Page 38 - ATZ11 November 2019 Professional

COVER STORY INTERIOR

Push/pull forces at 0° misalignment between the two sliding speeds. This
450 Current possibility ‒ minimum clearance SprinGlide solution ‒ minimal clearance is recorded with only a minor increase
Current possibility ‒ nominal clearance SprinGlide solution ‒ nominal clearance in friction forces at higher speeds. The
350
Current possibility ‒ maximum clearance SprinGlide solution ‒ maximum clearance injection molded plastic solution, how-
250 ever, again shows higher sliding force in
both dry and lubricated (wet) conditions,
Push/pull force [N] -50 as well as high stick-slip friction. For
150
50
customers a high sliding force means
high effort required operating the seat-
ing adjustment mechanisms. A high
-150
stick-slip means a clunky, low quality
feel.
-250
The combination of PTFE and spring
-350 steel delivers a clearance-free bearing,
-450 which reduces rattle noise, while main-
0 100 200 300 400 500 taining consistently low friction through-
out typical tolerance ranges. This notice-
Extension [mm]
ably improves the quality perception of
FIGURE 4 Push/pull forces, having an effect on an interior sliding system for the minimum, nominal and
maximum clearance; the SprinGlide PTFE and spring steel solution significantly reduces the required the interior systems which use the tech-
operating forces and allows for a higher quality feel for a travel between 0 to 500 mm – compared to nology, for instance seats, as they elimi-
a current plastic injection molding possibility (© Saint-Gobain) nate the stick-slip friction that is associ-
ated with low quality bearings. With this
combination, design engineers no longer
Injection moulded plastic PTFE and spring steel
have to face the dilemma of high friction
70
variation or rattle noise. And, without
60 the need for lubrication, overall system
costs and complexity of assembly can
Rattle noise [dB(A)] 40 MAKING QUIET FUTURE
both be reduced as well.
50

A REALITY
30
20
may seem less important at first glance
as their impact on driver and passenger
10 Bearing solutions for passenger seats
comfort in the vehicle of the future is not
0 obvious, FIGURE 7. But the seemingly
10 m/s² 5 m/s² 10 m/s² 5 m/s²
insignificant component “bearing bush-
10-70 Hz 70-200 Hz 10-70 Hz 70-200 Hz ing” can greatly reduce the perceived
quality of a vehicle, adds stress for the
Front-back Left-right
driver and might ultimately even affect
FIGURE 5 Measurement of rattle noise from two sliding systems; one system fitted with the injection future purchasing decisions negatively.
molded plastic and another system retrofitted with the SprinGlide PTFE and spring steel solution; the sys-
tems were tested by vibrating it in both the front-back and left-right directions; both tests with 10 m/s² Anyone who has ever heard a mysterious
showing an 8-dB(A) reduction at low frequencies for the PTFE and spring steel solution (© Saint-Gobain) rattle while driving can confirm that.
Therefore, bearing bushing design
requires the same attention as the con-
struction of the crash-proof seat frame,
8 dB(A) for the PTFE and spring steel OPERABILITY OF INTERIOR in order to avoid any unnecessary harm
solution at low frequencies and a smaller ELEMENTS – IMPROVING to the driving experience. The tests
decrease at high frequencies, FIGURE 5. USER EXPERIENCE described here, targeted complete seat-
An 8-dB(A) increase in sound pressure ing systems, not just bushings, and
level is perceived as about 70 % louder. Last but not least, Saint-Gobain’s design ensured that overall quality can be opti-
As the new PTFE coated spring steel engineers performed tests on the consis- mized. Especially with the increased
solution minimizes such rattle, it can tency of sliding force at two different number of seat designs in autonomous
reduce the overall rattle noise signifi- sliding speeds (5 and 25 mm/s, both vehicles or the new demands on the
cantly. This translates to a quieter vehi- with and without lubricant ECL 429, adjustment mechanisms in the context of
cle interior, ensuring that passengers in dry/wet). The results, shown in FIGURE 6, car sharing, such bearings solutions are
the ever-evolving car of the future will reveal that both the PTFE and spring becoming increasingly important. This
not notice rattle noises that are currently steel solution and the injection molded enables vehicle manufacturers to give
masked by louder combustion engines. plastic possibility are fairly consistent the millennials the high-quality look and
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