U.S. patent application number 11/961622 was filed with the patent office on 2008-10-02 for pump.
Invention is credited to Andrew Best, Robin Child, Stephen Hodge.
Application Number | 20080240960 11/961622 |
Document ID | / |
Family ID | 37758938 |
Filed Date | 2008-10-02 |
United States Patent
Application |
20080240960 |
Kind Code |
A1 |
Hodge; Stephen ; et
al. |
October 2, 2008 |
Pump
Abstract
A pump assembly including a gerotor pump having an inlet and an
outlet, and comprising an annulus and a lobed rotor, one, but not
both, of the rotor or annulus being split axially into two parts,
the pump further comprising indexing means for angularly shifting
one part relative to the other part, the indexing means comprising
a chamber having a first indexing port and a second indexing port,
and a partition which divides the chamber into a first portion
including the first indexing port and a second portion including
the second indexing port, wherein the partition comprises a part
which is pivotally mounted within the chamber for angular movement
within the chamber.
Inventors: |
Hodge; Stephen;
(Staffordshire, GB) ; Best; Andrew; (York, GB)
; Child; Robin; (Warwickshire, GB) |
Correspondence
Address: |
JONES, WALKER, WAECHTER, POITEVENT, CARRERE;& DENEGRE, L.L.P.
5TH FLOOR, FOUR UNITED PLAZA, 8555 UNITED PLAZA BOULEVARD
BATON ROUGE
LA
70809
US
|
Family ID: |
37758938 |
Appl. No.: |
11/961622 |
Filed: |
December 20, 2007 |
Current U.S.
Class: |
418/61.3 ;
418/109; 418/166 |
Current CPC
Class: |
F04C 14/22 20130101;
F04C 2/10 20130101 |
Class at
Publication: |
418/61.3 ;
418/109; 418/166 |
International
Class: |
F04C 2/10 20060101
F04C002/10; F04C 14/10 20060101 F04C014/10; F04C 14/22 20060101
F04C014/22 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 22, 2006 |
GB |
GB 0625765.3 |
Claims
1. A pump assembly including a gerotor pump having an inlet and an
outlet, and comprising an annulus and a lobed rotor, one, but not
both, of the rotor or annulus being split axially into two parts,
the pump further comprising indexing means for angularly shifting
one part relative to the other part, the indexing means comprising
a chamber having a first indexing port and a second indexing port,
and a partition which divides the chamber into a first portion
including the first indexing port and a second portion including
the second indexing port, wherein the partition comprises a part
which is pivotally mounted within the chamber for angular movement
within the chamber.
2. A pump assembly according to claim 1 wherein the indexing means
comprises first and second chambers each of which is provided with
a first and second indexing port and a partition which divides the
chamber into a first portion including the first indexing port and
a second volume including the second indexing port, wherein each
partition comprises a part which is pivotally mounted in the
chamber for angular movement between a first orientation and a
second orientation.
3. A pump assembly according to claim 2 wherein the first and
second pivotal partition parts are mounted on a common pivot.
4. A pump assembly according to claim 1 wherein the pivotal part is
rotatable between a first position in which the volume of the first
portion of the chamber is minimised and the volume of the second
portion of the chamber is maximised, and a second position in which
the volume of the first portion of the chamber is maximised and the
volume of the second portion of the chamber is minimised.
5. A pump assembly according to claim 1 wherein the indexing ports
are arranged such that the first indexing port is in communication
with the first portion of the chamber and the second indexing port
is in communication with the second portion of the chamber when the
pivotal part is in either the first position or the second
position.
6. A pump assembly according to claim 5 wherein each of the
indexing ports is located in a recess in a wall of the chamber.
7. A pump assembly according to claim 5 wherein the pivotal part is
provided with a first and second cut out portion which each provide
the pivotal part with an edge which extends around the periphery of
the respective indexing port when the pivotal part is in its first
or second position respectively.
8. A pump assembly according to claim 1 wherein the partition
further includes an angularly fixed part which engages with a
bearing portion of the pivotal part so as substantially to prevent
leakage of fluid between the first portion and the second portion
of the chamber.
9. A pump assembly according to claim 8 wherein the indexing means
includes biasing means which engages with the angularly fixed part
and biases the angularly fixed part into engagement with the
bearing portion of the pivotal part.
10. A pump assembly according to claim 1 wherein the pump has a
single annulus and the rotor being split axially into two parts
such that the pump includes two rotors which are relatively
angularly adjustable.
11. A pump assembly according to claim 10 wherein the first rotor
is angularly fixed with respect to a drive shaft and the second
rotor is movable relative the first rotor.
12. A pump assembly according to claim 11 wherein the second rotor
is mounted on an eccentric mounting part carried by a second shaft
which extends along the annulus axis.
13. A pump assembly according to claim 12 wherein the pivotal part
of the indexing means is mounted on the second shaft, such that
rotation of the pivotal part causes rotation of the shaft and the
eccentric on which the second rotor is mounted.
14. A pump assembly according to claim 1 wherein the first and
second indexing ports are connected to a valve, the valve having a
first inlet port which is connected to a source of pressurised
fluid and exhaust port which is connected to a low pressure fluid
reservoir.
15. A pump assembly according to claim 1 wherein the valve includes
a valve member which is movable between a first position in which
the first indexing port is connected to the exhaust and the second
indexing port is connected to a source of pressurised fluid, and a
second position in which the first indexing port is connected to a
source of pressurised fluid and the second indexing port is
connected to the exhaust port.
16. A pump assembly according to claim 15 wherein the valve further
includes biasing means which biases the valve member into the first
position.
17. A pump assembly according to claim 16 wherein the valve member
is be configured such that pressurised fluid from the first inlet
port acts on the valve member so as to move the valve member from
the first position to the second position when the fluid pressure
at the first inlet port exceeds a predetermined amount.
19. A pump assembly according to claim 16 wherein the valve
includes a second inlet port which is connected to a second source
of pressurised fluid, pressurised fluid from the second inlet port
acting on the valve member so as to move the valve member from the
first position to the second position when the fluid pressure at
the second inlet port exceeds a predetermined value.
Description
[0001] The present invention relates to a pump, in particular to a
variable output internal gerotor pump.
[0002] Variable output internal gerotor pumps comprising an
internally lobed annulus and a male lobed rotor in which one, but
not both, of the annulus or rotor are split axially into two parts,
and in which indexing means are provided for angularly shifting one
part relative to the other, are known, for example from GB 2313411
and EP0565340A. Such angular shifting of one part relative to the
other alters output flow rate of the pump.
[0003] In such known pumps, angular shifting of one part relative
to the other is achieved by means of a rack or worm and pinion
arrangement. In the pump disclosed in EP0565340A, a rack is
provided on a piston rod of a piston provided in a cylinder
connected to a source of pressurised fluid, such as the pump
output. Thus, the relative angular orientation of the two parts can
be achieved by varying the pressure of fluid supplied to the
cylinder. Such rack/worm and pinion arrangements can, however, be
bulky and the inherently elongate nature of the rack or worm can
make the pump difficult to package, particularly in an automotive
engine compartment where space is restricted.
[0004] According to a first aspect of the invention we provide a
pump assembly including a gerotor pump having an inlet and an
outlet, and comprising an annulus and a lobed rotor, one, but not
both, of the rotor or annulus being split axially into two parts,
the pump further comprising indexing means for angularly shifting
one part relative to the other part, the indexing means comprising
a chamber having a first indexing port and a second indexing port,
and a partition which divides the chamber into a first portion
including the first indexing port and a second portion including
the second indexing port, wherein the partition comprises a part
which is pivotally mounted within the chamber for angular movement
between a first orientation and a second orientation.
[0005] The pivotal partition part may be connected directly to one
of the parts of the annulus or rotor, such that rotational movement
of the partition part causes angular movement of one of the parts
relative to the other without the need for an intervening, and
bulky, rack or worm and pinion arrangement.
[0006] The indexing means may comprise first and second chambers
each of which is provided with a first and second indexing port and
a partition which divides the chamber into a first portion
including the first indexing port and a second volume including the
second indexing port, wherein each partition comprises a part which
is pivotally mounted in the chamber for angular movement between a
first orientation and a second orientation. In this case, the first
and second pivotal partition parts are mounted on a common
pivot.
[0007] The pivotal part is preferably rotatable between a first
position in which the volume of the first portion of the chamber is
minimised and the volume of the second portion of the chamber is
maximised, and a second position in which the volume of the first
portion of the chamber is maximised and the volume of the second
portion of the chamber is minimised. In this case, the indexing
ports are preferably arranged such that the first indexing port is
in communication with the first portion of the chamber and the
second indexing port is in communication with the second portion of
the chamber when the pivotal part is in either the first position
or the second position. This ensures that neither of the indexing
ports can be blocked by the pivotal part, when the pivotal part is
at the extreme of its travel. This may be achieved by locating each
of the ports in a recess in a wall of the chamber. Alternatively,
or additionally, this may be achieved by providing the pivotal part
with a first and second cut out portion which each provide the
pivotal part with an edge which extends around the periphery of the
respective indexing port when the pivotal part is in its first or
second position respectively.
[0008] The partition may further include an angularly fixed part
which engages with a bearing portion of the pivotal part so as
substantially to prevent leakage of fluid between the first portion
and the second portion of the chamber. In this case, indexing means
may include biasing means which engages with the angularly fixed
part and biases the angularly fixed part into engagement with the
bearing portion of the pivotal part.
[0009] Preferably, the pump has a single annulus and the rotor
being split axially into two parts such that the pump includes two
rotors which are relatively angularly adjustable.
[0010] In this case, preferably the first rotor is angularly fixed
with respect to a drive shaft and the second rotor is movable
relative the first rotor. Moreover, the second rotor is preferably
mounted on an eccentric mounting part carried by a second shaft
which extends along the annulus axis. Thus, the phase of the second
rotor relative to the first rotor may be shifted by rotation of the
second shaft about the annulus axis.
[0011] The pivotal part of the indexing means may be mounted on the
second shaft, such that rotation of the pivotal part causes
rotation of the shaft and the eccentric on which the second rotor
is mounted. Thus, by virtue of this arrangement, the volume
occupied by the indexing means is minimised.
[0012] The first and second indexing ports are preferably connected
to a valve, the valve having a first inlet port which is connected
to a source of pressurised fluid and exhaust port which is
connected to a low pressure fluid reservoir. The valve may include
a valve member which is movable between a first position in which
the first indexing port is connected to the exhaust and the second
indexing port is connected to a source of pressurised fluid, and a
second position in which the first indexing port is connected to a
source of pressurised fluid and the second indexing port is
connected to the exhaust port. The valve preferably further
includes biasing means which biases the valve member into the first
position.
[0013] The valve member may be configured such that pressurised
fluid from the first inlet port acts on the valve member so as to
move the valve member from the first position to the second
position when the fluid pressure at the first inlet port exceeds a
predetermined amount. Alternatively, the valve may include a second
inlet port which is connected to a second source of pressurised
fluid, pressurised fluid from the second inlet port acting on the
valve member so as to move the valve member from the first position
to the second position when the fluid pressure at the second inlet
port exceeds a predetermined value.
[0014] Embodiments of the invention will now be described, by way
of example only, with reference to the drawings, of which:
[0015] FIG. 1 is an illustration of cross-section through a pump
according to the invention;
[0016] FIG. 2 is an illustration of a first embodiment of indexing
means for the pump illustrated in FIG. 1;
[0017] FIG. 3 is a schematic illustration of the indexing means of
FIG. 2, along with a valve via which fluid is supplied to the
indexing means, the indexing means being in a) a first position and
b) a second position;
[0018] FIG. 4 is a schematic illustration of an alternative
embodiment of indexing means and valve, the indexing means being a)
in a first position, and b) in a second position; and
[0019] FIG. 5 is a schematic illustration of a further alternative
embodiment of indexing means and valve, the indexing means being a)
in a first position, and b) in a second position.
[0020] Referring now to FIG. 1 there is shown a gerotor pump 10
having an inlet 12 and an outlet 14, and comprising an annulus 16
and first 18 and second 20 male lobed rotors. The annulus 16 is
provided with a plurality of internal lobes with which the lobes of
the rotors 18, 20 mesh, the rotors 18, 20, in this example, each
having one fewer lobe than the annulus 16. It will, of course, be
appreciated that the rotors 18, 20 may have more than one fewer
lobes than the annulus 16.
[0021] The first rotor 18 is mounted fast and centrally on a drive
shaft 22 such that the axis of the rotor 18 coincides with the
longitudinal axis A of the drive shaft 22, and movement of the
rotor 18 with respect to the drive shaft 22 is substantially
prevented. The drive shaft 22 is connected to a prime mover,
typically an internal combustion engine, but could be driven by an
electric motor. In this example, the prime mover is connected to
the drive shaft by means of a drive gear 24.
[0022] The second rotor 20 is mounted fast on bearing 27, the
bearing 27 being rotatably mounted on the eccentric 26, rotation of
the second rotor 20 with respect to the eccentric 26 thus being
permitted. The eccentric 26 is in turn integral with a second shaft
28, such that the axis B of the second rotor 20 is parallel to but
spaced from the longitudinal axis C of the second shaft 28. It will
be appreciated, of course, that the eccentric 26 may be mounted
fast on the second shaft 28, and these two components need not be
integral.
[0023] The drive shaft 22 is supported in bearing 32 provided in a
pump housing 30a, and the second shaft 28 is supported in bearing
34 provided in a pump housing cover 30b. The bearings 32, 34 may
each include a seal assembly which substantially prevents fluid
from leaking out of the housing 30 around the shaft 22, 28, but the
seal assembly may be omitted, particularly if the pump is located
in a "wet" environment such as an oil sump.
[0024] The housing 30a and cover 30b form a housing assembly 30
which surround the annulus 16, and prevents significant
translational movement of the annulus 16 whilst permitting rotation
of the annulus 16 relative to the housing assembly 30. The axis of
rotation of the annulus 16 coincides with longitudinal axis C of
the second shaft, and is therefore off-set relative to the axes of
rotation A, B of the rotors 18, 20 such that the lobes of the
rotors 18, 20 mesh with the internal lobes of the annulus 16.
[0025] As will be appreciated from the applicant's previous
applications, GB2313411 and EP0565340, as result of the meshing of
the lobes of the first rotor 18 with the internal lobes of the
annulus 16, rotation of the drive shaft 22 and the first rotor 18
causes the annulus 16 to rotate, which in turn causes the second
rotor 20 to rotate as a result of meshing of the lobes of the
second rotor 20 with the internal lobes of the annulus 16. Chambers
formed between the lobes of the rotors 18, 20 and the annulus 16
change in volume as the annulus 16 and rotors 18, 20 rotate, the
chambers increasing in volume in during a first half of the
rotation and decreasing in volume during the second half of the
rotation.
[0026] The pump inlet 12 is positioned in the housing assembly 30
so that it is adjacent to the chambers between the first rotor 18
and the annulus 16 as these increase in volume, so that fluid at
the inlet 12 is drawn into the chambers, whilst the pump outlet 14
is positioned in the housing so that it is adjacent to the chambers
between the first rotor 18 and the annulus 16 as these decrease in
volume, so that fluid in the chambers is ejected through the outlet
14.
[0027] As is explained in detail in GB2313411 and EP0565340, when
the second shaft is arranged such that the axis B of the second
rotor 20 coincides with the axis of rotation of the first rotor 18,
as illustrated in FIG. 1, the rotors are in phase, and their lobes
are in the same angular relationship to one another. When the pump
10 is operated in this configuration, the flow rate of pumped fluid
is maximum for any given speed of rotation of the drive shaft 22.
Rotation of the second shaft 28 causes the second rotor 20 to move
out of phase with the first rotor 18, so that its axis B is no
longer coincident with the axis of rotation A of the first rotor,
and the flow rate of pumped fluid at a given speed of rotation of
the drive shaft 22 decreases. Thus, the flow rate of pumped fluid
can be varied whilst the pump speed remains constant simply by
rotation of the second shaft 28. This is known as indexing of the
pump 10, and the second rotor 20 is known as the indexing
rotor.
[0028] In accordance with the present invention, in order to
achieve such indexing, the pump 10 is provided with indexing means
36 comprising a chamber 38 having a first indexing port 40 and a
second indexing port 42, and a partition 44 which divides the
chamber 38 into a first portion 38a including the first indexing
port 40 and a second portion 38b including the second indexing port
42, the partition 44 comprising a part 46 which is pivotally
mounted within the chamber 38 for angular movement relative to the
chamber 38 between a first position in which the volume of the
first portion 38a of the chamber 38 is minimised and the volume of
the second portion 38b of the chamber 28 is maximised and a second
position in which the volume of the first portion 38a of the
chamber 38 is maximised, and the volume of the second portion 38b
of the chamber 38 is minimised.
[0029] A first embodiment of indexing means 36 is illustrated in
FIG. 2, and FIGS. 3a and 3b. In this embodiment, the chamber 38 is
generally wedge shaped and uppermost and lowermost generally
parallel walls, and three side walls which extend generally normal
to the lowermost and uppermost walls, of which a first side wall
48a is arcuate, and the second 48b and third 48c side walls are
generally straight and arranged at an angle of around 120.degree.
to one another. The chamber 38 thus forms a sector of a circle
subtending an angle of around 120.degree.. The second 48b and third
48c side walls do not, however, meet at a point, as a
part-cylindrical recess is provided at the intersection of the
second and third side walls, the part-cylindrical recess
accommodating a pivotally mounted cylindrical pin 50 from which
extends a vane 52. The pin 50 and vane 52 extend between the
lowermost wall and the uppermost wall of the chamber 38, and from
the sidewall in the part cylindrical recess to the first side wall
48a of the chamber 38, so that together, the pin 50 and vane 52
form the partition 44 which divides the chamber 38 into the first
38a and second 38b portions. When the partition 44 is in its first
position, as illustrated in FIG. 3a, the vane 52 engages with the
second sidewall 48b, and when the partition 44 is in its second
position, the vane 52 engages with the third sidewall 38c, as
illustrated in FIGS. 2 and 3b. The pin 50 and vane 52 are fitted
sufficiently close to the chamber walls 48a, 48b, 48c so as
substantially to prevent flow of fluid between the first 38a and
second 38b portions of the chamber 38, whilst not being so tightly
fitted that rotational movement of the partition 44 within the
chamber 38 is prevented.
[0030] Two further recesses are provided in the chamber wall in
which are located the indexing ports 40, 42. The first indexing
port 40 is located in a first recess at the intersection between
the first sidewall 48a and the second sidewall 48b and the second
indexing port 42 is located at the intersection between the first
sidewall 48a and the third sidewall 48c. It will be appreciated
that the location of the indexing ports 40, 42 in such recesses
prevents either port from being blocked by the vane 52 when it
engages with the second 48a or third sidewall 48b when in either
the first or second position.
[0031] In this example, the pin 50, second shaft 28 and eccentric
26 are integral, the chamber 38 is provided in the housing cover
30b adjacent the indexing rotor 20, and the pin 50 is provided by
an end of the second shaft 28 which extends into the chamber 38. By
virtue of this arrangement, the indexing means 36 need not
contribute to any significant increase in pump size.
[0032] As will be appreciated rotation of the partition 44 within
the chamber 38 causes the second shaft 28 to rotate, and the phase
of the indexing rotor 20 relative to the first rotor 18 to change.
In this example, the pin 50 and vane 52 are arranged such that when
the partition 44 is in the first position the indexing rotor 20 is
in phase with the first rotor 18, and the flow rate of fluid pumped
by the pump 10 at any given drive shaft speed to be maximum.
Similarly, when the partition 44 is in the second position, the
indexing rotor 20 is around 120.degree. out of phase with the first
rotor 18 and the flow rate of fluid pumped by the pump 10 at any
given drive shaft speed is at a minimum. It will be appreciated
that the angle subtended by the second 38b and third 38c sidewalls
of the chamber 38 may be varied up to around 180.degree. so as to
vary the maximum angular shift of the indexing rotor 20 relative to
the first rotor 18, and hence alter the flow rate range of the pump
10. For example, if the second 48b, and third 48c sidewalls of the
chamber 38 are parallel, movement of the partition 44 to the second
position, may bring the indexing rotor 20 180.degree. out of phase
with the first rotor 18.
[0033] A second embodiment of indexing means 36 is illustrated in
FIGS. 4a and 4b. In this embodiment, the chamber 38 is disc-shaped,
having circular uppermost and lowermost surfaces, and a cylindrical
side wall 48a', and the partition 44 comprises a fixed vane 54
which extends radially into the chamber 38 from a retaining slot 55
provided in the chamber walls, and bears against a generally
semi-circular bearing surface 56 of the pivotal part 46 of the
partition 44. The vane 54 is biased into engagement with the
bearing portion 56 by means of a helical compression spring 57
which is mounted in the retaining slot 55, such that leakage of
fluid between the fixed vane 54 and the bearing portion 56 is
substantially prevented. It will be appreciated, of course, that
the biasing means need not be a helical compression spring. It may
be, for example, a leaf spring or hydraulic fluid may be used to
urge the fixed valve 54 into engagement with the bearing portion
56.
[0034] The pivotal part 46 of the partition 44 further includes a
virtually semicircular barrier portion 58 with substantially the
same radius as the chamber 38. The radius of the bearing surface 56
is substantially less than the radius of the barrier portion 58 and
the chamber 38, and therefore the pivotal part 46 includes two
generally straight edges 60a, 60b which, in this example, are
generally parallel, and which extend virtually radially between the
bearing surface 56 and the outermost semi-circular edge of the
barrier portion 58.
[0035] The pivotal part 46 is mounted fast on an end of the second
shaft 28 which extends into the chamber 38 through an aperture at
the centre of the circular lowermost surface of the chamber 38,
movement of the pivotal part 46 relative to the second shaft 28
being substantially prevented. The second shaft 28 is positioned
such that the distance between the second shaft 28 and the bearing
surface 56 is generally constant over the entire extent of the
bearing surface 56, and the distance between the second shaft 28
and the outermost semicircular edge of the barrier portion 58 is
generally constant over the entire extent of the barrier portion
58. Thus, the outermost edge of the barrier portion 58 bears
against the cylindrical sidewall 48a' of the chamber 38 to provide
a substantially fluid tight seal whilst permitting rotation of the
pivotal part 46 relative to the chamber 38.
[0036] The pivotal part 46 thus extends from the fixed vane 54 to
the cylindrical sidewall 48a' of the chamber 38, and both the
pivotal part 46 and the fixed vane 54 extend between the lowermost
and uppermost chamber walls. The pivotal part 46 and the fixed vane
54 together divide the chamber 38 into first 38a and second 38b
portions, and substantially prevent flow of fluid between the first
38a and second 38b portions. The pivotal part 46 is rotatable
through 180.degree. between a first position in which its first
straight edge 60a engages with a first side of the fixed vane 54,
as illustrated in FIG. 4a, a second position in which its second
straight edge 60b engages with a second side of the fixed vane 54
as illustrated in FIG. 4b. When the pivotal part 46 is in the first
position, the volume of the first portion 38a of the chamber 38 is
minimised and the volume of the second portion 38b of the chamber
38 is maximised. Similarly, when in the pivotal part 46 is in the
second position, the volume of the first portion 38a of the chamber
38 is maximised and the volume of the second portion 38b of the
chamber 38 is minimised.
[0037] The indexing ports 40, 42 are provided in the lowermost
circular chamber wall, directly adjacent the cylindrical side wall
48a', one either side of the fixed vane 54. The pivotal part 46 of
the partition 44 include two cut-out portions 62a,62b at the
intersection between the outmost edge of the barrier portion 58 and
the straight edges 60a, 60b. The edges of the barrier portion 58
surround the indexing ports 40, 42 so that the barrier portion 58
does not block the first indexing port 40 when the pivotal part 56
is in the first position or the second indexing port 42 when the
pivotal part 56 is in the second position.
[0038] By virtue of mounting the pivotal part 46 on the second
shaft 28, rotation of the partition 44 within the chamber 38 causes
the second shaft 28 to rotate, and the phase of the indexing rotor
20 relative to the first rotor 18 to change. In this example, the
pin 50 and vane 52 are arranged such that when the partition 44 is
in the first position the indexing rotor 20 is in phase with the
first rotor 18, and the flow rate of fluid pumped by the pump 10 at
any given drive shaft speed to be maximum. Similarly, when the
partition 44 is in the second position, the indexing rotor 20 is
around 180.degree. out of phase with the first rotor 18 and the
flow rate of fluid pumped by the pump 10 at any given drive shaft
speed is at a minimum.
[0039] It will, of course, be appreciated that the partition 44 may
be configured such that the straight edges 60a, 60b are not
parallel, so as to vary the degree of rotational movement through
which the partition 44 can turn, and hence the degree of indexing
provided.
[0040] In both embodiments of indexing means 36, rotation of the
pivotal part 46 of the partition 44 is achieved by the supply of
pressurised fluid to the indexing ports 40, 42. The partition 44 is
moved from the first position to the second position by the supply
of pressurised fluid at the first inlet 40, the pressurised fluid
filling the first portion 38a of the chamber 38 as the volume of
the first portion 38a of the chamber 38 increases. Return of the
partition 46 to the first position is achieved by the supply of
pressurised fluid at the second inlet 42, the pressurised fluid
filling the second portion 38b of the chamber 38 as the volume of
the second portion 38b of the chamber 38 increases, and allowing
the fluid in the first portion 38a of the chamber 38 to be ejected
through the first indexing port 40.
[0041] The first and second indexing ports 40, 42 are connected to
a valve 64, the valve 64 having a first inlet port 66 which is
connected to a source of pressurised fluid and exhaust port 68
which is connected to a low pressure fluid reservoir. The valve 64
may include a valve member 70 which is movable between a first
position in which the first indexing port 40 is connected to the
exhaust port 68 and the second indexing port 42 is connected to the
source of pressurised fluid, and a second position in which the
first indexing port 40 is connected to the source of pressurised
fluid and the second indexing port 42 is connected to the exhaust
port 68. The valve 64 also includes a biasing means, in this
example a helical compression spring 72, which biases the valve
member 70 into the first position.
[0042] A first embodiment of valve 64 is illustrated in FIGS. 3a
and 3b, and corresponds to the shuttle valve shown and described in
EP0565340. The inlet port 66 of this valve is adapted to be
connected to either the pump outlet 14, or, where the pump 10 is
used to pump lubricant to a main lubricating gallery, or rifle, of
an internal combustion engine, to the main lubricating gallery.
Thus, when the valve member 70 is in the first position,
pressurised fluid from the pump outlet, main gallery or any other
suitable point in the lubrication system, is supplied to the second
indexing port 42, whilst the first indexing port 40 is connected to
the low pressure fluid reservoir, the partition 44 of the indexing
means 36 adopts the first position, as illustrated in FIG. 3a, and
the indexing rotor 20 is in phase with the first rotor 18. The flow
rate of fluid pumped by the pump 10 is therefore at its maximum for
a given drive speed, and will increase as the drive speed
increases.
[0043] The spring 72 is selected such that the pressurised fluid at
the valve inlet 66 can overcome biasing force of the spring 72 and
move the valve member 70 from the first position to the second
position, as illustrated in FIG. 3b, when the fluid pressure at the
pump outlet 14 or in the main lubricating gallery exceeds a
predetermined amount. When the valve member 70 moves to the second
position, pressurised fluid from the pump outlet or main gallery is
supplied to the first indexing port 40, whilst the second indexing
port 42 is connected to the low pressure fluid reservoir, the
partition 44 of the indexing means 36 moves to the second position,
and the indexing rotor 20 is moved out of phase with the first
rotor 18. Thus, when the fluid pressure at the pump outlet or main
gallery exceeds a predetermined amount, the flow rate of fluid
pumped by the pump 10 decreases.
[0044] This decrease in flow rate of pumped fluid will, of course,
result in a decrease in fluid pressure at the pump outlet 14 or
main gallery, which in turn causes the valve member 70 to return to
the first position, and the rotors 18, 20 to be brought back into
phase. In practice, therefore, the valve member will oscillate
between the first and second positions, and the partition 46 of the
indexing means 44 will attain an equilibrium position between its
first and second positions. Further increases in drive speed will
alter this equilibrium position, driving the rotors 18, 20 further
out of phase, and the flow rate of pumped fluid, and pressure at
the pump outlet or in the main gallery, will reach a plateau.
[0045] A second embodiment of valve 64 is illustrated in FIGS. 4a
and 4b, and corresponds to the spool valve shown and described in
UK application number GB0606210.3. This operates to cap the flow
rate of pumped fluid in much the same way as the first embodiment
of valve 64, but in this embodiment, the valve inlet 66 is
connected to the main gallery, and a second valve inlet 74 is
connected to the pump outlet 14. The valve member 70 is configured
such that when in its first position, as illustrated in FIG. 4a,
the second indexing port 42 is connected to the pump outlet 14
whilst the first indexing port 40 is connected to the low pressure
fluid reservoir via a second exhaust port 68', and when in its
second position, as illustrated in FIG. 4b, the first indexing port
40 is connected to the pump outlet 14 whilst the second indexing
port 42 is connected to the low pressure fluid reservoir via the
first exhaust port 68, the valve member 70 being moved from the
first position to second position when the fluid pressure in the
main gallery is sufficient to overcome the biasing force of the
spring 72.
[0046] As explained in GB0606210.3, this embodiment of valve member
has advantages that the pressure at which the flow rate of pumped
fluid plateaus is determined by the fluid pressure in the main
gallery, but no fluid is drawn from the main gallery in achieving
indexing of the pump 10, and that the fluid pressure available for
indexing of the pump 10 is the maximum pressure in the system, i.e.
that at the pump outlet.
[0047] It should be appreciated that whilst the two embodiments of
valve 64 described above are actuated by means of fluid pressure
acting against the biasing force of a spring 72, the valves 64 may
alternatively be partially or completely electrically actuated. In
the case of a partially electrically actuated valve, an electrical
solenoid is used to adjust the spring resistance so that the fluid
pressure required to move the valve member 70 is altered, whereas
in a completely electrically actuated valve, the use of fluid
pressure to move the valve member 70 is dispensed with, and
movement of the valve member 70 is achieved using an electrical
solenoid.
[0048] A third embodiment of indexing means is shown in FIGS. 5 a
and 5b, and includes first and second wedge shaped chambers 38,
38', each of which is provided with a first 40, 40' and second 42,
42' indexing port and a partition 44 which divides each chamber
into a first portion 38a, 38a' including the first indexing port
40, 40' and a second portion 38b, 38b' including the second
indexing port 42, 42'. Each partition 44 comprises a vane 52, 52',
the vanes 52, 52' extending diametrically opposite one another from
a common pivot 50 which is connected to the second shaft 28 as
previously described in relation to the first and second
embodiments of indexing means. The vanes 52, 52' are thus pivotally
mounted in the chambers 38, 38' for angular movement between a
first orientation, in which the volume of the first portion 38a,
38a' of the chamber 38, 38' is minimised and the volume of the
second portion 38b, 38b' of the chamber 38, 38' is maximised (as
illustrated in FIG. 5a), and a second orientation in which the
volume of the first portion 38a, 38a' is maximised and the volume
of the second portion 38b, 38b' is minimised (as shown in FIG.
5b).
[0049] This embodiment of indexing means is shown in FIGS. 5a and
5b as being connected to a valve 64 of the type described above in
relation to FIGS. 3a and 3b. It will be appreciated, however, that
this embodiment of indexing means could equally be connected to the
type of valve 64 described above in relation to FIGS. 4a and 4b.
The first indexing ports 40, 40' are connected to the valve such
that when the valve member 70 is in a first position, the first
indexing ports 40, 40' are connected to the exhaust port 68 and the
second indexing ports 42, 42' are connected to the source of
pressurised fluid 66. Fluid pressure at the second indexing ports
42, 42' thus acts on the vanes 52, 52' and causes the indexing
means to adopt the first position shown in FIG. 5a. When the valve
member 70 is in a second position, the first indexing ports 40, 40'
are connected to the source of pressurised fluid 66 whilst the
second indexing ports 42, 42' are connected to the exhaust port 68.
Fluid pressure at the first indexing ports 40, 40' thus acts on the
vanes 52, 52' and causes the indexing means to adopt the second
position shown in FIG. 5b.
[0050] It will be appreciated that, by virtue of providing two
vanes 52, 52' mounted on a common pivot the force available for
actuating the indexing means at a given fluid pressure, can be
doubled without significantly increasing the size and volume
occupied by the indexing means.
[0051] The vanes 52, 52' may be integral with the pivot 50, or may
be separate from the pivot 50. In the latter case, preferably the
vanes 52, 52' are formed from a single part mounted in a slot in
the pivot 50 so that movement of the vanes 52, 52' along the length
of the slot is permitted. This configuration allows the vanes 52,
52' to float in the slot, and adjust their position to accommodate
any irregularities in the shape of the indexing chambers 38, 38'
and to achieve optimum positioning in the indexing chambers 38,
38'.
[0052] When used in this specification and claims, the terms
"comprises" and "comprising" and variations thereof mean that the
specified features, steps or integers are included. The terms are
not to be interpreted to exclude the presence of other features,
steps or components.
[0053] The features disclosed in the foregoing description, or the
following claims, or the accompanying drawings, expressed in their
specific forms or in terms of a means for performing the disclosed
function, or a method or process for attaining the disclosed
result, as appropriate, may, separately, or in any combination of
such features, be utilised for realising the invention in diverse
forms thereof.
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