Skew Bevel Driving Pinions; Bevel Gear Pinions; Bearing Service Life - Bosch Rexroth MAD Project Planning Manual

MAD / MAF Asynchronous Housing Motors
9.14.4

Skew bevel driving pinions

9.14.5

Bevel gear pinions

9.15

Bearing service life

By attaching skew bevel driving pinions directly to the drive shaft, the motor
bearings are exposed to inadmissible operation conditions in the vicinity of
the force reversal point (reversal point between acceleration and deceleration
or vice versa). What is more, the flange-side end of the output shaft may be
displaced in relation to the motor housing due to thermal effects, thus ex‐
ceeding the allowed axial forces of the motor bearings.
It is not allowed to directly attach skew bevel driving pinions to the
output shaft of the motor. If skew bevel driving pinions have to be
used nevertheless, no other drive elements may be used than
self-bearing drive elements which are connected to the motor
shaft via axially compensating couplings.
Depending on the motor bearings selected, the flange-side end of the output
shaft may be displaced in relation to the motor housing due to thermal ef‐
fects, thus exceeding the allowed axial forces of the motor bearings.
When bevel gear pinions directly attached to the output shaft are used, this
change in length results in a thermally induced axial force if the drive pinions
are located axially on the machine side. This causes the risk of exceeding the
maximum permissible axial force or of the gear backlash increasing to an im‐
permissible degree.
For this reason, bevel gear pinions may only be directly attached
to the motor shaft if the motor is equipped with an A bearing. If
bevel gear pinions have to be used nevertheless in connection
with a different bearing variant, no other drive elements may be
used than self-bearing drive elements which are connected to the
motor shaft via axially compensating couplings.
The bearing lifetime is an important criterion for the availability of motors. The
bearing service life is divided into the "mechanical service life" of bearing
components and material on the one hand and "grease service life" of the
bearing lubricant on the other hand.
If MAD/MAF motors are operated within the limits specified for radial and ax‐
ial loads, the mechanical service life of the bearings is
L = 30000 operating hours
10h
(calculated according to ISO 281, version 1993.01)
This applies to all MAD/MAF motors based on the following assumptions:
● The allowed motor load specified in chapter
iants and shaft load" on page 212
● The motor is operated under the allowed conditions of use and within
the allowed surrounding air temperature range of 0 °C to +40 °C.
● The "mean speed" used over the entire machining cycle complies with
the following characteristic curves for the grease service life, where
Application notes
chapter 9.13 "Bearing var‐
is never exceeded.
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