Search Results

The prime factor which influences noise and vibrations of electro-mechanical drives is wear at the components. This paper discusses the numerical methods developed for abrasion, vibration calculations and the coupling between wear and Noise Vibration and Harshness (NVH) models of the drive unit. The vibration domain model, initially, focuses on the calculations of mechanical excitations at the gear shafts which are generated via a nonlinear dynamic model. Furthermore, the bearings are studied for the influences on their stiffness and eventually their impact on the harmonics of the drivetrain. Later, free and forced vibrations of the complete drivetrain are simulated via a steady-state dynamic model. Consequently, the paper concentrates on the abrasion calculations at the gears. Wear is a complex process and understanding it is essential for determining the vibro-acoustics characteristics.

This paper looks at the underlying fundamentals of diesel fuel system lubrication for the highly-loaded contacts found in fuel injection equipment like high-pressure pumps. These types of contacts are already occurring in modern systems and their severity is likely to increase in future applications due to the requirement for increased fuel pressure. The aim of the work was to characterise the tribological behavior of these contacts when lubricated with diesel fuel and diesel fuel treated with lubricity additives and model nitrogen and sulphur compounds of different chemical composition. It is essential to understand the role of diesel fuel and of lubricity additives to ensure that future, more severely-loaded systems, will be free of any wear problem in the field.

The emissions legislation in the US and Europe introduces the need for the application of diesel particulate filters (DPF) in most diesel vehicles. In order to fulfill future OBD legislations, which include more stringent requirements on monitoring the functionality of those particulate filters, new sensors besides the differential pressure sensor are necessary. The new sensors need to directly detect the soot emission after DPF and withstand the harsh exhaust gas environment. Based on multi layer ceramic sensor technology, an exhaust gas sensor for particulate matter (EGS-PM) has been developed. The soot-particle-sensing element consists of two inter-digitated comb-like electrodes with an initially infinite electrical resistance. During the sensor operation, soot particles from the exhaust gas are collected onto the inter-digital electrodes and form conductive paths between the two electrode fingers leading to a drop of the electrical resistance.

Today's wide range oxygen sensors are based on the limiting current principle, where an applied voltage induces electrochemical reactions in a ceramic cell. Since the diffusive transport of exhaust gas to the electrodes is limited by a transport barrier, the resulting electric current can be related to the exhaust gas composition. A model is presented which describes the transient transport of gas mixtures from the bulk exhaust gas to the electrodes of an oxygen sensor at variable pressure and composition. The internal structure of the transport barrier was accounted for by geometrical parameters. A variety of numerical results are compared with experimental data.

Within the scope of this work, the convective mass transfer to the zirconia sensor element of an exhaust oxygen sensor was analyzed experimentally and numerically. For the experimental setup, a heightened model of an oxygen sensor was built from Lucite® considering the similarity theory. Mass transfer is measured based on the absorption of ammonia and subsequent immediate color reaction. For the numerical investigation, a three-dimensional model of the test rig was built. To predict the flow pattern and the species transport inside the protection tubes, the commercial CFD-Code FLUENT® is used. The model for the mass transfer to the surface is implemented through user-defined functions.

Future emission standards for heavy-duty vehicles like Euro 4, Euro 5, US '07 require advanced engine functionality. One contribution to achieve this target is the catalytic reduction of nitrogen oxides by injection of urea water solution to the exhaust gas. An overview on a urea dosing system, also called DENOXTRONIC, is given and a dosing strategy is described.

The study presented in this paper focuses on measures to minimize exhaust gas emissions to meet SULEV targets on a V6 engine by using a cost efficient system configuration. The study consists of three parts. A) In the first stage, the influence of engine management both on raw emissions and catalyst light off performance was optimized. B) Afterwards, the predefined high cell density catalyst system was tested on an engine test bench. In this stage, thermal data and engine out emissions were used for modeling and prediction of light-off performance for further optimized catalyst concepts. C) In the final stage of the program, the emission performance of the test matrix, including high cell density as well as multifunctional single substrate systems, are studied during the FTP cycle. The presented results show the approach to achieve SULEV emission compliance with innovative engine control strategies in combination with a cost effective metallic catalyst design.

Ceramic protective coatings on cutting tools for steel machining are state of the art in industrial applications. Several concepts to improve the efficiency of machining processes as for instance high-speed or dry cutting yield increasing demands regarding the wear and corrosion resistance of the protective tool coatings. The generic process characteristics of PVD-coating techniques offer opportunities to tailor the coatings in terms of microstructure and residual stress states by adjusting appropriate process parameters. Besides chemical composition and microstructure the residual stresses in the coatings strongly influence their in-service performance and, are therefore important to assess and to correlate with process parameters.

This study reports on laser-based diagnostics to temporally track the evolution of liquid and gaseous fuel in the cylinder of a direct injection production type Diesel engine. A two-dimensional Mie scattering technique is used to record the liquid phase and planar laser-induced fluorescence of Diesel is used to track both liquid and vaporised fuel. LIF-Signal is visible in liquid and gas phase, Mie scattering occurs only in zones where fuel droplets are present. Distinction between liquid and gaseous phase becomes therefore possible by comparing LIF- and Mie-Signals. Although the information is qualitative in nature, trends of spray evolution are accessible. Within this study a parametric variation of injection pressure, in-cylinder conditions such as gas temperature and pressure as well as piston geometry are discussed. Observations are used to identify the most sensitive parameters and to qualitatively describe the temporal evolution of the spray for real engine conditions.

In view of tight emission standards, injection strategies to reduce raw HC-emissions during the cold starting of port fuel injected engines are evaluated in this study. The relevance of spray targeting and atomization is outlined in the first part of this paper. The foundation and performance of different injector concepts with respect to spray characteristics are discussed. Laboratory experiments demonstrate that concepts relying on auxiliary energy, such as air-assistance, fuel heating and injection at elevated system pressures, are capable of producing spray droplet sizes in the SMD-range of 25μm. For future injection strategies aimed at the compliance of SULEV emission levels, this target value is considered to be essential. In the second part of this paper, emission tests of selected injector concepts are carried out using a V6-3.2I ULEV engine operated both in a vehicle and on a test bench.

A major source for soot particle formation in Gasoline-Direct-Injection (GDI) engines are fuel-rich zones near walls as a result of wall wetting during injection. To address this problem, a thorough understanding of the wall film formation and evaporation processes is necessary. The wall temperature before, during and after fuel impingement is an important parameter in this respect, but is not easily measured using conventional methods. In this work, a recently developed laser-based phosphor thermography technique is implemented for investigations of spray-induced surface cooling. This spatially and temporally resolved method can provide surface temperature measurements on the wetted side of the surface without being affected by the fuel-film. Zinc oxide (ZnO) particles, dispersed in a chemical binder, were deposited onto a thin steel plate obtaining a coating thickness of 17 μm after annealing.

In recognition of safety considerations, modern fuel tanks are frequently extremely irregular in shape. This places limits on the application of conventional potentiometric sensors. Required are more universal sensors without mechanically-moving parts. These sensors should also be characterized by especially good resolution and precision in the residual-quantity range, that is, the zero point precision should be of a high order. One type of metal rod can be bent into any of a variety of shapes to provide an effective means of monitoring the fuel level. In this metal rod, the propagation characteristics of a certain type of sound wave, known as bending waves, display major variations according to the level of the surrounding medium: The waves spread more rapidly through the exposed section of the rod than through the area which remains submerged. Thus the rod's characteristic oscillation frequency varies as a function of immersion depth.

Secondary air injection after cold start gives two effects for reduced exhaust emissions: An exothermic reaction at the hot exhaust valves occurs, which increases the temperature of the exhaust gas. It gives sufficient air to the catalyst during the cold start fuel enrichment that is necessary to prevent driveability problems. Handicaps for the wide use of air injection include space constraints, weight and price. An electrical air blower was choosen to best satisfy all these requirements. The development steps are described. The result is a three stage radialblower with extremly high revolutions of about 18000 rpm. The system configuration and the outcome are demonstrated on the new C-Class of Mercedes-Benz. The results show emission reductions higher than 50 %, while also satisfying the development goals of noise, volume, weight and cost requirements.

Tapping of one or more torques (ranges 10 Nm and 60 Nm) on the steering column for the purpose of servo control must satisfy high accuracy requirements on the one hand and high safety requirements on the other hand. A suggestion for developing a low-cost solution to this problem is described below: Strain gages optimally satisfy both these requirements: However, for cost reasons, these are not applied directly to the steering column but to a prefabricated, flat steel rod which is laser welded to the torque rod of the steering column. The measuring direction of the strain gages is under 45° to the steering column axis. The strain gages are either vacuum metallized onto the support rod as a thin film or laminated in a particularly low-cost way by means of a foil-type intermediate carrier.

This paper presents advanced planar ZrO2 oxygen sensors being developed at Robert Bosch using a modified tetragonal partially stabilized zirconia (TZP) with high ionic conductivity, high phase stability and high thermo-mechanical strength. Green tape technology combined with highly automated thickfilm techniques allows robust and cost effective manufacturing of those novel sensing elements. Standardization of assembling parts reduces the complexity of the assembly line even in the case of different sensing principles. The sensor family meets the new requirements of modern ULEV strategies like fast light off below 10 s and linear control capability as well as high quality assurance standards. High volume production will start in 1997 for European customers.

Modern zirconia oxygen sensors are heated internally to achieve an optimal detection of the oxygen concentration in the exhaust gas and fast light off time. The temperature of the gas in the exhaust pipe varies in a wide range. The zirconia sensor is cooled by radiation and forced convection caused by cold exhaust gas. If the zirconia temperature falls, the oxygen detection capability of the sensor decreases. To minimize the cooling effects, protection tubes cover the zirconia sensor. However, this is in conflict with the aim to accelerate the dynamics of the lambda sensor. In this paper, the heat transfer at the surface of a heated planar zirconia sensor with two different double protection tubes of a Bosch oxygen sensor is examined in detail. The geometric configuration of the tubes forces different flow patterns in the inner protection tube around the zirconia sensor. The zirconia sensor is internally electrically heated by a platinum heater layer.

The paper will give an introduction to the principle of the giant magneto resistive - GMR - effect and the silicon system integration of GMR sensors. The two main applications of a GMR as a magnetic field strength sensor and as an angular field direction sensor will be discussed under consideration of automotive requirements. The typical applications of a magnetic field strength GMR sensor in incremental position and speed sensing and those of GMR angular field sensors in position sensing will be summarized. Finally advantages of GMR in those applications will be discussed and conclusions on the use of GMR in automotive sensing will be drawn.

Aerodynamic styling is playing an increasing role in the design of today's passenger cars. The profile sections of the frontends of cars imply that the available installation space for the headlamps - particularly its overall depth and height is decreased in size. New types of headlamps had to be developed. One result of extensive investigations are stepped reflectors with up to six paraboloids with different focal lengths arranged around the same focal point. This type of reflector (called homofocular reflector) cannot be formed from sheet steel but from plastic by injection molding. Depending on thermal, mechanical and geometric boundary conditions three different reflector materials can be used: lacquered thermosets, unlacquered thermoplastics by one or two material injection moldings. Similar to sheet steel the use of glass lenses reduces considerably the freedom of the designer. This disadvantage of offset by the use of plastic lenses.

The manufacture of semiconductor sensors requires high investment and does not become economically viable until very high production numbers come into consideration. In the case of low production numbers, of the kind that come into consideration for production startups, and in the case of variations e.g. in the measuring range and similar, as may be the case due to the adaptation of models, it may be more viable to employ other techniques which likewise have a high rationalization potential which comes into effect already at low production numbers and which exhibits greater flexibility. The film techniques offer alternative sensor concepts for many measured quantities, whose production is reasonable in price even at smaller production numbers and possesses the necessary alteration flexibility. Besides these, are the advantages of the laser adjustment and the seamless connection of the evaluation electronics. Even possibilities laying within micro-machining technology can be used.

Ultrasonic transducers are widely used in automotive and industrial applications for surround sensing. Anisotropic directivity patterns with a narrow-angled beam in the vertical plane and a wide-angled beam in the horizontal plane are needed in automotive applications particularly. Today’s ultrasonic transducers for automotive applications are mainly metal based, pot-like ultrasonic transducers. The anisotropic directivity pattern is achieved by increasing the thickness of the vibrating plate-like part of the structure locally. Composites with locally structured fiber reinforcements open up the possibility to design the dynamical behavior of components without changing its contour. Using this new dimension of design to modify the directivity pattern of sound radiating components is less examined in literature.