The Design Of A Sensor Measuring The Oil Film Thickness Between Cylinder And Piston Ring In Diesel Engine

Cylinder-piston ring friction pairs are one of the most important friction pairs in internal combustion engines, it is widly used in billions of internal combustion engines. The research indicated, the 25%～50% frictional power loss of internal combustion engine is wasted by Cylinder-piston ring friction pairs. Therefore the performance of this friction pairs directly affect the internal combustion engine's performance. The change and the distribution rule of the lubricant film thickness between cylinder and piston ring are one of the important contents in internal combustion engine tribological study. If we can accurate measure this thickness, it will be of great help in designing piston, reducing friction loses between cylinder and piston ring, lengthening the piston's service life.In this paper, the diesel engine is the research object. Comparing each kind of lubrication film thickness test method in detail, the optical fiber sensor technology is chosen. Through a thorough study of the optical fiber sensor technology and analyzes the object, a fiber optical displacement sensor to measure the lubricant film thickness between cylinder and piston ring is designed, which is based on optic intensity modulation principle. It is composed by light source, fiber optical probe, opto-electronic conversion circuit, the signal processing circuit and the microprocessor. The square-wave impulse modulation actuates the non-coherent light source infrared light emitter diode, reduces the shining time, lengthens its life, and makes it stable; the single optical fiber Y structure and the self-focusing lens constituted fiber optical probe, the structure is simple, the volume is small and exquisite, the manufacture and installment is simple, satisfies the request of this topic; The PIN silicon photorectifier that works in the photovoltaic pattern realizes photoelectricity transformation; the signal processing circuit includs the pre-amplification circuit, the band-pass circuit and the AC/DC circuit three parts, the processed signal inputs the microprocessor to be further processesed; the selected microprocessor is MSP430F149, and designed the related display circuit and the RS-232 interface circuit. The microprocessor data processing program is developed, which includes main program, A/D transformation program, LED display program and serial interface data sending program. Demarcated the sensor, presented the result and analyzed the way of actual application. Finally, based on the summaries and conclusions of all research works, the proposal and the forecast for further study are put forward.