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Technical Paper

Effect of Diamond-Like Carbon Coating on Anti-Scuffing Characteristics of Piston Pins

2019-04-02
2019-01-0184
It has been proposed that downspeeding combined with high boost levels would effectively reduce fuel consumption in heavy-duty diesel engines. Under low-speed and high-boost operating conditions, however, the in-cylinder gas pressure, which acts on the piston crown, is greater than the piston inertia force (such that there is no force reversal), over the entire range of crank angles. Therefore, the piston pin never lifts away from the main loading area (the bottom) of the connecting rod small-end bushing where the contact pressure against the piston pin is highest. In such operating conditions, lubricant starvation is easily induced at the interface between the piston pin and small-end bushing. Through carefully devised engine tests, the authors confirmed that the piston pin scuffing phenomenon arises when the boost pressure exceeds a critical value at which the no-force reversal condition appears.
Technical Paper

A Study on Reducing Cooling loss in a Partially Insulated Piston for Diesel Engine

2018-04-03
2018-01-1276
To improve the thermal efficiency of an engine, it is particularly important to reduce the cooling loss from the combustion gas to the combustion chamber wall, which constitutes a major proportion of the total loss [1]. Previous studies addressing cooling loss reduction attempted to use ceramic in place of the conventional aluminum or iron alloys, but this led to a reduction in the volumetric efficiency and increased smoke emissions. This was caused by the ceramics having both a low thermal conductivity and high heat capacity, relative to aluminum and iron. These characteristics cause the piston wall temperature, which rises during combustion, to remain high during the intake stroke, thus increasing the intake temperature and reducing the volumetric efficiency. This increases the smoke emissions [2].
Technical Paper

A Study on the Effects of a Higher Compression Ratio in the Combustion Chamber on Diesel Engine Performance

2016-04-05
2016-01-0722
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.
Technical Paper

Development of Fuel Economy Engine Oil for Heavy Duty Diesel Engine

2015-09-01
2015-01-2034
More stringent emissions regulations, fuel economy standards, and regulations are currently being discussed to help reduce both CO2 and exhaust emissions. Vehicle manufacturers have been developing new engine technologies, such as downsizing and down-speeding with reduced friction loss, improved engine combustion and efficiency, heat loss recycling, power-train friction loss recycling, and reduced power-train friction loss. The use of more efficient fuel economy 5W-30 engine oils for heavy duty commercial vehicles has started to expand since 2009 in Japan as one technological solution to help reduce CO2 emissions. However, fuel economy 5W-30 oils for use in heavy duty vehicles in Europe are mainly based on synthetic oils, which are much expensive than the mineral oils that are predominantly used in Japan.
Technical Paper

Development of Road's Gradient Anticipatory Algorithm for Hybrid Heavy Duty Truck

2014-09-30
2014-01-2377
For the purpose of reducing fuel consumption, a hybrid heavy duty truck was considered. Generally, HV (Hybrid Vehicle)'s energy is regenerated from deceleration energy in urban area. Hybrid heavy duty truck's energy is regenerated from potential energy on highway. Under this circumstance, some portion of energy may not be accumulated, because capacity of HV battery is limited. In order to maximize accumulating energy in the next descent, HV battery's energy shall be adequately reduced beforehand. This can be achieved by optimizing motor assist torque considering road's altitude and gradient. In this paper, performance of the algorithm is discussed.
Technical Paper

Effects of Alloying Elements on Wear Resistance of Automobile Cast Iron Materials

2014-04-01
2014-01-1011
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.
Technical Paper

Mechanism of and Fuel Efficiency Improvement by Dimple Texturing on Liner Surface for Reduction of Friction between Piston Rings and Cylinder Bore

2014-04-01
2014-01-1661
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.
Technical Paper

A Study of the Rankine Cycle Generating System for Heavy Duty HV Trucks

2014-04-01
2014-01-0678
In heavy duty (HD) trucks cruising on expressway, about 60% of input fuel energy is wasted as losses. So it is important to recover them to improve fuel economy of them. As a waste heat recovery system, a Rankine cycle generating system was selected. And this paper mainly reports it. In this study, engine coolant was determined as main heat source, which collected energies of an engine cooling, an EGR gas and an exhaust gas, for collecting stable energy as much as possible. And the exergy of heat source was raised by increase coolant temperature to 105 deg C. As for improving the system efficiency, saturation temperature difference was expanded by improving performance of heat exchanger and by using high pressure turbine. And a recuperator which exchanges heat in working fluid between expander outlet and evaporator inlet was installed to recover the heat of working fluid at turbine generator. Then a working fluid pump was improved to reduce power consumption of the system.
Technical Paper

Application of Set-Based Design Method to Ride Comfort Design with a Large Number of Design Parameters

2014-04-01
2014-01-0881
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.
Technical Paper

Investigation of Thermal Fatigue Evaluation Method for Cast Iron

2013-04-08
2013-01-0393
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.
Technical Paper

Ride Comfort Evaluation of Horizontal Vibration in Tractor-Trailer Considering Human Body Motion of Driver

2013-04-08
2013-01-0992
In a tractor-trailer, ride comfort affected by horizontal human body motions, so called “wavy” and “shaky” feelings, is at issue. Insight about “wavy” and “shaky” feelings which is important for efficient vehicle development is not enough. Experiments using 6-axis motion generator and motion capture and inverse-analysis using multi-body human model indicated the characteristics of each feeling. Motion observation and transfer function indicated that while a bad subjective score of “wavy” feeling corresponds to same-phase roll motion of chest and pelvis up to 0.7Hz, “shaky” correlates to an antiphase of them around 2Hz. By multiple regression, dominant vibration components of the human body and the vehicle to subjective evaluation of the feelings above were identified. Explanatory variables for the “wavy” feeling are roll rate and lateral jerk and those for the “shaky” are lateral acceleration and longitudinal acceleration.
Journal Article

Study of the Impact of High Biodiesel Blends on Engine Oil Performance

2011-08-30
2011-01-1930
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.
Technical Paper

A Study on the Mechanism of Engine Oil Consumption- Oil Upwards Transport via Piston Oil Ring Gap -

2011-04-12
2011-01-1402
Reduction of oil consumption of engines is required to avoid a negative effect on engine after treatment devices. Engines are required fuel economy for reduction of carbon-dioxide emission, and it is known that reduction of piston frictions is effective on fuel economy. However friction reduction of pistons sometimes causes an increase in engine oil consumption. Therefore reduction of engine oil consumption becomes important subject recently. The ultimate goal of this study is developing the estimation method of oil consumption, and the mechanism of oil upward transport at oil ring gap was investigated in this paper. Oil pressure under the oil ring lower rail was measured by newly developed apparatus. It was found that the piston slap motion and piston up and down motion affected oil pressure rise under the oil ring and oil was spouted through ring-gap by the pressure. The effect of the piston design on the oil pressure generation was also investigated.
Journal Article

Unregulated Harmful Substances in Exhaust Gas from Diesel Engines

2009-06-15
2009-01-1870
The volatile organic compounds (VOC) from diesel engines, including formaldehyde and benzene, are concerned and remain as unregulated harmful substances. The substances are positively correlated with THC emissions, but the VOC and aldehyde compounds at light load or idling conditions are more significant than THC. When coolant temperatures are low at light loads, there are notable increases in formaldehyde and acetaldehyde, and with lower coolant temperatures the increase in aldehydes is more significant than the increase in THC. When using ultra high EGR so that the intake oxygen content decreases below 10%, formaldehyde, acetaldehyde, benzene, and 1,3-butadiene increase significantly while smokeless and ultra low Nox combustion is possible.
Technical Paper

Advanced Safety Technologies for Large Trucks

2007-08-05
2007-01-3589
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.
Technical Paper

Noise-Generating Mechanism and Noise Reduction of Reciprocating Air Compressor for Heavy Duty Vehicles

2007-05-15
2007-01-2374
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.
Technical Paper

A Study on the Measurement and Estimation Method of Skew Motion of Roller-Tappets in an OHV Type DI Diesel Engine

2006-10-16
2006-01-3348
Roller-Tappets have been adopted on the valve train systems of OHV type diesel engines, due to their low friction losses. When a roller-tappet is actuated by the cam, it moves upwards and downwards in the guide with a slight skew motion. This motion affects the life of cam and tappets. The purpose of this study was, therefore, to establish the skew estimation method. The skew motion was measured under the engine motoring condition, and its calculation based on the assumed mechanism was carried out. The calculated skew motion showed good agreement with the measured.
Technical Paper

A Study on the Mechanism of Lubricating Oil Consumption of Diesel Engines - 3rd Report: Effect of Piston Motion on Piston Skirt Oil Film Behavior

2006-10-16
2006-01-3349
The necessity of the reduction of the lubricating oil consumption of diesel engines has been increasing its importance to reduce the negative effect of exhausted oil on after treatment devices for exhausted gas. The final purpose of the studies is clarifying the mechanism of the oil consumption and developing the method of its estimation. For the basic study, the mechanism of oil film generation on the piston skirt could be explained by hydrodynamic lubrication in our first and second reports [1, 2]. In this paper, the piston skirt was calculated using the measured piston motion to clarify the effect of the piston motion to the piston skirt oil film behavior.
Technical Paper

A Study on the Mechanism of Lubricating Oil Consumption of Diesel Engines - 4th Report: The Measurement of Oil Pressure Under the Piston Oil Ring -

2006-10-16
2006-01-3440
Clarifying the mechanism of the oil consumption of engines is necessary for developing its estimation method. Oil moves upwards on the piston to the combustion chamber through ring sliding surfaces, ring backs and ring gaps. The mechanisms of oil upwards transport through the ring gaps are hardly analyzed. In this report, oil pressure just under the oil ring was successfully measured by newly developed method to clarify the oil transport mechanism at the ring gap. It was showed that the generated oil pressure pushed up the oil at the ring gap.
Technical Paper

A Study on the Mechanism of Lubricating Oil Consumption of Diesel Engines -1st report: The Effect of the Design of Piston Skirt on Lubricating Oil Consumption-

2005-05-11
2005-01-2169
Decrease of engine lubricating oil consumption is necessary to reduce environmental impact. Usually oil consumption is estimated experimentally at the engine development stage, and it is expensive in terms of both time and cost. Therefore it is essential to develop its calculation method. The purposes of this study are clarifying the mechanism of engine lubricating oil consumption and developing the calculation method for the estimation of oil consumption. In this report, oil film on the piston skirt, which affected on oil volume supplied to the oil ring, was observed. Furthermore the effect of piston skirt design on oil consumption was investigated. Findings showed that the splashed oil on the cylinder liner had much effect on the oil film on the piston skirt hence oil consumption. It was suggested that the splashed oil on the cylinder liner affected on supply oil volume and it should be considered in the calculation of oil consumption.
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