Tilting Pad Journal Bearing Width Variation Reduces Oil Leakage

Solution Overview

Problem

Tilting pad type journal bearings face issues with oil leakage and increased oil supply requirements due to constant sliding surface width, leading to decreased oil film cross-sectional area and increased carry-over oil, necessitating higher lubricating oil input.

Innovation Solution

The sliding surface of each pad is designed to increase in width from the front edge to the rear edge, and the nozzle is configured with a groove that directs oil flow towards the center, reducing oil leakage and enhancing carry-over oil flow, thereby reducing the overall oil supply needed.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the sliding surface width is kept constant from front edge to rear edge, then the pad structure is simple and easy to manufacture, but the oil film cross-sectional area decreases downstream causing increased oil leakage

Engineering Contradiction:

Improvepad structure simplicityVSAvoidoil leakage

Core Design Contradiction:

Ease of manufactureVSLoss of substance

Solution Approach 1:

The sliding surface width is made non-uniform along the circumferential direction, with the width at the rear edge being larger than at the front edge. This local variation in geometry compensates for the decreasing oil film thickness downstream, maintaining a relatively constant oil film cross-sectional area and reducing oil leakage through the side edges.

Inventive Principle:

Principle #3Local quality

2Loss of substance

If the sliding surface width increases from front edge to rear edge, then the oil film cross-sectional area is maintained and oil leakage is reduced, but the pad manufacturing complexity increases

Engineering Contradiction:

Improveoil leakageVSAvoidpad structure simplicity

Core Design Contradiction:

Loss of substanceVSEase of manufacture

Solution Approach 1:

The sliding surface width is made non-uniform along the circumferential direction, with the width at the rear edge being larger than at the front edge. This local variation in geometry compensates for the decreasing oil film thickness downstream, maintaining a relatively constant oil film cross-sectional area and reducing oil leakage through the side edges.

Inventive Principle:

Principle #3Local quality

3Reliability

If more lubricating oil is supplied to compensate for side edge leakage, then adequate lubrication is maintained, but the oil consumption increases

Engineering Contradiction:

Improvelubrication adequacyVSAvoidoil supply amount

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The sliding surface width is made non-uniform along the circumferential direction, with the width at the rear edge being larger than at the front edge. This local variation in geometry compensates for the decreasing oil film thickness downstream, maintaining a relatively constant oil film cross-sectional area and reducing oil leakage through the side edges.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent addresses the oil leakage problem by modifying the geometry in the axial direction (width variation) to compensate for the circumferential thickness decrease, effectively using a dimensional approach to control oil flow distribution and reduce overall consumption.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

4Reliability

If the nozzle is positioned closer to the pad to improve lubrication, then oil delivery is enhanced, but oil leakage through side edges increases due to constant width

Engineering Contradiction:

Improvelubrication effectivenessVSAvoidoil leakage

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The sliding surface width is made non-uniform along the circumferential direction, with the width at the rear edge being larger than at the front edge. This local variation in geometry compensates for the decreasing oil film thickness downstream, maintaining a relatively constant oil film cross-sectional area and reducing oil leakage through the side edges.

Inventive Principle:

Principle #3Local quality

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 oil film cross-sectional area and increases the carry-over oil ratio, resulting in a reduced need for lubricating oil supply, enhancing efficiency and reducing leakage.

Implementation Method 1

Lubricating oil is supplied to the gaps between the peripheral surface of the rotary shaft and sliding surfaces of the pads to form oil films, and the rotary shaft is supported by the pressure of the oil films

Methodology Applied

Scientific EffectHydrodynamic lubrication: Lubrication

Implementation Method 2

Since the tilting angle of each pad changes according to the pressure distribution of the oil film, unstable oscillation such as the so-called 'oil whip' can be suppressed

Methodology Applied

Scientific EffectHydrodynamic pressure distribution: Pressure Gradient

Data Source

PatentEP3032123B1Tilting pad type journal bearing

Publication Date: 2020.02.12 MITSUBISHI HITACHIPOWER SYST LTD

Figure 1
Figure 2A~2B
Figure 3~4

AI summary

Provided is a tilting pad type journal bearing capable of reducing the amount of oil that has to be supplied to the bearing. A bearing comprises nozzles 5 which are each arranged between pads 2 to supply lubricating oil to sliding surfaces 14 of the pads 2. The sliding surface 14 of each of the pad 2 is formed so that the width of the sliding surface 14 increases as it goes from a front edge part towards a rear edge part thereof. A tip end part of each of the nozzles 5 has a groove part 18 which induces a flow heading from lateral parts towards the center in the width direction, in an oil flow from the rear edge part of the sliding surface 14 of an upstream pad 2 to the front edge part of the sliding surface 14 of a downstream pad 2.