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Technical Paper

Validation of Wireless Power Transfer up to 11kW Based on SAE J2954 with Bench and Vehicle Testing

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.
Technical Paper

Development of Plastic Region Tightening 1.6-GPa Ultra-High Strength Bolt with High Delayed Fracture Resistance

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.
Journal Article

Development of Low Viscosity API SN 0W-16 Fuel-Saving Engine Oil Considering Chain Wear Performance

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.
Journal Article

Advanced Technology for Dry Multi-Plate Clutch in FWD HEV Transmission (JATCO CVT8 HYBRID)

There has been a growing need in recent years to further improve vehicle fuel efficiency and reduce CO2 emissions. JATCO began mass production of a transmission for rear-wheel-drive (RWD) hybrid vehicle with Nissan in 2010, which was followed by the development of a front-wheel-drive (FWD) hybrid system (JATCO CVT8 HYBRID) for use on a midsize SUV in the U.S. market. While various types of hybrid systems have been proposed, the FWD system adopts a one-motor two-clutch parallel hybrid topology which is also used on the RWD hybrid. This high-efficiency system incorporates a clutch for decoupling the transmission of power between the engine and the motor. The hybrid system was substantially downsized from that used on the RWD vehicle in order to mount it on the FWD vehicle. This paper describes various seal technologies developed for housing the dry multi-plate clutch inside the motor, which was a key packaging technology for achieving the FWD hybrid system.
Technical Paper

Development of GF-5 0W-20 Fuel-Saving Engine Oil for DLC-Coated Valve Lifters

A suitable GF-5 engine oil formulation is investigated to improve the fuel economy of gasoline engines with hydrogen-free DLC-coated valve lifters. Molybdenum dithocarbamate (MoDTC) is shown to be a suitable friction modifier for low viscosity grade engine oils like 0W-20. A suitable Ca salicylate detergent is also determined from several types examined for maximizing the friction reduction effects of MoDTC. The most suitable Ca salicylate has a chemical structure capable of forming a borophosphate glass film on metal surfaces, which is known to improve the effects of MoDTC. A high viscosity index Group III base oil (VI>140) is also effective in improving fuel efficiency. It is further clarified that the structural design of the polymethacrylate viscosity modifier is another important factor in reducing engine friction.
Journal Article

Analysis of Oil Film Generation on the Main Journal Bearing Using a Thin-Film Sensor and Elasto-Hydrodynamic Lubrication (EHL) Model

Reducing friction in the crankshaft main bearings is an effective means of improving the fuel efficiency of reciprocating internal combustion engines. To realize these improvements, it is necessary to understand the lubricating conditions, in particular the oil film pressure distributions between crankshaft and bearings. In this study, we developed a thin-film pressure sensor and applied it to the measurement of engine main bearing oil film pressure in a 4-cylinder, 2.5 L gasoline engine. This thin-film sensor is applied directly to the bearing surface by sputtering, allowing for measurement of oil film pressure without changing the shape and rigidity of the bearing. Moreover, the sensor material and shape were optimized to minimize influence from strain and temperature on the oil film pressure measurement. Measurements were performed at the No. 2 and 5 main bearings.
Technical Paper

High Power Density Motor and Inverter for RWD Hybrid Vehicles

This paper describes the motor and inverter of Nissan's newly developed parallel hybrid system for rear-wheel-drive hybrid vehicles. The new system incorporates a high-power lithium-ion battery and a one-motor-two-clutch powertrain to achieve both highly responsive acceleration and better fuel economy. As the main components of the hybrid system, both the motor and the inverter have been developed and are manufactured in house to attain high power density for providing responsive acceleration, a quiet EV drive mode and improved fuel economy. Because the motor is located between the engine and the transmission, it had to be shortened to stay within the length allowed for the powertrain. The rotary position sensor and clutch actuator are located inside the rotor to meet the size requirement. High-density winding of square-shaped wire and a small power distribution busbar also contribute to the compact configuration.
Technical Paper

Development of High Response Motor and Inverter System for the Nissan LEAF Electric Vehicle

This paper describes the motor and inverter system developed for the Nissan LEAF that has been specifically designed as a mass-produced electric vehicle. The system produces maximum torque of 280 Nm and maximum power of 80 kW. The motor achieves a small size, high power, and high efficiency as a result of adopting the following in-house technologies. The magnetic circuit design was optimized for an interior magnet synchronous motor to attain the maximum performance figures noted here. The material technologies of the rotor and the stator facilitate high efficiency and the production technology achieves high density winding. The cooling mechanism is optimally designed for a mass-produced electric vehicle. The inverter incorporates the following original technologies and application-specific parts to obtain cost reductions combined with reliability improvements. The power module has an original structure with the power devices mounted directly on the busbars.
Technical Paper

Development of a New 5.6 L V8 Gasoline Engine

This paper describes the new VK56VD engine, which was developed in response to growing demand for cleaner automobiles, better fuel economy, and improved engine performance. A 5.6 L V8 engine, the VK56VD will go into the new Infiniti M56 premium sport luxury sedan. To boost power and efficiency and lessen its environmental impact, this engine will utilize key technologies such as Continuous Variable Valve Event and Lift (VVEL) and Direct Injection Gasoline (DIG). Details of the VK56VD are presented here along with highlights of the applied technologies and the development means.
Technical Paper

A Lubrication Analysis of Multi Link VCR Engine Components using a Mixed Elasto-Hydrodynamic Lubrication Theory Model

Research is under way on an engine system [1] that achieves a variable compression ratio using a multiple-link mechanism between the crankshaft and pistons for the dual purpose of improving fuel economy and power output. At present, there is no database that allows direct judgment of the feasibility of the specific sliding parts in this mechanism. In this paper, the feasibility was examined by making a comparison with the sliding characteristics and material properties of conventional engine parts, for which databases exist, and using evaluation parameters based on mixed elasto-hydrodynamic (EHD) lubrication calculations. In addition, the innovations made to the mixed EHD calculation method used in this study to facilitate calculations under various lubrication conditions are also explained, including the treatment of surface roughness, wear progress and stiffness around the bearings.
Technical Paper

High Throughput Computation of Optical Flow with a High Frame-Rate Camera

This paper presents a new method for calculating optical flow using data from a high frame-rate camera. We focused on a feature of image data captured with a high frame-rate camera in which objects do not move more than one pixel between successive frames. This approach eliminates repetitive processing for object identification among frames taken at different sampling times. High-speed processing hardware architecture was designed with sequential processing only, and the algorithm was implemented in a field programmable gate array. The resultant unit can calculate optical flow for a 640×120 pixel size image with a 480-Hz processing cycle and 0.5-μsec processing latency.
Technical Paper

Evaluations of Physical Fatigue during Long-term Driving with a New Driving Posture

In a previous study, we developed and validated a new driving posture focused on biomechanical loads for physical fatigue reduction in static long-term sitting. In this study, the posture was evaluated in dynamic long-term driving condition by qualitative and quantitative measurements. The results showed physical fatigue of the new posture was halved in comparison with the one of the conventional posture in same car by subjective evaluations. Physiological indices had same tendency with subjective evaluations. From the results, we extracted seven physiological indices as good measures of physical fatigue while driving. Therefore, fatigue reduction of the new posture was qualitatively validated by physiological measurements.
Technical Paper

Analysis of Tooth Surface Fatigue Strength of Automotive Transmission Gears

The life of automotive transmission gears today is often governed by pitting fatigue life. Being able to predict pitting fatigue life accurately is a crucial issue. Pitting fatigue life is substantially influenced by surface hardness and tooth surface geometry. For that reason, this study examined a new method of predicting pitting fatigue life that takes into account changes in these factors over time. This method makes it possible to predict the pitting fatigue life of automotive transmission gears under a wide range of evaluation conditions with markedly better accuracy than conventional methods used previously.
Technical Paper

Development of a New Driving Posture Focused on Biomechanical Loads

Fatigue resulting from long-term driving can be classified into physical and mental fatigue. Physical fatigue seems to be mainly caused by driving posture. The purpose of this study is to develop a new driving posture for reduction of causal factors of physical fatigue, that is, biomechanical loads caused by the posture. In this paper, driving posture was optimized by subjective optimizations of seat contours and biomechanical analysis considering necessary conditions for driving operations and forward view. The new driving posture was tested by subjective evaluations and pelvic movement measurements. It was found that the new posture reduced physical fatigue dramatically.
Technical Paper

Application Development of Low Carbon Type Dual Phase 980MPa High Strength Steel

Use of high strength steel (HSS) could be an important consideration in achieving competitive weight and safety performance of the body-in-white (BIW). This study covers key technical issues in the application development. Many aspects were studied such as formability, weldability and impact strength for application of this grade to the BIW. One of the key issues is spot weldability, especially in the assembly of heavy gauge materials for structural parts. The spot weld strength appears not to satisfy the target for some HSS applications, when hardness of the nugget is high. The relation between weld strength and the chemical composition of steel sheets was studied, because hardness can be controlled by chemical composition and welding conditions. It was found that using lower carbon content or carbon equivalent compared to conventional grades could improve weld strength.
Technical Paper

Improvement of the High Rigidity Power-Roller Support Structure in a Half-Toroidal CVT

This paper describes the improvement made to the high rigidity power-roller support structure in a dual-cavity half-toroidal CVT to further increase torque capacity. As a result of re-analyzing the function and parts composition of the previous structure, a high rigidity power-roller support structure, which permits power roller movement only in the horizontal direction, has been adopted. This structure enables the thrust and radial stiffness of the power-roller support to be substantially improved over the previous structure.
Technical Paper

A Study on the Cyclic Plastic Zone Size Method, ω*, for Digital Fatigue Life Prediction of Arc-Welded Joints

Various prediction methods have been proposed for evaluating the fatigue life of welded joints by combining finite element analysis (FEA) with an experimental database. However, to obtain more universal and accurate fatigue life predictions, it is necessary to have criteria for making integrated evaluations of the fatigue strength of welded joints. This paper presents a study that focuses on the local cyclic plastic zone size (ω*) as the criterion of fatigue strength and investigates its validity. The definition of ω* was given by the relationship between the stress state at the notch tip and the elastic strain which was defined along the strain-life fatigue curve (ε - N diagram) of a base metal. As a result of using ω*, it was found that an integrated fatigue life prediction was possible to a certain extent for notch and arc-welded joint specimens.
Technical Paper

Development of High Impact Strength Case Hardening Steel

Improving the impact strength of the differential gears is one way to reduce the size and weight of the final drive unit. Previously, we developed high-strength steel for gear use by adding molybdenum and reducing impurities such as phosphorus and sulfur. However, additional improvement of impact strength is required these days due to higher engine torque and demands for further weight reductions. Toward that end, we focused on boron, which has been used as an element for improving hardenability, and analyzed what effect its addition would have on impact strength. Useful knowledge was obtained for improving impact strength through enhancement of grain boundary toughness. Various steels were then produced experimentally and used in gear strength tests. The results made it possible to improve impact strength while reducing the content of other alloys, resulting in the development of a chromium-molybdenum-boron case hardening steel with superior cold forgeabilty.
Technical Paper

Work Hardening and Strength Analysis of Steel Structure with Special Cross Section

This paper presents the results of a strength analysis of a newly developed steel structure featuring a special cross section achieved with the hydroforming process that minimizes the influence of springback. This structure has been developed in pursuit of further weight reductions for the steel body in white. A steel tube with tensile strength of 590 MPa was fabricated in a low-pressure hydroforming operation, resulting in thicker side walls. The results of a three-point bending test showed that the bending strength of the new steel structure with thicker side walls was substantially increased. A finite element crush analysis based on the results of a forming analysis was shown to be effective in predicting the strength of the structure, including the effect of work hardening.
Technical Paper

Thermal Fatigue Life of Exhaust Manifolds Predicted by Simulation

A combined computational fluid dynamics (CFD) and finite element (FE) analysis approach has been developed to simulate in the early stages of design the temperature distribution and estimate the thermal fatigue life of an engine exhaust manifold. To simulate the temperature distribution under actual operating conditions, we considered the external and internal flow fields. Digital mock-ups of the vehicle and engine were used to define the geometry of the engine compartment. External-air-flow simulation using in-house CFD code was used to predict the flow fields in the engine compartment and the heat transfer coefficients between the air and the exhaust manifold wall at various vehicle speeds. Unsteady-gas-flow calculation using the STAR-CD thermal- fluids analysis code was to predict the heat transfer coefficients between the exhaust gas and the manifold wall under various operating conditions.