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The running direction of a vehicle can be controlled by not only wheel steer but also torque steer. This paper introduces the tractive torque steer effect produced by a newly developed electropneumatic control system, the limited-slip differential for large-sized vehicles. This system enhances the vehicle's running stability and controllability by controlling the tractive force of the drive axle. The tractive force maintains a stable running course against disturbances such as road roughness and wind gusts, thereby enhancing the steering response and providing a better feeling of handling to the driver. The system also improves mobility. especially on low-μ roads. It is expected that a single axle equipped with this system will exhibit good performance comparable to that of tandem axle.

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. This report is designed to determine how high biodiesel blends affect oil quality through testing on 2005 regulations engines with DPFs. When blends of 10-20% rapeseed methyl ester (RME) with diesel fuel are employed with 10W-30 engine oil, the oil change interval is reduced to about a half due to a drop in oil pressure. The oil pressure drop occurs because of the reduced kinematic viscosity of engine oil, which resulting from dilution of poorly evaporated RME with engine oil and its accumulation, however, leading to increased wear of piston top rings and cylinder liners.

A driving simulator system for developing steering road feel has been developed. A new steering gear box or an electronic steering system is installed on the simulator and its road feel and control algorithm are developed according to the characteristics of any vehicle which has been programed into the engineering work-station. The vehicle model programed into the engineering work station runs according to the driver's operations, which are fed through the new steering system to be tested. The steer-restoring torque of the vehicle programed into the engineering work-station is produced by an actuator, and gives the impression through the new system of having been fed back from an actual road.

In this paper, the flow patterns and velocity distributions of coolant flow around cylinder liners of diesel engine are studied by numerical calculation and experimental observation. The experiment is carried out by oil film method and direct observation with a transparent acrylic cylinder liner. The calculation is performed with the 3-dimensional model by FEM for fluid flow. The motion of coolant flow by calculation corresponds with the result by oil film method and direct observation with transparent cylinder liner. The visualization of the 3-dimensional calculation gives a good understanding about motion of coolant flow and pressure distribution in water chamber. This method is applied to improve the coolant flow with the stagnation around cylinder liner. The effect of improved design is confirmed by experiment. That is, there are no stagnations in the flow around cylinder liners.

The noise-generating mechanism of a reciprocating air compressor for heavy duty vehicles during idling was investigated. It was elucidated that the gear rattling noise of the air compressor drive gear train caused by the negative value of the air compressor drive torque was a major noise source. To completely suppress the gear rattling phenomenon, a new loading device with an air cylinder that cancels the negative value of the air compressor drive torque was fabricated. When the loading device was worked, the impulsive sound level was reduced to 10 dB(A). It was found that the impulsive sound level during gear rattling is closely related to the difference in gear teeth velocity between the crankshaft gear and the air compressor drive gear, as one of the characteristics that are needed to obtain a guide for carrying out estimations in the calculation simulation.

Noise reduction of diesel engines installed in heavy duty vehicles is one of the highest priorities from the viewpoints of meeting the regulations for urban traffic noise abatement and noise reduction in the cabin for lightening fatigue with comfortable long driving. It is necessary that noise reduction measures then be applied to those causes. Noise reduction measures for the diesel engine can be classified into five categories on the noise radiation block-diagram. These are, reduction of combustion and mechanical forces, deformation and vibration control of cylinder block, vibration control of fastened components, prevention of standing wave and close fitting shields. All noise reduction measures for the diesel engine researched for the purpose of practical use are fully described in this paper.

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.

Japan's new 2005 long-term emissions regulation was implemented in October 2005. Both NOx and PM emissions standards were reduced to 2 g/kWh and 0.027 g/kWh, which were 40 and 85 percent lower than the 2003 new short-term emissions standards, respectively. These emissions standards are as stringent as the Euro5 standards that are scheduled for implementation in 2008. In addition, the transient-cycle test procedure for emissions compliance, labeled JE05, was introduced to replace the D13-mode steady-state test procedure. This paper describes exhaust emissions reduction technologies developed for Hino's 13-liter heavy-duty diesel engine so that it meets the above standards. A production catalyzed wall-flow DPF was employed to reduce PM emissions in both mass and small particles. NOx emissions were reduced by improving combustion with cooled EGR and without use of a NOx aftertreatment device.

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.

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.

Vehicle responsiveness to the driver's steering maneuvers and external turbulences caused by irregularities in the road surface and wind gusts are two opposing factors to be studied for better stability and controllability of vehicles. The cruising speeds of vehicles on freeways have been becoming higher, and wider physiological differences in the driving ability of drivers are appearing with the increase in elderly drivers. Therefore, to meet the requirements of higher cruising speeds and the expanding physiological differences between drivers, an electro-hydraulic feedforward control power steering system has been developed for trucks and buses. This is a parallel operating system consisting of a mechanical route and an electronic route, and improves vehicle responsiveness so as to absorb the physiological differences of drivers.

This paper describes the experimental studies of turbocharged and intercooled diesel engines with particular emphasis on combustion characteristics following increase of boost pressure. Through these studies, it has become possible to determine the optimum air quantity for minimizing fuel consumption at each engine speed range under the restrictive conditions of NOx emission, exhaust smoke and maximum cylinder pressure. Discussed also is the lack of air quantity in the low engine speed range of high-boost turbocharged diesel engines. Various turbocharging systems to improve air quantity in this speed range are introduced herein. Practically the engine performance of conventional turbocharging, waste gate control turbocharging and variable geometry turbocharging are discussed from the viewpoint of torque recovery in the low engine speed range.

Wear resistance is the important characteristics of cast iron materials for automobile components. Because the phenomenon of wear is a highly complicated mechanism involving many factors such as surface conditions, chemical reactions with lubricants, metals, and physics, it has not been fully explained. Therefore, it will be necessary to confirm and explain the wear mechanism to develop effective improvements. The purpose of this study was to investigate the structural change behavior and effects of alloying elements when the material top surface becomes worn, in order to improve the wear resistance of cylinder liners and other cast iron materials. For this purpose, several types of prototype materials were produced, and the relationship between components and wear resistance was investigated by using a laser microscope for quantitative observation of the degree of pearlite microstructure fineness.

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 objective of this study was to develop a test method for heavy-duty HEVs using a hardware-in-the-loop simulator (HILS) to enhance the type-approval-test method. To achieve our objective, HILS systems for series and parallel HEVs were actually constructed to verify calculation accuracy. Comparison of calculated and measured data (vehicle speed, motor/generator power, rechargeable energy storage system power/voltage/current/state of charge, and fuel economy) revealed them to be in good agreement. Calculation error for fuel economy was less than 2%.

Hino has developed new J-series medium-duty diesel engines for trucks and buses. The new J-series comprises four, five and six-cylinder engines with the same cylinder bore and stroke and with both naturally aspirated and charge air cooled. Both output and torque have been enhanced along with fuel efficiency in an engine that is lighter and more compact than ever and reaches new heights of durability and reliability. J-series engine features a 4-valve system and OHC valve train design, which achieved an uniform combustion by a centered nozzle and combustion chamber design. This decreases the maximum combustion temperature and hence improved the NOx,smoke and PM emissions. And a reduced pumping loss results in improving the fuel consumption. J-series engines thus meet the Japanese 1994 emission regulations. Another feature is a fully electronically controlled common-rail fuel injection system, which is equipped in a specified engine of naturally aspirated 6 cylinder.

The sensitivity of steering increases as the vehicle speed rises. It requires a driver to make different steering maneuvers at high speed zone from that at low speed zone. In order to reduce the difference and to have a better steering “feel” for the driver, the characteristics of steering should be studied from both “the vehicle lateral movement corresponding to steering effort” and “the time lag of the vehicle lateral movement to steering effort”. And both should be decreased as vehicle speed rises. This paper explains how the above conclusion was reached through the development of engine/vehicle speed sensing power steering for commercial vehicles.

Experiments on a large number of soluble fuel additives were systematically conducted for diesel soot reduction. It was found that Ca and Ba were the most effective soot suppressors. The main determinants of soot reduction were: the metal mol-content of the fuel, the excess air factor, and the gas turbulence in the combustion chamber. The soot reduction ratio was expressed by an exponential function of the metal mol-content in the fuel, depending on the metal but independent of the metal compound. A rise in excess air factor or gas turbulence increased the value of a coefficient in the function, resulting in larger reductions in soot with the fuel additives. High-speed soot sampling from the cylinder showed that with the metal additive, the soot concentration in the combustion chamber was substantially reduced during the whole period of combustion. It is thought that the additive acts as a catalyst not only to improve soot oxidation but also to suppress soot formation.