Search Results

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.

In order to improve the brake thermal efficiency of the engine, such as cooling and friction losses from the theoretical thermal efficiency, it is necessary to minimize various losses. However, it is also essential to consider improvements in theoretical thermal efficiency along with the reduction of the various losses. In an effort to improve the brake thermal efficiency of heavy-duty diesel engines used in commercial vehicles, this research focused on two important factors leading to the engine's theoretical thermal efficiency: the compression ratio and the specific heat ratio. Based on the results of theoretical thermodynamic cycle analyses for the effects of the above two factors, it was predicted that raising the compression ratio from a base engine specification of 17 to 26, and increasing the specific heat ratio would lead to a significant increase in theoretical thermal efficiency.

An energy management method and model for small electric buses was studied. The model consists of a drive motor & inverter, a lithium ion battery, electric auxiliary devices and a mechanical powertrain. A small electric bus was developed based on the short travel distance, high charging frequency concept. Since 2012, two buses have operated as community buses in two different regions, and another bus started operations in a third region in 2013. The development of an energy management model accounting for operating conditions made it possible to keep the lithium ion battery capacity to a minimum. This paper describes energy management for this small electric bus, the design of the vehicle and the results of evaluating actual operation.

Design work for truck suspension systems requires multi-objective optimization using a large number of parameters that cannot be solved in a simple way. This paper proposes a process-based systematization concept for ride comfort design using a set-based design method. A truck was modeled with a minimum of 13 degrees of freedom, and suspension performance under various vehicle speeds, road surface conditions, and load amounts was calculated. The range of design parameters for the suspension, the range of performance requirements, and the optimal values within these ranges were defined based on the knowledge and know-how of experienced design engineers. The final design of the suspension was installed in a prototype truck and evaluated. The performance of the truck satisfied all the objectives and the effectiveness of the set-based design approach was confirmed.

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.

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.

The U.S. Environmental Protection Agency (EPA) issued new emissions regulations, which came into effect in January, 2010. These EPA 2010 regulations are the most stringent emissions standards in the world, reducing both particulate matter (PM) and nitrogen oxides (NOx) to nearly zero levels. Hino Motors improved upon its previous EPA 2007-compliant engine, developing a new exhaust after-treatment system in which a Diesel Particulate active Reduction System (DPR), a Urea-Selective Catalytic Reduction (SCR) System and a Burner System are employed to meet EPA 2010 emissions regulations for medium duty commercial vehicles. DPR was already developed and utilized to reduce PM to meet EPA 2007 standards, but the Urea-SCR System is newly developed technology used to reduce NOx emissions to comply with EPA2010 emissions regulations. In addition, a Burner System is used to elevate exhaust gas temperatures in order to improve both SCR performance and DPR active Regeneration.

The new Diesel Particulate active Reduction (DPR) system was developed for a medium-duty commercial vehicle as a deNOx catalyst combined with the conventional DPR system to achieve the Japan Post New-Long-Term (JPNLT) emissions regulations. It consists of a catalyst converter named as the new DPR cleaner, a fuel dosing injector, NOx sensors, temperatures and pressure sensors. The new DPR cleaner was constructed from a Front Diesel Oxidation Catalyst (F-DOC), a catalyzed particulate Filter (Filter), and a Rear Diesel Oxidation Catalyst (R-DOC). A newly developed Hydrocarbon Selective Catalyst Reduction (HC-SCR) catalyst was employed for each catalyst aiming to reduce NOx emissions with diesel fuel supplied from the fuel dosing injector. While the total volume of the catalyst was increased, the compact and easy-to-install catalyst converter was realized through the optimization of the flow vector and flow distribution in it by means of Computational Fluid Dynamics (CFD) analysis.

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.

Ultra-low energy consumption and ultra-low emission vehicle technologies have been developed by combining petroleum-alternative clean energy with a hybrid electric vehicle (HEV) system. Their component technologies cover a wide range of vehicle types, such as passenger cars, delivery trucks, and city buses, adsorbed natural gas (ANG), compressed natural gas (CNG), and dimethyl ether (DME) as fuels, series (S-HEV) and series/parallel (SP-HEV) for hybrid types, and as energy storage systems (ESSs), flywheel batteries (FWBs), capacitors, and lithium-ion (Li-ion) batteries. Evaluation tests confirmed that the energy consumption of the developed vehicles is 1/2 of that of conventional diesel vehicles, and the exhaust emission levels are comparable to Japan's ultra-low emission vehicle (J-ULEV) level.

DPR is a particulate-emissions reduction system that has been developed to reduce particulate emissions in production commercial vehicles and consists of a multiple fuel-injection system, an engine electronic control unit, and a DPR-Cleaner which includes an oxidation catalyst, a catalyzed particulate filter, and silencers. DPR performs active regeneration to accelerate the regeneration of the filter under engine operating conditions where regeneration by passive regeneration alone is not sufficient. Thus, DPR makes it possible to regenerate the filter regardless of the exhaust gas temperature and enables significant reduction of particulate in commercial vehicles to levels below 0.027 g/kWh under Japan's D13 mode operating conditions. The authors describe development results of the DPR.

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.

In diesel engine trucks, the sound quality improvement as well as the noise level reduction is demanded because of their annoying exterior noise. The semantic differential method was applied to evaluate the sound quality of trucks. In order to improve the analytical accuracy, subjects who can evaluate the characteristics of sound quality were statistically selected among all the subjects. Comfortability and powerfulness were extracted as the principal components by using the data of the selected subjects. It has been clarified that the comfortability strongly relates to high frequency element ratio, high frequency level, etc. The powerfulness strongly relates to the Zwicker loudness.

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.

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.

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.

Recently, a long distance Inter City Bus Network has been developed in Japan. The maxi mum traveling distance is approximately 1,000 km. The driver and passengers must endure long periods of sitting in the same seat. Therefore, the ride comfort ability is the most important characteristic for the Inter City Bus. Noise and vibration level have the greatest effect on ride comfort, therefore they must be considerably reduced to realize the good comfortability. This paper presents the methods of analysis and improvement to reduce the bus body vibration excited by road surface roughness. Modal Analysis Method and Finite Element Method are applied to the bus body construction. Further more, the relationship between the bus body vibration and engine suspension system characteristics are investigated.

A large-size truck is equipped with a variety of audible warning devices. These warning devices are grouped into three categories by their usage, i.e., malfunction type, proximity type and attention type. The sound characteristics of warning sound that are investigated for each type are signal envelope, fundamental frequency and the number of harmonics. Many sounds are synthesized with nine fundamental frequencies, ten or fewer harmonics and two signal envelopes. With volume fixed, these sounds are evaluated using an unpleasantness rating scale, and the functional impression of these sound is also chosen. From the results, the range of fundamental frequencies, the number of harmonics and the shapes of signal envelopes for preferable sound quality are determined.

Diesel particulate trap systems are one of the effective means for the control of particulate emission from diesel vehicles. Hino has been researching and developing various diesel particulate trap systems for city buses. This paper describes two of the systems. One uses a wall flow filter equipped with an electric heater and a sensing device for particulate loading for the purpose of filter regeneration. Another makes use of a special filter named “Cross Flow Filter” with an epoch-making regeneration method called “Reverse Jet Cleaning”, by which it becomes possible to separate the part for particulate burning from the filter. Both systems roughly have come to satisfy the functions of trap systems for city buses, but their durability and reliability for city buses are not yet sufficient.

This paper introduces the Japanese standards and regulations of automobiles with brakes as the central subject and clarifies the difference from those of Europe and USA by comparison. Further, this paper describes not only the application status of the standards and regulations in Japan but also the features of structure and performance of Japanese trucks that are designed and produced under such standards and regulations. It can be said that the Japanese trucks are comparatively simple in structure but are in a level equal to or higher than European and USA automobiles in respect of performance. Also in respect of the international harmonization, the internationalization of standards is being conducted in Japan on the basis of ISO and the internationalization for regulations is considered to be under preparation.