75 Jahre Sonceboz 75 years Sonceboz

75 Jahre Sonceboz
2008, p. 72
The torque generates a clockwise, (c) in
❹, or counter-clockwise, (b), rotation,
per the principle that opposite magnet
polarities on the rotor and stator attract
each other. An axial ball bearing,
(4), balances the attraction force between
the rotor and the stator, thus
maintaining the air gap (E) constant.
It is worth noting that the relationship
between the electric current and
the torque is linear in Eq. 1 ❺. Thanks
to this linear relationship, the available
range of high torque dynamics is expanded
offering torque boost capability.
The fact that torque does not increase
linearly with current at high angles
in ❺ is ascribed to magnetic saturation,
which depends on the magnetic
properties and dimensions of the ferromagnetic
parts. The torque without current
is very low, thanks to a construction
that minimises friction, and also to
a detent torque. The detent torque is
negligible over the useful stroke owing
to the magnetic design. This very low
residual torque helps minimising the
size of the return spring, which is either
required to guarantee a fail-safe operation
of the system, or to return it to zero.
The stroke is approximately 75°,
since the positions at 0° and 90° with
alignment of rotor and stator magnetic
patterns are equilibrium positions with
no useful torque, ❺ and (d) in ❹.
Without position control, the DC
brushless actuator operates as an onoff
actuator between two end stops
within the useful stroke. In order to
control position, a contactless sensor
function is integrated in the same
package. It features a magnet, (8) in
❸, attached to the backside of the ferromagnetic
yoke, (6), which generates
a magnetic field sensed by a Hall-effect
probe, (9). The probe is integrated in
an ASIC which computes the field angular
orientation and delivers an analog or
digital voltage signal. This sensor principle
is insensitive to temperature and
assembly tolerances. The electronic
components are fixed to a plastic cover,
(11) in ❸, with integrated connector,
(10), mounted on the overmolded stator,
(12). Once the actuator is assembled on
the final application, the sensor voltage
characteristic can be calibrated by
clamping the desired voltage value with
respect to the end stops of the application.
This completely cancels the tolerance
stack-up of the entire assembly,
thereby offering an optimum part-topart
repeatability for the sensor output.
Positioning times below 100 ms can be
easily achieved via a conventional PID
regulation scheme, which adjusts the
voltage supplied by a standard H-bridge
to the actuator coils. OBD compliance
is guaranteed thanks to the sensor
characteristics.
Typical features such as fixation
pattern, connector type, or 100 % waterproofness,
can be adapted per the
application specification. The performance
is best described by the motor
constant, an invariant expressed in
Nm/√W that only varies with the permanent
magnet grade (B r
) and does not
depend on the coil wire gauge and turn
number, ❻. The mechanical work available
for a specific current corresponds
to the area underneath the torque curve
❺. Connecting the actuator and application
rotating shafts through a fourbar
mechanical linkage or lever cam
system permits the adjustment of the
functional torque and stroke requirements
at the application shaft. This is
particularly useful in the case of a variable-geometry
turbocharger, where the
useful stroke may be 35°, thus maximising
the torque delivered to the application
shaft ❼, [5]. The same principle
can be applied to throttle flaps by maximising
the torque at closed position,
e. g. 90°. Another benefit brought by
mechanical linkages is efficient thermal
decoupling between both actuator and
application shafts.
More compact, higher life time
As integration surrounding the engine
becomes increasingly complex with
packaging space a scarce resource, constant
effort is committed towards reducing
the size of the direct-drive DC brushless
actuator. Downsizing increases engine
power density resulting in a smaller
package volume, which will expose
the actuators to higher thermal constraints.
Reduction in cylinder count
means new and possibly harsher vibration
spectra for the sub-systems. The
ability to guarantee an extended life
time at temperatures above 150 °C is an
enabling factor for the continuous development
of new compact and robust
direct-drive DC brushless actuators.
References
[1] Bareis, B.; Blank, T.; Deichmann, G.; Flaig, B.: Bibliothek
der Technik, Vol. 270: Abgasrückführsysteme.
Munich: Moderne Industrie, 2004
[2] Flaig, B.; Zimmermann, F.: Elektrisches Abgasrückführventil.
In: MTZ 61 (2000), No. 9 , pp. 572 – 575
[3] Flaig, B.; Beyer, U.; André, M.-O.: Abgasrückführung
bei Ottomotoren mit Direkteinspritzung. In:
MTZ 71 (2010), No.1, pp. 34 – 40
[4] André, M.-O.; Gassmann, C.; Reghenzi, P.: Torque-
Motoren als Aktuatoren im Ansaug- und Abgasbereich.
In: MTZ 67 (2006) No. 6, pp. 462 – 467
[5] Schnell und stark. In: Automobil-Produktion, June
| | ❶ Diesel EGR valve with direct-drive DC brushless
actuator
| | ❷ Variable-geometry turbocharger with directdrive
DC brushless actuator
| | ❸ Construction of the direct-drive DC brushless
actuator
32
| | ❹ Operating principle of the direct-drive DC
brushless actuator
| | ❺ Typical torque vs. angle plot of a direct-drive
DC brushless actuator (the dashed surface
corresponds to the mechanical work available
at 1 A)
| | ❻ Motor constant and peak torque of the Sonceboz
direct-drive DC brushless actuators.
| | ❼ Examples of mechanical linkages between actuator
and application shafts: multiplication
ratio (solid curves) and stroke reduction (blue
dashed curve) or extension (red dashed curve).