Journal Bearing Gap Layout for Rotary Shaft Vibration Damping
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Solution Overview
Problem
In rotary machines with journal bearings, vibrations can occur due to differences in vibration damping characteristics between bearings, leading to increased vibrations as the rotary shaft's revolutions increase, particularly in configurations where bearings are spaced along the central axis.
Innovation Solution
A rotary machine design featuring a journal bearing with load support surfaces arranged along the central axis, incorporating a first gap and a second gap to form an oil film with the rotary shaft and bearing housing, which integrates bearing portions and an intermediate facing portion to suppress both conical and parallel mode vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If bearings are arranged at an interval in the direction of the central axis, then the rotary shaft can be supported to be rotatable, but vibrations are generated due to difference in vibration damping characteristics between the plurality of bearings
Solution Approach 1:
The bearing is divided into a first bearing portion and a second bearing portion arranged at an interval in the central axis direction, with each portion having load support surfaces that face the rotary shaft. This segmentation allows independent optimization of vibration damping characteristics for each portion while maintaining rotational support functionality.
Solution Approach 2:
Different gap dimensions are created at different locations: a first gap between the first bearing portion and the rotary shaft, and a second gap between the second bearing portion and the rotary shaft. By making the second gap smaller than the first gap, local quality differences are introduced to equalize vibration damping characteristics between the two bearing portions, thereby suppressing vibrations.
2Power
If the number of revolutions of the rotary shaft increases, then the power output increases, but the generated vibrations increase
Solution Approach 1:
The bearing design incorporates dynamic gap control where the second gap is smaller than the first gap, creating different oil film characteristics that adapt to varying rotational speeds. This dynamic configuration ensures that vibration damping characteristics remain balanced across different operating conditions, allowing power output to increase without proportional increase in vibrations.
3Force
If multiple load support surfaces are arranged along the central axis, then the load capacity increases, but the complexity of the bearing structure increases
Solution Approach 1:
The first bearing portion and second bearing portion are merged into a single integrated bearing structure that shares a common body and lubricant supply system. This merging approach allows multiple load support surfaces to be arranged along the central axis for increased load capacity, while avoiding the complexity of multiple separate bearing components.
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 design effectively reduces vibrations in the rotary shaft by maintaining an oil film in the second gap, enhancing vibration damping and stabilizing the rotary shaft's operation across varying revolutions.
Implementation Method 1
an oil film of a lubricant is held between the second gap and at least one of the rotary shaft and the bearing housing. Accordingly, it is possible to achieve a vibration damping effect of the rotary shaft.
Implementation Method 2
an oil film is formed by a lubricant between an inner peripheral surface of the bearing and an outer peripheral surface of the rotary shaft, and between an outer peripheral surface of the bearing and an inner peripheral surface of a bearing housing for supporting the bearing.
Data Source
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AI summary
A turbocharger (1A) includes a rotary shaft (2), a journal bearing (5A), and a bearing housing (10). The journal bearing (5A) includes load support surfaces (14 and 15), a first gap forming portion (F1), and a second gap forming portion (F2). The first gap forming portion (F1) forms a first gap (101) in a radial direction between the load support surfaces (14 and 15) adjacent to each other in a direction of a central axis (O). The second gap forming portion (F2) forms a second gap (102) smaller than the first gap in the radial direction between the load support surfaces (14 and 15) adjacent to each other in the direction of the central axis (O).