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The purpose of this paper is to outline a new computer controlled transfer for four-wheel drive vehicles, which AISIN-WARNER LIMITED of Japan has developed in cooperation with TOYOTA MOTOR CORPORATION. Certain difficulties still remain with shafting of a conventional transfer. Coupled with a 4-speed automatic transmission, the new transfer discussed in this paper consists of 3 wet clutches, a simple planetary gear set, a chain for front drive and a control unit. This transmission-transfer combination (30-80LE) has realized “ON THE GO SHIFT” for easier operations of the 4WD applications.

Recently,four-wheel drive vehicle (hereinafter abbreviated as 4WD vehicle) chassis dynamometer has been developed and in the course of practical use for many kinds of test. The 4WD chassis dynamometer technology, however, involves many new requirements and advanced techniques which were not required for conventional chassis dynamometers. This study has described a generation mechanism for driving force distribution through construction of a dynamic model for the resolution of unsolved issues in composite dynamic systems of 4WD vehicle and 4WD chassis dynamometer. Additionally, we have clarified the reasons why driving force distribution on-the-road is different from that on the chassis dynamometer, and clarified that the work value of driving shaft depends upon the combination of chassis dynamometer types and 4WD vehicles types. The micro-slip theory (hereinafter abbreviated as MS theory) utilized for the analysis is the basic theory that can explain that inclinations.

Technologies of 4WD chassis dynamometers (CHDY hereinafter) have advanced dramatically over the past several years, enabling 4WD vehicles to be tested without modifying their drive-train into 2WD. These advances have opened the use of 4WD-CHDY in all fuel economy and emission evaluation tests. In this paper, factors that influence the accuracy of fuel economy tests on 4WD CHDY are discussed. Fuel economy tests were conducted on 4WD CHDY and we found that most of the vehicle mechanical loss is the tire loss and that stabilizing the tire loss of the test vehicle is essential for the test reproducibility.

This paper describes the development of an innovative AWD system called Dynamic Torque Vectoring AWD for all-wheel drive (AWD) vehicles based on a front-wheel drive configuration. The Dynamic Torque Vectoring AWD system helps to achieve high levels of both dynamic performance and fuel efficiency. Significant fuel economy savings are achieved by using a new compact disconnection mechanism at the transfer and rear units, which prevents any unnecessary rotation of the propeller shaft. In addition, the system is also capable of independently distributing torque to the rear wheels by utilizing electronically controlled couplings on the left and right sides of the rear differential. This greatly enhances both on-road cornering performance and off-road driving performance.

In hybrid electric vehicles, engine starting and stopping occur frequently to provide better fuel economy. Specifically, the structure of the series-parallel hybrid system transmits engine torque pulsations to the driving wheels during engine starting and stopping, which may degrade the quality of the ride. In addition, the quick response of the electric motor can easily cause drivetrain vibration. This paper presents a motor control system for a series-parallel hybrid vehicle designed to reduce these vibrations. The proposed motor control system consists of two parts; one controller functions to compensate the engine torque pulsation during engine starts, and the other controller functions to control torsional vibration of the propeller shaft and drive shaft generated by rapid increases or decreases in driving torque. The proposed vibration reduction motor control method was added to the motor controller on the first rear wheel drive hybrid vehicle (Lexus GS450h).

Toyota has developed and confirmed the efficiency of a hybrid system using a continuously variable transmission (CVT) for relatively large vehicles like minivans. The fuel economy is double that of vans of the same class (in the Japan 10-15 test mode), and the system meets the emissions requirements for the U-LEV category. The hybrid system is configured for four-wheel drive. The front drive unit has a gasoline engine and an electric motor that are connected to a power-switching device, the output from which is conveyed to the CVT. The rear drive unit has an electric motor and a reduction gear that are independent of the front unit.

1 The new L110 hybrid transmission was developed for use in front-engine, rear wheel drive (FR) vehicles with 3.5-liter engines. The project goals were to develop a compact, slim structure that could be installed on a platform with an FR layout, and to provide the power performance, high-speed performance, and quietness of a luxury car while maintaining the fuel economy performance of a hybrid. To accomplish this, a new gear train, motor, and other components were developed. The newly developed hybrid transmission also uses coordinated control between the shift mechanism and the motor to achieve acceleration performance without causing the driver to feel any shock from an abrupt change of speed. This paper describes the main structural elements of the transmission and various aspects of its performance.

A new type of torque transmit coupling has recently been developed for 4WD cars, that provides a better match to ABS, is of lighter weight, and uses a simpler operating mechanism. This coupling transmits torque with a multi-disc clutch that is engaged by the pressure of high viscosity silicone oil. The rotary blade generates variably the silicone oil pressure, according to both differential speed and direction of rotation between the front and rear wheels. This coupling provides a good match between 4WD performance and four wheel Anti-lock Braking System (ABS) by a modification of the rotary blade shape. No additional devices are needed. This paper describes the characteristics of this coupling and the in-vehicle performance.

Toyota Motor Corporation has developed a new super-flat torque converter for the Flex Start System. It is installed in a new six-speed automatic transaxle (U660E) for front engine, front wheel drive vehicles. The Flex Start System is the first technology in the world that can start smoothly and reduce torque converter slipping loss by using a lock-up clutch at start. The newly developed super-flat torus achieves a high torque capacity and a maximum efficiency of 90%. Fuel economy is increased further by adding an efficient damper for low-speed lock-up in the free space provided by utilizing the super-flat torus. Toyota also developed a simple and super-flat structure at the one-way clutch (O.W.C.) area. This paper describes the structure, features, and performance of this new torque converter and the Flex Start System.

In June 2001, Toyota introduced its second hybrid vehicle to the Japanese market. It adopted a newly developed hybrid system that includes the world's first electrical four-wheel drive (4WD) system. In the development of this electrical 4WD system, it was necessary to determine the required rear motor torque to allow practical 4WD performance while maintaining excellent fuel economy. Initially, the factors affecting 4WD performance were quantitatively analyzed and then the rear wheel drive unit torque was optimized. This results in a new hybrid vehicle with practical 4WD performance and high efficiency.

The original Toyota Hybrid System (THS) was installed in the Prius and was introduced in 1997 as the world's first mass-produced hybrid passenger car. Since then, THS has been continuously improved. In 2003 THS-II (marketed as Hybrid Synergy Drive [HSD]), was installed in a new larger Prius. In 2006 HSD was installed in a Rear Wheel Drive Vehicle: the LEXUS GS450h. This system achieved both 4.5-liter class power performance and compact class fuel economy with outstanding emissions performance. In 2007, this system is expanded to a mechanical all-wheel-drive(AWD) in the LEXUS LS600hL(with new V8 engine). This paper will explain this hybrid system which achieved both V12 class power performance and mid-size class fuel economy, while meeting the most stringent emission standard SULEV as a full-size vehicle.

A new hybrid transmission has been developed for all-wheel-drive (AWD) cars, and is used in the new Lexus LS600h and LS600hL for its first application. It has a compact layout consisting of a power-split device, generator, high-output electric motor, and a two-stage speed reduction device. Combined with a 5-liter V-8 engine, it achieves power performance rivaling 6-liter engine vehicles, the fuel efficiency of a medium-class vehicle, and outstanding quietness. This paper describes the structure, performance, and shift control technology of this hybrid transmission.

The authors have developed an intelligent four-wheel drive system (I-4WD) designed to distribute the driving force to the front and rear wheels at the optimum ratio according to the running condition of the vehicle. The I-4WD consists of a center differential which distributes 30 percent of the driving force to front wheels and 70 percent to rear wheels (30:70), a hydraulic multi-disk clutch, an electronic control unit and a hydraulic control circuit. The driving force distribution can be steplessly varied from 30:70 up to the rigid state by controlling the hydraulic pressure on the clutch. The main control algorithm is based on the“yaw velocity model following control.” This composition has allowed us to accurately balance the cornering performance and stability without spoiling the critical limit predictability which is that the driver knows in advance the critical limit of vehicle dynamics.

Aisin AW (AW) and Toyota Motor Corporation (TMC) have developed a new rear wheel drive (RWD) 10-speed automatic transmission, AWR10L65 (TMC name: AGA0), suitable for RWD/AWD luxury passenger cars and sports cars. This 10-speed automatic transmission provides enhanced drivability leading to outstanding driver satisfaction. This has been accomplished using a close ratio gear train with optimized gear steps for rhythmic shift changes and quick acceleration. Low rpm lock-up and highly responsive shift changes result in a direct shift feel. This automatic transmission contributes to improved fuel economy by having higher efficiency and lower mass than current 8-speed RWD automatic transmissions.

This paper describes the development of a high performance hydraulic strut mount, which has low complex stiffness at high frequency range. To improve vehicle noise and vibration, the dynamic characteristics of the hydraulic mount were enhanced. A hydraulic chamber model was applied in the design of the strut mount which has low complex stiffness at high frequency range. A high performance hydraulic strut mount with the inner orifice is designed by applying the result of the analysis of a hydraulic chamber model and experimentally measured data. A well designed hydraulic strut mount reduces road noise for front wheel drive car.

The need for small personal mobility vehicles is growing as urbanization, the aging of society, traffic congestion, and parking become major issues, particularly in inner-city areas. The aging of society also means that more short trips within communities will be made. The i-REAL personal mobility vehicle is a next-generation single-passenger electric vehicle that enables the driver to move around town using a smaller amount of energy. This compact EV has three wheels: two front wheels driven by in-wheel motors and one rear wheel. According to the driver's needs, the i-REAL switches driving modes by changing its wheelbase. It can go slowly, allowing the driver to meet the eyes of passers-by when driving in parks, on sidewalks, or inside shopping malls. When on the road, it can lower its height and drive quickly like a bicycle or motorcycle. The body of the i-REAL leans automatically based on the speed and the turn angle to maintain the balance of the vehicle for any driver.

Toyota has developed the world's first 8-speed automatic transmission (AA80E) for RWD automobiles. The transmission will first be used in the all-new Lexus LS460. In addition, a novel control system has been developed to maximize the predictability, response, efficiency, and initial quality of the powertrain while utilizing the high number of gear steps.

A new compact five-speed automatic transmission (A650E) has been developed for front engine rear wheel drive cars. The development of this transmission has been aimed at improving fuel consumption, power performance, engine noise reduction during highway cruising and smooth acceleration by employing a wide range of gearing and close gear ratios. Generally a five-speed automatic transmission is larger than a four-speed, because of additional friction elements and gears. This can result in a change in the floor panel of the car body. However, by removing a one-way clutch for second gear and employing a unique gear-train layout, this transmission has the same circumference and length as the conventional four-speed automatic transmission (A340E)(1).1 In order to reduce first or second gear noise, gear specification and supporting structures of planetary gears have been optimized by FEM analysis.

The design requirement for more efficient vehicle moves a compact car toward front wheel drive arrangement, which requires an entire redesign of its power train. Toyota, with systematic approach from its planning stage, has developed a new automatic transmission series including one 3-speed and two 4-speed transmissions. An extensive examination on gear train arrangements enabled the 3-speed light, compact and highly reliable under the arrangement of Simpson gear train, and freewheel shifts with one-way clutches at every shifting. Two different 4th gear packages with freewheel shift are combined with the 3-speed unit to provide the versatility for the 4-speed units in various installations. Besides, these transmissions feature lock-up clutch converter, oil pump of a new tooth profile and two different control systems: hydraulic and electro-hydraulic.

Toyota Motor Corporation has developed a new five-speed automatic transmission (A750E/A750F) for longitudinal front engine rear wheel drive (RWD) vehicles. The development of this transmission has been aimed at improving fuel economy and power performance, achieving the world's top-level weight and compactness, while maintaining high torque capacity. In order to achieve this purpose, the gear train, torque converter, and other components are completely changed, and advanced technology has been applied. Moreover, this automatic transmission has achieved high-quality shift feel and quiet performance. This paper describes the major features and performance of this transmission in detail.