Turbocharger Wastegate Spring Layout for Stable Shaft Preload
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Solution Overview
Problem
Existing wastegate arrangements in exhaust gas turbochargers face issues with vibration-induced axial play changes and high contact forces due to small gap distances and spring element preload fluctuations, leading to potential component failure and wear.
Innovation Solution
The design offsets the spring element's first end to rest on a pressure surface within the turbine housing, eliminating the need for it to be in the small gap between the bearing bushing and actuating lever, allowing for a larger axial gap and reduced spring rate, thus minimizing preload changes and component loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the spring element is installed in the small gap between the bearing bushing and actuating lever, then the gap distance is kept small as desired, but the preload force changes significantly due to spring rate and tolerance variations, causing high contact forces and component wear
Solution Approach 1:
The spring element is repositioned from a radial/axial gap location to a circumferential location around the shaft. The spring now acts in a circumferential direction rather than axially, utilizing a different spatial dimension. This allows the spring to engage with a larger effective area and provides a more stable preload that is less sensitive to manufacturing tolerances and thermal expansion.
Solution Approach 2:
The spring element is designed as a circumferential spring ring that can be segmented or installed in sections around the shaft. This segmentation allows for easier installation and adjustment, and distributes the preload forces more evenly around the circumference, reducing localized contact forces and wear on the bearing bushing and actuating lever.
2Device complexity
If the spring element is installed in the small gap between the bearing bushing and actuating lever, then the compact design is achieved, but high contact forces occur due to small contact surfaces, promoting wear and potential component failure
Solution Approach 1:
The spring element operates in a circumferential dimension rather than axially in a small gap. This dimensional change provides access to a much larger effective contact area around the shaft circumference, significantly reducing contact forces and wear while maintaining compact overall device dimensions.
Solution Approach 2:
The spring element is designed with varying local properties - it has different stiffness characteristics at different circumferential positions to optimize force distribution. The spring can be configured with varying wire diameter, coil density, or segment stiffness to locally adapt to the specific load requirements at different positions around the shaft, reducing peak contact forces.
3Reliability
If the spring element has a high spring rate to compensate for axial play changes, then the preload stability is improved, but unintentional block contact can occur causing lasting damage to the spring element
Solution Approach 1:
The circumferential spring element provides dynamic compliance that adapts to thermal expansion and axial play changes without generating excessive forces. The spring's circumferential configuration allows it to absorb dimensional changes more gracefully, maintaining preload stability while avoiding the block contact damage that occurs with high-rate axial springs.
Solution Approach 2:
The circumferential spring element acts as a pre-configured cushioning element that anticipates and absorbs thermal expansion and dimensional changes before they can cause block contact. By positioning the spring circumferentially, it provides a buffer zone that prevents the shaft from contacting stop surfaces under thermal or vibrational loading conditions.
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 enhances operational reliability by stabilizing the spring preload, reducing wear, and lowering component loads, while simplifying assembly and reducing the risk of unintentional block contact and component failure.
Implementation Method 1
a spring element, which rests indirectly or directly on a second spring end on a support surface of the actuating lever, is used and wherein the support surface is disposed at least sectionally around the shaft
Implementation Method 2
a spring element... is used... to generate a spring preload
Implementation Method 3
During operation, the axial play of the shaft changes due to temperature changes or vibrations. The spring element compensates this change in axial play.
Implementation Method 4
the vibration excitation of the wastegate valve to the bearing bushing is optimized
Data Source
AI summary
The invention relates to a wastegate arrangement for an exhaust gas turbocharger comprising a turbine housing (10) having a bearing mount (19), wherein the bearing mount (19) receives a bearing bushing (50) having a drilled hole (51), wherein the drilled hole (51) holds a shaft (31) having a first shaft end (31.1) disposed in the turbine housing (10), and having a second shaft end (31.2) retained outside the turbine housing (10), wherein the first shaft end (31.1) of the shaft (31) is coupled to a wastegate flap (37) disposed in the turbine housing (10) to close a wastegate passage (15) in a closed position and to release a wastegate passage (15) in an open position, wherein the shaft (31) bears an actuating lever (24) at its second shaft end (31.2) outside of the turbine housing (10), wherein the bearing bushing (50) has a second bearing bushing end (53), which faces the actuating lever (24) in the zone of the outer surface of the turbine housing (10), wherein a spring element (40), a second spring end (40.2) of which rests indirectly or directly on a support surface (24.2) of the actuating lever (24), is used, and wherein the support surface (24.2) is disposed at least sectionally around the shaft (31). In order to achieve improved operational reliability in such a wastegate arrangement, provision is made in accordance with the invention for the turbine housing (10) to have a pressure surface (18), that the pressure surface (18) is disposed offset in the axial direction of the shaft (31) in the direction of the first shaft end (31.1) with respect to the second bearing bushing end (53), and for a first spring end (40.1) of the spring element (40), which faces away from the second spring end (40.2), to rest on the pressure surface (18) of the turbine housing (10) to generate a spring preload between the pressure surface (18) and the support surface (24.2).