U.S. patent application number 13/432060 was filed with the patent office on 2012-10-04 for internal gear pump.
This patent application is currently assigned to Magna Steyr Fahrzeugtechnik AG & Co KG. Invention is credited to Michael Haid, Franz MAYR.
Application Number | 20120251370 13/432060 |
Document ID | / |
Family ID | 45851408 |
Filed Date | 2012-10-04 |
United States Patent
Application |
20120251370 |
Kind Code |
A1 |
MAYR; Franz ; et
al. |
October 4, 2012 |
INTERNAL GEAR PUMP
Abstract
An internal gear pump for delivering a fluid, in particular one
of the gerotor pump type, having a driven gear wheel, a rotatable
annular gear interacting with the gear wheel, and a substantially
cylindrical housing, in which the gear wheel and the annular gear
are arranged. The housing has a base portion, an annular portion
and a cover portion, the base portion having a pressure port, which
forms a delivery chamber of the pump or opens into the latter. A
thrust ring is arranged between the gear wheel and the annular gear
on the one hand and the cover portion of the housing on the other.
At least one connecting passage on or in the housing of the pump
extends from the delivery chamber of the pump up to a gap between
the thrust ring and the cover portion of the housing, in order to
carry fluid from the delivery chamber into the gap.
Inventors: |
MAYR; Franz; (St. Marein bei
Graz, AT) ; Haid; Michael; (Graz, AT) |
Assignee: |
Magna Steyr Fahrzeugtechnik AG
& Co KG
Graz
AT
|
Family ID: |
45851408 |
Appl. No.: |
13/432060 |
Filed: |
March 28, 2012 |
Current U.S.
Class: |
418/61.3 |
Current CPC
Class: |
B60Q 1/2669 20130101;
B60Q 3/267 20170201 |
Class at
Publication: |
418/61.3 |
International
Class: |
F04C 2/10 20060101
F04C002/10 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 1, 2011 |
DE |
DE 10 2011 017 37 |
Claims
1. A gear pump for delivering a fluid, comprising: a driven gear
wheel; a rotatable annular gear operatively communicating with the
driven gear wheel; a housing in which the driven gear wheel and the
rotatable annular gear are arranged, the housing comprising a base
portion, an annular portion and a cover portion, the base portion
having a pressure port which forms a fluid delivery chamber; a
thrust ring arranged between the driven gear wheel and the
rotatable annular gear and also the driven gear wheel and the cover
portion; a gap formed between the thrust ring and the cover
portion; and at least one fluid connecting passage extending from
the fluid delivery chamber up to the gap in order to carry fluid
from the delivery chamber into the gap.
2. The gear pump of claim 1, wherein the connecting passage
comprises at least one connecting groove which extends along the
inner circumference of the annular portion of the housing.
3. The gear pump of claim 2, wherein the connecting groove along
the inner circumference of the annular portion is aligned parallel
to the axis of rotation of the rotatable annular gear.
4. The gear pump of claim 1, wherein the connecting passage
comprises a connecting groove which extends from the delivery
chamber of the pump along the base portion of the housing.
5. The gear pump of claim 1, wherein the connecting passage opens
into an annular groove which extends circumferentially along a
transition between the annular portion and the cover portion of the
housing and along the thrust ring.
6. The gear pump of claim 1, wherein the cover portion of the
housing comprises at least one distribution groove which extends
radially inward on the inside surface of the cover portion.
7. The gear pump of claim 6, wherein the distribution groove of the
cover portion extends radially inward from the outer circumference
of the cover portion to a central aperture of the cover
portion.
8. The gear pump of claim 1, wherein the thrust ring comprises at
least one distribution groove which on the side of the thrust ring
facing the cover portion of the housing extends radially inward
from the outer circumference of the thrust ring.
9. The gear pump of claim 8, wherein the distribution groove of the
thrust ring extends radially inward from the outer circumference of
the thrust ring to a central aperture of the thrust ring.
10. The gear pump of claim 1, wherein the surface of the thrust
ring facing the cover portion of the housing is one of tapered,
truncated cone shape, and convexly curved.
11. The gear pump of claim 1, wherein the housing comprises an
outlet port configured to conduct a proportion of the fluid,
carried out of the delivery chamber towards the gap, to another
component to thereby lubricate the component.
12. The gear pump of claim 1, wherein the thrust ring extends in
one piece in a radial direction between the driven gear wheel and
the rotatable annular gear.
13. The gear pump of claim 1, wherein the thrust ring is
rotationally fixed to the annular gear.
14. The gear pump of claim 1, wherein the rotatable annular gear
and the thrust ring are integrally formed.
15. A gear pump for a gerotor pump, the gear pump comprising: a
gear wheel which is rotatable about a first axis; an annular gear
which is rotatable about a second axis; a thrust ring rotationally
fixed to the annular gear; a housing which houses the gear wheel,
the annular gear and the thrust ring, the housing having a fluid
delivery chamber and a cover portion; a gap formed between the
thrust ring and the cover portion; and a fluid connecting passage
in the housing through which fluid flows from the fluid delivery
chamber to the gap to thereby form a hydrodynamic lubricating film
in the gap which reduces operational friction between the thrust
ring and the cover portion.
16. The gear pump of claim 15, wherein the fluid connecting passage
comprises: a first connecting groove extending radially and in
communication with the fluid delivery chamber; a second connecting
groove extending axially and in communication with the first
connecting groove; and a third connecting groove extending radially
and in communication with the second connecting groove and the
gap.
17. The gear pump of claim 15, wherein the thrust ring has a
plurality of distribution grooves on a surface thereof which faces
the gap and which are configured to distribute the fluid into the
gap.
18. The gear pump of claim 17, wherein the plurality of
distribution grooves extend from an outer circumference to an inner
circumference of the thrust ring portion.
19. The gear pump of claim 17, wherein the plurality of
distribution grooves extend from an outer circumference of the
thrust ring portion to a predetermined distance from the inner
circumference of the thrust ring portion.
20. A gear pump comprising: a gear wheel; an annular gear; a thrust
ring; a housing having a fluid delivery chamber and a cover portion
configured for placement such that a gap is formed between the
thrust ring and the cover portion; and a fluid connecting passage
through a fluid flows from the fluid delivery chamber to the gap to
thereby form a hydrodynamic lubricating film in the gap which
reduces operational friction between the thrust ring and the cover
portion, wherein: the fluid connecting passage has a first
connecting groove in communication with the fluid delivery chamber,
a second connecting groove in communication with the first
connecting groove, and a third connecting groove in communication
with the second connecting groove and the gap, and the thrust ring
has a plurality of distribution grooves on a surface thereof which
faces the gap and which are configured to distribute the fluid into
the gap.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority under 35 U.S.C.
.sctn.119 to German Patent Application No. 10 2011 017 374 (filed
on Apr. 1, 2011), which is hereby incorporated by reference in its
entirety.
FIELD OF THE INVENTION
[0002] The invention relates to an internal gear pump for
delivering a fluid, in particular one of the gerotor pump type.
BACKGROUND OF THE INVENTION
[0003] Such an internal gear pump has a driven gear wheel (also
referred to as an inner rotor) and an annular gear (also referred
to as an external rotor) interacting with the gear wheel, the
annular gear having at least one tooth more than the gear
wheel.
[0004] FIG. 7 illustrates a cross-sectional view of a conventional
gerotor pump 101 (also referred to as an annular gear pump). The
pump 101 has a substantially cylindrical housing having an annular
portion 103. An annular gear 105 is supported on the circular inner
circumference of the annular portion 103 so that it is free to
rotate about an axis A1. A gear wheel 107, which is driven by way
of a drive shaft (not shown) to rotate clockwise about an axis A2,
for example, is arranged radially inside the annular gear 105 and
eccentrically in relation to the annular gear 105. The gear wheel
107 has an external toothing, and the annular gear 105 has an
internal toothing with a greater number of teeth than that of the
gear wheel 107. The gear wheel 107 meshes with the annular gear 105
and thereby drives the annular gear 105 to rotate. Owing to the
greater number of teeth, however, the annular gear 105 rotates more
slowly than the gear wheel 107.
[0005] Also illustrates in FIG. 7 are a suction port 109 and a
pressure port 111, which are formed on a base portion 113 of the
pump housing, on which the annular gear 105 and the gear wheel 107
rest. Axially offset from the base portion 113 relative to the axes
A1, A2, the annular gear 105 and the gear wheel 107 are covered by
a cover portion of the housing (not shown). Due to the rotation of
the gear wheel 107 relative to the housing (annular portion 103,
base portion 113 and cover portion), rotating pump chambers of
variable volume, into which a fluid is drawn from the suction port
109, are formed between the gear wheel 107 and the annular gear
105. The fluid is finally expelled into a pressure chamber 115 of
the pump 101, into which the pressure port 111 opens or which is
formed by the pressure port 111 itself.
[0006] One particular problem of such an internal gear pump is the
friction between the gear wheel 107 and the annular gear 105 on the
one hand and the surrounding portions of the housing on the other.
This friction causes an unwanted loss of power, which is
accompanied by a heating and impairment of the fluid.
[0007] German Patent Publication DE 43 15 432 A1, therefore,
discloses the arrangement of a thrust ring, which is rotationally
fixed to the rotating annular gear, between the gear wheel and the
annular gear on the one hand and the cover portion of the housing
on the other. The thrust ring reduces the power loss by virtue of a
reduction in the differential speed and hence a reduction in the
friction. In particular, the thrust ring may be composed of a
material having a low coefficient of friction, or it may be
provided with a coating of a material having a low coefficient of
friction. This is comparatively costly, however, and even then
still does not bring about the feasible reduction of the friction
losses consistent with cost-effective manufacturing.
SUMMARY OF THE INVENTION
[0008] An object of the invention is to create an internal gear
pump of said type, which being of simple construction exhibits a
low degree of friction between the gear wheel and the annular gear
on the one hand and the housing on the other.
[0009] A further object of the invention is to stabilize the
alignment of the gear wheel.
[0010] At least these objects are achieved by an internal gear pump
that includes at least the following: a thrust ring arranged
between a gear wheel and an annular gear on the one hand and a
cover portion of the housing on the other, at least one connecting
passage on or in the housing of the pump extending from the
delivery chamber of the pump up to a gap between the thrust ring
and the cover portion of the housing, in order to carry fluid from
the delivery chamber into the gap.
[0011] At least these objects are further achieved by an internal
gear pump that includes at least the following: a driven gear
wheel; a rotatable annular gear operatively communicating with the
driven gear wheel; a housing in which the driven gear wheel and the
rotatable annular gear are arranged, the housing comprising a base
portion, an annular portion and a cover portion, the base portion
having a pressure port which forms a fluid delivery chamber; a
thrust ring arranged between the driven gear wheel and the
rotatable annular gear and also the driven gear wheel and the cover
portion; a gap formed between the thrust ring and the cover
portion; and at least one fluid connecting passage extending from
the fluid delivery chamber up to the gap in order to carry fluid
from the delivery chamber into the gap.
[0012] At least these objects are also achieved by an internal gear
pump that includes at least the following: a gear wheel which is
rotatable about a first axis; an annular gear which is rotatable
about a second axis; a thrust ring rotationally fixed to the
annular gear; a housing which houses the gear wheel, the annular
gear and the thrust ring, the housing having a fluid delivery
chamber and a cover portion; a gap formed between the thrust ring
and the cover portion; and a fluid connecting passage in the
housing through which fluid flows from the fluid delivery chamber
to the gap to thereby form a hydrodynamic lubricating film in the
gap which reduces operational friction between the thrust ring and
the cover portion.
[0013] At least these objects are further achieved by an internal
gear pump that includes at least the following: a gear wheel; an
annular gear; a thrust ring; a housing having a fluid delivery
chamber and a cover portion configured for placement such that a
gap is formed between the thrust ring and the cover portion; and a
fluid connecting passage through a fluid flows from the fluid
delivery chamber to the gap to thereby form a hydrodynamic
lubricating film in the gap which reduces operational friction
between the thrust ring and the cover portion. The fluid connecting
passage has a first connecting groove in communication with the
fluid delivery chamber, a second connecting groove in communication
with the first connecting groove, and a third connecting groove in
communication with the second connecting groove and the gap. The
thrust ring has a plurality of distribution grooves on a surface
thereof which faces the gap and which are configured to distribute
the fluid into the gap.
[0014] Between the thrust ring and the inside of the cover portion
of the housing facing the thrust ring a gap is formed, which may
extend over the entire surface of the thrust ring or merely a part
thereof. A connecting passage on or in the housing of the pump
leads from the delivery chamber of the pump up to the gap, in
particular right behind the thrust ring, when viewed from the base
portion of the housing. The pressurized fluid can therefore flow
from the delivery chamber up to the gap, in order to build up a
hydraulic pressure between the thrust ring and the cover portion of
the housing and to form a hydrodynamically effective lubricating
film as the thrust ring rotates.
[0015] It is possible here that the gap will only actually be
formed by the pressurized fluid flowing in between the thrust ring
and the cover portion of the housing. In other words, although the
thrust ring may rest directly on the cover portion of the housing
when the pump is at a standstill, when the pump is in operation it
is important that a minimum clearance be provided between the
thrust ring and the cover portion of the housing, in order to allow
the formation of a fluid cushion or a lubricating film. For this
purpose the fluid delivered by the pump is specifically carried
along the connecting passage up to the gap between the rotor disc
and the cover portion of the housing, the pressurized fluid, when
necessary, being structurally configured to lift the thrust ring
off slightly from the cover portion of the housing.
[0016] This results in a hydrodynamic lubrication, which serves to
reduce the power loss still further. The additional design cost is
minimal, since the connecting passage can be formed on or in the
pump housing through simple production operations. A further
advantage consists in that feeding the pressurized fluid to the
rear side of the thrust ring exerts a force, which serves to reduce
or even avoid any tilting or wobbling of the gear wheel.
Furthermore, the specifically diverted fluid serves for
hydraulically centring the annular gear, thereby increasing the
service life of the pump still further.
[0017] The thrust ring is preferably rotationally fixed to the
annular gear. In particular, the annular gear and the thrust ring
may be integrally formed. Alternatively, however, the thrust ring
may also be rotatably coupled to the gear wheel, or the thrust ring
is "floating," that is to say, supported so that it is free to
rotate.
[0018] Where, in connection with the pump in accordance with the
invention, reference is made to a "base portion" of the housing,
this relates to the portion of the housing on which the pressure
port is provided, which opens into the delivery chamber of the pump
or which forms the delivery chamber. Where reference is made to a
"cover portion" of the housing, this relates to the portion of the
housing on which the thrust ring rests. In other words, the terms
"base portion" and "cover portion" of the housing are used
irrespective of whether the "base portion" in the pump installation
position is arranged on an underside or an upper side of the pump,
for example.
[0019] The connecting passage may be formed by one or more bores in
the housing of the pump, for example, in particular by a bore in
the base portion of the housing and/or by a bore in the annular
portion of the housing.
[0020] In accordance with a preferred embodiment, however, the
connecting passage includes at least one connecting groove, which
extends along the inner circumference of the annular portion of the
housing. It is therefore only necessary to apply a groove to the
inside of the pump housing, for example by machining or by
moulding, in order to carry the pressurized fluid up to the gap.
The connecting groove in the annular portion of the housing may
extend, for example, up to the transition between the annular
portion and the cover portion of the housing. The connecting groove
along the inner circumference of the annular portion of the housing
preferably extends parallel to the axis of rotation of the annular
gear. Alternatively, the connecting groove may also be slanted at
an angle conducive to the flow and need not necessarily have a
rectilinear course.
[0021] Such an "axial" connecting groove may emerge directly from
the delivery chamber of the pump. Alternatively, a further
connecting groove may be provided, which extends from the delivery
chamber of the pump along the inside of the base portion of the
housing up to the connecting groove in the annular portion of the
housing, in particular radially outwards, in order to form a duct
of L-shaped longitudinal section for the fluid.
[0022] In accordance with an advantageous embodiment the connecting
passage (in particular the connecting groove in the annular portion
of the housing) opens into an annular groove, which extends
circumferentially along the transition between the annular portion
and the cover portion of the housing and/or along the thrust ring.
This allows the pressurized fluid to be distributed along the
circumference of the thrust ring and/or the cover portion of the
housing, in order to penetrate into the gap between the thrust ring
and the cover portion of the housing in multiple different angular
positions, and therefore, to form a lubricating film that is as
uniform as possible.
[0023] It is particularly advantageous if the cover portion of the
housing includes at least one distribution groove, which extends
radially inwards on the inside of the cover portion facing the
thrust ring. This is particularly effective in conducting the fluid
into the gap between the thrust ring and the cover portion of the
housing, in order to form the desired lubricating film. To do this
the respective distribution groove need not extend radially inwards
in an exact straight line, other courses and alignments also being
possible (for example, a slanting alignment, a laterally offset
arrangement or a curved path with a component directed radially
inwards). The distribution groove preferably extends radially
inwards starting from the transition between the annular portion
and the cover portion of the housing and/or from the annular
groove. A plurality of such distribution grooves are preferably
provided.
[0024] With regard to the distribution groove in the cover portion
of the housing it is preferred, in order to avoid additional
leakage losses, if this groove has only a limited length, that is
to say if the distribution groove does not extend radially inwards
all the way through. In other words, the distribution groove is in
this case to be formed as a stepped groove. This is particularly
important if the thrust ring and/or the cover portion of the
housing has a central through-hole for a drive shaft. If additional
leakage is required, however, it is alternatively advantageous if
the distribution groove of the cover portion is continuous, that is
to say if the distribution groove extends radially all the way
inwards.
[0025] Alternatively, or in addition to the distribution groove in
the cover portion of the housing, on the side facing the cover
portion (that is to say on its rear side) the thrust ring may also
have at least one distribution groove, which extends radially
inwards from the outer circumference of the thrust ring. Such a
distribution groove on the thrust ring also serves to enhance the
distribution of the pressurized fluid inside the gap between the
thrust ring and the cover portion of the housing, so that a more
uniform build-up of pressure and a more efficient hydrodynamic
lubrication is obtained. The distribution groove in the thrust ring
also need not be aligned radially inwards in an exact straight
line, other courses and alignments being feasible.
[0026] With regard to the distribution groove in the thrust ring it
is likewise possible for this to have a limited length, in order to
reduce leakage losses in the radially inner area of the pump.
Alternatively, the distribution groove in the thrust ring may
extend radially inwards all the way through, in order to bring
about a specific leakage, as explained above in connection with the
distribution groove in the cover portion of the housing.
[0027] In an accordance with another embodiment of an
advantageously simple design, the side of the thrust ring facing
the cover portion of the housing may be of plane design. It is also
advantageous, however, if the side of the thrust ring facing the
cover portion of the housing is of tapered design, truncated
cone-shaped design or convexly curved. Such a shaping of the thrust
ring is a simple way of ensuring that along the entire
circumference a minimum gap always exists between the thrust ring
and the cover portion of the housing, at least in a radially outer
area, in order to ensure an efficient hydrodynamic lubrication.
[0028] Alternatively, or in addition to this, the inside of the
cover portion of the housing facing the thrust ring may also be of
tapered design, truncated cone-shaped design or convexly curved. In
these embodiments distribution grooves may additionally be provided
on the cover portion of the housing and/or on the thrust ring, in
particular without or with specific leakage, as explained
above.
[0029] Where a specific leakage of the fluid carried into the gap
between the thrust ring and the cover portion of the housing is
brought about (for example, by a distribution groove in the cover
portion or the thrust ring extending radially inwards all the way
through), an advantage may lie, for example, in a reduced pressure
level at higher rotational speeds (lower mechanical losses).
Furthermore, such a specific leakage creates an additional facility
for cooling the pump and/or the fluid. Such a specific leakage can
furthermore serve to provide an interim storage of fluid not needed
in certain operating states.
[0030] As an alternative or addition, in the case of such a
specific leakage the fluid (particularly if the fluid is a
lubricating oil) may be used for the lubrication of components
close to the pump (for example through the use of a slinger ring).
For example, the fluid may be carried out of the gap or directly
out of the distribution groove to another component, which is
arranged on or adjacent to the pump. In particular, the housing of
the pump may have an outlet port, in order to conduct a proportion
of the fluid, carried out of the delivery chamber towards the gap,
to another component and thereby to lubricate the latter. The
outlet port may, in particular, be provided in a radially inner
area of the pump housing, for example, in the area of a central
through-hole in the cover portion of the housing intended for a
drive shaft. However, such a through-hole in the cover portion
intended for a drive shaft need not be present in all embodiments
of a pump in accordance with the invention.
[0031] It is furthermore preferred if the thrust ring extends in
one piece in a radial direction between the gear wheel and the
annular gear. In other words, the thrust ring in accordance with
this embodiment should at least partially cover not only the
annular gear, but also the gear wheel in a radial direction, there
being no possibility for direct communication of the gap
(hydrodynamic lubrication gap between the thrust ring and the cover
portion of the housing) with the pump chambers, which are formed
between the gear wheel and the annular gear. For a simple
construction, the thrust ring therefore ensures that no significant
leakage losses occur in an axial direction (relative to the axis of
rotation of the gear wheel and of the annular gear).
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] Advantageous refinements of the invention will emerge from
the dependent claims. An exemplary embodiment of the invention will
be discussed in principle below on the basis of the drawing, in
which:
[0033] FIG. 1 illustrates a view in longitudinal section through an
internal gear pump.
[0034] FIG. 2 illustrates a cross-sectional view of an internal
gear pump.
[0035] FIGS. 3a and 3b illustrates a top view and a side view
respectively of a thrust ring in accordance with embodiments.
[0036] FIG. 4 illustrates a top view of a thrust ring in accordance
with embodiments.
[0037] FIG. 5 illustrates a view in longitudinal section through a
thrust ring in accordance with embodiments.
[0038] FIG. 6 illustrates a view in longitudinal section through a
thrust ring in accordance with embodiments.
[0039] FIG. 7 illustrates a cross-sectional view of a conventional
internal gear pump.
DETAILED DESCRIPTION OF EMBODIMENTS
[0040] FIG. 1 illustrates an internal gear pump 1 in accordance
with the invention of the gerotor pump type. The pump 1 includes a
gear wheel 7, which is driven to rotate about an axis A2 by a shaft
17 passing through the pump. The pump 1 further includes a freely
rotatable annular gear 5, that is to say an internal gear, the
internal toothing of which meshes with the external toothing of the
gear wheel 7. The axis of rotation A1 of the annular gear 5 is
eccentric to the axis of rotation A2 of the gear wheel 7. A thrust
ring 19 is rotationally fixed to the annular gear 5, for example,
via weld or bond. Alternatively, the thrust ring 19 is integrally
formed with the annular gear 5. The thrust ring 19 may be composed,
for example, of steel. Apart from a central through-hole for the
shaft 17, the thrust ring 19 is closed (that is to say it is
without apertures) and is formed in one piece. The outside diameter
of the thrust ring 19 corresponds to or is otherwise substantially
equal to that of the annular gear 5.
[0041] The gear wheel 7, the annular gear 5 and the thrust ring 19
are accommodated in a housing of the pump 1, which includes a
hollow cylindrical annular portion 3. The annular gear 5 is
rotatably supported on the inner circumference of the annular
portion 3.
[0042] The housing of the pump 1 further includes a base portion
13, on which the gear wheel 7 and the annular gear 5 rest and which
in the exemplary embodiment illustrated in FIG. 1 is integrally
formed with the annular portion 3. A delivery chamber 15 of the
pump 1 is formed in the base portion 13 of the housing The housing
of the pump 1 further includes a cover portion 21, which in the
exemplary embodiment illustrated in FIG. 1 takes the form of a
separate cover.
[0043] The thrust ring 19 is arranged spatially between the gear
wheel 7 and the annular gear 5 on the one hand and the cover
portion 21 of the housing on the other. A gap 23 of very narrow
size is formed between the thrust ring 19 and the cover portion 21.
Inside the housing the gear wheel 7, the annular gear 5 and/or the
thrust ring 19 may be pre-tensioned in an axial direction relative
to the axes of rotation A1, A2 (not illustrated).
[0044] When the pump 1 is in operation, the annular gear 5,
together with the thrust ring 19 coupled thereto, rotates more
slowly than the gear wheel 7. The thrust ring 19 therefore
contributes to a certain reduction of the friction losses, since
the differential speed between the gear wheel 7 and the cover
portion 21 is effectively reduced owing to the arrangement of the
thrust ring 19 between the gear wheel 7 and the cover portion 21 of
the housing.
[0045] A further reduction of the friction losses is achieved in
the internal gear pump 1 in accordance with the embodiment
illustrated in FIG. 1 in that a connecting passage on the housing
of the pump 1 extends from the delivery chamber 15 up to the gap 23
between the thrust ring 19 and the cover portion 21 of the housing.
Pressurized fluid is carried from the delivery chamber 15 along the
connecting passage into the gap 23, the fluid in the gap 23 forming
a hydrodynamically effective lubricating film.
[0046] For this purpose the connecting passage comprises a
connecting groove 25, which on the inside of the base portion 13 of
the housing facing the annular gear 5 extends in a radial direction
from the delivery chamber 15 up to the inner circumference of the
annular portion 3 of the housing. The radial connecting groove 25
is circumferentially closed by the underside of the annular gear 5.
The radial connecting groove 25 opens into and is in communication
with an axial connecting groove 27 of the connecting passage, and
extends along the inner circumference of the annular portion 3 of
the housing parallel to the axis of rotation A1 of the annular gear
5. The axial connecting groove 27 is circumferentially closed by
the outer circumference of the annular gear 5. The radial
connecting groove 25 and the axial connecting groove 27, therefore,
form a duct of L-shaped longitudinal cross-section as illustrated
in FIG. 1 for the fluid of the pump 1. The connecting grooves 25,
27 may form a cross-sectional aperture of between 1 to 5 mm.sup.2,
for example, apertures of a different cross section naturally also
being possible. The suitable cross section generally depends on the
output of the pump, the viscosity of the fluid and the pressure
range of the pump.
[0047] The axial connecting groove 27 opens at the transition
between the annular portion 3 and the cover portion 21 of the
housing into a radial distribution groove 29. The radial
distribution groove 29 is formed on the inside, that is to say, on
the side of the cover portion 21 of the housing facing the thrust
ring 19, and which, extending radially inward, is of limited
length. Through the connecting passage comprising connecting
grooves 25, 27 and distribution groove 29, a proportion of the
fluid delivered by the pump 1 can pass or otherwise flow from the
delivery chamber 15 into the gap 23 between the thrust ring 19 and
the cover portion 21 of the housing, in order to form a
hydrodynamically effective lubricating film in the gap 23. The
lubricating film acts between the rotating thrust ring 19 and the
fixed cover portion 21 of the housing. The friction between the
thrust ring 19 and the cover portion 21 of the housing is thereby
considerably reduced. This contributes to a reduced wear and
reduced heating and impairment of the fluid.
[0048] The cover portion 21 of the housing may obviously comprise a
plurality distribution grooves 29, particularly in a regular
angular arrangement, in order to achieve a more uniform
distribution of the fluid along the circumference of the thrust
ring 19. For this purpose a separate connecting passage, emerging
from the delivery chamber 15, may be provided for each distribution
groove 29 in the cover portion 21. Alternatively, an annular groove
(not illustrated), which distributes the fluid delivered from the
delivery chamber 15 along the connecting grooves 25, 27 along the
circumference of the thrust ring 19 or the cover portion 21 of the
housing, may be provided on the annular portion 3 of the housing,
on the cover portion 21 of the housing and/or along the outer
circumference of the thrust ring 19.
[0049] FIG. 2 illustrates a cross-sectional view of an internal
gear pump in accordance with the invention. FIG. 2 illustrates the
radial connecting groove 25 in the base portion 13 and the axial
connecting groove 27 in the annular portion 3 of the housing, which
form the connecting passage described, extending from the delivery
chamber 15 to the thrust ring 19 and the cover portion 21 of the
housing.
[0050] As illustrated in FIGS. 3a and 3b, alternatively or in
addition to the formation of a distribution groove 29 along the
cover portion 21 of the housing illustrated in FIG. 1, one or more
distribution grooves 31 may be provided on a surface of the rear
side 33 of the thrust ring 19 facing the gap 23 (that is to say, on
the upper side of the thrust ring 19 in the representation
illustrated in FIG. 1). As illustrated in FIGS. 3a and 3b, a
plurality if of radial distribution grooves 31 are provided,
asymmetrically formed and arranged with a slight lateral
offset.
[0051] In the embodiment illustrated in FIGS. 3a and 3b the
distribution grooves 31 in the thrust ring 19 are formed all the
way through, that is to say they extend from the outer
circumference up to the inner circumference (central through-hole
for the shaft 17). In this way specifically desired leakage effects
can be produced, for example, for a build-up of pressure,
additional cooling or the lubrication of further components by
leakage oil.
[0052] As illustrated in FIG. 4, alternatively, the distribution
grooves 31 are formed as stepped grooves, which extend radially
inwards only along a limited length from the outer circumference of
the thrust ring 19, for example, up to approximately 1 mm from the
inner circumference of the thrust ring 19. This serves to minimize
leakage losses.
[0053] In the embodiments illustrated in FIGS. 1, 3a, 3b and 4, the
rear side 33 of the respective thrust ring 19 is of plane
design.
[0054] As illustrated in FIG. 5, alternatively, the rear side 33 of
the thrust ring 19 facing the cover portion 21 of the housing may
be of tapered design. This serves, as an alternative or addition to
the provision of distribution grooves 31, to bring about an
enhanced distribution of the fluid delivered via the connecting
passage.
[0055] As illustrated in FIG. 6, alternatively, the rear side 33 of
the thrust ring 19 may have a bowed or arcuate design, that is to
say, of convexly curved design. This serves, as an alternative or
addition to the provision of distribution grooves 31, to bring
about an enhanced distribution of the fluid delivered via the
connecting passage.
[0056] Alternatively or in addition to such a tapered, truncated
cone-shaped or convexly curved design of the rear side 33 of the
thrust ring 19, the inside surface of the cover portion 21 of the
housing (FIG. 1) facing the thrust ring 19 may be of tapered,
truncated cone-shaped or convexly curved design. In both cases, the
gap 23 between the thrust ring 19 and the cover portion 21 of the
housing (FIG. 1) has, at least in portions, an overall height
diminishing radially inwards.
[0057] Although embodiments have been described herein, it should
be understood that numerous other modifications and embodiments can
be devised by those skilled in the art that will fall within the
spirit and scope of the principles of this disclosure. More
particularly, various variations and modifications are possible in
the component parts and/or arrangements of the subject combination
arrangement within the scope of the disclosure, the drawings and
the appended claims. In addition to variations and modifications in
the component parts and/or arrangements, alternative uses will also
be apparent to those skilled in the art.
* * * * *