a Study on the Effect of Piston stiffness on Pin Rotation in a Diesel Engine

Kentaro Seki･Akemi Ito (Tokyo City University)･Yorimasa Tsubota･Junichi Miwa (Isuzu Motors)

To elucidate the rotational generation mechanism of full- floating piston pins with superior anti-seizure properties, the torque for pin rotation was measured using a newly developed testing apparatus. The effect of the stiffness of the pin boss bearing of a piston was investigated. It wasfound that pistons exhibiting low structural stiffness generate insufficient rotational force. Furthermore, the tests demonstrated that uneven contact resulted from bearing deformation were key factors that significantly impede proper pin rotation.

Oil Film Distribution and Skirt Friction Loss in the Concave Created by Piston Skirt Profile or Pattern Coating

Junpei Oshima･Kenta Sato･Hisanobu Kawashima･Hidekazu Suzuki･Tsuneaki Ishima (Gunma University)

The FMEP reduction of the skirt with the concave on the sliding surface has been estimated by calculations. Pistons with the concave in skirt profile were tested. The distribution of the oil film in the concave area was observed, and the process of oil inflow into the concave area was investigated. The skirt FMEP calculation was carried out using the results of obtained oil film distribution in the concave. The concave area has an effect of reducing skirt FMEP.

The effect of piston skirt lubrication on piston performance by modified piston shape

Kunihiko Kobayashi･Kenta Hayashi･Toshio Kobayashi･Hiroki Kosaka･Wataru Sakurai (Art Metal Mfg.)

The lubrication of the piston skirt, which moves in contact with the cylinder bore, is known to affect friction and vibration transmission to the cylinder block. In this study, when we change the lubrication of the piston skirt by modifying the stiffness and profile of the skirt, we investigate the effect of skirt lubrication on piston performance. And based on these results, we examine design guidelines to ensure the required lubrication.

Smoothing of Anodic Oxidation Film on Piston Top Ring Groove

Haruhiko Murakami･Masahiro Fujita･Shinya Suzuki (Suzuki Motor)

This study investigates the effect of smoothing the anodic oxide film on piston top ring grooves to reduce particulate number (PN) emissions immediately after cold start in direct-injection gasoline engines. Engine tests reveal a strong correlation between groove surface roughness (Ra, Rpk) and PN emissions, suggesting that roughness reduction effectively mitigates PN generation. We also confirmed that the superimposed AC/DC anodic oxidation method forms a more homogeneous film than the conventional DC method. Furthermore, we propose an ultra-low-pressure shot blasting technique aiming at mass-production applicability, which successfully reduces Ra and Rpk. This process improves oil behavior, demonstrating significant potential for suppressing PN emissions.

A Study on the effect of the Anodized Coating in the Piston Top Ring Groove on the Running-in Process and Oil Consumption

Ryuto Furumizo･Shunsuke Ito･Akemi Ito (Toyko City University)･Masahiro Fujita･Haruhiko Murakami (Suzuki Motor)

Anodized coating is applied to the piston top ring groove to prevent wear. The coating is also expected to promote early running-in and reduce PN. In this study, the effects of properties of the coating on oil consumption, which is a substitute characteristic of PN, and running-in process were investigated.

Observation of Land Oil Distribution to Elucidate Upward Oil Transport Pathways

Ryo Takenaka･Kenta Sato (Gunma University)･Noriaki Ida (Mitsubishi Heavy Industries)･Hisanobu Kawashima･Hidekazu Suzuki･Tsuneaki Ishima (Gunma University)

The oil distribution on the piston lands area was visualized to clarify the dragging oil flow phenomena by using a test engine with transparent sapphire cylinder. The tests were carried out under conditions of both 2-piece and 3-piece oil rings, as well as top rings with different gaps. The oil flow is primarily affected by the accumulated oil on the piston land area, while the ring specifications have a relatively less significant influence on it.