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Since the sizes of the flywheel and clutch have been enlarged due to downsizing of diesel engines, the mass and moment of inertia at the crankshaft rear end have increased. Consequently, the serious bending stresses have appeared in the crankshaft rear. This paper describes the characteristics of those serious bending stresses, based on the mechanism for whirl resonance. The whirl resonance is largely impacted by the mass of the flywheel and clutch and by the distance from the crank-journal center of the rear end to the center of gravity of the flywheel and clutch.

As the issue of global warming has become more serious, needs for downsizing or weight saving of an engine has been getting stronger, and forces exerted on engine parts, especially force on a crankshaft, have been getting larger and larger. In addition, since a crankshaft is a heavy engine part, needs for saving weight have been getting stronger and stronger. Therefore, determining the mechanism of high stress generation in a crankshaft system is urgently needed. This paper describes the characteristics and mechanism of a severe bending stress caused by the whirl of crankshaft rear end of an inline 6-cylinder medium-duty diesel engine. The authors measured bending stress on the fillets of the crankshaft, and found severe levels of sharp peaks in the stress curves for the crankshaft rear. To figure out why the severe levels of sharp peaks appear, they analyzed and studied the measured data.

This paper describes the characteristics and mechanism of crankshaft impact noise that radiates from the cylinder body at full load medium engine speeds, based on the mechanism for axial vibration of crankshaft coupled with torsional vibration of crankshaft.

Improving idle sound quality as well as reducing idle noise level is increasingly demanded for diesel engines. Therefore, unusual noise occurrence at idle is a serious problem, and the noise must be removed. This paper describes the characteristics and mechanism of ticking noise that is unusual noise radiated from the journal bearing of the camshaft at low idle speeds, based on the mechanism of cavitation in oil film existing between the journal and bearing.

A torsional damper is attached to a crankshaft to control the torsional vibration of the crankshaft system. However, the damper, which has a rubber part in between a damper mass and a damper hub, possesses a three-dimensional inertia moment and an inertia mass that could excite the crankshaft system. This paper discusses the generating mechanisms of the bending strain on the bolt to fasten the damper hub to the crankshaft, from the measured bolt strains and the measured behavior of the damper mass and the damper hub under the engine operating conditions.

The noise of diesel engines operating at low idle is an important noise evaluation criterion in both commercial vehicles and passenger cars. At low idle, a quiet, pleasant noise is required. Accordingly, unusual noise occurrence at low speed is a serious problem, and the noise must be prevented. In this paper, characteristics of the stick-slip noise, which is an unusual noise that radiates from the oil seal at low idle and the generating mechanism of the stick-slip noise in the six-cylinder-inline diesel engine are discussed. In addition, a method to prevent the stick-slip noise is presented.

Engine vibration is a great disadvantage of a V-type six-cylinder engine because ignition does not occur at regular intervals. The engine achieves ignition at regular intervals by having a crank pin offset crankshaft. The shape of the crank pin offset crankshaft is so complex that the location of the crank pin on which bending stress concentrates cannot be obtained easily. This paper reports on the mechanism that generates bending stresses on the crank pin, and discusses the location at which the maximum bending stress is generated with crank pin offset crankshaft.

Engine crankshafts have been designed to avoid low-harmonic-order resonant torsional vibration in a commonly-used engine speed range, but the authors have found that, in some engines, especially turbo-charged engines, a significant degree of a low-harmonic-order exciting torque acts on the crankshaft. In these engines, the amplitude of non-resonant low-harmonic-order torsional vibration is almost as large as that of the resonant one. The authors conclude that the 3rd-order non-resonant torsional amplitude is not only significant but also characteristic of the turbo-charged engine in comparison with the naturally-aspirated engine, and recommend that crankshafts on turbo-charged diesel engines should be made stiffer than those on naturally-aspirated engines.

This paper describes measurement and calculation method for determining pressure on an engine gasket under the static and dynamic condition. At first, the relationship between the strain of the cylinder liner and the pressure on the gasket was determined. Then the strain of the cylinder liner was measured under the static condition as well as under the dynamic condition. The gasket contact pressure was also calculated by computer using FEM model. The calculation results were compared with the measurement results. Finally, the effects of the combustion pressure and heat on the gasket contact pressure were discussed based on the strains.

Experiment results were compared with computation analysis results for torsional vibration on a crankshaft system with/without a torsional viscous damper on a six-cylinder in-line type turbocharged diesel engine and a V type ten-cylinder naturally-aspirated diesel engine respectively. At first, the boundary conditions for boundary element method (BEM) model were determined to estimate the torsional stiffness of the crank-throws of the crankshafts. Then, the estimated stiffness was used to calculate the natural frequencies of the torsional vibration without the damper by dynamic stiffness matrix method. As a result, the calculated natural frequencies approximately agreed with the measured ones. Finally, the torsional vibration with the damper was analyzed by using the dynamic stiffness matrix method and complex viscous damping coefficients for the damper. The calculated torsional amplitudes and resonant engine speeds agreed with the experiment results.