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A simple method is frequently used to calculate a reciprocating engine’s bearing load from the measured cylinder pressure. However, it has become apparent that engine downsizing and weight reduction cannot be achieved easily if an engine is designed based on the simple method. Because of this, an actual load on a bearing was measured, and the measured load values were compared with a bearing load distribution calculated from cylinder pressure. As a result, it was found that some of actual loads were about half of the calculated ones at certain crank angles. The connecting rod’s elastic deformation was focused on as a factor behind such differences, and the rod’s deformation due to the engine’s explosion load was studied. As a result, it was found that the rod part of the engine’s connecting rod was bent by 0.2 mm and became doglegged. Additional investigation regarding these findings would allow further engine downsizing.

Reducing friction in the crankshaft main bearings is an effective means of improving the fuel efficiency of reciprocating internal combustion engines. To realize these improvements, it is necessary to understand the lubricating conditions, in particular the oil film pressure distributions between crankshaft and bearings. In this study, we developed a thin-film pressure sensor and applied it to the measurement of engine main bearing oil film pressure in a 4-cylinder, 2.5 L gasoline engine. This thin-film sensor is applied directly to the bearing surface by sputtering, allowing for measurement of oil film pressure without changing the shape and rigidity of the bearing. Moreover, the sensor material and shape were optimized to minimize influence from strain and temperature on the oil film pressure measurement. Measurements were performed at the No. 2 and 5 main bearings.

For various densities of gas jets including very light hydrogen and relatively heavy ones, the penetration length and diffusion process of a single high-speed gas fuel jet injected into air are computed by performing a large eddy simulation (LES) with fewer arbitrary constants applied for the unsteady three-dimensional compressible Navier-Stokes equation. In contrast, traditional ensemble models such as the Reynolds-averaged Navier-Stokes (RANS) equation have several arbitrary constants for fitting purposes. The cubic-interpolated pseudo-particle (CIP) method is employed for discretizing the nonlinear terms. Computations of single-component nitrogen and hydrogen jets were done under initial conditions of a fuel tank pressure of gas fuel = 10 MPa and back pressure of air = 3.5 MPa, i.e., the pressure level inside the combustion chamber after piston compression in the engine.

The piston rings, the engine sliding parts, are required to further contribute on mechanical loss reduction in order to improve fuel efficiency. However, many cases of the abnormal combustion due to oil upward flow, as well as the increase in oil consumption have been reported. Therefore, elucidation of the mechanism of those phenomena is still an urgent task. It is widely known that the distribution of the sliding face pressure in between the piston ring and the cylinder bore largely influence the oil flow via the sliding face of the piston ring. However, there are many unknown aspects in this field. Therefore, verification of the sliding face pressure during the actual operation is necessary in order to elucidate the mechanism of oil consumption. The thin-film sensor, since it has little influence on shape, is widely used as a measurement method of the sliding face pressure between two different faces, however this method has never been applied to the piston ring in the past.

An apparatus that automatically samples lubricating oil and measures the size distribution of particles in the oil has been developed in order to monitor the state of engines and transmissions in operation. It is a widely known fact that when an engine or transmission seizes or experiences unusual wear, comparatively large pieces of wear debris are released. The goal of the use of the apparatus is to detect these particles of wear debris, stop testing before damage occurs, and clarify the causes. Seizure was, therefore, artificially induced in a transmission, and the wear debris in the oil was closely analyzed following the test. The results showed that when the simulated seizure occurred, large, elongated particles of wear debris were produced. Similar wear debris was observed in oil recovered from the market following the seizure of a component, and at present this is believed to be a type of wear debris characteristic of seizure.