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In recent years, although experiment technologies on real engines and simulation technologies has been improved rapidly, the tribology contributing factors have not been quantitatively well evaluated to reveal critical lubrication failure mechanisms. In this study the oil film thickness of the main bearings in multicylinder diesel engines was measured, and the data was analyzed using response surface methodology, which is a statistical analysis methods used to quantitatively derive the factors affecting oil film thickness and the extent of their contribution. We found that the factor with the strongest effect on minimum oil film thickness is oil pressure. Lastly, as a verification test, bearing wear on the main bearings was compared under various oil pressure conditions. Clear differences in bearing wear were identified.

Understanding and prediction of flash-boiling spray behavior in gasoline direct-injection (GDI) engines remains a challenge. In this study, computational fluid dynamics (CFD) simulations using the homogeneous relaxation model (HRM) for not only internal nozzle flow but also external spray were evaluated using CONVERGE software and compared to experimental data. High-speed extinction imaging experiments were carried out in a real-size axial-hole transparent nozzle installed at the tip of machined GDI injector fueled with n-pentane under various ambient pressure conditions (Pa/Ps = 0.07 - 1.39). The width of the spray during injection was assessed by means of projected liquid volume, but the structure and timing for boil-off of liquid within the sac of the injector were also assessed after the end of injection, including cases with different designed sac volumes.

An accurate prediction of internal nozzle flow in fuel injector offers the potential to improve predictions of spray computational fluid dynamics (CFD) in an engine, providing a coupled internal-external calculation or by defining better rate of injection (ROI) profile and spray angle information for Lagrangian parcel computations. Previous research has addressed experiments and computations in transparent nozzles, but less is known about realistic multi-hole diesel injectors compared to single axial-hole fuel injectors. In this study, the transient injector opening and closing is characterized using a transparent multi-hole diesel injector, and compared to that of a single axial hole nozzle (ECN Spray D shape). A real-size five-hole acrylic transparent nozzle was mounted in a high-pressure, constant-flow chamber. Internal nozzle phenomena such as cavitation and gas exchange were visualized by high-speed long-distance microscopy.

Hino Motors had developed an electronically controlled mechanical automatic transmission and employed it for the ′85 models of large size buses, and also ′86 models of heavy/ medium duty trucks. This system gives minimum fuel consumption and even smoother/easier driving than an automatic transmission with torque converter, by controlling an engine also with a transmission and employing an oil spray clutch. The trade name of this system is EE-Drive which means easy and economy drive.

A newly developed viscous-rubber damper, which employed an innovative structure and a new heat resistant rubber, solved some tough problems. This paper dealt more closely with the features of the new viscous-rubber damper and the new calculation method for the viscous-rubber damper. This damper has been employed for Hino new K13C (K-II) higher boost turbocharged and air to air charge-cooled diesel engine, which has extreme severity on the torsional vibration.

This paper investigates the effects of Fischer-Tropsch Diesel (FTD) (a completely a paraffinic fuel) on the fuel supply system in automotive applications. In particular, the effects of Gas to Liquid (GTL) (an FTD synthesized from natural gas) on the elastomer components has been investigated by laboratory scale tests and field trials. In the field trials, GTL was supplied to a commercial vehicle operator and the effect of real running conditions was observed. Also, the laboratory scale testing to simulate the actual condition of usage of a commercial vehicle was conducted under stringent conditions, and a correlation with the field trials was investigated. As a result, no negative effects related to GTL were found.

Historically the high speed diesel engine for commercial vehicles has been developed along with its combustion system in compliance with political and economical changes. After the 1970's, stricter exhaust emission regulations and fuel economy requirements induced combustion developments and application of turbocharged and inter cooled engines. From the late 1980's, high pressure fuel injection has been investigated and recognized as an essential tool for lowering emissions especially of particulate matter. Although turbulence effects on both in-cylinder air motion and during the combustion process are quite effective, they show different phenomena in conventional and advanced high pressure fuel injection systems. In the 1990's, multiple injection with high pressure has been attempted for further reduction of NOx and particulate matter.

Since in-cylinder flame temperature has a direct effect on an engine's NOx characteristics, these phenomena have been studied in detail in a DI diesel engine using a newly developed method allowing the in-cylinder temperature distribution to be measured by the two color method. The flame light introduced from the visualized combustion chamber of the engine is divided into two colors by filters. The images of combustion phenomena using the two wavelengths are recorded with a framing streak camera which includes a CCD camera. The flame temperature is immediately calculated by a computer using two color images from the CCD camera. A parameter study was then carried out to determine the influence of intake valve number of the engine, and fuel injection rate (pilot injection) on the in-cylinder temperature distribution.

Large truck accidents sometimes result in severe damages or give large disturbance of traffic and there are demands of improving vehicle safety characteristics. Main types of traffic accidents concerned are rear-end collision and single accident. As countermeasures for rear-end collisions, world-first collision mitigation brake for commercial vehicles; Pre-crash Safety System, was developed. If there is possibility of collision, warning to driver and brake control intervention is carried out in stepwise fashion and collision speed is decreased. To achieve higher effect in collision mitigation, it is necessary to activate warning or brake-force in earlier timing. Inter-vehicle or infrastructure-vehicle communication offer promising prospect. Tractor-trailer combinations show some instable behaviors. “Roll Stability Assist” and “Vehicle Stability Control” were developed to assist drivers to avoid the occurrence of these instable behaviors.

This paper describes the combustion optimizations of heavy-duty diesel engines for the anticipated future emissions regulations by means of an electronically controlled common rail injection system. Tests were conducted on a turbocharged and aftercooled (TCA) prototype heavy-duty diesel engine. To improve both NOx-fuel consumption and NOx-PM trade-offs, fuel injection characteristics including injection timing, injection pressure, pilot injection quantity, and injection interval on emissions and engine performances were explored. Then intake swirl ratio and combustion chamber geometry were modified to optimize air-fuel mixing and to emphasize the pilot injection effects. Finally, for further NOx reductions, the potentials of the combined use of EGR and pilot injection were experimentally examined. The results showed that the NOx-fuel consumption trade-off is improved by an optimum swirl ratio and combustion chamber geometry as well as by a new pilot concept.

The requirements for emission control, lower fuel consumption and higher engine output have changed the engine valve train system to 4-valve/cylinder and higher cam lift designs, and these changes make the cam/tappet lubrication conditions more severe than before. Under such a working condition, there is a high possibility that cam/tappet surface damages such as scuffing, pitting and wear may occur. Among the damages, the wear of cam/tappet is the most difficult to predict since the wear mechanism still remains unclear. To understand the lubrication condition and therefore, the wear mechanism at the cam/tappet contact, friction was measured with a newly developed apparatus. Measurement results showed that the lubrication condition between cam and tappet is predominantly in the mixed and boundary lubrication conditions.

In the '97 Dakar Rally, Hino FT model, 8,000cc engine truck, won 1st, 2nd and 3rd places by defeating upper class trucks having engine of 19,000cc. The average speed of the '97 Hino model was increased more than 15 km/h over the '96 model by improving the riding comfort and handling stability. Larger diameter tires, and softer parabolic leaf springs with long and inclined axle-locus for reducing road impact, gas charged dampers, suspension rods which control compliance-steer-motion and wind-up motion of unsprung masses were adopted for the '97 model.

The Advanced Safety Vehicle (ASV) project phase 2 was organized by the Japanese ministry of lands, infrastructures and transport in 1996 as a five year project. Hino Motors participated in the project and developed an intelligent truck “HINO ASV-2”. HINO ASV-2 was equipped with safety systems for accident prevention and accident avoidance, which were most effective in reducing accidents in freight transport. These intelligent systems aimed to reduce driving fatigue, minimize the chance of driver’s mistake, and prevent the occurrence of accidents. Human-machine interface, and front underrun protection device were also studied. Through the development of the ASV systems, the feasibility and basic functions of these systems were studied. Further development is necessary to implement the ASV systems in production vehicles.

The separation of combustion noise and mechanical noise from the total noise of a four-cylinder in-line diesel engine at idling was carried out with high accuracy by changing the fuel injection timing. The mechanical noise, which accounts for the major share at 93%, was then separated into noises from the typical mechanical causes, and the valve train was found to be the major noise source. From analysis of the noise generating mechanism for the valve train, it was clarified that the noise was caused mainly by the gear rattling owing to the variation in the camshaft drive torque.

A diesel engine is advantageous in its high thermal efficiency, however it still wastes about 50% of total input energy to exhaust and cooling losses. A feasibility study of thermoacoustic refrigerator was carried out as one of the means to recuperate waste heat. The thermoacoustic refrigerator prototyped for this study showed a capability to achieve cooling temperature lower than -20 degree C, which indicated that the system has a potential to be used in refrigerator trucks not only for cargo compartment cooling but also for cabin cooling.

Technical impacts on engine oil performance by the use of waste cooking oil as bio-diesel fuel (BDF) are not well understood while the industry has made significant progress in studies on quality specifications and infrastructure. The authors, who consist of a consortium organized by Japan Lubricating Oil Society (JALOS), examined technical effects of waste cooking oil as BDF on engine oil performance such as wear and high temperature corrosion using vehicle fleets and bench tests to identify technical issues of engine oil meeting the use of BDF. The study brings fundamental information about technical impacts of BDF on engine oils.

A 2-LEG NOx Storage-Reduction (NSR) catalyst system is one of potential after-treatment technology to meet stringent NOx and PM emissions standards as Post New Long Term (Japanese 2009 regulation) and US'10. Concerning NOx reduction using NSR catalyst, a secondary fuel injection is necessary to make fuel-rich exhaust condition during the NOx reduction, and causes its fuel penalty. Since fuel injected in the high-temperature (∼250 degrees Celsius) exhaust instantly reacts with oxygen in common diesel exhaust, the proportion of fuel consumption to reduce the NOx stored on NSR catalyst is relatively small. A 2-LEG NSR catalyst system has the decreasing exhaust flow mechanism during NOx reduction, and the potential to improve the NOx reduction and fuel penalty. Therefore, this paper studies the 2-LEG NSR catalyst system. The after-treatment system consists of NSR catalysts, a secondary fuel injection system, flow controlled valves and a Catalyzed Diesel Particulate Filter (CDPF).

The correlation between newly approved EN 15751 and the internal diesel injector deposits (IDID) due to fuel oxidative deterioration has not been made clear. In the present research, the Rancimat method was slightly modified to research the relationship between fuel oxidative deterioration and the deterioration products generated from the fuel. After heating fuel at 120 to 150°C for a set period, insoluble deterioration products (IDID-like substances) were generated and their weights were measured. At the same time, the shifts of the conductivity in trap water were analyzed from a new perspective, and its relationship with the deterioration products was investigated. At 120°C and 130°C, conductivity rising rates after the inflection point (this set of data represents the rate of organic acid generation in the fuel, and we named “Oxidation rate”) exhibited a strong correlation with the quantity of deterioration products.

Approximately 200,000 units of Hino J-series diesel engine were produced for 7 years. The J-series engines had a reputation all over the world for their performance, reliability, lightweight, and installation ability. They are composed of 4, 6 cylinders engines and unique 5-cylinder engine J07C. In 2002, newly modified J-series engines, which met the Japan 2001 noise emission regulations, were developed and J07C-TI, 5-cylinder TI engine, equipped with a common-rail fuel injection system was added in the J-series. Common-rail fuel injection system was equipped in order to achieve the emission targets in the future as well as to meet the current emission regulations. Achieving higher injection pressure level through the all engine speed, include excess low speed, was effective in reduction of PM emissions and in increasing of low engine speed torque drastically.

Recently, as one of the effective measures for engine noise reduction, vibration damping steel sheets (VDSS) have been increasingly applied to engine oil sumps. This paper describes the formability of VDSS. Various factors closely related to drawability are considered. This study has been carried out in a production engineering process of manufacturing exceedingly deep, single blank sheet, oil sump for heavy-duty truck diesel engines. Some treatment of the surface of the VDSS was found to be a principal factor influencing deep drawability.