Hans-Joachim Unrau

Der Einfluss der Fahrbahnoberflaechenstruktur auf das Kraftschlussverhalten von Pkw-Reifen bei trockener und nasser Fahrbahn

Die Fahrbahnoberflachenstruktur hat einen masgeblichen Einfluss auf das Kraftschlussverhalten von Reifen. Der folgende Artikel, in dem beispielhaft die Wirkung auf Umfangskraft-Schlupf-Kennlinien behandelt wird, zeigt einen Ausschnitt aus den Forschungsergebnissen des Instituts fur Maschinenkonstruktionslehre und Kraftfahrzeugbau der Universitat Karlsruhe (TH) zu diesem Thema [1]. Neben theoretischen Herleitungen werden die Ergebnisse umfangreicher Reifenmessungen vorgestellt, die es ermoglichen, Reifenkennlinien von einer Fahrbahnoberflache auf eine andere umzurechnen.

The transfer characteristics of wheel suspensions for passenger cars in the comfort-relevant frequency range

The fine adjustment of the comfort characteristics of a passenger car in an early phase of development of the vehicle is dependent on an efficient and meaningful test and simulation technique to analyse the vertical and horizontal dynamics of the system tyre-wheel suspension. This article, which is based on a dissertation completed at the Institute of Machine Design and Automotive Engineering of the University of Karlsruhe (TH) [1], describes new methods for the reliable modelling and measurement of the transmission characteristics of wheel suspensions and their components in the comfort-relevant frequency range of 0 to 100 Hz.

Übertragungsverhalten von Radaufhängungen für Personenwagen im komfortrelevanten Frequenzbereich

Eine Feinabstimmung der Komforteigenschaften eines Automobils in der fruhen Phase der Fahrzeugentwicklung setzt eine effiziente und aussagefahige Versuchs- und Simulationstechnik zur Analyse der Vertikal- und Horizontaldynamik des Systems Reifen-Radaufhangung voraus. Dieser Artikel, der auf einer an der Universitat Karlsruhe erstellten Dissertation basiert [1], beschreibt neuartige Methoden zur verlasslichen Modellierung und messtechnischen Erfassung des Ubertragungsverhaltens von Radaufhangungen und deren Komponenten im komfortrelevanten Frequenzbereich 0 bis 100 Hz.

Ermittlung der Reibwerte von Gummistollen zur genauen Parametrierung von Reifenmodellen

Alle Fuhrungs-, Antriebs- und Bremskrafte von Strasenfahrzeugen werden uber eine etwa postkartengrose Kontaktflache, den sogenannten Latsch, vom Reifen auf die Fahrbahn ubertragen. Die Kraftubertragung beruht auf Haft- und Gleitreibungsvorgangen zwischen Reifengummi und Fahrbahnoberflache. Die Daimler-Chrysler AG und das Institut fur Maschinenkonstruktionslehre und Kraftfahrzeugbau der Unversitat Karlsruhe wollen mit diesem Bericht die Kraftschlussvorgange im Reifenlatsch detailliert analysieren und schlieslich zur Klarung beitragen, inwieweit die Kraftubertragung zwischen Reifen und Fahrbahn weiter erhoht werden kann

The influence of the track surface structure on the frictional force behaviour of passenger car tyres in dry and wet track surface conditions

The track surface structure has a substantial influence on the frictional force behaviour of tyres. The following paper, which deals with the effect on longitudinal force/longitudinal slip curves, shows some of the research results from the “Institut fur Maschinenkonstruktionslehre und Kraftfahrzeugbau” of Karlsruhe University (TH) in this field [1]. In addition to theoretical deductions, this paper presents the results of extensive tyre measurements that allow the mathematical conversion of the characteristic curves of tyres for different track surfaces.

A model for prediction of the transient rolling resistance of tyres based on inner-liner temperatures

ABSTRACT Measurements of rolling resistance in thermal equilibrium of a tyre, like measurements according to ISO 28580, do not allow statements about rolling resistances under other driving conditions. Such statements, however, are necessary to determine the energy consumption in driving cycles. Especially for the proper calculation of electric-vehicle remaining ranges and the selection of the respective driving strategies, the real amount of energy consumption is required. This paper presents a model approach, which by means of only one standardised rolling resistance measurement can be parameterised and, considering the present driving speed and tyre temperature, can predict the respective current rolling resistance.

3D brush model to predict longitudinal tyre characteristics

ABSTRACT A 3D tyre brush model, which aims to predict the longitudinal tyre characteristic under steady-state conditions by modelling the occurring physical effects in the tyre–road contact patch, is presented. The model includes an analytical method to describe the tyre footprint geometry, the pressure distribution, the slip due to the lateral tyre contour, the slip due to braking or traction and the longitudinal as well as the lateral shear stresses on a flattened tyre. The presented development tool offers a method to investigate different rubber friction data (caused by different tread compounds and/or surface textures) and to analyse its influence on longitudinal tyre characteristics. The tyre design is fixed (same casing, dimension and pattern). The results include the shear stresses as well as the different sliding velocities in the contact patch for different slip conditions. The model was developed for a standard summer pattern design and a standard tyre dimension (205/55R16). It can also be adapted to other tread designs and tyre dimensions. To offer a good comparability between model results and test bench measurements, the surface curvature of an internal test rig is considered.

Kraftschluss messungen auf Schnee mit dem Reifen-Innentrommel-Prüfstand

Im Bereich Kraftfahrzeugbau der Universitat Karlsruhe wurde in Zusammenarbeit mit der Continental AG ein Reifen-Schnee-Prufstand entwickelt, der ganzjahrig Tests von Winterreifen auf Kunstschnee ermoglicht. Da hierbei sowohl die Fahrbahn- als auch die Umgebungsbedingungen einstellbar sind, konnen die Reifentests unter reproduzierbaren Bedingungen durchgefuhrt werden. In diesem Beitrag wird unter anderem durch einen Vergleich mit Messungen im Freien das grose Potenzial dieser Prufeinrichtung fur die Entwicklung von Winterreifen aufgezeigt.

Determination of the friction coefficients of rubber ribs: For the exact parameterisation of tyre models

All guidance, drive and braking forces of road vehicles are transmitted from the tyre to the road surface via an area of contact that has approximately the size of a postcard, the so-called contact area. The transmission of forces is based on adhesion and sliding friction processes between the tyre rubber and the road surface. Daimler-Chrysler and the Institut fur Maschinenkonstruktionslehre und Kraftfahrzeugbau of Karlsruhe University want to analyse the processes in the tyre contact area in this article in detail and, finally, contribute to clarify to what extent the transmission of forces between tyre and road surface can be increased.

Road wetness quantification via tyre spray

Road wetness can lead to a significant loss in tyre traction. Although a driver can easily distinguish between dry and wet roads, the thickness of a water film on the road (wetness) and its impact on the vehicle dynamics are more difficult for a driver to classify. Furthermore, autonomous vehicles also need a graded classification of road conditions. There are known sensors, which are able to classify road conditions, but these are either not able to quantify the road wetness or are not suitable for mass production. Therefore, this work analyses a method to measure the road wetness by analysing tyre spray with plain acceleration sensors at positions like wheel arch liner or side skirt. It discusses influences of vehicle speed, road wetness, tyres, road structure and sensor positioning. The results show that a quantification of road wetness is possible, but it relies on the sum of all boundary conditions.