Note: Descriptions are shown in the official language in which they were submitted.
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Displacement Punnp with Variable Voltune Flow
The invention relates to displacement pumps, in particular internal-axle gear
pumps, but also
wing cell pumps or for example also pendulum slider pumps, whose volume flow
can be varied
according to requirement, i.e. can be adjusted. The pumps in accordance with
the invention are
preferably used as lubricant oil pumps for internal combustion engines,
wherein the internal
combustion engine itself preferably drives the lubricant oil pump in question.
The internal
combustion engine can in particular be a drive motor, preferably a piston
motor, of a vehicle.
The specific volume flow, i.e. the volume flow delivered per revolution of a
delivery wheel of
the pump, can preferably be adjusted continuously. The displacement pumps can
also be
advantageously used as supply pumps for automatic transmissions in vehicles
and when used in
this way are also preferably driven by the drive motor of the vehicle in
question. Although the
displacement pump of the invention, which can be adjusted according to
requirement, is suitable
in particular for such applications, in which with increasing drive speed, the
fluid requirement
increasingly falls short of the delivery volume of pumps whose specific
delivery volume is
constant, a pump in accordance with the invention can also be advantageously
employed in other
situations, in which for example the drive speed of the pump is constant and
the fluid requirement
of the aggregate to be supplied fluctuates for other reasons.
Displacement pumps formed as gear ring pumps, such as the invention also
relates to in
particular, are known from DE 297 03 369 U1 and EP 0 846 861 B1 which is based
on it.
In the known variable pumps, the external rotor of the gear ring running set
is rotatably mounted
in a variable ring which surrounds the external rotor and rolls off without
slipping in the pump
casing via an internal-external soothing, such that in accordance with these
kinematic ratios, the
eccentric axis of the gear ring running set rotates by up to 90°
relative to the casing during the
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varying process. This enables a delivery amount to be varied from a maximum to
almost zero,
with as small an adjusting path as possible.
However, it has proven in practice that the design space available in
increasingly compact
reciprocating piston motors is becoming smaller and smaller. Since these pumps
are preferably
arranged in the oil sump of the crankcases and since a mass-balance shaft
often also has to be
additionally accommodated in this region, together with other influencing
factors such as
conductor frame fortification of the crankcase and a highly pitched oil pan
for ground clearance
and the arrangement of the vehicle steering parts, the outer diameter of the
variable pump is too
large. Since, due to the heated idling at low motor speed, the pump has to
exhibit a specific
minimum delivery amount, the diameter of the gear ring running set cannot be
arbitrarily
reduced. Limits are also set on enlarging the running set width, for reasons
of space and due to
the suction limits of the teeth. Wide running sets have the additional
disadvantage that during
speed regulation, the overthrust losses between the converging and diverging
teeth cells caused
by differential varying are very high.
It is therefore an object of the invention to provide a displacement pump
which exhibits smaller
dimensions, with respect to both the diameter and width of the running set,
for the same specific
delivery amount.
The invention solves the object by the subjects of the independent claims. The
sub-claims
describe advantageous embodiments.
The displacement pump with variable volume flow in accordance with the
invention comprises a
casing and a chamber which is formed in the casing and comprises an inlet
opening on a low
pressure side and an outlet opening on a high pressure side for a fluid. The
pump can for
example be an internal gear pump, a wing cell pump or a pendulum slider pump.
The pump
further comprises an internal rotor which is accommodated in the chamber and
can be rotated
about a rotational axis, and a ring which is accommodated in the chamber and
has a central ring
axis which surrounds the internal rotor. In the case of rotary driving at
least one of the internal
rotor and the ring, the ring and the internal rotor form at least one delivery
cell in which the fluid
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is delivered from the low pressure side to the high pressure side. An
adjusting device is arranged
such that during an adjusting movement, it rolls off on the casing without
slipping. In accordance
with the invention, the internal rotor is fixed to the adjusting device such
that it can be rotated
about the rotational axis. Furthermore, the position of the rotational axis
relative to the ring axis ,
of the ring can be adjusted by the adjusting movement of the adjusting device.
By adjusting the internal rotor relative to the casing and the surrounding
ring in order to adjust
the specific volume flow, sealing the delivery space formed between the
internal rotor and the
outer ring can be simplified.
If the pump is a gear ring pump, then the outer ring forms an external rotor.
In such
embodiments, driving the gear ring running set formed by the internal rotor
and the external
rotor via the external rotor is facilitated. As compared to rotary driving via
the internal rotor, the
pump speed in the case of rotary driving via the external rotor is
advantageously increased in
accordance with the ratio of the numbers of teeth of the internal rotor and
the external rotor,
hence the diameter of the pump can be reduced. The outer ring is also a rotor
in a pendulum
slider pump, such as is for example described in FR 980 766. In a wing cell
pump, the outer ring
can be fixed relative to the casing, or the casing itself can form the
internal cylindrical surface for
a wing wheel forming the internal rotor.
It is advantageous if an adjusting device which adjusts the specific volume
flow does not surround
the internal rotor a~ the outer ring but is arranged axially adjacent to them.
It is particularly
advantageous if arranging the adjusting device adjacent to the internal rotor
andJor the outer ring
is combined with adjusting the specific volume flow by adjusting the internal
rotor. The adjusting
device preferably rotationally mounts the internal rotor such that it slaves
the internal rotor
during its own adjusting movement by being fixedly connected to the internal
rotor with respect
to the adjusting movement. The adjusting device can for example comprise a
toothing which is in
toothed engagement with a toothing of the casing during an adjusting movement.
The soothing of
the adjusting device is preferably a round-flank toothing. A centre point of a
flank circle of a
tooth of the toothing of the adjusting device can for example approximately
describe a
hypocycioid when rolling off on the casing.
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By omitting the variable ring around the external rotor and by increasing the
speed of the internal
rotor in proportion to the numbers of teeth from the external rotor to the
internal rotor as
compared to the drive speed, the design space of the variable pump required is
reduced
superproportionally, for the same specific delivery amount.
Such a variable pump in accordance with the invention is thus also suitable
for small-volume
internal combustion engines, in which particular value is placed on reducing
the hydrostatic
losses and the circulated amount of oil at high speeds.
The compactness of a variable displacement pump in accordance with the
invention can hardly be
surpassed. Since the shaft bearings are rid of any hydrostatic load, and are
only then loaded by
the traction rod of a continuously variable transmission Such as is preferably
used for driving, the
diameter of the shaft can be reduced. The smaller effective running set width
also improves the
suction capacity and reduces the danger of cavitation. The volumetric
efficiency is also improved
due to the augmented high-speed running. This is also due to the fact that the
pinion engagement
between the external rotor and the internal rotor then trails at the point of
maximum toothed
engagement, such that the pressure side of the toothing is sealed better than
the suction side.
In accordance with preferred embodiments, the adjusting device adjusts
hydraulically by being
charged with a fluid pressure which is fed back from the high pressure side of
the pump to the
adjusting device. The high pressure side of the pump reaches from the high
pressure side of the
pump chamber to the point or points of the aggregate or number of aggregates
to be supplied,
from which the fluid, relieved of pressure, is fed back to a fluid reservoir.
It can also be
advantageous to tap the fluid pressure of the high pressure side of the pump
at a location outside
the displacement pump and to charge the adjusting device with the pressure in
order to vary the
volume flow. The pressure can for example be tapped at a crankshaft main
gallery of the motor.
In a preferred embodiment, the fluid pressure acting in the pump chamber on
the high pressure
side, in combination with the fluid pressure fed back to the adjusting device,
generates the
adjusting force for adjusting. The adjusting force can for example be formed
from at least one of
the two hydraulic adjusting forces which act on the adjusting device and/or
internal rotor. In
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particular, the adjusting device can be adjusted by an adjusting force against
the force of an
elastic component. The two adjusting forces are advantageously superimposed
positively on each
other, preferably by generating adjusting moments in the same direction. In
this way, it is
possible to achieve a varying which reacts particularly sensitively to changes
in pressure. The
invention thus also relates to a displacement pump with variable volume flow,
comprising the
features of the preamble of at least one of the independent claims in
combination with feeding the
fluid pressure back to the adjusting device and charging the adjusting device
with the fluid
pressure fed back, in a direction such that the adjusting force thus generated
is superimposed
positively on an adjusting force generated by the fluid pressure of the high
pressure side of the
pump chamber acting on one of the internal rotor and the outer ring, the sum
of the two forces
being greater than each of the two individual forces.
For the adjustability of the variable pump, such an embodiment gives rise to
the advantage that
the hydraulic adjusting forces of the internal rotor are added, over its
bearing journal on the one
hand and those between the adjusting device - preferably formed as an
adjusting plate - and the
casing, and not subtracted as with the known displacement pump. This advantage
is very
important, particularly for cold starts in which a quick adjustment to a zero
delivery amount is
necessary in order to prevent damage to the oil filter and oil conduits. Up
until now, it has been
necessary here to provide an additional pressure control valve due to the
inertia of the adjustment
to zero.
Although positively superimposing the two hydraulic adjusting forces is
particularly advantageous
in its own right alone, this embodiment is preferably combined with adjusting
the internal rotor
or arranging the adjusting device axially adjacent to the internal rotor
and/or the outer ring, and
particularly preferably combined with both these features.
Due to the machinability of the internal toothing in the casing for the
adjusting transmission, the
number of teeth here cannot be selected to be arbitrarily large. A round-flank
toothing is most
suitable on the adjusting plate, such that the internal toothing in the casing
- which preferably
comprises one tooth more than the external toothing of the adjusting plate -
can be machined
using a rotating cutting tool (drill rod), as is known from the known variable
pump comprising a
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variable ring in Figure 10 of EP 0 846 861 B1. The centre point of the flank
circle of the tooth
on the adjusting plate describes a hypocycloid when rolling off in the casing,
although in practice
the hypocycloid is not entirely free of overlap. A radial elevation stroke
therefore arises during
rolling off, such that the eccentricity of the variable plate in the casing
therefore fluctuates. The
magnitude and/or the rotational angular position of an eccentricity between
the rotational axis of
the internal rotor and the central ring axis of the ring can for example be
adjusted by the
adjusting movement. A fluctuation in the eccentricity can, however, be
undesirable in the pump
running set, since it leads to noise and wear on the pump toothing. Guiding
cylinders or cylinder
segments which roll off on each other are therefore preferably provided on the
adjusting plate and
on the casing (in the drawings, on the pump casing in this case), having
diameters whose
difference is equal to twice the eccentricity of the pump running set.
Therefore, the adjusting
plate does not roll off in the coarse systematic toothing but on the two
exactly machined circular
cylinders. The difference in the diameters of these guiding cylinders is equal
to 2e with respect to
the variable plate and the casing, where a signifies the eccentricity of the
pump delivery set,
preferably of the pump running set, and of the toothings between the variable
plate and the
casing. Thus, a radial elevation stroke while rolling the variable plate off
in the casing, and thus
a fluctuation in the eccentricity of the pump delivery set during the varying
process, is avoided.
In particular, the magnitude of the eccentricity can be constant.
No eccentric chucks are required for machining the casing parts, since the
shaft and external
rotor bearings are concentric. The depth of the internal toothing of the
casing is minimised and
no longer has to be machined over the entire running set width, as with the
known design. This
toothing can be high-precision manufactured on a CNC machine with a C axis and
path-
controlled HSC (high speed cutting) spindle unit in a clamp together with the
other machining
operations. This results in a considerable reduction in the expenditure of
time for machining the
toothing of the casing.
The subject of the invention is shown in the drawings by way of the example of
a variable
internal gear pump, arranged in the oil sump, for a four-cylinder passenger
car engine. This does
not, however, mean that the invention is restricted to such an application. It
could also, for
example, be used in an automatic transmission as an oil pressure pump for
switching and for
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supplying the transmission parts with oil. The variable pump would then be
positioned at the end
of a continuous transmission input shaft, such that in this case, the chain
wheel shown in the
drawings is omitted, and instead the pump shaft is coupled, concentrically and
rotationally fixed,
to the transmission input shaft.
Example embodiments of the invention are explained below on the basis of
figures. Features
disclosed by the example embodiments, each individually and in any combination
of features,
advantageously develop the subjects of the claims and also the embodiments
described above.
Specifically, there is shown:
Figure 1 an axial section in accordance with the gradient A-A in Figure 2;
Figure 2 a longitudinal section in accordance with the intersection line E-E
in Figure
1;
Figure 3 a longitudinal section in accordance with the intersection line B-B
in Figure
1;
Figure 4 a view of the variable plate, the variable spring and the pump
running set in
the pump casing, with the cover (30) removed, in the position in which the
pump exhibits its maximum possible delivery amount;
Figure 5 the same view as in Figure 4, but in the position in which the pump
exhibits
its minimum possible delivery amount;
Figure 6 a longitudinal section through the pump along the intersection line D-
D in
Figure 5; and
Figures 7 and 8 an illustrative representation of the variable plate 13
together with its
rolling off cylinder 25.
For explaining the function in the individual figures, the rotational
direction of the running set
shall be in the indicated direction of the arrow 32, such that the respective
suction and pressure
side in accordance with the expanding and compressing delivery cells of the
teeth is clearly
provided. In the cover 30, the suction support 31 is arranged on the suction
side of the running
set, on which side the variable spring 28 can also be seen. Thus, the spaces
of the variable spring
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28 and the rolling cylinders 24 and 25, and the sections of the toothing shown
on the right of the
image in Figures 4, 5, 6 and 7 between the variable plate 13 and the casing 1
are under suction
pressure, since the variable plate 13 is fitted in between the cavern base 33
of the casing and the
casing-cover partition line, forming an axial seal but able to move. The
pressure space 35, which
is hydraulically connected to the compressing delivery cells of tire gear ring
running set with the
minimum possible choke (not shown in the drawings), is thus sufficiently
sealed against
excessively high volumetric losses with respect to the suction side. The
delivery cells of the gear
ring running set are also sealed against each other by a minimum axial
clearance between the
variable plate 13 and the slaving disc 26, such that here too, a clear
hydraulic partition between
the high pressure side and the suction side is provided. Figures 1 and 4 show
the centre point of
the internal rotor in a position in which the pump exhibits its largest
possible delivery amount,
since the eccentric axis E-E (in Figure 1) of the running set toothing
coincides with the axis of
symmetry of the suction and pressure nodules in the casing and in the
adjusting plate 13. This
position is always needed at low pump speeds, if the oil viscosity is
relatively low, i.e. when the
motor is hot and in particular during heated idling, in order that the oil
consumers of the motor
are supplied with a sufficient amount of oil at a sufficient oil pressure. The
minimum pressure in
the pressure chamber 35 should not drop substantially below 1 bar, even when
bearing clearances
of the motor parts have been enlarged by wear. This maximum position is
ensured by an exactly
calculated bias on the variable spring which holds the adjusting plate 13
fixed on a stopper 36.
The velocity pole for the rotational movement of the variable plate thus lies
at M1 in Figure 4.
As the viscosity of the oil increases (e.g. during cold starts) or as the
speed of the pump
increases, the system pressure in the pressure chamber 35 and in the
compressing delivery cells
of the gear ring running set increases. A sum of adjusting moments arises
around the velocity
pole via the radial acting surfaces on the internal rotor 4 and on the
adjusting plate 13, such that
the variable spring 28 is no longer capable of holding the adjusting plate 13
on the stopper 36.
The variable system thus enters a poise which is determined by the moment
equilibrium between
the sum of the hydraulic adjusting moments and the moment of the variable
spring 28 about the
velocity pole M1. As the system pressure in the pressure chamber 35 increases,
the adjusting
plate 13 rotates clockwise in accordance with the representation in Figure 4,
wherein the velocity
pole M1 migrates on the reference circle of the toothing of the casing towards
the position M2 in
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Figure 5. Simultaneously, the centre point D, of the internal rotor 4 moves
anti-clockwise out of
the position P1 on its hollow shaft 16, around the shaft centre point DA on an
orbit having the
radius e, towards the position P2 in Figure S. Given the numbers of teeth of
the adjusting plate
13 and of the casing 1 provided (10:11 in the drawings), the angular rotation
of the internal rotor
centre point and thus of the eccentricity axis of the gear ring running set
anti-clockwise is ten
times greater than the rotation of the adjusting plate 13 clockwise about its
own axis. As can be
seen from Figure 5, a rotation of the adjusting plate 13 clockwise by just
9° generates a rotation
of the eccentricity axis a of the gear ring running set anti-clockwise by
90°. In this 90° position in
accordance with Figure 5, the expanding and compressing delivery cells in the
gear running set
have thus also been rotated by 90° with respect to the casing and thus
with respect to the reniform
suction and pressure nodules, and even by 99° with respect to the
adjusting plate 13. This means
that a delivery amount of the pump is no longer possible. Within the suction
and pressure
nodules, there then remains only an exchange of liquid between the converging
and diverging
tooth chambers.
The position P2, i.e. a rotation by 90° of the centre point D, of the
internal rotor 4 in accordance
with Figure 5, is of course never assumed during normal motor operation, since
as the speed of
the system as a whole increases, the motor bearings always have a finite oil
requirement which,
however, does not remotely increase in proportion to the speed, as opposed to
the delivery
amount of a non-variable pump. The oil requirement of the motor only increases
roughly in
proportion to the system pressure in the pressure chamber 35, adapted to the
flow resistance of
all the oil consumers, the viscosity of the oil and the degree of wear of the
shaft bearings of the
motor. The poise of the variable system of the adjusting pump in accordance
with the invention is
thus automatically set, such that the delivery amount of the pump exactly
covers the oil
requirement for the respective operational state of the system as a whole. The
designer then has
the option of adapting the adjusting pump to the motor by varying the bias and
the slope of the
spring characteristic. Thus, a new pump does not necessarily have to be
designed for each engine
size motor, as long as the range in size varies within certain limits.
As already mentioned in the introductory part of the description, it is
expedient for the adjusting
plate 13 not to roll off on the reference circles of the too'ags between the
adjusting plate 13 and
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the casing 1 but on two cylinder attachments, which roll off on each other, on
the adjusting plate
and the casing. The embodiment of the cylinder attachment on the adjusting
plate is shown
somewhat more clearly in Figures 7 and 8. The cylinder attachment 24 can also
be seen on the
left of the image in Figure 3.
Latterly, attempts have been made to control the delivery amount of the pump
in accordance with
the oil pressure in front of the crankshaft bearings by providing one or more
pressure sensors in
the main gallery of the crankshaft which tap the oil pressure there and supply
it to the pressure
chamber 35 of the adjusting pump. In this case, the pressure chamber 35 would
then have to be
hydraulically partitioned from the main flow channel of the pressure side of
the pump.
