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In this study, it is purpose to make clear the effect of cavitation phenomenon on the spray atomization. In this report, the cavitation phenomenon inside the nozzle hole was visualized and the pressure measurements along the wall of the nozzle hole were carried out by use of 25-times enlarged acrylic nozzle. For the representatives of regular gasoline, single and two-component fuels were used as a test fuel. In addition, various cavitating flow patterns same as experimental conditions were simulated by use of Barotropic model incorporated in commercial code of Star-CD scheme, and compared with experimental results.

An active suspension system controls a spring constant and an attenuater in real time using a power supply. Generally, the hydraulic pressures are used for transmitting the power. Therefore, a highly reliable and inexpensive control system has been required for a commercial use. This has been achieved by developing a mechanical fluid servo valve which comprises a simple combination of a solenoid valve and a spool valve. The technical problem of the valve vibrations has been solved through the numerical analyses, the fluid flow visualization tests and the vehicle tests.

Grip feeling is an important facet in vehicle dynamics evaluation from a driver satisfaction and enjoyment standpoint. To improve grip feeling, we analyzed the subjective comments from test driver's about grip feeling and an evaluated human sensitivity to lateral motion. As a result, we found that drivers evaluate transient grip feeling according to the magnitude of lateral jerk. Next, we analyzed what vehicle parameters affect lateral jerk by using theoretical equations. As a result, we found that cornering power is an important parameter, especially the cornering power of rear tires as they can be create larger lateral jerk than can front tires.

Improvement of vehicle dynamics in limit cornering have been studied. Simulations and tests have verified that vehicle stability and course trace performance in limit cornering have been improved by active brake control of each wheel. The controler manages vehicle yaw moment utilizing difference braking force between left and right wheels, and vehicle deceleration utilizing sum of braking forces of all wheels.

In-wheel motors (IWM) will be a key technology that contributes to the popularization of electric vehicles. Combining electric drive with IWM enables both good vehicle dynamics and a roomy interior. In addition, the responsiveness of IWM is also capable of raising dynamic control performance to an even higher level. IWM enable vertical body motion control as well as direct yaw control, electric skid control, and traction control. This means that IWM can replace most control actuators used in a vehicle chassis. The most important technology for IWM is to enable the motor to coexist with the brake and the suspension arms inside the wheel. The IWM drive unit described in this paper can be installed with a front double wishbone suspension, the most difficult configuration.

This paper describes and confirms the effect of low frequency sinusoidal steering torque input on vehicle response and steering behavior using vehicle test, analysis with equations of motion and simulations. The vehicle response by low frequency torque input is quite different to the vehicle response by low frequency steer angle input. Steering system parameters such as moment of inertia, damping, friction and power steering assist torque have an effect on low frequency torque input steering system dynamics. The dynamic response of the vehicle with electric power steering (EPS) system, which has a big moment of inertia with electric motor and friction of the reduction gear, is affected by the steering system dynamic properties. The vehicle response by low frequency torque input test has capability for contribute to vehicle evaluation such as steer feel or maneuverability of handling.

In vehicle control systems such as ABS (anti-lock braking system) or active suspension control, sensors for detecting longitudinal and/or lateral acceleration of vehicles (acceleration of up to ± 9.8 m/s2, with frequency range of DC to 20 Hz) is necessary. The principle of acceleration detection for this sensor is as follows. A permanent magnet levitates steadily in magnetic fluid by the action of the magnetic field generated by the magnet itself. The magnet moves by the application of acceleration on the mass of the magnet. This change of position of the magnet is detected by the Hall element, and thus acceleration is measured as an electrical signal. This sensor consists of only magnetic fluid, a permanent magnet, housing, a pair of Hall elements and an electronic circuit.

Sensors which can detect minimal acceleration such as ± 9.8 m/sec2 in longitudinal and lateral direction of a vehicle, for DC to 20 Hz range, are required to control ABS (anti-lock braking system) or suspension system. To fulfill these requirements, we have developed a one-dimensional acceleration sensor, using magnetic fluid, to control the vehicle. In 1992, we submitted a paper on this sensor at the SAE International Congress and Exposition. Based on this one-dimensional acceleration sensor, we have developed an acceleration sensor which can detect two dimensional acceleration using a single inertia mass. This sensor is compact and can detect minimal acceleration with high accuracy. Spring and damping functions were obtained via the adoption of magnetic fluid, as in the case of the former one-dimensional acceleration sensor. This sensor can sustain mechanical shocks.

A phosphor thermometry, for measurements of two-dimensional gas-phase temperature was examined in turbulent combustion in an engine. The reasonable temperature deviation and the agreement with calculated data within 5% precision were achieved by single-shot images in the ignition process of compression ignition engine. Focusing on the local flame kernel, the flame structure could be quantitatively given by the temperature. It became evident that the HCCI flame kernels had 1-3 mm diameter and the isolated island structures. Subsequently, the HTR zone consisted of the combined flame kernels near TDC.

Excessive throttle pedal operation while driving on slippery roads causes the wheels to spin, consequently reducing vehicle stability and traction. Driving a vehicle under these conditions imposes additional and unneccessary burdens on the driver. To solve the problem, a traction control (TRC) system controlling engine torque and brake force has been developed to prevent the driven wheels from excessive spinning. The TRC system consists of some additional components to the Antilock Brake System (ABS), a system which had previously been developed to prevent wheels from locking up during hard braking. The combination of the ABS and the TRC system will now be effective to assist the driver to improve the vehicle driving performance on slippery road surfaces.

TOYOTA MOTOR CORPORATION had developed the world's first microprocessor controlled suspension system, Toyota Electronic Modulated Suspension (TEMS), which is now being offered on the Toyota Soarer from Feb. '83. This system consists of sensors, switches, electronic control unit (ECU), actuators and shock absorbers. TEMS uses a microprocessor to adjust the damping forces of the front and rear shock absorbers. As a result, suspension can be tuned in two stages (hard and soft cushioning) and driver can choose three control modes (AUTO, SPORT, NORMAL). In AUTO mode, the TEMS system has achieved attitude controls (i.e. squat control, roll control and nosedive control). The TEMS system achieved a 15 - 30% decrease of squat, a 20 - 30% decrease of roll angle, a 10 - 30% decrease of nose-dive and a 30 - 40% decrease of shift-squat.

Advanced electronic control system of suspension and air springs are combined with the double wishbone type suspension. Damping force, spring rate and vehicle height can be automatically con-trolled among three levels in response to the vehicle running conditions.

Toyota has developed a new full time 4WD system, called “EC-HYMATIC” or Electronically Controlled - HYdraulic Multi-plate clutch Active Traction Intelligent Control. This system permits an automatic torque transfer, depending on driving conditions, for front and rear wheels under control of the speed difference between the two. The system developed consists of a center differential, a speed difference control clutch system employing multi-plate clutch, and a gear set for rear axle drive. The speed difference control clutch system is controlled by a unique electro-hydraulic system using a microcomputer. An extensive use of computer simulations and vehicle test and evaluation has successfully developed an appropriate control strategy for the clutch system. The new 4WD system, EC-HYMATIC, considerably improves handling characteristics, traction performance and stability of a 4WD vehicle.

One of the innovations for the Lexus LS400 is the development of a traction control system (TRAC system). The TRAC system suppresses the spinning of the driven wheels, which occurs easily on slippery roads during excessive acceleration, and it improves the acceleration performance and the stability of the car. The TRAC system controls the engine sub-throttle angle and the brake hydraulic pressure for the driven wheels in the same way as the traction control system for the 1987 Toyota Crown. But, acceleration performance and stability of Lexus LS400 is better than Crown as a result of good wheel spinning control by additional improvements of the throttle and brake control methods. Especially as the TRAC system controls the brake hydraulic pressure individually for left and right wheel, the car acceleration performance on split-μ surfaces is improved notably.

In order to adapt to energy security and the changes of global-scale environment, further improvement of fuel economy and adaptation to each country’s severer exhaust gas emission regulation are required in an automotive engine. To achieve higher power performance with lower fuel consumption, the engine’s basic internal design such as an engine block and cylinder head were changed and the combustion speed was dramatically increased. Consequently, stroke-bore ratio and valve layout were optimized. Also, both flow coefficient and intake tumble ratio port were improved by adopting a laser cladded valve seat. In addition, several new technologies were adopted. The Atkinson cycle using a new Electrical VVT (Variable Valve Timing) and new combustion technology adopting new multi-hole type Direct fuel Injector (DI) improved engine power and fuel economy and reduced exhaust emissions.

In many countries, cetane number and distillation properties of diesel fuel have been changing, thus affecting the performance of diesel engines. This paper describes investigations made on the effect of diesel fuel quality on white smoke (one of the important emissions of diesel engines). The result of simple laboratory tests simulating high altitude conditions plus field tests using three types of disel engines supplied with various types of diesel fuels is given. It was found that white smoke appearing tendency correlated best with cetane number and the 90 percent distillation point of the fuel. The field tests performed at high altitude correlated well with the simple laboratory tests.

The effects of diesel fuel properties (aromatic content, cetane index and T90), cetane improver, oxygenates, high boiling point hydrocarbons and aromatics distribution on diesel exhaust emissions were studied under the Japanese 10-15 test cycle and the ECE+EUDC test cycle. The test vehicle was a TOYOTA COROLLA with a natural aspirated, 2.0L displacement, IDI diesel engine. It was demonstrated that particulate emissions are highly correlated with T90 and that NOx is affected by the aromatic content of fuel. A reduction in particulates emissions was observed in fuel with a lower cetane number by adding cetane improver, but this reduction was limited. Cetane improver had no effect on NOx emissions in the 45 # 60 cetane number range. Oxygenates reduced particulate emissions remarkably but had little effect on NOx emissions. A decrease in the soot in particulates was particularly observed.

Roadway departure mitigation systems for helping to avoid and/or mitigate roadway departure collisions have been introduced by several vehicle manufactures in recent years. To support the development and performance evaluation of the roadway departure mitigation systems, a set of commonly seen roadside surrogate objects need to be developed. These objects include grass, curbs, metal guardrail, concrete divider, and traffic barrel/cones. This paper describes how to determine the representative color of these roadside surrogates. 24,762 locations with Google street view images were selected for the color determination of roadside objects. To mitigate the effect of the brightness to the color determination, the images not in good weather, not in bright daylight and under shade were manually eliminated. Then, the RGB values of the roadside objects in the remaining images were extracted.

Eliminating brake squeal generated during brake application is an important task for the improvement of comfort in the vehicle. There has been a lot of research made on the problem of brake squeal in the past. And most of the papers presented elaborate on low frequency brake squeal (2-3kHz). However, brake squeal has often the high-frequency vibration. For this reason, we have made research into the high-frequency brake squeal (5-10kHz). Double-Pulsed Laser Holography is a useful method for visualizing small vibration of brake components during brake squeal generation. The results obtained using Holographic Interferometry show the rotaing disc vibrates in the bending mode with diametral nodes. Consequently, we think that the modification of brake disc can eliminate brake squeal, which is caused by self-excited vibration. Then we have calculated natural frequency and its vibration mode of a circular-plate added mass.

It is very important for the vehicle comfort quality to eliminate brake noise. The brake noise can be defined into two phenomena: One is the high-frequency brake squeal (frequency 1-15kHz), we have presented in 1989 SAE Congress(890864) * (2),and the another is the low-frequency brake groan (frequency 200-500Hz). In this paper,the brake groan has been discussed by constituting the theoretical model,in order to clarify the cause of disc brake groan noise. According to the previous study(3), the groan noise has been occurred by the increase of the disc temperature which has influenced on the disc width and the disc material. On the other hand, the groan noise can be observed in the condition of atmosphere temperature indeed. So that the precise phenomenon and cause should be defined. After observing the groan noise on the test bench, we have constructed the theoretical model and taken the numerical method.