Note: Descriptions are shown in the official language in which they were submitted.
:A 02792841 2012 09 11
Method for controlling and/or regulating a metering pump
The present invention concerns a method of controlling and/or
regulating a metering pump. A metering pump generally has a drive motor
with a shaft driven by the motor, and a displacement member disposed in a
metering head. In that case the rotary movement of the shaft is converted
into an oscillating movement of the displacement member so that the
displacement member, interacting with an outlet and inlet valve in
alternate succession, leads to a pump stroke (pressure stroke) and an
intake stroke (suction stroke) and thus delivery of a medium to be
metered.
Those metering pumps operate on the basis of the volumetric
principle, that is to say the metering operation is implemented by
displacement of a closed chamber volume by means of a displacement
member. The metering volume in each stroke is determined by the product
of the stroke and the effective surface area of the displacement member.
In such a metering pump the generally continuous rotary movement
of the drive motor is converted into an oscillating movement of the
displacement member by a transmission unit. The
drive of the
displacement member can be positively controlled or can also be effected at
one side in positively locking relationship only in the pressure stroke. In
the latter case measures must be provided for moving the displacement
member back again. That can be effected for example by a suitable return
spring.
The conventional metering pumps are generally powerful and have
metering properties adequate for most applications.
In the simplest case the drive motor is switched on continuously for
ongoing metering or is switched on for a given time for performing
individual metering strokes. The motor speed is predetermined by the
electric frequency of the mains voltage or the motor actuation system and
therefore defines the duration of each stroke together with the
:A 02792841 2012 09 11
2
corresponding transmission step-down ratio and the transmission
characteristic which for example is sinusoidal in the case of an eccentric
transmission. In continuous operation the duration for each stroke is
calculated from the effective motor speed in the load condition and the
transmission step-down ratio. When the drive motor is switched on or off
to perform individual strokes or partial strokes, corresponding start-up and
braking times must be taken into consideration, which correspondingly
prolong the duration per stroke. The stroke length can be adjusted for
example by adjusting the eccentricity of an eccentric transmission or by
using an adjustable abutment, the abutment can for example limit the
movement of the displacement member in the suction stroke before
reaching the rear dead point of the eccentric transmission. That
predetermines the starting point of the stroke movement while the end
point derives from the completely implemented deflection movement of the
displacement member.
The movements of the displacement member result from the
interaction of the mechanical components such as for example the
transmission. During the forward movement (pressure stroke) the drive
operates against the force acting on the push rod by the displacement
member (and the possibly present return spring).
There are embodiments, so-called diaphragm metering pumps, which
use an at least partially flexible diaphragm as the displacement member.
That diaphragm can be deformed during the pressure and suction strokes.
The amount of that deformation which is built up in a first part of the stroke
movement, which part is not used for the metering process, is lost to the
effectively performed stroke movement and has the result that the
metering amount decreases with increasing working pressure. With those
pumps it is therefore necessary to perform suitable calibration
measurement. After calibration has been effected however the pump can
only be reliably used in a given working pressure range. If the working
pressure should change re-calibration has to be effected. If calibration is
not done, for example because the fluctuation in working pressure is not
observed, that gives a metering error.
:A 02792841 2012 09 11
3
For better adjustment of the metering process and for increasing the
metering accuracy it is already proposed in EP 1 754 891 that the
displacement member is connected to a reference element whose position
is sensed' by a position sensor, the position sensor delivering an actual
signal which is fixedly related to the position of the reference element and
therewith the displacement member and by means of which knowledge
about the movements of the displacement member is acquired so that the
electronic control of the metering pump can react to operating conditions of
the metering circuit and the pump.
With that background of the described state of the art therefore the
object of the present invention is to provide a method of controlling and/or
regulating a metering pump, which in principle manages without a position
sensor on the thrust rod and can establish the metering behaviour of the
pump with a high level of precision.
According to the invention that object is attained by a method of
controlling and/or regulating a metering pump comprising a drive motor
having a shaft driven by the motor and a displacement member arranged in
a metering head, in which the rotary movement of the shaft is converted
into an oscillating movement of the displacement member, wherein the
displacement member, interacting with an outlet and inlet valve in
alternate sequence, leads to a pump stroke (pressure stroke) and an intake
stroke (suction stroke) and thus to delivery of a medium to be metered, in
which at least one motor operating parameter, preferably a motor voltage
U or a motor current I, is measured, at least one regulating parameter is
calculated from the at least one measured motor operating parameter and
optionally further known motor characteristics, the at least one regulating
parameter is compared to a predetermined guide parameter, and a
comparison signal dependent on the result of the comparison is outputted,
and can be used as a status, actuating and/or regulating signal.
It is for example possible to calculate the actual torque MAcTuAL and
optionally the magnetic actual flux cOACTUAL of the motor, preferably an
asynchronous motor, as the regulating parameter, and to compare it to a
predetermined reference guide parameter, that is to say the reference
:A 02792841 2012 09 11
4
torque and the reference flux of the motor. A comparison signal can be
outputted in dependence on the result of the comparison. The comparison
signal can be used for example as a status signal, that is to say the signal
indicates whether a given condition is or is not met. The status signal can
then serve for example as a warning signal or as a triggering means for
given measures.
It is also possible to use the comparison signal as an actuating
signal, that is to say to control a parameter, for example a motor operating
parameter, with that signal. Alternatively the signal can also be used as a
regulating signal.
Depending on the respective regulating parameter, not only motor
operating parameters such as for example motor voltage and motor current
are necessary for calculation purposes, but further properties characteristic
of the motor or the transmission such as for example the step-up or step-
down transmission ratio.
In a further preferred embodiment it is preferred that as the
regulating parameter the actual motor speed is measured preferably a
plurality of times, particularly preferably at least five times, during a
motor
revolution, or is calculated from the motor operating parameters preferably
from the actual torque M
-ACTUAL and the magnetic actual flux do
- ACTUAL of the
motor, and the difference between the actual motor speed and a
predetermined reference motor speed is outputted as the comparison signal
and the comparison signal is used as a regulating signal for adaptation of
motor current I and/or motor voltage U to adapt the actual motor speed to
the reference motor speed.
In the simplest case measurement of the actual motor speed is
effected by means of a rotary angle sensor. It is however also possible for
the actual motor speed to be calculated from the motor operating
parameters in completely contactless fashion.
In dependence on the transmission configuration the motor load
varies in dependence on the current eccentric position. The motor must
therefore be designed with its power output in such a way that it can apply
the desired rotary speed, even in the most disadvantageous eccentric
:A 02792841 2012 09 11
position. If the power of the motor is too low, the result is that the desired
speed is not reached in many eccentric positions, that is to say the stroke
duration is prolonged. The power of the motor can be better utilised by the
specified measure as the rotary speed is slightly reduced in the region of
5 maximum eccentric deflection, in which force transmission is at its most
disadvantageous, while the resulting prolongation in the stroke duration is
compensated by the rotary speed being increased in a region involving
advantageous force transmission.
In a further preferred embodiment it is provided that as the
regulating parameter the actual motor magnetisation is calculated,
preferably a plurality of times, particularly preferably at least five times
during a motor revolution, from the actual torque M
-ACTUAL and optionally
further known motor characteristics, and a predetermined reference motor
magnetisation is selected as the guide parameter and the difference
between the regulating parameter and the guide parameter is outputted as
the comparison signal and the comparison signal is used as the regulating
signal for the adaptation of motor current I and/or motor voltage U to
adapt the actual motor magnetisation to the reference motor
magnetisation, wherein preferably the reference motor magnetisation is a
periodic function with a period duration corresponding to the period
duration of the displacement member.
Preferably there is provided a pressure element which presses the
contact surface in the direction of the eccentric so that upon rotation of the
shaft the pressure element can hold the contact surface in contact with the
eccentric at least portion-wise and an intake stroke can be performed. The
pressure element can be for example a spring.
In a further preferred embodiment the actual torque M
-ACTUAL and
optionally the magnetic actual flux ACTUAL ACTUAL of the motor, preferably an
asynchronous motor, is calculated as the regulating signal and the actual
torque MACTUAL and optionally the magnetic actual fluxdo
- ACTUAL of the motor is
substantially continuously determined over at least one period duration and
the time-dependent actual torque M
-ACTUAL calculated in that way and
optionally the time-dependent magnetic actual flux cb
- ACTUAL of the motor is
:A 02792841 2012 09 11
6
compared to at least one pre-determined pattern function as the guide
parameter. The comparison signal represents the degree of similarity
between the regulating parameter and the guide parameter and if the
degree of similarity exceeds a predetermined value the comparison signal is
used as the status signal. For example an overload protection function, for
example in the form of an excess pressure shut-down, can be called up in
reaction to the status signal.
Usually a metering pump presents wear phenomena in the course of
time. That can involve for example bearing damage, warped gears or a
damaged eccentric. Such wear phenomena mean that the force to be
applied by the motor changes. According to the invention it is therefore
provided that characteristic trouble patterns or a pattern function are
associated with given wear phenomena. If for example a gear is missing a
tooth then the missing tooth will be manifested in a periodic disturbance in
the force implementation. If now the
actual torque is calculated
substantially continuously and the signal calculated in that way is compared
to the pattern functions, for example by forming a correspond cross-
correlation function, it is possible at a very early stage to recognise that
the
metering pump is presenting wear phenomena and it is optionally possible
solely on the basis of the forces involved to determine which component is
exhibiting wear phenomena and then has to be specifically replaced.
It can further happen that air passes into the metering head, which
can cause the entire metering operation to fail although the mechanical
movement of the displacement member is still occurring. In this case also
the compression process, that is to say the rise in force, can be evaluated
by evaluation of the actual torque and, if the compression variation points
to aeration of the metering head, for example a corresponding message
can be produced or counter-measure can be automatically initiated such as
for example automated venting of the metering head.
In a further preferred embodiment it is provided that the metering
pump has a displacement member with an at least partially elastic
diaphragm, wherein the metering amount is calculated as the regulating
parameter from the actual torque M
-ACTUAL and optionally the magnetic actual
=
:A 02792841 2012 09 11
7
flux (DACTUAL of the motor having regard to further motor characteristics,
wherein the influence to be expected by virtue of flexing of the elastic
diaphragm on the metering amount is taken into consideration and the
difference between the actual metering amount and a predetermined
reference metering amount is outputted as the comparison signal and used
as the regulating signal for the adaptation of motor current I and/or motor
voltage U to adapt the actual metering amount to the reference metering
amount.
By virtue of that measure the metering pump can be used over a
wide range of different working pressures without involving any metering
error worth mentioning. If more specifically there is an unexpected change
in the working pressure the method according to the invention, by way of
the calculation of the actual torque, allows reliable recognition and
correction of the metering error by virtue of the flexing of the diaphragm of
the displacement member.
Furthermore in a preferred embodiment it is provided that an actual
stroke length of the displacement member is calculated as the regulating
parameter from the actual torque M
-ACTUAL and optionally the magnetic actual
flux OACTUAL and the difference between the actual stroke length and a
predetermined reference stroke length is outputted as the comparison
signal. The comparison signal can either be used as a status signal to
possibly stop the pump or it can be used as the regulating signal for the
adaptation of motor current I and/or motor voltage U to adapt the actual
stroke length to the reference stroke length. By virtue of that measure the
stroke length can be adapted to ongoing operation if that is necessary for
the area of use.
The present invention also concerns a metering pump having a
control and/or regulating device for carrying out the described method.
The described method means that the metering pump can also be used in a
pendulum stroke mode, that is to say the direction of rotation of the motor
is inverted after at most one pump and one intake stroke.
CA 02792841 2016-07-13
7a
According to a first aspect of the present invention, there is provided a
method of controlling and/or regulating a metering pump comprising a drive
motor having a shaft driven by the motor and a displacement member arranged
in a metering head, in which the rotary movement of the shaft is converted
into
an oscillating movement of the displacement member, wherein the displacement
member, interacting with an outlet and inlet valve in alternate sequence,
leads to
a pump stroke (pressure stroke) and an intake stroke and thus to delivery of a
medium to be metered,
characterised in that
at least one motor operating parameter is measured,
at least one regulating parameter is calculated from the measured motor
operating parameters,
the at least one regulating parameter is compared to a predetermined
guide parameter, and
a comparison signal dependent on the result of the comparison is
outputted for use as a status, actuating and/or regulating signal.
According to one aspect of the present invention, there is provided a
method of controlling and/or regulating a metering pump comprising a drive
motor having a shaft driven by the motor and a displacement member arranged
in a metering head, in which the rotary movement of the shaft is converted
into
an oscillating movement of the displacement member, wherein the displacement
member, interacting with an outlet and inlet valve in alternate sequence,
leads to
a pump stroke and an intake stroke and thus to delivery of a medium to be
metered,
characterised in that
at least one motor operating parameter is measured,
at least one regulating parameter is calculated from the at least one motor
operating parameter,
CA 02792841 2016-07-13
7b
the at least one regulating parameter is compared to a predetermined
guide parameter,
a comparison signal dependent on the result of the comparison is
outputted for use as a status, actuating and/or regulating signal, and
the metering pump is controlled and/or regulated, having a transmission
for conversion of a rotary movement into a translatory movement, which
connects the driven shaft of the motor to the displacement member.
=
=
..
. :A 02792841 2012 09 11
8
Further advantages, features and possible uses will be apparent from
the description hereinafter of a preferred embodiment and the related
Figures in which:
Figure 1 shows a perspective longitudinal sectional view through a
5 metering pump,
Figure 2 shows a diagrammatic view of the motor pump,
Figure 3a shows a diagrammatic view of the torque of the motor and
the displacer movement during a revolution for a full stroke,
Figure 3b shows a diagrammatic view of the torque of the motor and
10 the displacer movement during a revolution for a partial stroke,
Figure 4a shows a diagrammatic view of the torque of the motor and
the displacer movement during a revolution for a full stroke with
incomplete suction stroke,
Figure 4b shows a diagrammatic view of the torque of the motor and
15 the displacer movement during a revolution for a partial stroke with
incomplete suction stroke,
Figure 5 shows a diagrammatic view of the rotary speed and the
torque in relation to time for known motors (solid line) and for a motor
regulated in accordance with a preferred embodiment (broken line).
20 Figure 1 shows the structure of a metering pump. The metering
pump substantially comprises three components, namely the drive motor 2
with transmission unit, the eccentric drive in the eccentric housing 1 and
the electronic housing 29 with the electronic control contained therein and
the electronic components and assemblies used there. The electronic
25 housing 29, on the underside, has a bottom plate 4 with fixing bores
while
the eccentric housing 1 which is fitted on to the electronic housing 29 and
fixedly connected thereto carries the drive motor 2 with transmission unit
which is connected for example by way of screws to the eccentric housing.
The components of the eccentric drive are fixed on the housing
30 formed by the eccentric housing 1 and the electronic housing 29, in the
upper part. The components of the eccentric drive are mounted in an
eccentric carrier 22 which ensures positional matching of the individual
parts to each other and is fixed in the eccentric housing 3. A three-phase
= :A 02792841 2012 09 11
9
asynchronous motor 2 is flange-mounted together with a step-down
transmission 11 which is in the form of an angle transmission as a
structural unit to the eccentric housing 1 from the outside, and connected
with screws. The output shaft of the transmission motor forms a right
angle with the axis of the shaft of the motor and either forms the drive
shaft of the eccentric drive directly or, as in the illustrated embodiment, is
connected thereto in co-axial relationship by way of a coupling. The drive
shaft of the eccentric drive, the eccentric shaft 17, is mounted rotatably in
the eccentric carrier 22 and carries an eccentric in the form of a part
fixedly
connected thereto. The eccentric shaft passes with the eccentric through a
corresponding cut-out thrust ring 20. The eccentric shaft 17 is driven in
rotation by the motor/transmission unit by way of the shaft coupling when
the motor 2 is actuated and further drives the thrust ring 20 in an inside
surface of its cut-out opening, namely the running contact surface with the
outside surface of the eccentric. The thrust ring 20 drives a thrust rod 19
which is fixedly connected thereto, for example being injection-moulded
there. The unit consisting of the thrust ring 20 and the thrust rod 19 is
supported longitudinally slidably in two sliding bushes. The axis of the
eccentric shaft 17 and the longitudinal axis 18 of the thrust ring 20 and the
thrust rod 19 are respectively disposed in the horizontal plane and form a
right angle to each other. One of the two bushes 26 for the thrust rod 19 is
supported in a bearing disk 24 which at the pressure head end is fixed to
the eccentric carrier 22. A further bush 27 which accommodates the
trunnion, that is remote from the metering head side, of the thrust ring 20
is fitted in the stroke adjusting pin 8. An adjusting member 7 which is to
be actuated by hand for adjustment of the stroke adjusting pin 8 is screwed
into a thread of the eccentric carrier 22 on the same axis as the
longitudinal axis 18 of the thrust rod 19; the thread limits the axial
movement of the thrust ring 20 in the suction phase and thus in the stroke
of the metering pump.
In addition the housing contains the electronic control system in its
lower part in a closed-off space, the electronic housing 29.
:A 02792841 2012 09 11
Arranged on the same axis as the longitudinal axis 18 of the thrust
rod, on the side opposite the control lines 10, is a metering head 12 in
which a diaphragm 13 made for example from plastic material operates as
the displacement member, the diaphragm being fixedly clamped at its
5 periphery. The metering head 12 further carries an inlet valve 14 and an
outlet valve 15 to press the medium to be sucked in by way of the inlet
vale 14 between the diaphragm 13 and the metering head 12 in the
metering chamber 16 into the metering line by way of the outlet valve 15.
The metering pump operates in accordance with the volumetric principle,
10 that is to say in each stroke a predetermined volume is to be sucked in on
the one hand and expelled by way of the outlet valve 15 on the other hand.
The diaphragm 13 is displaced in an oscillating movement by means of the
eccentric drive which reciprocates the thrust rod 19 on the longitudinal
axis. Arranged between the thrust ring 20 and a shoulder of the disk 24 is
a compression spring 23, for example a coil spring, which causes the thrust
ring 20 to bear against the eccentric in positively locking relationship at
any
moment in time. In the forward phase of the eccentric movement, that is
to say in the movement of the thrust rod towards the metering head, the
thrust ring with the thrust rod is moved towards the compression spring, at
the same time the diaphragm 13 is pressed into the metering chamber 16,
with the consequence that an increased pressure is produced in the
metering chamber, the outlet valve 15 opens and the medium to be
metered is pressed into the metering line. In the return phase of the
eccentric movement, that is to say in the movement of the thrust rod away
from the metering head, the thrust ring 20 is moved in the opposite
direction in relation to the stroke adjusting pin 8 by the compressed
compression spring 23 which for example can be in the form of a coil
spring, to follow the eccentric movement, with the result that the thrust rod
19 connected to the diaphragm 13 entrains the diaphragm in its
movement, whereby in the metering chamber 16 there is a reduced
pressure which opens the inlet valve 14 so that medium to be metered can
be sucked a further time into the metering chamber.
:A 02792841 2012 09 11
11
Figure 2 shows a diagrammatic view of the metering pump. In the
illustrated embodiment the force exerted on the displacement member is
calculated from the motor current I and the motor voltage U and the known
motor characteristics, that is to say the known transmission arrangement.
Figure 3a diagrammatically shows the variation in time of the torque
(above) and the movement of the displacer element (below) over a stroke
period.
The movement of the displacer element is substantially sinusoidal.
During a pressure stroke hp the displacer moves from the minimum
deflection SmiN to the maximum deflection SmAx. During the subsequent
suction stroke the displacer is moved from the maximum deflection SMAX
back to the minimum deflection SmIN. The total stroke period H is
composed of the pressure stroke hp and the suction stroke hs. If the
torque shown above in Figure 3a is considered, it will be seen that the
torque moves between a base torque Mo and a peak torque M1. It is only
during the pressure stroke hi, that the torque differs from the base torque
Mo. Outside the pressure stroke the motor does not have to apply any
force to the medium to be delivered so that essentially only the base torque
Mo is required, because of frictional losses. The displacer is moved back
into its starting position by a spring element.
The variation in the torque during the pressure stroke hp is here also
substantially sinusoidal and depends on the transmission characteristic. At
the beginning and the end of the pressure stroke hp the force to be applied
is very low by virtue of the transmission step-up ratio. Therebetween it
rises to the maximum value M1.
Figure 3b diagrammatically shows the variation in time of the torque
(above) and the movement of the displacer element (below) over a stroke
period, wherein the situation is shown here in which only a partial stroke is
performed.
If the displacement element can no longer be moved back to the
minimum deflection SmIN, either because an adjustable abutment limits the
stroke length or because the stroke length is limited for other unpredictable
reasons, only a partial stroke is performed. It will be seen from the
= :A 02792841 2012 09 11
12
diagrammatic view of the displacer movement, shown at the bottom in
Figure 3b, that the deflection is now between a deflection SA and the
maximum deflection SmAx. Consequently the pressure stroke hp and the
suction stroke hs are markedly reduced in comparison with the pressure
and suction stroke in Figure 3a.
It will also be seen at the top in Figure 3b that the variation in time
of the torque differs markedly from that shown in Figure 3a. Consequently,
conclusions about the actually performed stroke length can be drawn from
the variation in torque, and same can be compared to a predetermined
reference stroke length. If the actual stroke length should not be the same
as the reference stroke length, then in a preferred embodiment the actual
stroke length can be adapted to the reference stroke length by an
alteration in the motor current and/or motor voltage. Nonetheless even if
such adaptation to the reference stroke length is not wanted or is not
possible, the actual stroke length can be determined by the method
according to the invention, the metering volume can be calculated
therefrom, and the latter can be compared to the reference metering
volume. Possibly then the speed of the motor has to be increased to
compensate for the reduced metering volume per stroke.
Blockade detection is also possible. While in the known
embodiments a position sensor would have to detect the position of the
displacement member, and then a blockade which under some
circumstances has occurred could be deduced therefrom, the embodiment
according to the invention provides that the pump is switched off if the
torque to be applied by the motor exceed a predetermined limit value.
Blockade shut-down according to the invention can therefore under some
circumstances prevent damage to the motor.
It will be appreciated that blockade detection can also be such that a
blockade situation is assumed to apply when the predetermined limit value
is exceeded at a given moment in time or over a period longer than a
predetermined period. It is also possible for the predetermined limit value
to be deduced from the eccentric position, that is to say it is possible for
the predetermined limit value to be adapted to be variable in time.
:A 02792841 2012 09 11
13
An incomplete suction stroke can be determined in this same
manner. Figure 4a diagrammatically shows the variation in time of the
torque (above) and the displacer movement (below). The solid
corresponds to the configuration shown in Figure 3a. If now sufficient
medium to be delivered cannot flow into the delivery chamber in the
suction stroke for any reasons, the displacement member will not be able
to follow the eccentric, but will lift off same. That situation is shown in
broken line in Figure 4a. Instead of following the eccentric movement the
metering chamber only gradually fills so that the eccentric is already
moving in the direction of its maximum deflection again before the
metering chamber is filled. The result of this is that the pressure stroke hp
is shortened, as shown in Figure 4a. Consequently the torque variation
also changes, as is also shown in broken line.
Figure 4b shows the same situation in the case of a partial stroke.
From the time shift tv it can be deduced that an incomplete suction stroke
has occurred and suitable measures can optionally be taken in order
nonetheless to maintain the metering effect or a corresponding error signal
can be outputted.
The method according to the invention further permits slippage
detection within the stroke travel and optionally immediate stabilisation
control also within a stroke period. While the rotary speed is usually
determined by way of measurement of the stroke and the rotary speed is
optionally adapted for the entire stroke, in the preferred embodiment it is
provided that the torque is adapted with increasing slippage within a
pressure and suction stroke.
For illustration purposes Figure 5 shows the rotary speed versus time
for known motors (solid line) and for a motor regulated by the method
according to the invention (broken line). While the speed periodically drops
because of the increased load within a period duration in the known
motors, the rotary speed remains constant with the regulation according to
the invention. To achieve that the motor torque must be varied at the
appropriate moment in time within a stroke.
:A 02792841 2012 09 11
14
That measure provides that the length of the pressure stroke is
reduced and also the length of the stroke period is adjusted to its ideal
value while the length of the pressure stroke and the stroke period would
increase in length due to the reduction in speed.
The method according to the invention therefore makes it possible to
keep the metering output constant, even at a high load which would
otherwise lead to a reduction in rotary speed.
The method according to the invention therefore makes it possible to
deduce the hydraulic pressure, that is to say the working pressure, from
the torque. Thus it is possible for example to determine the torque
generated by the motor and to compare it to a reference torque and, upon
a deviation between actual torque and reference torque of for example
more than 30%, to stop the pump to prevent an overload and thus to
protect the drive from self-destruction.
As already stated the pressure and suction stroke involves flexing of
the displacement diaphragm so that the metering volume depends on the
working pressure.
If the method according to the invention allows the working pressure
to be determined from the motor core parameters, the metering error can
be corrected in dependence on the ascertained working pressure. A further
advantage of the method according to the invention is that in principle any
motion curve of the displacement member can be set. Thus for example
metering and suction intake can be effected at a constant reduced speed,
by the variation in speed being compensated on the basis of the deflection
angle of the eccentric, whereby uniform metering occurs and the necessary
peak power output of the motor is reduced. In addition it is possible to
implement an electronic suction intake assistance upon first filling of the
suction intake line and the metering head (start-up of operation) if for
example the motor is operated in the pendulum stroke mode and the full
stroke length is performed in the suction intake situation.
In addition it is possible to actuate the motor in need-oriented
relationship at any moment in time by predictive adaptation of the motor
actuating parameters along the stroke travel as the rise in torque is known
= :A 02792841 2012 09 11
by virtue of the eccentric. In that way the motor can be operated in more
energy-saving fashion.
It is known that cavitation can occur, leading to incomplete suction
intake and increased material wear, for example in the valves. The
5 described evaluation of the variation in force and/or the movements
involved make it possible to detect the cavitation in the suction stroke and
it is possible to immediately take counter-measure such as for example
throttling the intake suction speed.
:A 02792841 2012 09 11
16
List of references
1 Eccentric housing
2 Drive motor
4 Bottom plate
7 Adjusting member
8 Stroke adjusting pin
Control lines
11 Step-down transmission
12 Metering head
10 13 Diaphragm
14 Inlet valve
Outlet valve
16 Metering chamber
17 Eccentric shaft
15 18 Longitudinal axis
19 Thrust rod
Thrust ring
22 Eccentric carrier
23 Compression spring
20 24 Bearing disk
27 Slide bush
29 Electronic housing
