Offset-Groove Rack Bush for Faster Steering Response
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Solution Overview
Problem
In rack-and-pinion steering mechanisms, the displacement of the rack bush, rack bar, and tie rod due to reaction forces from tires leads to a time lag in steering operations, affecting the feeling of steering due to the compression and deformation of elastic rings, resulting in reduced rigidity and increased friction torque.
Innovation Solution
A rack bush design with a mounting groove axis shifted from the bush body axis, allowing the elastic ring to protrude or be embedded differently, positioning the rack bush to directly contact the reaction force surface without intervening gaps, enhancing rigidity and reducing time lag in steering responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the elastic ring is mounted on the bearing body with the mounting groove axis aligned with the bush body axis, then the structure is simple and easy to manufacture, but the rack bush displaces under reaction force causing time lag in steering operation
Solution Approach 1:
The mounting groove axis is intentionally offset from the bush body axis, creating an asymmetric structure. This asymmetry allows the elastic ring to be positioned such that it does not interfere with the reaction force transmission path, eliminating the displacement issue while maintaining manufacturing simplicity
Solution Approach 2:
The problem is solved by moving the mounting groove to a different spatial position (offset in radial direction) rather than changing the alignment in the axial direction. This dimensional change allows the elastic ring to be positioned in a location that does not conflict with the reaction force path
2Reliability
If the elastic ring is compressed to tighten the rack bar, then the clearance between the bearing body and rack bar is eliminated, but the elastic ring deforms under reaction force causing displacement and increased friction torque
Solution Approach 1:
The harmful function of the elastic ring (deformation under reaction force) is separated from the useful function (tightening the rack bar). The elastic ring is positioned in an offset location where it performs tightening without being in the path of reaction force, thus eliminating the source of friction torque variation
Solution Approach 2:
Different regions of the rack bush are given different functions: the offset mounting groove region handles elastic ring mounting for tightening, while the central axis region handles reaction force transmission. This local differentiation allows each region to optimize its specific function without interfering with the other
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
This design improves the rigidity against reaction forces, reduces the time lag in steering operations, and maintains optimal sliding characteristics by eliminating the need for shortened elastic rings, thereby enhancing the overall feeling of steering responsiveness.
Implementation Method 1
a bush body (2), which can be freely expanded and contracted in a radial direction; and an elastic ring (3) mounted on the bush body (2)
Data Source
AI summary
Provided is a rack bush capable of reducing an effect on the feeling of a steering operation. A rack bush (1) comprises: a rack bush 1 housed in a cylindrical housing (4), which supports a load applied to a rack bar (5) while allowing movement of the rack bar (5) in the direction of the axis (O) and can be freely expanded and contracted in the radial direction; and elastic rings (3) mounted on the bush body (2). The bush body (2) has mounting grooves (28), which are formed in the circumferential direction on an outer peripheral surface (22) for mounting the elastic ring (3). An axis (P) of the mounting groove (28) are shifted from the axis (O) of the bush body (2). By this arrangement, there are formed an elastic ring protruding part (10), where the elastic rings (3) protrude greatly from the outer peripheral surface (22) of the bush body (2), and an elastic ring embedded part (11), where the elastic rings (3) are embedded in the outer peripheral surface (22) of the bush body (2).