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When truck tires have a deformation such as radial runout, flat spot, and abnormal wear as a result of panic braking, they affect vehicle vibration in the form of displacement input whose spectrum involves higher order terms of tire revolution. While a truck has vibration modes of frame bending as well as pitching and unsprung-mass viberation in the input frequency range, the tire displacement input induces vehicle vibration as a combination of these modes. Results of calculations and experiments of a 4x2 medium-duty truck are analyzed and an example of means for improving ride comfort is described in this paper.

Mud adhesion to the rear surfaces of trucks, vans and buses causes troublesome results such as aesthetic degradation, hindered rear view and laborious washing. To raise the product value of trucks and buses, it is important to develop effective measures for suppressing such mud adhesion. In this research the authors first clarified the mechanism of mud adhesion through flow visualization tests. Then, wind tunnel tests were performed to predict the effects of various countermeasures, and prospective ones were put under actual driving tests to verify their effects. The following measures were found effective in suppressing mud adhesion. (1) Aerodynamic improvement by attaching corner vanes to the upper and side edges of the rear surface. (2) Blocking road splash with a slanted plate under the truck and close to the base.

Mitsubishi Motors Corporation succeeded in mass production of the electric vehicle “i-MiEV” which features leading-edge technologies epitomized by lithium-ion battery. The EV was released into the Japanese market in July 2009 and the European market in January 2011. In order to be used all over the world, the EV has to be practical and durable even under severe weather of extremely cold or extremely hot regions. In this paper we report some results of the tests conducted under extremely cold weather as well as extremely hot weather. From the test results the validity of the vehicle control system and the practicality of the EV are verified.

The effect of the use of the EGR system on the lubrication of a passenger car diesel engine was investigated. The higher the EGR rate, the more soot in the oil. And the most detrimental effect was found in valve train wear. Some engine tests, including motoring tests, were carried out to investigate the contribution of soot to valve train wear. The mechanism of cam and rocker arm wear in used oils was studied by analyzing for elements on the lubricated metal surface and subsequently the mechanism was more thoroughly studied using the four-ball test. Soot seems to act as an abrasive on the anti-wear solid film formed by the oil on the metal surface and this film contains Ca, O, P and S. Some hardware modifications and oil formulations to reduce valve train wear are also discussed.

Three Japanese automobile manufacturers-Mitsubishi Motors Corp., Nissan Motor Co., Ltd., and Toyo Kogyo Co., Ltd.-have been making efforts over the past three years to design and develop effective thermal reactor-exhaust gas recirculation and catalytic converter systems suitable for small engines. The work is being done by members participating in the IIEC (Inter-Industry Emission Control) Program, and the exhaust emission levels of the concept vehicles developed by these companies have met the goal established by the IIEC Program at low mileage. Each system, however, has a characteristic relationship between exhaust emission level and loss of fuel economy. Much investigation is required, particularly with respect to durability, before any system that will fully satisfy all service requirements can be completed. This paper reports the progress of research and development of the individual concept vehicles.

Mitsubishi Motors Corporation uses spiral bevel gears in the transfer system for 4-wheel drive passenger cars modified from the front wheel drive configuration. This transfer gear ratio is near 1:1, and gears have uniform depth teeth cutting by the continuous generating method of OERLIKON cutting machine. In this method, the cutter and the work rotations are timed together to accomplish continuous indexing and cutting in order to enable high productivity. In general, it is difficult to reduce the meshing noise of spiral bevel gears and control its quality. The authors established the tooth surface coordinates, to reduce the meshing noise, by studying the influence of tooth surface coordinates on the meshing transmission error (MTE).

An efficient cooling system will ensure the reliability of the EV/HEV (Electric Vehicle/Hybrid Electric Vehicle) battery system and extend their lifetime. In order to shorten design period or increase design iterations, a high-speed and high-precision prediction method for cooling is indispensable. For models, such as Mitsubishi i-MiEV, which use fresh air to cool batteries in the battery pack, a transient approach based on loosely coupled method is developed to predict temperature change of batteries. The results by our new approach are in good agreement with the experimental data. Moreover, for the EV/HEV using circulated air to cool its batteries, a second approach is also developed, which can predict the temperature variations of both EV/HEV batteries in the battery pack and the cooling air.

In the heavy-duty commercial vehicle market in Japan, particularly in the segment of dump trucks and tractors, naturally aspirated engines maintain a dominant market share because of their superior torque characteristics in the low speed range. In order to meet the ever increasing needs for higher speeds of transportation, better fuel economy and higher reliability, and the needs for increasingly strict exhaust emission regulations, Mitsubishi Motors Corporation (MMC) has developed the 8M20, a 20 liter V8 diesel engine. The '92 model series of “THE GREAT”, MMC's main heavy-duty trucks, has featured this new and powerful engine and has been in the market place since October, 1991. The 8M20 is a naturally aspirated engine that provides an output of 294kW/2200rpm, complying with the current Japanese exhaust emission regulations.

The 4M5 series of four-cylinder, in-line, direct-injection diesel engines has been released by Mitsubishi Motors Corporation for light and medium-duty trucks and buses. Featuring an updated structure and reflecting the employment of state-of-the-art technology in the design of every component, the new engine series offers high reliability and compact dimensions. Moreover, the new series well meets contemporary demands for high performance, low noise, and clean combustion.

In the light commercial vehicles (LCV) market, primarily cross-country 4-wheel drive station wagons and derived cargo vans, diesel powered vehicles have been gaining popularity among customers because of their increased fuel economy. In the Japanese market particularly, total sales of such types of vehicles have been rapidly growing. The volume is about 3 times larger than the last five years with diesel engines having a steady share of about 90 percent. Under such circumstances the customers' requirements for diesel vehicles are becoming more severe. Their primary demands have been for increased power, low noise, low vibration and clean smoke, similar to those found in gasoline engines. On the other hand, the exhaust gaseous emission regulations of the diesel engines are getting strict and will become very severe in the near future. We, MITSUBISHI MOTORS CORPORATION, have been producing a 2.5 L 4-cylinder diesel, the 4D56 Series, for the LCVs.

Global environment protection, Co2 emission reduction and so on, is an important problem in automotive industry. An Electric Vehicle (EV) production is one of policies. Co2 emission of EV is lower than Internal Combustion Engine (ICE), petrol and diesel engine. On the other hand, customer's needs for the comfort on driving increase year after year. So it's an important factor for new car performance. Generally speaking, it's thought that the noise and vibration performance of EV have the better of ICE performance. However the aerodynamic noise and road noise contribution for interior noise in EV rise in comparison with ICE, and moreover the sound quality change by new noise component of the motor noise. Therefore new sound evaluation method is needed for EV. So this paper demonstrates each noise component contribution in EV by new noise separation technology, and show the comparison result with EV and ICE.

From the standpoint of safety, the demands are growing in recent years for better controllability and stability of automobiles and in particular in trucks. The truck, however, when compared with the passenger car, is subject to larger changes in gross vehicle mass and center of gravity depending on its load placement. In addition, since the cornering power generated by the truck tire per load is smaller than that generated by the passenger car tire, it is difficult to introduce significant improvements in controllability and stability simply by use of passive techniques like suspension characteristic tuning. Therefore, studies were performed on the applicability of the 4WS system, an active vehicle dynamic characteristic control technique, to a Truck as a means for solving these problems.

This paper presents several methods for reducing engine weight primarily through substitution with light-weight materials. The efficiency and performance of the engine were reviewed using a light-weight experimental engine (hereinafter called “weight-reduced engine”) constructed by the authors in order to investigate the possibility of practical use of the proposed weight reduction measures. The weight-reduced engine is based on an in-line 4-cylinder, 2.0 liter, gasoline engine with the base engine weight of 162 kg excluding engine oil and coolant and was reduced by 37 kg by applying alternative light-weight materiaLs and new manufacturing techniques. This corresponds to 23 % weight reduction. The materials used in the weight-reduced engine are 53 % steel, 33 % aluminum, 7 % plastics and 7 % other light-weight materials. It was found that by application of light-weight materials, the engine performance of the weight-reduced engine could be improved.

To improve vehicle startability and transient response of turbocharged diesel trucks, their phenomena have been investigated and analyzed in detail and various supercharging systems have been developed and installed on a truck for comparison of their characteristics. The systems considered were ceramic, variable geometry, variable entry,and air-assisted turbochargers and a combined supercharging system. The variable entry turbocharger has two turbine scrolls with different nozzle areas and two switching valves to get three different turbine flow capacities. The combined supercharging system consists of a mechanical supercharger and a turbocharger. These are linked in series. Both work in a low engine speed range, and the turbocharger only works in middle and high engine speed ranges. Among these systems, the combined supercharging system is the best for improving both vehicle startability and transient response of a truck.

In recent year, higher strength for truck and bus transmission gear has become necessary. For the transmission gears, carburized gears have generally been used. We have examined the effects of shot peening and grinding using a CBN grindstone on the pitting strength and the bending fatigue strength of a carburized gear, and further evaluated a material which reduces the structual anomalies produced during carburization. As a result, it has been found that shot peening or CBN grinding is more effective for improving both pitting strength and bending fatigue strength than improving the material composition. Therefore, it is evident that residual compressive stress caused by shot peening or CBN grinding suppresses the propagation of cracks.

In this study, the oxidation stability, soot dispersancy, antiwear performance, and friction-reducing capability of friction modifiers (FMs) were evaluated, and an SAE 5W-30 fully synthetic oil with MoDTC type FMs was developed for heavy-duty diesel engines. In several engine tests, it was confirmed that the developed oil can double the oil drain interval in comparison with API CD SAE 30, even when EGR is applied, and improves the fuel efficiency.

Austempered ductile iron (ADI) is a material having excellent mechanical properties and damping capacity. However practical mass production of ADI gears has not been possible due to ADI's poor machinability and distortion during the austempering heat treatment. With a new process method of carrying out hobbing before austempering when the material is in its soft condition, then austempering it and lastly, conducting the shave finishing process, we have diminished the above defects and developed practical ADI gears. These new gears generate less noise than ordinary nitrocarburized steel gears and are superior in pitting resistance.

An investigation of anti-corrosion steel sheets (non-galvanized) which contain copper for automobile body parts has been conducted. Copper additives accelerate the formation of amorphous substrates. These substrates decrease the rate of corrosion. In order to retain the steel's formability and weldability, the contents of the alloying elements have been optimized. As a result, this newly developed steel sheet can be used for many different applications such as door sashes and door panels of mass produced cars. This paper describes the key properties of the newly developed steel sheet and additionally the mechanism of corrosion prevention, weldability, formability, and so on.

This is to introduce a development history of Doubles-Combinations in Japan and a several important technological points briefly. We understand that our wide promotion of these development activities are strongly supported by the General/Technical Committee members. And totally 10 - million kirometers practical operation data included by 3 - famous Japanese fleet owners, these must be very much useful and valuable for anyone interesting those of Trailer-Combination technologies.

This paper describes a control strategy for autonomous vehicles in an intelligent vehicle/highway system. The control concept aims at the compatibility of passenger riding comfort and vehicle controllability. The main subject of this paper is lateral control of vehicles. In order to analyze riding comfort, we have experimented on the lateral riding comfort during a lane change. It was found that the riding comfort is mainly related to the jerk more than the acceleration, and that the trajectory pattern is important. According to the experimental results, a motion control system was designed. We found through the computer simulation and the experiment with an autonomous test vehicle that comfortable ride is realized along with system stability. Lastly, in order to apply this strategy to the longitudinal direction, we have experimented on the longitudinal acceleration with the test vehicle. The results shows that the same strategy is applicable to the longitudinal direction.