Stepped Bushing for Valve Timing Adjuster Wear Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing hydraulic valve timing adjusting devices face issues with reduced contact area between the assist spring and the bushing member, leading to increased contact pressure and wear, due to the placement of the assist spring on the outer side of the gap between the bushing member and the housing, which reduces the contact area and causes wear.
Innovation Solution
A valve timing adjusting device with a bushing member shaped in a stepped cylindrical tubular form, where the small diameter portion supports the housing and the large diameter portion contacts the assist spring, maintaining a larger contact area and reducing wear by ensuring the assist spring is not placed on the outer side of the gap, thus maintaining the contact between the assist spring and the bushing member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the assist spring is placed on the outer side of the gap between the bushing member and the housing, then the device structure is simplified, but the contact area between the assist spring and the bushing member is reduced, leading to increased contact pressure and wear
Solution Approach 1:
The assist spring is nested within the space formed by the large diameter portion of the bushing member and the housing, rather than being placed externally. This nesting arrangement allows the assist spring to be supported by the large diameter portion while maintaining adequate contact area, resolving the contradiction between structural simplification and contact area preservation.
Solution Approach 2:
The bushing member employs a stepped cylindrical design with varying diameters (small diameter portion and large diameter portion) along the axial direction. This dimensional variation creates distinct functional zones: the small diameter portion provides clearance from the housing, while the large diameter portion provides adequate support area for the assist spring, thereby maintaining contact area without increasing overall device complexity.
2Ease of manufacture
If the assist spring is placed on the outer side of the gap, then installation is easier, but wear increases due to reduced contact area and increased contact pressure
Solution Approach 1:
The assist spring is nested within the housing-bushing member space, specifically supported by the large diameter portion. This nested configuration naturally guides the assist spring into its correct position during assembly, maintaining ease of installation while ensuring adequate contact area to reduce wear through distributed contact pressure.
Solution Approach 2:
The bushing member's outer diameter is varied along the axial direction, creating a large diameter portion that increases the contact area with the assist spring. This parameter change (diameter variation) reduces contact pressure and wear while maintaining a straightforward installation process, as the stepped design itself provides alignment and positioning features.
3Ease of manufacture
If the bushing member has a uniform diameter, then manufacturing is simpler, but the assist spring cannot be properly supported without reducing contact area
Solution Approach 1:
The bushing member is segmented into two distinct cylindrical portions along the axial direction: a small diameter portion that provides clearance from the housing, and a large diameter portion that provides adequate support for the assist spring. This segmentation allows each portion to fulfill its specific function optimally, ensuring proper assist spring support while maintaining manufacturing feasibility through a straightforward stepped cylindrical design.
Solution Approach 2:
The bushing member exhibits local quality variation through its stepped design, where the large diameter portion is specifically engineered to provide enhanced contact area and support for the assist spring, while the small diameter portion maintains clearance from the housing. This localized differentiation of diameter allows the bushing member to simultaneously achieve proper assist spring support and acceptable manufacturing complexity.
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 configuration maintains the contact area between the assist spring and the bushing member, reducing wear and allowing for increased output torque from the assist spring while minimizing leakage of hydraulic oil, thus effectively adjusting valve timing with reduced maintenance and operational costs.
Implementation Method 1
The assist spring is configured to urge the vane rotor in an advancing direction or a retarding direction relative to the housing
Implementation Method 2
a valve timing adjusting device that includes a housing, a vane rotor, an assist spring and a bushing member... configured to use a hydraulic pressure to adjust a valve timing
Data Source
AI summary
A bushing member includes: a large diameter portion which is inserted on a radially inner side of a coiled segment of an assist spring and includes a straight portion which extends in an axial direction; and a small diameter portion which is located on a radially inner side of a housing and has an outer diameter that is smaller than an outer diameter of the large diameter portion. The coiled segment includes a contact portion that contacts the straight portion at a radially inner surface of the contact portion. In an axial direction, a location of an end of the straight portion, which is located on one axial side where a driven shaft is placed, coincides with a location of an end of the contact portion located on the one axial side, or is on the one axial side of the location of the end of the contact portion.