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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.

Hino Motors is about to launch a new truck model FA as a family product of the model FB class 5 category trucks which have been sold since 1986, Model FA, a class 3 category cab-over-engine truck has a GVW of 13,500 Lbs. and is powered by a 3.8 liter direct injection turbocharged diesel engine which produces 125 HP in conformity with federal exhaust gas emission regulations for 50 states. The new truck was designed and developed to satisfy several principal design objectives such as excellent maneuverability, driving comfort, superior fuel economy as well as sufficient reliability and durability within the simplest possible structure. This paper describes its design objectives, features focusing on cab and engine and technologies devoted to the development.

Newly designed laboratory measurement system, which reproduces particle number size distributions of both nuclei and accumulation mode particles in exhaust emissions, was developed. It enables continuous measurement of nano particle emissions in the size range between 5 and 1000 nm. Evaluations of particle number size distributions were conducted for diesel vehicles with a variety of emission aftertreatment devices and for gasoline vehicles with different combustion systems. For diesel vehicles, Diesel Oxidation Catalyst (DOC), urea-Selective Catalytic Reduction (urea-SCR) system and catalyzed Diesel Particulate Filter (DPF) were evaluated. For gasoline vehicles, Lean-burn Direct Injection Spark Ignition (DISI), Stoichiometric DISI and Multi Point Injection (MPI) were evaluated. Japanese latest transient test cycles were used for the evaluation: JE05 mode driving cycle for heavy duty vehicles and JC08 mode driving cycle for light duty vehicles.

Reducing friction between the piston ring and cylinder is an effective way of meeting the demand for lower fuel consumption in vehicle engines. To that effect, the authors have proposed a new and efficient friction reduction treatment for the cylinder. At first glance, this treatment seems similar to typical microtexture treatments, but it is built on a different approach. Through a rig tester, it was confirmed that optimizing the shape of the dimples and the treatment area for the cylinder improves FMEP between the piston ring and the cylinder liner by 17%. This report presents an analysis of the test results to explain the mechanism by which this effect is achieved. Fuel consumption was measured in an actual engine, and a maximum fuel consumption improvement of 3.2% was confirmed after conversion to the Japanese heavy duty vehicle fuel economy standards (Category T2). Lubricating oil consumption, blow-by and durability were also examined.

It is preferable that power steering permits “static park” and has a good “road Feel” when running. In order to permit “static park”, a large bore actuation cylinder with high flow pump is required. Such a method, however, has two defects, a loss power for driving a large volume pump and a poor “road feel”. Resolving these problems and achieving the above matters. Hino has developed a load sensing power steering system. This system, which employes two actuation cylinders controlled by means of a unique load sensing valve arrangement, is designed to permit use of only one cylinder for highway speeds and both cylinders during a static park maneuver. When the system is combined with the preceding speed sensing power steering, “static park” is further facilitated and a tasty “road feel” is available in accordance with vehicle speed.

We have developed a new test method in which temperature of cavity lip of a piston alone during engine rotation is reproduced, cavity lip strain is measured. As the results of strain measurement using the test method in a condition that simulates of conventional engines, a strain behavior was out-of-phase. And in a condition that simulates of high-load engines in future, strain behavior was clockwise-diamond cycle. It was found from the result of the test method developed that strain increased on the cavity lip. The fatigue life of the cavity lip was evaluated using the strain measured and isothermal fatigue curves which obtained by the strain controlled isothermal fatigue test. The result of engine durability test has revealed that the developed method was valid for thermal fatigue evaluation of the cavity lip.

The change in the smoke emissions from a diesel engine with the shapes of the combustion chamber and the in-cylinder density was investigated with focuses on the mixing and the soot formation in a spray flame. First, the mixing of the fuel and air between the nozzle exit and the set-off length was used as an indicator for the formation of soot. Although this indicator can explain the influence of the density, it cannot explain the changes in the smoke emissions with a change in the shape of the combustion chamber. Next, by focusing on the soot distribution in a quasi-steady-state spray flame, the soot formed in the high-density condition of an optically accessible engine was investigated by applying two-color method. These results showed that the positional relationship between the maximum soot amount position and the flame impinging position can be a major influence on the smoke emissions.

To reduce the vehicle fuel consumption at high speed, it is very effective to minimize the aerodynamic resistance of the vehicle, which forms most of the vehicle running resistance at high speed. This paper presents a reduction of the aerodynamic resistance of van type truck through the wind tunnel tests using 1/5 scaled model. Firstly, the aerodynamically desirable cab shape for cargo type truck is investigated by changing main cab shape factors such as corner curvatures. Secondly, several effective attachments for Van type truck are investigated, and lastly, the effect of these aerodynamic improvements on the fuel consumption are clearified by vehicle running test.

Diesel engine has a good fuel economy and high durability and used widely for power source such as heavy duty in the world. On the other hand, it is required to reduce NOx (Nitrogen Oxides) and PM (Particulate Matter) emissions further from diesel exhaust gases to preserve atmosphere. The urea-SCR (Selective Catalytic Reduction) system is the most promising measures to reduce NOx emissions. DPF (Diesel Particulate Filter) system is commercialized for PM reduction. However, in case that a vehicle has a slow speed as an urban area driving, a diesel exhaust temperature is too low to activate SCR catalyst for NOx reduction in diesel emissions. Moreover, the diesel exhaust temperature becomes lower as a future engine has less fuel consumption. The purpose of this study is reduction of NOx emission from a heavy-duty diesel engine using the Urea SCR system at the low temperature.

A fuel reforming technology using a low temperature oxidation was developed to improve a NOx reduction performance of HC-SCR (Hydrocarbons Selective Catalytic Reduction) system, which does not require urea. The low-temperature oxidization of a diesel fuel in gas phase produces NOx reduction agents with high NOx reduction ability such as aldehydes and ketones. A pre-evaporation-premixing-type reformer was adopted in order to generate a uniform temperature field and a uniform fuel/air premixed gas, and to promote the low temperature oxidation efficiently. As a fundamental study, elementary reaction analysis for n-hexadecane/air premixtures was carried out to investigate the suitable reformer temperature and fuel/air equivalence ratio for generation of oxygenated hydrocarbons. It was found that the reforming efficiency was highest at the reforming temperature around 623 to 673K, and aldehydes and ketones were produced.

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.

Emission regulations for diesel-powered vehicles have been gradually tightening. Installation of after-treatment devices such as diesel particulate filters (DPF), NOx storage reduction (NSR) catalysts, and so on is indispensable to satisfy rigorous limits of particulate matter (PM) and nitrogen oxides (NOx). Japan Clean Air Program II Oil Working Group (JCAPII Oil WG) has been investigating the effect of engine oil on advanced diesel after-treatment devices. First of all, we researched the impact of oil-derived ash on continuous regeneration-type diesel particulate filter (CR-DPF), and already reported that the less sulfated ash in oil gave rise to lower pressure drop across CR-DPF [1]. In this paper, impact of oil-derived sulfur and phosphorus on NSR catalyst was investigated using a 4L direct injection common-rail diesel engine with turbo-intercooler. This engine equipped with NSR catalyst meets the Japanese new short-term emission regulations.

Impact of oil-derived ash on the pressure drop of continuous regeneration-type diesel particulate filter (CR-DPF) was investigated through 600hrs running test at maximum power point on a 6.9L diesel engine, which meets the Japanese long-term emission regulations enacted in 1998, using approximately 50ppm sulfur content fuel. Sulfated ash content of test oils were varied as 0.96, 1.31, and 1.70 mass%, respectively. During the running test, the exhaust pressure drop through CR-DPF was measured. And after the test, the ventilation resistance through CR-DPF was also evaluated before and after the baking process, which was applied to eliminate the effect of soot accumulated in CR-DPF. The results revealed that the less sulfated ash in oil gave rise to lower pressure drop across CR-DPF. According to microscope examination of the baked DPF, ash was mainly accumulated on the wall surface of CR-DPF, and that seemed to be related to the magnitude of pressure drop caused by ash.

Biodiesel Fuel (BDF) Research Work Group works on identifying technological issues on the use of high biodiesel blends (over 5 mass%) in conventional diesel vehicles under the Japan Auto-Oil Program started in 2007. The Work Group conducts an analytical study on the issues to develop measures to be taken by fuel products and vehicle manufacturers, and to produce new technological findings that could contribute to the study of its introduction in Japan, including establishment of a national fuel quality standard covering high biodiesel blends. For evaluation of the impacts of high biodiesel blends on performance of diesel particulate filter system, a wide variety of biodiesel blendstocks were prepared, ranging from some kinds of fatty acid methyl esters (FAME) to another type of BDF such as hydrotreated biodiesel (HBD). Evaluation was mainly conducted on blend levels of 20% and 50%, but also conducted on 10% blends and neat FAME in some tests.

In Biodiesel Fuel Research Working Group(WG) of Japan Auto-Oil Program(JATOP), some impacts of high biodiesel blends have been investigated from the viewpoints of fuel properties, stability, emissions, exhaust aftertreatment systems, cold driveability, mixing in engine oils, durability/reliability and so on. In the impact on exhaust emissions, the impact of high biodiesel blends into diesel fuel on diesel emissions was evaluated. The wide variety of biodiesel blendstock, which included not only some kinds of fatty acid methyl esters(FAME) but also hydrofined biodiesel(HBD) and Fischer-Tropsch diesel fuel(FTD), were selected to evaluate. The main blend level evaluated was 5, 10 and 20% and the higher blend level over 20% was also evaluated in some tests. The main advanced technologies for exhaust aftertreatment systems were diesel particulate filter(DPF), Urea selective catalytic reduction (Urea-SCR) and the combination of DPF and NOx storage reduction catalyst(NSR).

Hino Motors developed J-series 4.7-liter inline-four cylinder and 7.7-liter inline-six cylinder engines for complying with the 2004 U.S. exhaust emissions regulations. Several technologies were incorporated in the development process to accomplish simultaneous reductions in both exhaust emissions and fuel consumption while the engine performance, reliability, and durability were maintained at the levels acceptable for truck application. Newly developed technologies include a cooled EGR system, a common-rail fuel injection system, a VNT system, and an engine control system for harmonized control of EGR valve and VNT. This paper reports the development approaches and results.

Tooth contact marking of gears is an important quality characteristic that affects tooth strength and gear noise. Tooth contact marking measurement is generally done by painting the tooth surfaces of two meshed gears, rotating the gears and visually observing contact marks. Since it requires much working hours and experience to judge such a measurement, a method of measuring contact tooth markers by image processing has been developed. In this measurement method, the tooth surfaces of rotating gears are continuously observed by a TV camera, and the images are stored in an image memory device. Such quantities as the tooth surface size and tooth surface brightness level are set as initial settings, and the set values are compared with the observed images by a microcomputer to give the results of the measurement.

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.

Recently, exhaust emission has been enforced on diesel engines for the countermeasure of environmental problems. Accordingly, the cylinder pressure in the engine is being increased to improve fuel efficiency, the engine bearings must be used under severe conditions of high specific load. Because the connecting rod bearings, particularly of diesel engines, are used at high specific loads that exceed 100 MPa, elastic deformation of the bearing surface occurs, and the oil film thickness decreases at the edges of the bearing length in the axial direction. This causes the bearings to contact with the crankshaft, thus resulting in the wear of the bearings, which could even result in seizure. The following factors contribute to seizure: bearing materials, bearing shapes, machining methods, and incorrect assembly. Focusing on these factors, this study evaluated the behaviors exhibited by connecting rod bearings in actual engines by using the rig testers.

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.