Tribological testing of CAM-roller follower systems
Pedro J. Amoroso is a PDEng student in the research group Surface Technology and Tribology (STT). His supervisor is prof.dr.ir. M.B. de Rooij from the Faculty of Engineering Technology (ET).
Cam-roller follower mechanisms are often found in diesel injection systems and valve trains of internal combustion engines. Their main function is to enable low-wear low-friction conversion of rotary motion into linear motion. From a tribological point of view, cam-roller followers are highly complex due to the interaction and interdependency of two tribological systems (i.e., the cam-roller and pin-roller tribosystems).
Tribological testing and modeling of cam-roller follower systems have been active subjects of study for several decades because of the considerable impact of these interfaces on the efficiency and reliability of engines. A crucial variable is the pin-roller frictional torque, which can, in some conditions, lead to roller slippage. The latter should be avoided or minimized to reduce wear and friction losses.
Throughout time, many test setups have been developed to evaluate the behavior of this interface and improve its tribological performance. However, during testing, the working conditions of these two interacting tribological systems are not always effectively imitated. The following work focuses on designing a testing method and a test setup (The CRT-01), together with a strategy to evaluate cam-roller follower systems under conditions that could be better correlated to real life. In this thesis, the design and construction process is reported starting from scratch.
In this design project, the stakeholders have been strongly involved to effectively encompass their needs into the final deliverables. As a result, the stakeholders' needs have been translated into system requirements and requirements into system functions. With that, a baseline has been established to then generate and select the most appropriate concept. The "winner" concept has been validated throughout modeling and simulation of tribological contacts and a proof-of-concept prototype.
Supported by the promising results, the concept has been refined and converted into a detailed design ready for construction. Finally, the stakeholders have been persuaded to provide the funding to acquire an extensive list of parts and manufacture several custom-designed components to ultimately bring the test setup to life.
The novel test setup and testing method present three novel aspects which are emphasized later on in this report, namely:
- The incorporation of a self-aligning mechanism to effectively generate a line contact.
- The simulation of pin-roller friction throughout the application of frictionless braking torques to induce roller slippage.
- The measurement of traction forces with negligible dissipation.