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Conventional power steering systems can be “tailored” to provide light steering efforts for parking and low speed, or high steering efforts for stability and “road feel” at high speed. In either case, the customer's preferred steering efforts are not provided at all times. Compromises are required. The need for a speed-sensitive steering effort system has prompted the introduction of several innovative variable-assist steering systems in the past few years, which are currently used in some European and Japanese vehicles. This paper describes a Ford-patented variable-assist system used on the 1988 Lincoln Continental, the first application of vehicle speed-sensitive steering to an American-designed and manufactured vehicle. The Ford Variable-Assist Power Steering System is a “rotary steering valve” system. It uses a modification of the current rotary valve to provide low steering efforts (low torsion bar twist) at low speed and higher efforts (more twist) as vehicle speed increases.

The cyclic behavior of single overlap aluminum joints joined through a number of different methods has been investigated using Alcan 5754-O, an alloy that potentially could be used in structural applications. Overlap shear tests of spot welded, clinched and riveted joints are compared on the basis of their fatigue performance. The fatigue response of the spot welded joint was the baseline to which the other fasteners were compared. Test results showed an improvement of approximately 25% for both the mechanical clinch joints and aluminum rivets in fatigue strength at 106 cycles. The most significant improvement in fatigue strength of 100% was found for the self piercing rivets at 106 cycles. The failure behavior of the various joining methods is discussed as well as the surface appearance.

Vehicle sound quality has become an important basic performance requirement. Traditionally, automobile noise studies were focused on quietness. It is now necessary for the automobile to be more than quiet. The sound must be pleasing. This paper describes a development process to improve both vehicle noise level and sound quality. Formal experimental design techniques were utilized to quantify various hardware effects. A-weighted sound pressure level, Speech Intelligibility, and Composite Rating of Preference were the three descriptors used to characterize the vehicle's sound quality. Engineering knowledge augmented with graphical and statistical techniques were utilized during data analysis. The individual component contributions to each of the sound quality descriptors were also quantified in this study.

A four-stroke, spark-ignition engine is described that seeks to achieve high expansion ratio and low throttling losses at light load, whilst retaining good knock resistance at full load operation and without the need for expensive mechanical changes to the engine. The engine does, however, incorporate a second inlet (transfer) valve and associated transfer port linked to the intake port. The timing of the transfer valve is different from that of the main inlet valve. Load modulation is achieved by control of the gas outflow from the transfer port. A computer model of the engine is first validated against measured data from a conventional engine. Comparisons are made of incylinder pressure at part load conditions, total air flowrate through the engine and intake port air velocities as a function of crank angle position.

This paper presents a new transient passenger thermal comfort model. The model uses as inputs the vehicle environmental variables: air temperature, air velocity, relative humidity and mean radiant temperature all of which can vary as a function of time and space. The model also uses as inputs the clothing level and the initial physiological state of the body. The model then predicts as a function of time the physiological state of the body and an effective human thermal sensation response (e.g. cold, comfort, hot, etc.). The advantage of this model is that it can accurately predict the human thermal sensation response during transient vehicle warm-up and cooldown conditions. It also allows design engineers the ability to conduct parametric studies of climate control systems before hardware is available. Here we present the basis of the new thermal comfort model and its predictions for transient warm-up and cooldown conditions.

The pumping system used in a step ratio automatic transmission can consume up to 20% of the total power required to operate a typical automotive transmission through the EPA city cycle. As such, it represents an area manufacturers have focused their efforts towards in their quest to obtain improved transmission efficiency. This paper will discuss the history of automatic transmission pumps that develop up to 300 psi along with a description of the factors used to size pumps and establish pump flow requirements. The various types of pumps used in current automatic transmissions will be described with a discussion of their characteristics including a comparison based upon observations of their performance. Specific attention will be focused on comparing the volumetric efficiency, mechanical efficiency, overall efficiency, pumping torque and discharge flow.

The present work discusses an objective test and analysis method developed to quickly quantify steering gear rattle noise heard in a vehicle. Utilizing envelope analysis on the time history data of the rattle signal, the resulting method is simple, fast, practical and yields a single-valued metric which correlates well to subjective measures of rattle noise. In contrast to many other rattle analysis methods, the approach discussed here is completed in the time domain. As applied to rattle noise produced by automotive electric steering systems, the metric produced with this analysis method correlates well with subjective appraisals of vehicle-level rattle noise performance. Lastly, this method can also be extended to rattle measurements at the component and subcomponent level.

Ribbed floor panels have been widely applied in vehicle body structures to reduce interior noise. The conventional approach to evaluate ribbed floor panel designs is to compare natural frequencies and local stiffness. However, this approach may not result in the desired outcome of the reduction in radiated noise. Designing a “quiet” floor panel requires minimizing the total radiated noise resulting from vibration of the floor panel. In this study, the objective of ribbed floor panel design is to reduce the total radiated sound power by optimizing the rib patterns. A parametric study was conducted first to understand the effects of rib design parameters such as rib height, width, orientation, and density. Next, a finite element model of a simplified body structure with ribbed floor panel was built and analyzed. The structural vibration profile was generated using MSCINastran, and integrated with the acoustic boundary element model.

In this paper we describe the application of optimization techniques to the design of valvetrains in high revving internal combustion engines. The methods presented are based on parameter optimization [1] and the minimum principle by Pontrjagin [2] and will be applied to cam lobe and valve spring optimization, aiming at reducing oscillation amplitudes and improving control of the valvetrain over a broad speed range. To put the task of optimization into context the engineering requirements for valvetrains and methods to allow their computer based analysis are described. Furthermore principle considerations for valve event curve generation and parametrization, and on optimization techniques are discussed. Based on these fundamentals, optimization aims and constraints are formulated. Furthermore different examples of the application of automated optimization are presented in the area of cam profile optimization and valve spring optimization.

The long term visual appearance of exterior chrome-plated parts is highly dependent on part design and supplier performance. The use of numerous complex designs coupled with the pressures of competition has caused a statistically high percentage of parts to be manufactured which do not fully meet customer expectations. A coordinated approach to improve supplier performance and simplification of part designs was required. A task force was established to address these issues in 1980 and desirable results were achieved.

The thermal comfort of passengers within a vehicle is often the main objective for the climate control engineer; however, the need to maintain adequate visibility through the front and side windows of a vehicle is a critical aspect of safe driving. This paper compares the performance of the side window defrosting and demisting mechanism of several current model vehicles. The study highlights the drawbacks of current designs and points the way to improved passive defrosting mechanisms. The investigation is experimental and computational. The experiments are carried out using full-scale current vehicle models. The computational study, which is validated by the experiments, is used to perform parametric investigation into the side window defrosters performance. The results show that the current designs of the side-defroster nozzles give maximum airflow rates in the vicinity of the lower part of the window, which yields unsatisfactory visibility.

This paper presents a Computational Fluid Dynamic(CFD) model for the oil pump simulations aimed at better understanding the flow characteristics for improving their designs and reducing product development cycles. Several advanced numerical technologies have been developed to handle the complex geometries of oil pumps and the moving interfaces between the rotating and stationary parts. Two basic oil pump configurations, a vane oil pump and a gerotor oil pump, have been studied with the present method. The numerical results are compared with the existing experimental data.

The technique of evaporating fuel by localized heating before entering the intake manifold is evaluated as a means of improving A/F ratio control. Techniques currently in use are briefly discussed, and attempts to analyze fuel evaporation in S.I. engines are reviewed. A test fixture which includes all the essential features of production feasible hardware is used to develop a basis of understanding for the evaporation process. Tests are conducted on a flow bench using water as “fuel”, and on an engine using isooctane and gasoline. A heat-mass transfer analogy is described and used to predict evaporation rates for water and isooctane. Predicted and measured rates are compared for both bench and engine tests. Engine tests with gasoline show the ability of the test configuration to evaporate all part throttle fuel flow before it enters the intake manifold.

Sliding door designs are applied to rear side doors on vans and other large vehicles with a trend towards dual sliding doors with power operation. It is beneficial for the vehicle user to reduce the weight of and space occupied by these doors. Alcoa, in conjunction with Ford, has developed a multi-product, multi-material-based solution, which significantly reduces the cost of an aluminum sliding door and provides both consumer delight and stamping-assembly plant benefits. The design was successfully demonstrated through a concept readiness/technology demonstration program.

The study presented in this paper is concerned with the application of a finite element based technique to deal with crankshaft-crankcase interaction. A finite element model of the crankshaft and the crankcase was developed and appropriately reduced. This model was used for a crankshaft optimization, strategy to analyse related effects on the NVH performance with focus on main bearing acceleration. The crankshaft and the cylinder block were modelled using beam and shell elements with structural and dynamic properties correlated up to 1600 Hz. The interaction between crankshaft and the cylinder block was represented by using non-linear properties. Applying this model, the dynamic crankshaft and engine block behaviour and repercussion on NVH performance was analysed by investigating main bearing acceleration.

A radial element centrifugal compressor vane has been analyzed by means of the Structural Analysis and Matrix Interpretive System (SAMIS). The displacement method and finite element technique were used. Initial studies of configurations where exact solutions were readily available were conducted to ensure the applicability of the method. The results of the stress analysis are presented along with the deflections. The first natural frequency was also determined along with the associated mode shape and these results are also presented.

This case study presents a new automated production noise test for power steering pumps. The test included adaptive noise cancellation, and a neural network implementation. The result mapped the pump acceleration signature into an objective repeatable noise metric. The test algorithm was a distributed DSP architecture designed for real-time measurement and decision processing. It was implemented with no increase in test cycle time. It accomplished the correlation of in-vehicle power steering pump noise to it's vibration characteristics, and retrofitting of accelerometers in place of microphones for acceptance testing.

Automatic headway control is an evolutionary step towards an automatic vehicle guidance and control system. This system expands the capability of the currently available production option-speed control. This paper describes the system from a theoretical and hardware viewpoint, with emphasis on the control logic. The electronic and electromechanical hardware design based on the theory presented is fully described. The limitations and advantages of the system are explained, based on test results from actual trial runs on an implemented vehicle. Capacity and safety benefits are made somewhat tangible by direct comparison with test results obtained on a roadway similar to that for which this system is recommended, under test conditions directly analogous to the operating characteristics of the automatic headway control system.

The ability to evaluate the bending fatigue behavior of carburized low alloy steels in a laboratory and relate these measurements to performance of high contact ratio helical gears is important to the design and development of transmissions. Typical methods of evaluating bending fatigue performance of carburized gear steels do not directly represent helical planetary gears because they lack the geometric and loading conditions of planetary pinions. The purpose of this study is twofold; 1) development of a lab fatigue test to represent the fatigue performance of planetary pinion gears tested in a dynamometer and 2) evaluation of the influence of alloy content on bending fatigue performance of two steel alloys. The steels under evaluation were modified 8620M and 4615M alloys machined into bend bars with a notch representing a gear root and carburized to a case depth of approximately 0.35 mm (using the same carburizing cycle as the planetary pinion gears).

Little information is available concerning the bending fatigue behavior of helical gears with tall thin teeth and high contact ratios, particularly for planetary pinions which are subjected to fully reversed loading. The most common methods to acquire gear bending fatigue data are either through a four-square recirculating power arrangement or unidirectional single tooth bending experiments on standardized spur gears. There are some advantages to these test methods, but they generally do not represent actual operating conditions of a planetary gear environment. The purpose of this study was to develop a bending fatigue test for planetary pinions in automatic transmissions which would better represent actual operating conditions. The new testing procedure was used to evaluate the bending fatigue behavior of three gear steel/processing combinations. The results from the planetary gear testing is compared with laboratory four-point bending experiments.