power steering system, comprising an electrical servomotor having a motor shaft, which servomotor drives a shaft (2) that meshes with a helical gear (4), the shaft (2) being arranged in a transmission housing (8) and being mounted for rotation about an axis of rotation (100) in a bearing assembly (7) having a rolling bearing (9), a preloading device (18) being comprised, which preloads a movable bearing element of the bearing assembly (7) elastically against the transmission housing (8) in order to set the play of the engagement between the helical gear (4) and the shaft (2), the transmission housing (8) comprising a housing portion (16) having a first contact surface (33) and a second contact surface (32), the normals of which do not intersect, the bearing assembly (7) having a bearing carrier (13) for the rolling bearing (9), which bearing carrier forms the movable bearing element and has a lever arm (19), which lever arm extends from a main body (24) of the bearing carrier (13) and has a free end (21), which free end lies against the transmission housing (8) at the second contact surface (32) in a second contact region (34), the bearing carrier (13) having, on its main body (24), an eccentric cam (14), which lies against the housing (8) at the first contact surface (33) in a first contact region (35).