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A series of NVH experiments were performed for a set of single cylinder engine models made of aluminum, with bore sizes of 100mm. Each engine model consists of a cylinder head, a cylinder block and a bedplate. Each has the same size of 150mm × 150mm, with different heights of 100mm, 200mm and 80mm, respectively. By choosing 112 measuring points on the structure surfaces, we performed a series of impact tests for the following cases, (a) The cylinder head and the bedplate were fastened to the cylinder block by two sets of ISO M10 Tap-bolts, each with the lengths l1=117mm and l2=97mm. (b) The cylinder head and the bedplate were fastened to the cylinder block together by a set of ISO M10 Through-bolts of grip length l3=380mm.

A series of NVH experiments were performed for a set of single cylinder engine models made of aluminum, consisting of a cylinder head, a cylinder block and a bed-plate. Each has the same outer size of 150mm × 150mm; the different heights are 100mm, 200mm and 80mm respectively. Those dimensions were determined following the dimensions for a diesel engine in lightweight commercial vehicle with the bore size of 100mm and the crankshaft main bearing diameter of 60mm. We chose 112 of measuring points on the structure surfaces and performed a series of impact tests, for the following cases: (a) When the cylinder head and the bed-plate were fastened to the cylinder block by two sets of four ISO M10 tap-bolts, each with the lengths ℓ1 =117mm and ℓ2 =97mm. (b) When the cylinder head and the bed-plate were fastened to the cylinder block together by a set of four ISO M10 through-bolts of grip length ℓ3 =380mm.

The dynamic behaviors of power-plant have much effect on interior noises and vibrations of passenger cars, especially, in the frequency range below 1000 Hz. So it is very important to estimate the vibrations of power-plant at the design stage. To predict the dynamic behaviors of power-plant including the rotating elastic crankshaft system, the time domain dynamic simulation methods have been applied, however such analyses require much time and resource of computer. In this report, the exciting forces to the cylinder block are derived in the frequency domain from both the dynamic stiffness of bearing oil films and the dynamic displacements of crankshaft journals, so that the computation time is reduced considerably. To estimate the displacements of the crankshaft journals, the vibrations of an engine crankshaft system including crank journal oil films under firing conditions are calculated using the dynamic stiffness matrix method in the frequency domain.

A newly developed OHC (Over-Head Camshaft) prototype of a six-cylinder in-line diesel engine (with bore size: 114mm, stroke size: 130mm) was studied, comparing with the previous version of OHV (Over-Head Valve) type engine (with bore size: 110mm, stroke size: 130mm). It was found that the new type of cylinder block (with 130.8 kg of mass) has significantly lower natural frequencies than those for the previous type of cylinder block (with 133.2 kg of mass). Furthermore, slightly more predominant engine noise and vibration were induced in the new engine. The vibration behavior and the excitation force transmission characteristics were investigated by EMA (Experimental Modal Analysis). We performed a series of impact tests for (1) free-free cylinder block, (2) free-free crankshaft substructure with torsional damper and flywheel attached, and (3) the case where (1) and (2) are assembled together.

By applying the dynamic stiffness matrix method, three-dimensional vibrations of the crankshaft system under firing conditions were investigated for an automobile engine, taking account of the vibration behavior of the torsional damper and the cylinder block. To simplify the analyses, the crankshaft was idealized by a set of jointed structures consisting of simple round rods and simple beam blocks of rectangular cross-section; the main journal bearings were idealized by a set of linear springs and dash-pots. For the flywheel of flexible structure, the dynamic stiffness matrix was derived from FEM. However, for the cylinder block, the dynamic stiffness matrix was constructed from the experimental values of the modal parameters obtained from the experimental modal analysis (EMA), because of the complicated structure.

In most high-speed engines of the OHC (over head camshaft) type, a number of gears are engaged with the crankshaft gear to drive the valve gear mechanism, the fuel injection pump, and other accessories such as the oil pump or power steering system. Each of the gears usually has a significant mass and moment of inertia. We investigated the influence of the masses and moments of inertia of the gears on three-dimensional vibrations of the crankshaft system. A four-cylinder in-line diesel engine (4 - ϕ115 × 110, 140ps / N = 3200pm) was used for a series of experiments and analyses. The three-dimensional vibrations of the crankshaft system were measured by the hammering tests and the shaker tests. We calculated the vibration behavior by applying an idealized simple modeling for the crankshaft system and the gear train.

Crankshaft torsional dampers are increasingly being used for the gasoline engines of compact cars as well as for ordinary high speed diesel and gasoline engines. Recently, so-called bending dampers are sometimes attached to the torsional dampers to reduce the bending and axial vibrations. To investigate the influence of such crankshaft torsional and bending dampers on the crankshaft vibrations, we first designed three kinds of dampers, each for the reduction of the crankshaft vibration, in the torsional, axial, and radial directions. Next, we developed two kinds of dampers for the simultaneous reduction in the torsional and axial modes, and in the torsional and radial direction modes. We measured the three-dimensional vibrations for both the dampers and the crankshaft, under engine operating conditions, A four-cylinder in-line diesel engine (4 - ϕ 115 x 110) was used for the experiments.

Torsional dampers have been attached to engine crankshafts only for the control of the crankshaft torsional vibrations. However, a torsional damper is a mass-spring system of three-dimensions, so the torsional damper could exert some influence on the three-dimensional vibrations of the crankshaft system. Since the inertia ring of the torsional damper has moments of inertia and it rotates with the crankshaft, gyroscopic vibrations of the inertia ring can also be generated. For a V-type ten-cylinder diesel engine (V- 10, ϕ119 × 150), the three-dimensional vibrations of the crankshaft system were calculated by the dynamic stiffness matrix method, taking account of the influence of the gyroscopic vibrations of the inertia ring of the torsional damper. The dynamic bending stresses were measured at the fillets of both the No.1 crank journal and the No.1 crank pin in the No.1 crank throw plane.

In most high-speed engines, the crankshaft systems can become one of the most dangerous excitation sources. Since the crankshaft has significant kinetic and elastic (potential) energy, and is subjected directly to the impulsive excitation forces, significant engine structure noise and vibrations can often be caused. However, all excitation forces would be transmitted from the rotating crankshaft system to the engine structure only through the crankshaft main bearings. To investigate the excitation interaction between the crankshaft system and the engine structure, and the correlation between the crankshaft vibrations and the engine structure noise and vibrations, three phenomena were measured: (1) the crankshaft three-dimensional vibration behavior, (2) the vibration behavior of each crank journal main bearing, and (3) the engine structure noise at 1 m from the engine side.

In a heavy-duty engine with solid-structure crankshaft (in which all crank-throws are arranged radially in different planes), since a torsional deformation in one crank-throw can induce axial and bending deformations in other crank-throws, significant bending stresses can be induced at particular portions in the crankshaft by crankshaft torsional vibrations. In this paper, the correlation between the crankshaft torsional vibrations and the dynamic bending stresses at the front and rear fillets of the No. 1 crank-pin under operating conditions were investigated for a Vee-type 10-cylinder diesel engine. The dynamic bending stresses at the front and rear fillet of the No. 1 crank-pin in the crank-throw plane, and the torsional vibrations at the front end of the crank-pulley, were simultaneously measured under firing conditions. The three-dimensional vibration behavior of the crankshaft was calculated by the dynamic stiffness matrix method.

To decrease the noise and vibration of an engine powerplant, the three-dimensional vibration behavior of the crankshaft system must be clarified precisely. However, the description of dynamic behavior in fixed coordinates would be extremely complex, since many time-variable parameters must be introduced in the equation of motion for the rotating crankshaft. In this research, the vibration behavior of a rotating crankshaft system was analyzed by a rotating coordinate system attached to the crankshaft system: (1) by deriving the time-invariable characteristic matrices of multi-degrees of freedom for the crankshaft system, and (2) by calculating the forced vibration behavior of the crankshaft system under operating conditions.

This paper describes the investigation of the mechanisms of engine front noise generation and the corresponding countermeasures employed in the development of Hino's medium duty diesel engine. The engine front noise, which had a noise peak in the 630 Hz 1/3 octave band, was investigated by experiment and it was concluded that there were two mechanisms as follows: 1) Combustion pressure excites the crankshaft. Noise is generated by the crankshaft pulley which vibrates with the crankshaft system mode shapes. 2) The cavity between the torsional damper and the timing gear case resonates as a result of the vibration of the torsional damper. Noise caused by the acoustic resonance is emitted to the front of the engine. Using both experimental and analytical methods, crankshaft vibration and acoustic resonance were reduced, thus yielding a substantial noise reduction.

For most light-weight, high-power high-speed engines, slight differences in the pulley size and flywheel size can cause significant differences in engine structure noise and vibrations. In this research, a four-cylinder in-line (turbocharged) diesel engine of 1.7 liter (4-79x86) capacity for passenger cars was used. The vibration behavior of the total crankshaft system was intentionally changed by attaching five kinds of front pullies, each with different masses and moments of inertia. The influences of the pulley's dimensions on crankshaft vibration behavior and on the excitation transmission behavior from the crankshaft to the engine structure were examined. The crankshaft axial vibration at the pulley, the cylinder block surface accelerations, and the engine noise level were measured simultaneously under firing conditions.

We have clarified the effects of engine vibration reduction and the design of a torsional-bending damper pulley by an experimental analysis focusing on the vibration behavior at the front end of a crankshaft. The test was conducted using a newly developed device which can easily measure the vibration in radial and axial directions at the front end of a crankshaft during engine firing. This test confirmed that the vibration in the radial direction was dominant compared with that in the axial direction at the front end of the crankshaft. It was observed that a torsional-bending damper pulley works effectively to reduce torsional vibration, as well as to reduce the bending vibration of a crankshaft.

The coupling behavior of the torsional, bending, and longitudinal vibrations in the crankshaft is described. The incidental excitation forces under crankshaft torsional vibration due to reciprocating and rotating masses are derived theoretically. Experiments on the coupling behavior of the crankshaft vibrations and the excitation behavior in the engine structure were performed in a four-cylinder automotive engine; their results are discussed.

The generation mechanism of the knocking-like, characteristic engine noise in a swirl-chamber-type, automotive engine was investigated. This characteristic engine noise was particularly dominant in cold weather and at idling conditions. It was found that in cold weather, cylinder pressure pulsations of significant amplitude can be induced in the main chamber by the cavity resonance of the swirl chamber and throat, but the pulsations distribute non-uniformly on the piston top surfaces. Collisons between the pistons and the cylinder liners were induced by the pulsating, non-uniformly distributed cylinder pressure, therefore engine structure noise was generated.