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To reduce the Body in White (BIW) mass, it is necessary to expand the application of Advanced High-Strength Steels (AHSS) to complex shaped parts. In order to apply AHSS to complex shaped parts with thinner gauge, high formability steel is required. However, higher strength steels tend to display lower elongations, compared with low/medium strength steels. Current AHSS are applied to limited parts for this reason. The new 1.2GPa material, with high formability, was developed to solve this issue. The mechanical property targets for the high elongation 1.2GPa material were achieved by precise metallurgical optimization. Many material aspects were studied, such as formability, weldabilty, impact strength, and delayed fracture. As the result of this development, 1.2GPa AHSS has been applied to a new vehicle launched in 2013.The application of this material was the 1st in the world, and achieved a 11kg mass reduction.

This paper describes the relationship between the design parameters used to define the geometry of an automotive torque converter and the resultant efficiency in relation to the internal flow characteristics. Taking the turbine bias angle and the contraction ratio of the pump flow passage as specific examples, the effects of each design parameter on the internal flow characteristics and the occurrence of loss were analyzed. A three-dimensional viscous flow analysis code was used in the numerical computation procedure and a method developed independently by the authors was used in the loss analysis. The flow near the wall was visualized experimentally using a technique resembling the so-called oil film method. The visualized results showed good qualitative agreement with the numerical analysis results.

A flatter design is becoming increasingly important for reducing torque converter axial size and weight. The conventional stator design method, in which the blade profile is geometrically determined and flow analysis of the profile may give some valuable information, is no longer sufficient for achieving efficient flow turning in the short axial length of flat torque converters. Here, after a brief review of the conventional design approach, an inverse design method is introduced, which yields a blade profile solution for a prescribed favorable velocity distribution along the blade. The performance improvement with this procedure has been demonstrated experimentally.

There has been a growing need to develop more compact automatic transmissions with a greater number of speeds for better fuel economy and better driveability. This study investigated a method for determining suitable planetary gear trains for today's transmissions. A computer program has been developed for application to five-speed transmissions consisting of two planetary gearsets. By analyzing various gear train possibilities, the program can identify which gearsets are suitable for different conditions, including the number of speeds, the number of binding elements, topological suitability and other factors.

An electronically controlled five-speed automatic transmission has been developed for use in new 2-liter models. This high-performance gearbox is the world's first five-speed automatic transmission for passenger car use to be equipped with a torque converter. It is designed with an ultra-wide range and close ratio gearing and incorporates a host of outstanding technologies to provide excellent performance and driveability. This paper describes the major features and performance of this new automatic transmission and some of the studies undertaken concerning multiplication of gear steps.

Building a toroidal continuously variable transmission (CVT) with multiple power rollers arranged in parallel is an effective way to improve its torque capacity. However, that requires a method for synchronizing the operation of all of the power rollers. This paper describes a method of synchronizing the four power rollers in a toroidal CVT that we have researched and developed. It also presents the results of an analysis of the cause of power roller vibration, which was a serious issue encountered in the development process, and describes an effective method for preventing it. The methods described here achieve sufficient synchronization performance for practical use of the toroidal CVT on production vehicles.

This paper proposes a new voice and data wireless communication method for telematics services. Data-voice (DV) modems have conventionally been used for simultaneous transmission of voice and data. With this method, however, one line is split between the data part and voice part. Lost data are retransmitted, but the voice signal is not resent because voice communication requires a real-time characteristic. The new voice and data wireless communication method proposed here switches voice to a voice line and data to a data line.

The mechanism causing the micro slip characteristic of a metal CVT belt during torque transmission was analyzed, focusing on the gap distribution between the elements. It was hypothesized that gaps between the elements cause slip to occur between the elements and the pulleys when the belt is squeezed between the two halves of the pulleys, and the slip ratio was calculated theoretically on that assumption. The μ-v (friction coefficient versus sliding velocity) characteristic between the elements and the pulleys was measured and the results were used in calculating the slip ratio. As a result, a simulation procedure was developed for predicting the slip-limit torque of the belt on the basis of calculations. The slip ratio found by simulation and the calculated slip-limit torque showed good quantitative agreement with the experimental data, thereby confirming the validity of the simulation procedure.

This paper describes a newly developed adaptive cruise control (ACC) system using continuously variable transmission (CVT) gear ratio control. This system provides excellent headway distance control performance at a reasonable cost. With this system, headway distance is measured with a laser radar, and the throttle position and CVT gear ratio are controlled under both acceleration and deceleration situations. The new ACC system consists of a target headway distance calculator, a headway distance controller, a vehicle velocity controller and a drive torque controller. Using a drive torque control method that was newly developed based on integrated control of engine torque and the CVT gear ratio, the following benefits are obtained. (1) It provides smoother acceleration and deceleration. (2) It maintains the target vehicle velocity on steep uphill and downhill grades. As a result, sufficient ACC performance can be attained even in 2.0-liter class vehicles.

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.

A new integrated control system has been developed for controlling an SI engine and a CVT proactively so as to obtain the demanded drive torque most efficiently. Taking into account ease of calibration, a control system configuration has been achieved that determines the CVT ratio from the target drive torque and vehicle speed, based on the steady-state relationship between the demanded drive torque and the vehicle speed, gear ratio, engine torque and fuel economy. An analysis was made of drive torque characteristics while the ratio was changing under transient conditions. The results showed that using engine torque to compensate for the ratio change response lag and inertia torque, which is proportional to the differential of the gear ratio, is effective in improving drive torque responsiveness.

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.

In recent years, the slip lock-up mechanism has been adopted widely, because of its fuel efficiency and its ability to improve NVH. This necessitates that the automatic transmission fluid (ATF) used in automatic transmissions with slip lock-up clutches requires anti-shudder performance characteristics. The test methods used to evaluate the anti-shudder performance of an ATF can be classified roughly into two types. One is specified to measure whether a μ-V slope of the ATF is positive or negative, the other is the evaluation of the shudder occurrence in the practical vehicle. The former are μ-V property tests from MERCON® V, ATF+4®, and JASO M349-98, the latter is the vehicle test from DEXRON®-III. Additionally, in the evaluation of the μ-V property, there are two tests using the modified SAE No.2 friction machine and the modified low velocity friction apparatus (LVFA).

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.

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.

The use of automatic transmissions is continually increasing because of their ease of operation. Transmission performance requirements that have become more important in recent years include smooth shift quality and a shift schedule that matches the driver's intentions. An electronically controlled automatic gearbox, which sets the shift schedule according to the vehicle speed and throttle valve opening, provides a dramatic improvement in shift quality over its hydraulically controlled counterpart. However, even with an electronically controlled automatic transmission, shift hunting occurs when driving uphill or towing an object Based on the use of fuzzy logic, a technique has been developed for estimating running resistance, represented by the road gradient. This technique has been incorporated in a new shift schedule control method that eliminates shin hunting Research is now under way on a fuzzy logic technique for inferring the driver's intention to accelerate

At Nissan we have developed a new parallel hybrid system for rear-wheel-drive hybrid vehicles. 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 be within the length allowed for the powertrain. Therefore, new technologies have been developed such as high-density, square-shaped windings and an optimized magnetic circuit specially designed for concentrated winding motors. The inverter is sized to a 12V battery, which it replaces in the engine compartment. Despite its compact size, the inverter must have rather large current capacity to drive a high-power motor. Heat management is critical to the design of a small but high-power inverter.

Nissan has developed a practical and available toroidal continuously variable transmission (T-CVT) for passenger vehicles for the first time in the world. This CVT is applicable to engines having an output of torque larger than 400 N-m and makes it possible to use a lock-up clutch at low vehicle speed, resulting in marked improvements in drivability and fuel economy. The authors have developed the T-CVT fluid, which is in this application, having excellent traction coefficient and sufficient capacity as the transmission fluid. This paper mainly describes the traction coefficient measurement procedure and the performance of the newly developed fluid.

Door guard beams have been developed through the utilization of ultra high strength steel (tensile strength>100 kg/mm2). At first, the sheet metal gauge was reduced in proportion to the strength of the ultra high strength without changing the shape of the beam section. This caused beam buckling and did not meet guard beam specifications. Analyzing this phenomena in accordance with the buckling theory of thin plates, a design criteria that makes effective use of the advantages of ultra high strength was developed. As a result, our newly designed small vehicle door guard beams are 20% lighter and 26% thinner than conventional ones. This makes it possible to reduce door thickness while increasing interior volume.

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.