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In order to replace PVC with TPO as I/P skin layer of invisible PAB, the elongation behavior, vacuum thermoforming, thermal, light resistance and low temperature PAB deployment of TPO were investigated. With the elongation properties; 50cN ↑ melt strength, 300mm/s ↑ breaking speed, 200s ↑ breaking time, TPO was vacuum-formed well like PVC. The thermal and light resistances of TPO were superior to PVC. In terms of low temperature airbag test, PVC was fractured with the brittle behavior during the deployment. TPO, however, showed the ductile fracture. And also when TPO was used for PAB cover, the elongation ratio of TPO was also important criterion for the normal break without any interference to I/P part, outside of PAB. The 300∼500% elongation ratio was most preferable.

With the advent of cars with computerized engines, drivers sometimes suffer discomfort with “check engine” light problem, and as a result, insist on increasing levels of reliability in their cars. Hence, reliability of the wiring harness has become a very important automotive design characteristic. On one hand, the more secure an engine mounting system is, the more stable the engine wiring harness is. In order to enhance their durability, car manufacturers need to perform many validation tests during the development phase which involves a lot of time and cost. In this study, a newly developed lab-simulation test is proposed to qualify the design of engine mounting and engine wiring early in the design cycle and reduce time and expense. The lab-simulation test has contributed to a significant cost and time reduction and has shown good correlation to the original proving ground test.

Recently, high speed direct injection (HSDI) diesel engines are rapidly expanding their application to passenger cars and light duty commercial vehicles in western European market and other countries such as Korea and Japan. These movements are strongly backed by the technological innovations in the area of air charging and high pressure fuel injection systems. Variable geometry turbine (VGT) turbocharger, which could overcome the typical weak point of the existing turbocharged engine, and the common rail fuel injection system, which extended the flexibility of fuel injection capability, became two of the most frequently referred keywords in recent HSDI technology. In this paper some aspects of VGT potential as a full load torque and power modulator will be discussed. Possibility to utilize the portion of full load potential in favor of part load emissions and fuel economy will be investigated.

A systematic process of optimization is suggested to obtain the best control maps for a parallel type hybrid electric vehicle. Taking the fuel consumption as the cost function and driving cycle as part of the constraints, an optimization problem for CVT pulley ratio control and motor torque control can be formulated. The change of the battery charge state between the start and end point of the given driving cycle also works as a constraint. In order to see the effect of various control strategies on system behavior and overall fuel consumption, a simulation model was built to accommodate the functional blocks representing hybrid powertrain subsystem components and corresponding control units.

With its advantage on the economic and environmental reason the preference of vehicles with diesel engine is growing in the domestic market as well as European market. And automobile makers are enthusiastic in the development of diesel engine vehicles with more comfortable interior atmosphere in order to meet consumers' requirements. Generally, when compared with gasoline engine, diesel engine has much bigger vibratory input to the mounting structure and produces higher level in interior noise and body vibration. In this paper, the improvement of NVH quality at the idle state of an SUV car with DI diesel engine has been achieved through tuning engine mounts based on TPA (Transfer Path Analysis) for low frequency vibration and interior booming noise.

The air fuel ratio of current gasoline engine is mostly controlled by various air flow meters. When CVVT (Continuous Variable Valve Timing) device is applied to gasoline engine for higher engine performance, MAP (Manifold Absolute Pressure) sensor can not be applied anymore due to intake valve motion. Therefore HFM (Hot film airflow meter) is used for measuring the intake air flow instead of MAP sensor. Usually HFM has a little sensitivity in flow direction, therefore reverse flow from engine to air cleaner can not be measured. Also, HFM maker request enough straight duct length nearly 10 times of a duct diameter making a fully developed flow. But, most vehicles have no enough space to install such an intake system in engine room. Thus the inserted duct was applied to confirm the stable fully developed flow in air duct. The various duct configurations in front of HFM effect on the sensitivity of HFM.

We analyzed the in-cylinder flow fields of an optical-access single cylinder diesel engine with the PIV and STAR-CD CFD code. The PIV analysis was carried out in the bottom and side view mode during a compression stroke (ATDC 220°-340°) at 600 rpm. The flow pattern traced by the streamlines, the location of vortex center, the generation and disappearance of tumble, and the squish effect agreed well, as visualized by the PIV and CFD. Vorticity and spatial fluctuation intensities abruptly increased from ATDC 310, reflecting more complicated flow pattern as approaching TDC. In a quantitative sense, the velocity magnitudes obtained from the PIV were, on an average, higher than those from the CFD by 1 m/s approximately and the difference in velocity magnitude between them was about 26 %. In the CFD analysis, the standard high Reynolds κ-ε and RNG k-ε model were adopted for calculation with tetra and hexa or their hybrid meshes, to determine the turbulence model dependencies.

Diesel engines are the most commonly used power train of the freight and public transportations in the world. From the viewpoint of global warming restraint, however, reduction of exhaust emissions from the diesel engine is urgent demand. Stringent emission regulations are being proposed with growing concern on NOx, PM and CO2 emissions. Future emission regulations require advanced emission control technologies, such as SCR(Selective Catalytic Reduction), LNT(Lean NOx Trap) and EGR(Exhaust Gas Recirculation). The EGR is a commonly used technique to reduce emission. In this study, a LP-EGR(Low Pressure Exhaust Gas Recirculation) system was investigated to evaluate its potential on emission reduction and fuel economy improvement, especially for a passenger diesel engine. A 3.0ℓ diesel engine equipped with the LP-EGR system was tested using an in-house control algorithm.

Recently, upon customer’s needs for noise-free brake, carmakers are increasingly widely installing damping kits in their braking systems. However, an installation of the damping kits may excessively increase softness in the brake system, by loosening stroke feeling of a brake pedal and increasing compressibility after durability. To find a solution to alleviate this problem, we first conducted experiments to measure compressibility of shims by varying parameters such as adhesive shims (e.g., bonding spec., steel and rubber thickness), piston’s shapes (e.g., different contact areas to the shims), and the numbers of durability. Next, we installed a brake feeling measurement system extended from a brake pedal to caliper. We then compared experimental parameters with brake feeling in a vehicle. Finally, we obtained an optimized level of brake feeling by utilizing the Design for Six Sigma (DFSS).

Charge boosting strategy plays an essential role in improving the power density of diesel engines while meeting stringent emissions regulations. In downsized two-stage turbocharged engines, turbocharger matching is critical to achieve desired boost pressure while maintaining sufficiently fast transient response. A numerical simulation model is developed to evaluate the effect of two-stage turbocharger configurations on the perceived vehicle acceleration. The simulation model developed in GT-SUITE consists of engine, drivetrain, and vehicle dynamics sub-models. A model-based turbocharger control logic is developed in MATLAB using an analytical compressor model and a mean-value engine model. The components of the two-stage turbocharging system evaluated in this study include a variable geometry turbine in the high-pressure stage, a compressor bypass valve in the low-pressure stage and an electrically assisted turbocharger in the low-pressure stage.

The market demands for CO2 reduction and fuel economy have led to a variety of new gear set concepts of automatic transmissions with 4 planetary gear sets and 6 shift elements in recent years. Understanding the relationship between the torque of clutch and brake and gear ratio in the design stage is very important to assess new gear set concepts and to set up the control strategy for enhancing shift quality and to reduce the heat generation of clutch and brake. In this paper, a new systematic approach is used to unify the relationship between torque and gear ratio during the gear shift for all multi-step planetary automatic transmissions. This study describes the unified concept model with a lumped inertia regardless of the specific transmission layout and derives the principal unified relationship equations using torque and energy analysis, which prove that the sum of brake torque is always gear ratio -1 in every in-gear.

This study presents the NVH characteristics of a passenger vehicle with a three-cylinder engine and a Continuously Variable Transmission (CVT) and an optimization procedure to achieve balance between fuel economy and NVH. The goal of this study is to improve fuel economy by extending the lock-up area of the damper clutch at low vehicle speed and to minimize booming noise and body vibration caused by the direct connection of the engine and transmission. Resonance characteristics of the chassis systems and driveline have been studied and optimized by the experiment. NVH behavior of the vehicle body structure is investigated and modifications for refinement of booming and body vibration are proposed by simulation using MSC NASTRAN. Calibration parameters for CVT control are optimized for fuel economy and NVH. As a result, the lock-up clutch area has been extended by 300RPM and the fuel economy has been improved by about 1%, while the NVH characteristics of the vehicle satisfy the targets.

This paper presents two closed-loop control methods for monitoring and improving the combustion behavior and the combustion noise on two 4-cylinder diesel engines, in which an in-cylinder pressure and an accelerometer transducer are used to monitor and control them. Combustion processes are developed to satisfy the stricter and stricter regulations on emissions and fuel consumption. These combustion processes are influenced by the factors such as engine durability, driving conditions, environmental influences and fuel properties. Combustion noise could be increased by these factors and is detrimental to interior sound quality. Therefore, it is necessary to develop robust combustion behaviors and combustion noise. For this situation, we have developed two closed-loop control methods. Firstly, a method using in-cylinder pressure data was developed for monitoring and improving the combustion noise of a 1.7L engine. A new index using the values calculated from the data was proposed.

This paper presents a transient vibration analysis of a nonlinear full-vehicle. The full-vehicle model consists of a powertrain, a trimmed body, a drive line, and front and rear suspensions with tires. It is driven by combustion forces and runs on a road surface. By performing time-domain simulation, it is possible to capture nonlinear behavior of a vehicle such as preload due to gravitational force, large deformation, and material nonlinearity which cannot be properly treated in the conventional steady state analysis. In constructing a full-vehicle, validation process is essential. Validation process is applied with respect to the assembling sequence. The validation starts with component levels such as tires, springs, shock absorbers, and a powertrain, and then the full-vehicle model is constructed. Model validation is done in two aspects; one is model accuracy and the other is model efficiency.

The engine indicated torque is not delivered entirely to the wheels, because it is lowered by losses, such as the pumping, mechanical friction and front auxiliary power consumption. The front auxiliary belt drive system is a big power consumer-fueling and operating the various accessory devices, such as air conditioning compressor, electric alternator, and power steering pump. The standard fuel economy test does not consider the auxiliary driving torque when it is activated during the actual driving condition and it is considered a five-cycle correction factor only. Therefore, research on improving the front end auxiliary drive (FEAD) system is still relevant in the immediate future, particularly regarding the air conditioning compressor and the electric alternator. An exertion to minimize the auxiliary loss is much smaller than the sustained effort required to reduce engine friction loss.

An efficient method to determine optimal bushing stiffness for improving noise and vibration of passenger cars is developed. In general, a passenger vehicle includes various bushings to connect body and chassis systems. These bushings control forces transferred between the systems. Noise and vibration of a vehicle are mainly caused by the forces from powertrain (engine and transmission) and road excitation. If bushings transfer less force to the body, levels of noise and vibration will be decreased. In order to manage the forces, bushing stiffness plays an important role. Therefore, it is required to properly design bushing stiffness when developing passenger vehicles. In the development process of a vehicle, bushing stiffness is decided in the early stage (before the test of an actual vehicle) and it is not validated until the test is performed.

The success of improved fuel economy is the proper integration of thermal management components which are appropriately performed to reduce friction and wasted energy. The thermal management systems of vehicle are able to balance the multiple needs such as heating, cooling, or appropriate operation within specified temperature ranges of propulsion systems. Since the propulsion systems of vehicle have changed from a single energy source based on conventional internal combustion engine to hybrid system including more electrical system such as full type of hybrid electric vehicle or plug-in hybrid electric vehicles, a new transition associated with vehicle thermal management arises. More efficient thermal management systems are required to improve the fuel economy in the hybrid electric vehicles because of the driving of electric traction motor and the increase of engine off time. The decrease of engine operation time may not sustain the proper temperature ranges of engine and gearbox.

The reduction of intake noise is a very important factor in controlling the interior noise levels of vehicles, particularly at low and major engine operating speeds. A vehicle intake system generally consists of air cleaner box, hose, duct, and filter element. Also, resonators and porous duct are included, being used to reduce intake noise. For more accurate estimation of the transmission loss (TL), it seems important to develop a CAE model that accurately describes this system. In this paper, simple methods, which can consider the effects of filter element and vibro-acoustic coupling, are suggested which could remarkably improve estimation accuracy of the TL. The filter element is assumed as equivalent semi-rigid porous materials characterized by the flow resistivity defined by the pressure drop, velocity, and thickness.

Advanced powertrain test, which is simulating real road load condition, was performed on the dynamic test bed. This cutting edge system can reproduce real road resistance based upon the vehicle dynamic model and wheel slip model. This wheel slip function is simulating the real behavior of the powertrain wheel as close as possible at each wheel independently. Additionally, low inertia of dynamometer motor themselves is another advantage for this purpose. This test bed is capable of testing all kinds of 2WD and 4WD powertrain configuration regardless of transmission type. Also, vehicle configuration can be mounted and tested on this test bed with small addition of supporting system alternatively. For the application, a four wheel drive powertrain was mounted on the test bed and driveline noise and vibration behavior such as transfer rattling noise and tip in/out shock were reproduced on this test bed.

As automotive technology has been developed, gear whine has become a prominent contributor for cabin noise as the masking has been decreased. Whine is not the loudest source, but it is of high tonal noise which is often highly unpleasant. The gear noise originates at gear mesh. Transmission Error acts as an excitation source and these vibrations pass through gears, shafts and bearings to the housing which vibrates to produce noise on surrounding air. As microgeometry optimization target to reduce the fundamental excitation source of the noise, it has been favored method to tackle gear whine noise, especially for manual transmission. However, practicality of microgeometry optimization for the planetary gear system has been still in question, because of complex system structure and interaction among multi mesh gear sets make it hard to predict and even harder to improve. In this paper, successful case of whine noise improvement by microgeometry is presented.