Ball Coupling Device Hinged Connection Sliding Shafts
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Solution Overview
Problem
Existing sliding shaft coupling devices for motor vehicle steering systems face issues with axial force variation during torque transmission, leading to increased sliding force, potential jolts, and reduced service life, as well as difficulties in assembly and absorption of axial movements.
Innovation Solution
A coupling device featuring balls arranged between inner and outer shafts with concave parts and raceways, where each ball moves on two raceways and is pushed by an elastic element, maintaining contact zones to reduce axial force and ensure high angular rigidity, and includes male and female grooves for torque transmission in case of ball loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the adjustment of the sliding of the two shafts during manufacture is relatively tight to delay the appearance of free play, then the service life is improved, but the axial force required during assembly increases, resulting in longer assembly time
Solution Approach 1:
The device incorporates an adjustment mechanism that pre-sets the optimal sliding adjustment during assembly. This preliminary action ensures that the shafts are correctly positioned before operation, delaying the appearance of free play and extending service life without requiring excessive axial force during the assembly process itself.
Solution Approach 2:
The invention allows for modification of the sliding parameters during assembly through its adjustment mechanism. By enabling parameter changes, the system can achieve tight adjustment for delayed free play appearance while controlling the axial force required, thus balancing service life improvement with reasonable assembly effort.
2Manufacturing precision
If the axial force is increased to maintain tight adjustment, then the sliding adjustment is maintained, but the sliding force increases proportionally to the torque to be transmitted and the coefficient of friction, causing sudden axial release and jolts
Solution Approach 1:
The device introduces an intermediary adjustment mechanism that mediates between the two shafts. This intermediary system allows for precise control of the sliding adjustment without requiring excessive axial force, thereby maintaining manufacturing precision while preventing the harmful jolts that would result from forceful engagement.
Solution Approach 2:
The invention incorporates dynamic elements that allow the system to adapt during operation. The adjustment mechanism can dynamically respond to torque variations, maintaining tight sliding adjustment while preventing sudden axial release and jolts by smoothly accommodating changes in transmitted torque.
3Force
If coupling devices use plastic injection on splined parts to reduce friction, then the sliding force is reduced, but the wear of the plastic injection reveals play after endurance cycles
Solution Approach 1:
The device employs composite material construction, combining different materials with complementary properties. The splined parts use a composite approach that reduces friction during sliding while incorporating wear-resistant elements that prevent play development after endurance cycles, thus maintaining both low sliding force and high reliability.
Solution Approach 2:
The invention incorporates protective features that cushion against wear before it becomes problematic. The splined parts are designed with beforehand cushioning elements that protect the plastic injection from excessive wear, preventing the development of play during the endurance cycle and maintaining reliability throughout the service life.
4Ease of operation
If rolling elements and stress springs are introduced between the shaft and tube to enable sliding, then the sliding function is achieved, but the angular rigidity is reduced because it is directly proportional to the stiffness and preload of the springs
Solution Approach 1:
The device segments the coupling function into distinct elements: rolling elements handle the sliding function while stress springs provide controlled compliance. This segmentation allows the sliding function to be achieved without compromising angular rigidity, as each element performs its specific function independently rather than relying on spring stiffness for both purposes.
Solution Approach 2:
The invention applies partial action by using rolling elements for the sliding function and stress springs only for necessary compliance. This partial use of elastic elements achieves the required sliding function while minimizing the reduction in angular rigidity, as the springs are used only to the extent necessary for operation rather than as the primary load-bearing elements.
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 reduces axial force during torque transmission, minimizes sliding effort variation, and maintains initial characteristics, ensuring no free play and easy assembly, while providing high resistance to endurance and absorbing dimensional tolerances.
Implementation Method 1
Each of the two raceways is pushed by an elastic element bearing in said concave part
Implementation Method 2
balls, which are arranged between the inner shaft and the outer shaft... each of said balls moves on two raceways
Implementation Method 3
Each of said balls moves directly against the concave part of the other shaft... two contact zones which determine the position of an axis of articulation
Data Source
AI summary
The invention relates to a device for coupling an inner shaft (1) and an outer shaft (2) sliding in the direction of the common axis (4) thereof, with balls (3) provided between the two shafts. The balls (3) are arranged in axial grooves (131) of the inner shaft (1) and in axial grooves (132) of the outer shaft (2). Each row (20) of balls (3) is maintained by a double elastic member (210) that bears in the groove (131) and urges the balls (3) along two rolling tracks (140) so that they come into contact with the groove (132), wherein each of the two rolling tracks (140) is hinged through a pivot surface (144) and a bearing surface (138, 139) of the corresponding shaft (1), and the difference between the radii defines two bearing areas defining a hinge axis (145) parallel to the common axis (4).