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This paper describes a newly developed hydraulic variable valve timing control (VTC) system, targeting the internal combustion gasoline engine, with an optimum angular position locking mechanism to reduce tailpipe emissions (TPE). In general, emission control catalysts are used as one measure to reduce TPE. However, there is the issue that catalysts cannot remove pollutants before reaching its light-off temperature at cold engine start. To address this issue, we have been using a method of increasing the valve overlap period between intake valve opening (IVO) and exhaust valve closing (EVC) by operating a VTC system at engine start. This brings engine-out emissions (EOE) back to the combustion chamber to be burned, thereby reducing EOE levels. However, this method requires about 3 seconds for the sufficient hydraulic pressure to start VTC operations.

Research is under way on an engine system [1] that achieves a variable compression ratio using a multiple-link mechanism between the crankshaft and pistons for the dual purpose of improving fuel economy and power output. At present, there is no database that allows direct judgment of the feasibility of the specific sliding parts in this mechanism. In this paper, the feasibility was examined by making a comparison with the sliding characteristics and material properties of conventional engine parts, for which databases exist, and using evaluation parameters based on mixed elasto-hydrodynamic (EHD) lubrication calculations. In addition, the innovations made to the mixed EHD calculation method used in this study to facilitate calculations under various lubrication conditions are also explained, including the treatment of surface roughness, wear progress and stiffness around the bearings.

A new variable valve event and lift (VVEL) system has been developed by applying a multiple-link mechanism. This VVEL system can continuously vary the valve event angle and lift over a wide range from an exceptional small event angle and small lift and to a large event angle and large lift. This capability offers the potential to improve fuel economy, power output, emissions and other parameters of engine performance. The valve lift characteristics obtained with the VVEL system consist of a synthesis of the oscillatory motion characteristics of the multiple-link mechanism and the oscillating cam profile. With the multiple-link mechanism, the angular velocity of the oscillating cams varies during valve lift, but the valve lift characteristics incorporate both gentle ramp sections and sharp lift sections, the same as a conventional engine.

A variable compression ratio (VCR) technology, that has a new piston-crankshaft mechanism with multi links, has been patented and developed by Nissan for some years (This technology has been detailed in previous SAE paper 2003-01-0921 and 2005-01-1134). This paper will present the use of this VCR technology for Diesel engine. The objective set with the use of VCR for Diesel engine is mainly to reduce as much as possible engine out emission to prepare for long-term, more strict emission standards. Results presented will include the description of the 2l Diesel VCR engine and its VCR mechanism adapted to Diesel constraints. Combustion tests have been performed with the use of HCCI (Homogeneous Charge Compression Ignition) combustion. This technology is still in a research phase in Renault: the adaptation of VCR technology to a Diesel engine consists in the modification of several parts with the addition of lower links, control links and control shaft.

Some automakers have been studying variable compression ratio (VCR) technology as one possible way of improving fuel economy. In previous studies, we have developed a VCR mechanism of a unique multiple-link configuration that achieves a piston stroke characterized by semi-sinusoidal oscillation and lower piston acceleration at top dead center than on conventional mechanisms. By controlling compression ratio with this multiple-link VCR mechanism so that it optimally matches any operating condition, the mechanism has demonstrated that both lower fuel consumption and higher output power are simultaneously possible. However, it has also been observed that fuel consumption does not reduce further once the compression ratio reached a certain level. This study focused on the fact that the piston-stroke characteristic obtained with the multiple-link mechanism is suitable to a longer stroke.

A multiple-link variable compression ratio (VCR) mechanism is suitable for a long-stroke engine by providing the following characteristics: (1) a nearly symmetric piston stroke and (2) an upper link that stays vertical around the time of the maximum combustion pressure. These two characteristics work to reduce force inputs to the piston. The maximum inertial force around top dead center is reduced by the effect of the first characteristic. The second characteristic is effective in reducing piston side thrust force and helps ease piston pin lubrication. Because of the combined effect of these characteristics, the piston skirt can be made smaller and the piston pin can be shortened. That makes it possible for the piston skirt and piston pin to move between the counterweights, resulting in a downward extension of the piston stroke. As a result, a longer-stroke engine mechanism can be achieved without making the cylinder block taller.

The concept of the Early or late Intake valve closing cycle has been examined over the years as a technique for improving fuel economy in conjunction with the use of a three-way catalyst for excellent exhaust emission performance. With this concept, the intake valve closing (IVC) timing is set either before or after bottom dead center. With the emergence of continuously variable valve timing and lift (VEL) systems in recent years, the Early IVC cycle has become a more familiar concept. However, the Early IVC cycle has an intrinsic drawback in that, although pumping losses decrease when charging efficiency is reduced in connection with IVC control, combustion performance deteriorates due to the decline in the effective compression ratio. In recent years, full-scale research has been undertaken on variable compression ratio systems as a new type of variable engine mechanism separate from variable valving.

A continuously variable valve event and lift (VEL) system, actuated by oscillating cams, can provide optimum lift and event angles matching the engine operating conditions, thereby improving fuel economy, exhaust emission performance and power output. The VEL system allows small lift and event angles even in the engine operating region where the required intake air volume is small and the influence of valvetrain friction is substantial, such as during idling. Therefore, the system can reduce friction to lower levels than conventional valvetrains, which works to improve fuel economy. On the other hand, a distinct feature of oscillating cams is that their sliding velocity is zero at the time of peak lift, which differs from the behavior of conventional rotating cams. For that reason, it is assumed that the friction and lubrication characteristics of oscillating cams may differ from those of conventional cams.

The authors have previously proposed an engine system that uses a new piston-crank system incorporating a multiple-link mechanism to vary the piston's motion at top dead center and thereby obtain the optimum compression ratio matching the operating conditions. This multiple-link variable compression ratio (VCR) mechanism can be installed without increasing the engine size or weight substantially by selecting a suitable type of link mechanism and optimizing the detailed specifications. Previous papers by the authors have made clear the features of the VCR mechanism that facilitates continuously variable control of the compression ratio [1][2]. It was shown that engine friction attributable to piston-side thrust can be reduced through an upright orientation of the upper link in the expansion strokes.

The authors have previously proposed an engine system that uses a new piston-crank system incorporating a mulitiple-link mechanism to vary the piston's position at top dead center and thereby obtain the optimum compression ratio matching the operating conditions. This multiple-link variable compression ratio (VCR) mechanism can be installed without increasing the engine size or weight substantially by selecting a suitable type of link mechanism and optimizing the detailed dimentions. We have previously reported that this system provides additional benefits by reducing second-order inertial forces and the friction losses caused by piston side thrust in the combustion and expansion processes. This paper first describes the further improvements made to the link dimensions since our previous report. An improved link geometry is presented in which the centerline of the cylinder bore is offset in the opposite direction from that of existing internal combustion engines.

This paper presents a variable compression ratio (VCR) system that has a new piston-crankshaft mechanism with multiple links. This multi-link mechanism varies the piston position at top dead center (TDC), making it possible to change the compression ratio of the engine continuously. Previous attempts have been made to achieve variable compression ratio with this type of method, but it was difficult to avoid various undesirable effects such as an increase in the engine size, substantial weight increases, increased engine block vibration due to a worsening of piston acceleration characteristics and increased friction resulting from a larger number of sliding parts. At the stage of developing the basic design of the multi-link geometry, emphasis was placed on selection of a suitable link geometry and optimization of the detailed dimensions with the aim of essentially resolving these previous issues.

A new variable valve actuation system that varies valve lift and timing events continuously has been devised and confirmed to substantially improve power and reduce fuel consumption when applied to a SI engine. The variable valve event and lift (VEL) system is a simple mechanism consisting of oscillating cams and linkages, enabling it to operate the valves smoothly even at high speed. Its compact size facilitates application to direct-acting valve trains and its ability to vary valve lift from a deactivated state (0) to a large lift amount allows the system to be used with a wide range of engine concepts. In this study, VEL was combined with a phase shifting function to enable the valve lift characteristic to be varied virtually arbitrarily, and test results showed that fuel consumption of a SI engine was reduced by nearly 10%.

This paper describes a new variable valve control device called VEL (Variable Valve Event and Lift Control Device), which enables continuous control of both valve events (opening duration) and valve lifts, from the lowest lift or deactivation state (0) to a long event and high lift state. VEL is composed of two subsystems. One is a mechanical valve train system, which converts crankshaft rotation into output cam oscillation via a transmission mechanism involving a rocker arm. The valves are moved by the output cam oscillation. The other is an electric powered actuator system, which varies valve events and lifts according to driving conditions by controlling the angular positions of a control shaft. This control shaft has a eccentric control cam inserted into the fulcrum cylinder of the rocker arm, so as to change the state of the transmission mechanism and the output cam.

Modern engine bearings have been operating under very harsh conditions. Consequently, a bearing wear propagates for a short time and a fatigue sometimes occurs on high loaded region. To reproduce the bearing damage in actual engines, the operating conditions of engine bearing were simulated on a rig test machine. The bearing wear was measured until the fatigue crack occurred in the simulation test. The wear progressed at the edges of the bearing length and the crack also was observed near the edges. The bearing damage is influenced by the bearing design and operating conditions. The experiment was conducted to change the design parameters in conditions. The experimental results were compared to the calculated results based on the elastohydrodynamic lubrication (EHL) theory. The correlation between bearing damage and bearing performance by theoretical analysis were investigated on effects of the design parameters.

The possibility of predicting engine bearing durability by elastohydrodynamic lubrication (EHL) calculations was investigated with the aim of being able to improve durability efficiently without conducting numerous confirmation tests. This study focused on the connecting rod big-end bearing of an automotive engine. The mechanisms of wear and fatigue, which determine bearing durability, were estimated by comparing the results of EHL analysis and experimental data. This comparison showed the possibility of predicting the wear amount and the occurrence of fatigue by calculation.

We succeeded in developing a parallel hybrid electric vehicle (HEV) with a fuel efficiency in the 10-15 mode more than double that of existing vehicles of the same class of driving performance. A prominent feature of this HEV system is the belt-drive continuously variable transmission (CVT) with built-in traction motor and powder clutch. Adopting a more efficient configuration proved effective in minimizing cost increases and loss of space utility and offered the same reliability provided by existing vehicles. This paper discusses the functional design aspects of the parallel HEV system, which holds great promise for viable mass production.

Engine bearings today are operating under very harsh conditions. Consequently, a wear propagates for a short time and a fatigue sometimes occurs on the bearings. In present study, on the rig test machine, the operating conditions of engine bearing were simulated to reproduce the bearing damage. The bearing wear was measured until the fatigue crack occurred. The bearing wear increased at the edges of the bearing length and the crack also was observed near the edges. The experimental results were compared to the calculated results based on the elastohydrodynamic lubrication (EHL) theory. The correlations between the bearing damage and the bearing performances by the theoretical analysis were investigated.

Achieving a multi-cylinder engine with excellent noise/vibration character sties and low friction at the main bearings requires an optimal design not only for the crankshaft construction but also for the bearing support system of the cylinder block. To accomplish that, it is necessary to understand crankshaft system behavior and the bearing load distribution for each of the main bearings. Crankshaft system behavior has traditionally been evaluated experimentally because of the difficulty in performing calculations to predict resonance behavior over the entire engine speed range. A coupled crankshaft-block analysis method has been developed to calculate crankshaft system behavior by treating vibration and lubrication in a systematic manner. This method has the feature that the coupled behavior of the crankshaft and the cylinder block is analyzed by means of main bearing lubrication calculations. This paper presents the results obtained with this method.

It is important to understand the influence of housing stiffness on bearing performance, particularly for the connecting rod bearings of automotive engines. It is known that the engine lubricant shows a piezoviscous characteristic whereby its viscosity changes under the influence of pressure. Engine bearings under a heavy load are apt to be influenced in this way. In this study, the effects of connecting rod stiffness and lubricant piezoviscosity on bearing performance were examined by elastohydrodynamic lubrication (EHL) analysis under conditions corresponding to the high-speed operation of an actual engine. The results indicated that under such heavy load conditions housing stiffness greatly affects friction loss because of lubricant piezoviscosity. It was also found that the piezoviscosity of the lubricant has a large effect on bearing performance, as does its viscosity under atmospheric pressure.

This paper presents a numerical model of the rotational and lateral dynamics of the piston (secondary motion) and piston slap in mixed lubrication. Piston dynamic behavior, frictional and impact forces are predicted as functions of crank angle. The model considers piston skirt surface waviness, roughness, skirt profile, thermal and mechanical deformations. The model considers partially-flooded skirt and calculates the pressure distributions and friction in the piston skirt region for both hydrodynamic and boundary lubrication. Model predictions are compared with measurements of piston position using gap sensors in a single-cylinder engine and the comparison between theory and measurement shows remarkable agreement.