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Mo-free 1.6-GPa bolt was developed for a Variable Compression Turbo (VC-Turbo) engine, which is environment friendly and improves fuel efficiency and output. Mo contributes to the improvement of delayed fracture resistance; therefore, the main objective is to achieve both high strength and delayed fracture resistance. Therefore, Si is added to the developed steel to achieve high strength and delayed fracture resistance. The delayed fracture tests were performed employing the Hc/He method. Hc is the limit of the diffusible hydrogen content without causing a delayed fracture under tightening, and He is the diffusible hydrogen content entering under a hydrogen-charging condition equivalent to the actual environment. The delayed fracture resistance is compared between the developed steel and the SCM440 utilized for 1.2-GPa class bolt as a representative of the current high-strength bolts.

This paper describes the equivalent temperature based on the mesh-free simulation proposed by the previous papers (Part1 and Part2) under the transient heating condition in a 3D-CAD vehicle cabin including the thermal manikin which takes into account the clothing shape. For this purpose, firstly, the experiments of vehicle cabin measuring for the thermal environment including the equivalent temperature are carried out under the transient heating condition. Then, the calculated results of the thermal environment in the vehicle cabin are compared with time series experimental data under the transient condition. They correspond to the experiments including transient changes well. The transient calculated equivalent temperature of thermal manikin is also compared with experiments. As a result, since it is difficult to control the thermal manikin ideally in the experiment, it is difficult to compare the transient behavior.

This paper describes a method for evaluating the equivalent temperature in vehicle cabins based on the new international standard ISO 14505-4, published in 2021. ISO 14505-4 defines two simulation methods to determine a thermal comfort index “equivalent temperature.” One method uses a numerical thermal manikin, and the other uses thermal factors to calculate. This study discusses the latter method to validate its accuracy, identify the key points to consider, and examine its advantages and disadvantages. First, the definition of equivalent temperature and the equation to calculate the equivalent temperature using thermal factors, such as air temperature, radiant temperature, solar radiation, and air velocity, are explained. In addition, the experiments and simulation methods are described.

The size and weight of the traction inverter needs to be reduced to ensure a sufficient cruising range of an electric vehicle. To this end, one approach involves changing materials of the inverter case from aluminum to resin. However, the resin in use of inverter case causes technical issues in terms of collision performance, electromagnetic compatibility (EMC), and cooling performance because of the difference in the material properties between the resin and the conventionally used aluminum. By solving the abovementioned issues, a resin water jacket case (hereinafter, resin water jacket) was successfully adopted with inverters designed for next-generation electric powertrain in mass production models for the first time. The resin-based structure had advantages to reduce the weight of the inverter case by ~35% and decrease the number of parts to ~3/5, compared to that for the conventional cases.

Nissan’s variable compression turbo (VC-Turbo) engine has a multilink mechanism that continuously adjusts the top and bottom dead centers of the piston to change the compression ratio and achieve both fuel economy and high power performance. Increasing the exhaust gas recirculation (EGR) rate is an effective way to further reduce the fuel consumption, although this increases the exhaust gas condensation in the cylinder bores, causing a more corrosive environment. When the EGR rate is increased in a VC-Turbo engine, the combined effect of piston sliding and exhaust gas condensation at the top dead center accelerates the corrosive wear of the thermal spray coating. Stainless steel coating is used to improve the corrosion resistance, but the adhesion strength between the coating and the cylinder bores is reduced.

Engine oil with viscosity lower than 0W-16 has been needed for improving fuel efficiency in the Japanese market. However, lower viscosity oil generally has negative aspects with regard to oil consumption and anti-wear performance. The technical challenges are to reduce viscosity while keeping anti-wear performance and volatility level the same as 0W-20 oil. They have been solved in developing a new engine oil by focusing on the molybdenum dithiocarbamate friction modifier and base oil properties. This paper describes the new oil that supports good fuel efficiency while reliably maintaining other necessary performance attributes.

This study focused on European NCAP activities of introducing a new head protection evaluation procedure, as proposed by BASt (Federal Highway Research Institute - GERMANY). Various kinds of E-bikes are available in the market, ranging from E-bikes that have a small motor to assist the rider’s pedal-power i.e., pedelecs to somewhat more powerful E-bikes which is similar to a moped-style scooter. This paper focused on identifying the factors influencing bicyclist head kinematics during bicycle vs. passenger vehicle (PV) collisions at the intersection. Two AM50 bicyclist FE models are developed using i) GHBMC Human Body Model (HBM) and ii) WorldSID (WS) side impact dummy. Head kinematics of bicyclists of pedal-assist E-bike and normal bike were compared using CAE simulation. It is found that the vehicle’s impact velocity, type of bicycle, the mass of E-bike and bicycle traveling speed will influence the head kinematics.

A side impact is one of the severest crash configurations among real-world accidents. In the US market, even though most vehicles have achieved top ratings in crash performance assessment programs in recent years, there has hardly been any sign of a decline in side-impact fatalities for the last few years, according to statistics retrieved from the National Highway Traffic Safety Administration’s Fatality Analysis Reporting System. In response to this trend, the Insurance Institute for Highway Safety (IIHS) is planning to introduce a new test protocol for side impact assessment. One of the points to be clarified in current side impact tests is whether the present side moving deformable barrier (MDB), which includes the barrier face and cart, faithfully reproduces a real-world car-to-car crash.

In order to improve the accuracy of the coil temperature prediction, detailed fundamental experiments have been conducted on thermal resistances that are caused by the void air gap and contact surfaces. The thermal resistance of the coil around the air gap can be calculated by an air gap distance and air heat conductivity. Contact surface thermal resistance between the core and the housing was constant regardless of the press-fitting state in this experiment. Prediction accuracy of the coil temperature is improved by including the heat resistance characteristics that is obtained by the basic experiment to conjugate heat transfer analysis model.

A new variable compression turbo (VC-Turbo) engine, which has a multi-link system for controlling the compression ratio from 8:1 to 14:1, requires high axial force for fastening the multi-links because of high input loads and the downsizing requirement. Therefore, it was necessary to develop a 1.6-GPa tensile strength bolt with plastic region tightening. One of the biggest technical concerns is delayed fracture. In this study, quenched and tempered alloy steels were chosen for the 1.6-GPa tensile strength bolt.

In the previous paper (Part 1), measurements of equivalent temperature (teq) using a clothed thermal manikin and modeling of the clothed thermal manikin for teq simulation were discussed. In this paper (Part 2), the outline of the proposed mesh-free simulation method is described and comparisons between teq in the calculations and measurements under summer cooling with solar radiation and winter heating without solar radiation conditions in a vehicle cabin are discussed. The key factors for evaluating teq on each body segment of the clothed thermal manikin under cooling and heating conditions are also discussed. In the mesh-free simulation, even if there is a hole or an unnecessary shape on the CAD model, only a group of points whose density is controlled in the simulation area is generated without modifying the CAD model. Therefore, the fluid mesh required by conventional CFD code is not required, and the analysis load is significantly reduced.

The present paper is Part 1 of two consecutive studies. Part 1 describes three subjects: definition of the equivalent temperature (teq), measurements of teq using a clothed thermal manikin in a vehicle cabin, and modeling of the clothed thermal manikin for teq simulation. After defining teq, a method for measuring teq with a clothed thermal manikin was examined. Two techniques were proposed in this study: the definition of “the total heat transfer coefficient between the skin surface and the environment in a standard environment (hcal)” based on the thermal insulation of clothing (Icl), and a method of measuring Icl in consideration of the area factor (fcl), which indicates the ratio of the clothing surface to the manikin surface area. Then, teq was measured in an actual vehicle cabin by the proposed method under two conditions: a summer cooling condition with solar radiation and a winter heating condition without solar radiation.

Wireless Power Transfer (WPT) promises automated and highly efficient charging of electric and plug-in-hybrid vehicles. As commercial development proceeds forward, the technical challenges of efficiency, interoperability, interference and safety are a primary focus for this industry. The SAE Vehicle Wireless Power and Alignment Taskforce published the Recommended Practice J2954 to help harmonize the first phase of high-power WPT technology development. SAE J2954 uses a performance-based approach to standardizing WPT by specifying ground and vehicle assembly coils to be used in a test stand (per Z-class) to validate performance, interoperability and safety. The main goal of this SAE J2954 bench testing campaign was to prove interoperability between WPT systems utilizing different coil magnetic topologies. This type of testing had not been done before on such a scale with real automaker and supplier systems.

There are strong demands for vehicle weight reductions so as to improve fuel economy. At the same time, it is also necessary to ensure crash safety. One effective measure for accomplishing such both requirements conflicting each other is to apply advanced high strength steel (AHSS) of 780 MPa grade or higher to the vehicle body. On the other hand, higher strength steels generally tend to display lower elongation causing formability deterioration. Nissan Motor Corporation have jointly developed with steel manufacturers a new 980 MPa grade AHSS with high formability with the aim of substituting it for the currently used 590 MPa grade high-tensile steel. Several application technologies have been developed through the verifications such as formability, resistance spot weldability, crashworthiness, and delayed fracture.

This paper describes a newly developed motor and inverter system with maximum torque of 320 Nm and maximum power of 110 kW for a 2018 model year EV. The system achieves this performance with no increase in size from the previous 2013 model year system with maximum torque of 254 Nm and maximum power of 80 kW. The specific features of the new system described in this paper are summarized below. A new inverter power module that adopts a direct cooling structure produces higher current density than the previous model. The designs of components experiencing structural and electrical variation that affects heat generation by the power semiconductors were confirmed. Furthermore, the motor temperature is estimated for thermal protection. These features allow for control logic that can optimally manage the temperatures of the power semiconductors and the motor to facilitate the high torque performance of the system.

In total, 865 intersection car-to-car crashes (NASS-CDS CY 2004-2014) are analyzed in detail to determine the injury level outcome based on different crash factors, such as delta-V, age, airbag deployment, number of events, impact locations (F,Y,P,Z,D,B-regions based on CDC codes), amount of compartment intrusion and impact angle. A multivariate logistic regression test was performed to predict the probability of MAIS3+ serious injuries using lateral delta-V, location of maximum deformation from B-PLR, age (0: <60/1: ≥60 years), number of events (0: single/ 1: multiple), intrusion (0: <16cm/ 1: ≥16cm), side airbag deployment (yes/no) and direction of impact (0: 9/ 1: 10 o’clock). It is found that direction of impact is one of the significant (p<0.05) parameters and 10 o’clock angle impact has more influence than 9 o’clock perpendicular lateral impact. Frequency of AIS3+ injuries was high in Y-region impact cases.

The purpose of this work was to gain a fundamental understanding of which fuel property parameters are responsible for particulate emission characteristics, associated with key intermediate behavior in the engine cylinder such as the fuel film and insufficient mixing. Accordingly, engine tests were carried out using various fuels having different volatility and chemical compositions under different coolant temperature conditions. In addition, a fundamental spray and film visualization analysis was also conducted using a constant volume vessel, assuming the engine test conditions. As for the physical effects, the test results showed that a low volatility fuel displayed high particulate number (PN) emissions when the injection timing was advanced. The fundamental test clearly showed that the amount of fuel film on the impingement plate increased under such operating conditions with a low volatility fuel.

A low viscosity API SN 0W-16 engine oil was developed to achieve a 0.5% improvement in fuel efficiency over the current GF-5/API SN 0W-20 oil. Oil consumption and engine wear are the main roadblocks to the development of low viscosity engine oils. However, optimization of the base oil and additives successfully prevent oil consumption and wear. First, it was confirmed in engine tests that NOACK volatility is still an effective indicator of oil consumption even for a low viscosity grade like 0W-16. As a result of base oil volatility control, the newly developed oil achieves the same level of oil consumption as the current GF-5/API SN 0W-20 oil. Second, it was found that the base oil viscosity and molybdenum dithiocarbamate (MoDTC) had a significant effect on chain wear in rig testing that simulated silent chain wear. For the same base oil viscosity, the new oil maintains the same oil film thickness under high surface pressure.

This paper presents the technologies incorporated in an electric vehicle (EV)/hybrid electric vehicle (HEV) inverter built with power semiconductors of silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) instead of conventional silicon (Si) insulated gate bipolar transistors (IGBTs). A SiC inverter prototype of 2.9 L in size for driving an 80-kW motor was fabricated and evaluated on a motor test bench. The SiC inverter prototype attained average efficiency of 98.5% in the Worldwide harmonized Light-duty Test Cycle (WLTC) driving mode. The two main technologies achieved with this SiC inverter prototype are described. The first one is a new direct-cooled power module with a thick copper (Cu) heat spreader located under the semiconductors that improves thermal resistance by 34% compared with a conventional direct-cooled power module.

The effects of lubricant oil and fuel properties on low speed pre-ignition (LSPI) occurrence in boosted S.I. engines were experimentally evaluated with multi-cylinder engine and de-correlated oil and fuel matrices. Further, the auto-ignitability of fuel spray droplets and evaporated homogeneous fuel/oil mixtures were evaluated in a combustion bomb and pressure differential scanning calorimetry (PDSC) tests to analyze the fundamental ignition process. The work investigated the effect of engine conditions, fuel volatility and various lubricant additives on LSPI occurrence. The results support the validity of aspects of the LSPI mechanism hypothesis based on the phenomenon of droplets of lubricant oil/fuel mixture (caused by adhesion of fuel spray on the liner wall) flying into the chamber and autoigniting before spark ignition.