From transmission error measurement to Pulley-Belt slip determination in serpentine belt drives: influence
Abstract —
Serpentine belt drives are often used in front
end accessory drive of automotive engine. The accessories
resistant torques are getting higher within new technological
innovations as stater-alternator, and belt transmissions
are always asked for higher capacity. Two kind of tensioners
are used to maintain minimum tension that insure power
transmission and minimize slip: dry friction or hydraulic
tensioners. An experimental device and a specific transmission
error measurement method have been used to evaluate
the performances of a generic transmission by determining
the pulley-belt slip for these two kinds of tensioner. A data
acquisition technique using optical encoders and based on
the angular sampling method is used with success for the
first time on a non-synchronous belt transmission. Transmission
error between pulleys, pulley/belt slip are deduced
from pulley rotation angle measurements.Results obtained
show that: the use of tensioner limits belt slip on pulleys,
pulley-belt slip is reachable from transmission error measurement,
belt non uniform characteristics are responsible
of low frequency modulations of transmission error.
Keywords: belt transmission, transmission error, pulley-belt slip,
tensioner
I. Introduction
Multi ribbed (serpentine) belt transmission are often used
in the industry machinery to transmit power. Another field
of application concerns the Front End Accessory Drive of
automotive engine, it recently asks for better performances
in order to allow the development of new technological innovations
as starter-alternator integration in the transmission.
Resistant torques of the driven accessories are getting
higher and design solutions have to be found in order to prevent
pulley-belt slip and belt fatigue. Because of ,serpentine
belt constitution based on cords and rubber, long belt
spans and operating conditions (engine acyclism, fluctuating
torques), the following phenomena occur during FEAD
operation: longitudinal and transverse belt span vibrations,
pulley-belt slip. In these transmissions, two kinds of tensioners
can be used in order to reduce vibration and insure
sufficient belt tension to transmit power and to avoid slip-
ping. They differ in the way damping is generated: one
is called dry friction tensioner, the other uses a hydraulic
damper( figure 1). Both are equipped with a spring (compression
or torsion) . Many works have conducted numerical
analysis on the dynamics of serpentine belt drives
[4], [1], [2], [3], [5], [10] , they aimed at determining belt
tension fluctuations, pulley rotations, belt longitudinal and
transverse vibrations. Pulley-belt slip has been investigated
both numerically and experimentally by Gerbert [9] on vbelt
in steady state operating conditions. Transmission error
of belt drives has been studied for synchronous belt [12],
[11]. The work presented here is an experimental analysis
that aims at determining pulley-belt slip from the transmission
error measurement in the case of a multi ribbed
belt generic transmission. A test bench has been designed
where pulley rotation angles are determined from optical
encoder signals using a specific data acquisition system and
process[7]. Angular sampling method is used for the transmission
error analysis. Such a method is applied here for
the first time on a non-discrete geometry.
II. Experimental set up
A. Belt drive description
The studied transmission consists of four pulleys linked
together by an automotive multi-ribbed belt, as shown in
Fig. 2. The input shaft speed (from 0 to 2000 rpm) is
controlled by a 60 kW electric motor . The driven shaft is
connected to a hydraulic pump. The output pressure of the
fluid is controlled to apply a mean torque on the driven pulley.
Due to the rotation direction, the upper span is tight and
the lower one is slack. Three configurations of transmission
are studied depending on the type of pulley 4, Fig. 3 : idler
pulley, dry friction tensioner or hydraulic tensioner. The
12th IFToMM World Congress, Besançon, June 18-21, 2007 CK-xxx
objectives are to show the influence of the tensioners on the
pulley-belt slip. of tensioner and belt characteristics


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