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Development of measurement apparatus of piston assembly friction in a small motorcycle engine

Nakashima Kohei, Matsunaga Kota, Uchiyama Yosuke, Yoshida Masao

Combustion Engines

2023

R. 62, nr 3

32--37

This study developed a friction measurement apparatus with a floating cylinder liner in a small motorcycle engine. In this measurement apparatus, joint plates were installed in the grooves on the outer periphery of the floating liner, and then the plates, as well as load washers of piezo type, were mounted in the cylinder block at both the thrust and the anti-thrust sides. A stepped ring, protruding inward, was mounted on the top of the floating liner so that cylinder pressure acting on the stepped portion was balanced in the vertical direction. Thus, it was possible to measure the friction in the sliding directions of the piston. Using this apparatus, the effect of the engine operating period on friction was investigated in a piston micro-dimpled with a fine particle bombarding process. Results indicated that, at low engine speeds, friction decreased with the operating period, but at high engine speeds, friction decreased after 10 hours of operation, and then increased after 20 hours of operation.

Influence of piston surface treatment on piston assembly friction in an eco-mileage vehicle engine

Nakashima Kohei, Uchiyama Yosuke

Combustion Engines

2022

R. 61, nr 1

18--23

This study investigated the effect on piston assembly friction after treating piston surfaces with a fine particle bombarding process, using a friction measurement apparatus with a floating cylinder liner, similar to an eco-mileage vehicle engine. Friction was measured in four conditions: (1) no treatment (standard piston in a commercially-available engine), (2) micro dimple treatment (45 μm ceramic particles were air-blasted onto the piston surface), (3) molybdenum disulfide (MoS2) shot treatment (1 μm MoS2 particles were air-blasted onto the piston surface), and (4) combination of the previous two micro dimple and MoS2 shot treatments (first 45 μm ceramic particles and then 1 μm MoS2 were air-blasted onto the piston surface). Results indicated that friction decreased in the following order: no treatment > micro dimple treatment > MoS2 shot treatment > combination of micro dimple and MoS2 shot treatments.

Experimental development of apparatus to measure piston assembly friction in an eco-mileage vehicle engine

Nakashima Kohei, Uchiyama Yosuke

Combustion Engines

2019

R. 58, nr 2

55--59

Apparatus was developed to measure piston assembly friction with a floating cylinder liner against crank angle, using components of an eco-mileage vehicle engine as much as possible. This apparatus was then used to investigate the effect of different sets of piston rings on piston assembly friction in an eco-mileage vehicle engine. Results indicated that, compared to the piston with all three rings (a top ring, a second ring and an oil ring), the piston with two rings (a top ring and an oil ring) reduced piston assembly friction at all engine temperatures and engine speeds. Another configuration of two rings, with the top ring and the second ring, but without the oil ring, reduced friction at a lower engine temperature and speed, but was almost the same as the three-ring set at a higher engine temperature and speed. Finally, a one-ring set, with only the top ring, further reduced friction, except at a higher temperature and speed, where friction was greater than the two-ring set without the second ring.