CAI Tool Case Study of Reducing Vibratio
Hyman Duan, Alp Lin, Leonid Batchilo, Marine Li,  IWINTALL, Inc.
Huiyu Wang,   DLoco, Co. Ltd.
 
Abstract
 
A real problem-solving case study about reducing vibration of diesel engine lubricating oil system is presented to illustrate the systematic workflow integrating the application of function analysis, problem reformulation, TRIZ Standards, and ontology-based functional knowledgebase in the CAI Tool, Pro/Innovator.
 
Testing of a new powerful diesel engine revealed high-level vibration of lubricating oil system of diesel engine, especially at the outlet of oil pump and in the pipeline. The root problems (oil pressure fluctuation and oil flow turbulence in oil pump, etc.) are identified with problem reformulation based on root cause analysis and TRIZ multi-screen thinking. By applying TRIZ Standards and searching prior art in ontology-based functional knowledgebase, several innovative concepts are generated. After evaluation and testing, final feasible concept is defined. To protect the patentable concepts, a patent application draft is also generated after function modeling of the proposed design of new oil pump.
 
Keywords: CAI, TRIZ, lubricating oil pump, vibration reduction
 
1 Initial Problem Situation
 
Testing of a new powerful diesel engine revealed high-level vibration of lubricating oil system of diesel engine, especially in three positions of outlet connections of oil pump and the pipeline: vibration speed in oil pump outlet was 30 to 40 mm/s, release control valve 50 to 60 mm/s, and bellows valve 35 to 50 mm/s. However the desired vibration speed in oil pump outlet should be 25 mm/s, release control valve 40mm/s, bellows valve 30mm/s.
 
The high vibration occurring around the working speeds of diesel engine decreases the working stability and reliability of lubricating oil system. Thus the problem is to reduce vibration of oil pump and pipeline?
 
The sketch of lubricating oil system is shown in Figure 1. The manufacturer of the diesel engine deployed a bellows damper and a bellows valve between oil pump and release control valve to prevent the propagation of the pipeline vibration. But the temporary solution merely alleviates the symptoms of the problem. The radical measures are needed to effect a permanent cure.
 
The structure of oil pump is shown in Figure 2. The upside driving gear (oblique tooth gear) is clockwise rotation, and the downside driven gear anti-clockwise rotation. Oil absorbed from left side is pressed in the passage formed by pump casing and gears then go to engine through right outlet. Pressure pulse is generated while a closed cavity is formed by teeth and casing. That is why oil pump produces high frequency vibration. Because oil pump is installed on engine and driven by crankshaft, engine-alternator vibration and torsional vibration of rotating parts can also effect oil pump vibration.
 
Figure 1. The sketch of lubricating oil system

 
Figure 2. The structure of oil pump
 
2 Workflow of Pro/Innovator
 
The Computer-Aided Innovation tool, Pro/Innovator [1], developed by IWINTALL, Inc., delivers systematic innovation methodologies and workflows to empower enterprises to achieve greater R&D ROI and manage their knowledge more effectively than before. With the interactions of ten modules and applications, sysAnalyzer, reFormulator, Solutions KB, TRIZ Techniques, Patent Search, Evaluation, Report Generation, Patent Generator, KB Editor and Project Navigation, Pro/Innovator supports new product/process development, improvement and troubleshooting of existing product/process, knowledge management and intellectual property protection.
 

Figure 3. Workflow of Pro/Innovator
 
3 Problem Reformulation
 
Although three fault phenomena (high vibration speeds) is measured in the outlet of oil pump, bellows valve, and release control valve initially, integrating Root Cause Analysis, TRIZ resources analysis and TRIZ multi-screen system thinking (i.e. nine window system operators) allows us to handle the problem situation beyond the area where the initial problem occurs and identify the root problems and available recourses in subsystem and super-system. [2]
 
As for the excessive vibration of oil pump outlet, with Root Cause Analysis (or Cause-Effect Analysis) and energy flow analysis, the sub-cause, excessive vibration of oil pump casing, and then three sub-sub-causes, (1) insufficient connection rigidity between diesel engine and oil pump, (2) excessive torsional vibration of driving gear and driven gear in oil pump, and (3) presence of the oil turbulence and cavitation noise in oil pump, and finally four root causes, (1) insufficient connection rigidity between diesel engine and oil pump, (2) excessive torsional vibration generated by external driving gear, (3) presence of the teeth engagement impact of driving and driven gears, (4) excessive oil pressure pulsation in pump which is identified in the initial problem situation discussion stage, are obtained (Figure 4).

 
Figure 4. Problems map of diesel engine lubricating oil system vibration
 


Figure 5. Reformulated problems tree of diesel engine lubricating oil system vibration
 
After testing and analyzing these four root causes, excessive oil pressure pulsation, torsional vibration, and teeth engagement impact of driving and driven gears are identified as the key factors of initial problem. Eliminating the excessive oil pressure pulsation needs drastic change of oil pump design, therefore one step is backed along the cause-effect axis and the sublevel root cause, presence of the oil turbulence and cavitation noise is selected as one of directions for future problem solving. That means, the passage to oil pump outlet is selected as the operation zone instead of teeth engagement area. Subsystem level and supersystem level resources analysis are also applied to these two problems, presence of the oil turbulence and cavitation noise and excessive torsional vibration (Figure 4). The tree view list of reformulated problems based on above cause-effect analysis and resources analysis is shown in Figure 5.
 
4 Concepts Generation
 
Root problem 1: how to remove the turbulence, cavitation noise in the passage to oil pump outlet, and consequently isolate the propagation of high frequency oil pressure pulsation?