Information
-
Patent Grant
-
6688866
-
Patent Number
6,688,866
-
Date Filed
Thursday, November 15, 200122 years ago
-
Date Issued
Tuesday, February 10, 200420 years ago
-
Inventors
-
Original Assignees
-
Examiners
Agents
- Bliss McGlynn, P.C.
- Dziegielewski; Greg
-
CPC
-
US Classifications
Field of Search
US
- 418 135
- 418 166
- 418 171
-
International Classifications
-
Abstract
A gerotor pump is provided that includes a pump housing having a pump cover and a pump end plate. The pump cover defines an open end, an axial bore, and a bottom end. The pump end plate engages the open end of the pump cover thereby enclosing the axial bore of the pump cover and creating an inner cylindrical chamber in the pump housing. A wear plate and a gerotor gear set assembly are operatively disposed within the inner cylindrical chamber such that the gerotor gear set assembly is operatively disposed between the wear plate and the pump end plate. A biasing member is disposed between the bottom end of the pump cover and the wear plate, and is adapted to operatively bias the wear plate against the gerotor gear set assembly and the pump end to create an axial zero tolerance condition between the pump elements.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The subject invention relates, generally, to gerotor pumps, more specifically to a gerotor pump having a housing that allows for variations in its internal axial tolerances.
2. Description of the Related Art
Gerotor pumps are commonly employed in the automotive industry for pumping oil to lubricate and cool various components of a typical automotive power train. For example, pumps of this type are often employed in transfer cases of automotive transmission assemblies. Gerotor pumps typically include a gerotor set having an externally toothed inner gear rotor intermeshed with an internally toothed outer gear rotor, wherein each rotor is disposed about respective eccentric axes. Other rotor pump sets are known that employ smooth surfaced rotors, one disposed within another and placed about respective eccentric axes. Regardless of the structure of the rotor set, the pumping action is accomplished by the rotational opening and closing of voids, or volumes, formed by the offset of the inner to the outer rotor during their rotation within a pump housing.
The gerotor set is typically seated in a cylindrical inner chamber of a pump housing and enclosed by an outer cover plate fixedly secured to the pump housing. A drive shaft rotates the inner rotor against the outer rotor to pump fluid between the intermeshed teeth from an inlet to an outlet in the housing.
The efficiency of the pump depends greatly upon the axial sealing of the gerotor set seated in the inner chamber between the pump housing on one axial side of the gerotor set and the outer cover plate on the other axial side of the gerotor set. The axial sealing of the gerotor set between the pump housing and the cover plate requires close manufacturing tolerances of the axial depth of the inner chamber housing the gerotor set. Such close manufacturing tolerances results in increase labor and expensive machining costs of the pump. The close tolerances also require a high torque input to initiate the rotation and pumping action of the pump elements. Additionally, in operation, when constructed with the necessary close tolerances for efficient pumping, the pump can easily exceed the desired design output pressure requiring supplemental structure for pressure relief.
Lastly, current manufacturing practices often call for the use of different materials for the pump elements and the pump housing to save weight. The use of different materials results in the undesirable effect of variations in the axial clearances as a function of temperature changes within the pump due to differing material coefficients of expansion. These temperature related changes in axial clearances, or tolerances, cause wide variations in pump performance.
Accordingly, it is desirable to provide a gerotor pump having a housing for enclosing the gerotor set which not only reduces the need for the close, exacting tolerances of prior art pumps, but also allows for variations in the thermal expansion of the pump elements while lowering the rotational torque input required to start the pump. Therefore, it is desirable to provide a gerotor pump having a variable tolerance housing.
SUMMARY OF THE INVENTION
The deficiencies in the related art are overcome by the present invention in a gerotor pump for pumping pressurized fluid between an inlet port and an outlet port. The gerotor pump includes a pump housing defined by a pump cover and a pump end plate. The pump cover defines an open end, an axial bore, a bottom end, and a central opening in the bottom end. The pump end plate is adapted to matingly engage the open end of the pump cover thereby enclosing the axial bore of the pump cover and creating an inner cylindrical chamber in the pump housing. A wear plate having a central opening is operatively disposed within the inner cylindrical chamber of the pump housing. Also, a gerotor gear set assembly having an inner and an outer rotor is disposed within the inner cylindrical chamber of the pump housing such that the gerotor gear set assembly is operatively set between the wear plate and the pump end plate. A shaft is received through the pump cover and the wear plate through the central openings and is operatively connected to the gerotor gear set assembly for rotating the gerotor gear set assembly within the inner cylindrical chamber of the pump housing. A biasing member is operatively disposed between the bottom end of the pump cover and the wear plate. The biasing member is adapted to bias the wear plate against the gerotor gear set assembly and the pump end to create an axial zero tolerance condition.
The present invention thereby overcomes the disadvantages and drawbacks of the current art by reducing the need for the close, exacting tolerances of prior art pumps, and also allows for variations in the thermal expansion of the pump elements while lowering the rotational torque input required to start the pump. This is accomplished by the variable tolerance characteristics of the pump housing that are available due to the use of the biasing member within the housing that causes the gerotor assembly to be held in zero tolerance to the other pump elements.
BRIEF DESCRIPTION OF THE DRAWINGS
Other advantages of the invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
FIG. 1
is a top view of one embodiment of the gerotor pump of the present invention;
FIG. 2
is an exploded perspective view of one embodiment of the gerotor pump of the present invention;
FIG. 3
is a cross-sectional view of one embodiment of the gerotor pump of the present invention taken along line
3
—
3
of
FIG. 1
;
FIG. 4
is a partial cross-sectional view of one embodiment of a gerotor pump of the present invention depicting a partial section across the inlet port taken along line
4
—
4
of
FIG. 1
;
FIG. 5
is a top view of a gerotor pump and flexible cover plate according to an alternate embodiment of the present invention;
FIG. 6
is a cross-sectional view taken along line
6
—
6
of
FIG. 5
;
FIG. 7
is a partially exploded perspective view of the gerotor pump and flexible cover plate of the embodiment of
FIG. 5
;
FIG. 8
is a cross-sectional view taken along line
8
—
8
of
FIG. 5
; and
FIG. 9
is cross-sectional side view of a gerotor pump and flexible cover plate according to an additional embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
Referring to the drawings, wherein like reference numbers represent like or corresponding parts throughout the several views, a gerotor pump according to one embodiment of the present invention is generally indicated at
10
in FIG.
1
. The pump
10
is employed for pumping a fluid media, such as oil, from an inlet port
12
at a lower pressure, out through a corresponding outlet port
14
at a higher pressure. As shown in
FIG. 2
, the gerotor pump
10
is of a generally cylindrical disc-shaped configuration and includes a pump housing
16
, a wear plate
18
, a gerotor gear assembly set
20
, and a biasing member
26
. The pump housing
16
is defined by a pump cover
22
and a pump end plate
24
.
The pump cover
22
of the pump housing
16
defines an open end
28
, an axial bore
30
, a bottom end
32
, and a central opening
34
in the bottom end
32
. The pump end plate
24
fits within, and is disposed in a mating manner against, the open end
28
, thereby enclosing the axial bore
30
and creating an inner cylindrical chamber
36
within the pump housing
16
. In turn, the open end
28
further defines a lower seating surface
38
, an inwardly sloping sealing surface
40
, and an upper seating surface
42
that concomitantly receive mating surfaces
44
,
46
, and
48
, respectively, of the pump end plate
24
, which are of similar dimensions. The axial bore
30
of the pump cover
22
also includes a plurality of retaining grooves
50
disposed axially about its circumference. When assembled, the wear plate
18
, gerotor gear assembly set
20
, and a biasing member
26
are disposed within the inner cylindrical chamber
36
of the pump cover
22
.
The wear plate
18
has an annular groove
52
, a central opening
54
, and a plurality of retaining tabs
56
that extend axially along its outer circumference. The plurality of retaining tabs
56
are disposed upon the wear plate
18
in such an manner as to correspondingly engage the plurality of retaining grooves
50
in the axial wall
30
of the pump cover
22
. The retaining tabs
56
and their corresponding retaining grooves
50
prevent the wear plate
18
from rotating within the inner cylindrical chamber
36
, yet allow for longitudinal movement of the wear plate
18
axially within the pump housing
16
.
The preferred embodiment of the present invention employs a gerotor gear set assembly
20
, as is commonly known in the art. The gerotor gear set assembly
20
includes an inner toothed gear rotor
58
having a central opening
60
disposed within an outer toothed gear rotor
62
. As in a typical gerotor design, the inner-toothed gear rotor
58
has one less tooth than the outer-toothed gear rotor
62
, and is offset from the central axis upon which the outer-toothed rotor
62
is disposed. Thereby, the inner toothed rotor
58
, in meshing relationship with the outer toothed rotor
62
, forms expanding and contracting volumes or chambers between the teeth, which act as pumping chambers for the fluid media as the gerotor gear set assembly
20
is rotated. The outer-toothed gear rotor
62
is seated within the inner cylindrical chamber
36
on top of the wear plate
18
such that it is encompassed by the axial wall
30
. Thus, the gerotor gear set assembly
20
is disposed between, and operatively supported by, the wear plate
18
and the pump end plate
24
within the inner cylindrical chamber
36
.
The pump end plate
24
includes a flat planar surface
64
having an inlet channel
66
and an outlet channel
68
machined in a known manner therethrough. In addition, the end plate
24
further includes a central opening
70
, and inlet and outlet ports
12
and
14
, respectively. When the pump end plate
24
is matingly engaged to the pump cover
22
, the flat planar surface
64
is seated against the gerotor gear set assembly
20
. In this manner, the inlet channel
66
and the outlet channel
68
are in fluid communication with both the gerotor gear set assembly
20
and the inlet and outlet ports
12
and
14
, respectively, for routing fluid media into the gerotor pump
10
at a lower pressure and out at a higher pressure.
The central openings
34
,
54
, and
70
of the pump cover
22
, the wear plate
18
, and the pump end plate
24
, respectively, concomitantly allow for receiving an axial extending, cylindrical drive shaft
72
therethrough for connection to the central opening
60
of the inner rotor
58
of the gerotor gear set assembly
20
. The drive shaft
72
is operatively connected in a manner commonly known in the art, using splines or the like, to the inner rotor
58
at
74
.
As best shown in
FIG. 1
, the center axis of the pump is indicated at “A”. The open end
28
and axial bore
30
of the pump cover
22
are coaxial to the center axis “A”. However, the central openings
34
,
54
, and
70
are coaxially offset to an axis “B” which is eccentric to the center axis “A” of the pump housing
16
, so that the inner rotor
58
of the gerotor gear set assembly
20
is offset relative to the outer rotor
62
. This offset between the inner rotor
58
and outer rotor
62
of the gerotor pump
10
provides the desired pumping action, as described above.
The drive shaft
72
is thereby used to rotate the gerotor gear set assembly
20
within the inner cylindrical chamber
36
of the pump housing
16
to pump the fluid media from the inlet
12
to the outlet
14
of the pump end plate
24
. It should be appreciated that the inlet
12
and the outlet
14
are further connected, in a known manner, in fluid communication with the next higher assembly in which the gerotor pump
10
is installed, such as a transfer case, for example.
The biasing member
26
is disposed within the annular groove
52
of the wear plate
18
such that, when the gerotor pump
10
is assembled, the biasing member
26
is in contact with both the wear plate
18
and the bottom surface
32
. The annular groove
52
of the wearplate
18
retains the biasing member
26
in a coaxial position relative to the inner cylindrical chamber
36
. It should be appreciated that the annular groove
52
may be disposed within either the wear plate
18
, the bottom surface
32
, or both to allow the biasing member
26
to be maintained in position yet contact both surfaces.
The biasing member
26
, within the pump housing
16
, causes the wear plate
18
to slide along the retaining grooves
50
, and press the gerotor gear set assembly
20
axially against the pump end plate
24
. This closes any clearances, or tolerances, between the pump elements and provides a “zero” axial tolerance condition. In the preferred embodiment, the biasing member
26
is an o-ring, manufactured of any of a group of known materials capable of maintaining high resiliency and crush resistance within a heat intensive and oil laden environment including fluorocarbon rubber or highly-saturated nitrile, for example. In another non-limiting embodiment, the biasing member
26
may be formed as a flat annular ring as shown in FIG.
4
. It should additionally be appreciated by those of ordinary skill in the art that the biasing member
26
may be formed in other various cross-sectional shapes without departing from the scope or spirit of the present invention.
In operation, in an initial, static state, the biasing member
26
presses against the wear plate
18
forcing the wear plate
18
and the gerotor gear set assembly
20
against the pump end plate
24
, thereby removing any axial gaps between these pump elements and holding the gerotor gear set assembly
20
to an axial “zero” clearance, or tolerance, between the wear plate
18
and the pump end plate
24
. The low physical rotational drag of this configuration allows for a low torque start with high prime characteristics. In its operating capacity, the resiliency and compression characteristics of the material of the biasing member
26
may be selected to provide a specific maximum pressure capability of the gerotor pump
10
. This is possible due to the fact that, as the pump pressure reaches the compression limits of the biasing member
26
, the biasing member
26
will allow the wear plate
18
to slightly move away from the gerotor gear set assembly
20
. As the wear plate
18
moves away from the gerotor gear set assembly
20
, the axial tolerances open and the output pressure is lowered due to cross-bleeding of the gerotor gear set assembly
20
. As the pressure drops, the biasing member
26
will recover and the axial tolerances will again be zeroed.
Another embodiment of the present invention is generally indicated at
110
, in
FIG. 5
, wherein like reference numbers are increased by a factor of
100
are used to designate like structure with respect to the embodiment illustrated in
FIGS. 1-4
. The gerotor pump
110
is used for pumping pressurized fluid between an inlet
112
and an outlet
114
. The gerotor pump
110
has a generally cylindrical disc-shaped configuration and includes a pump housing
116
having a cylindrical pump housing opening
128
as shown in FIG.
6
. The pump housing
116
further includes an axial wall
130
defining an inner cylindrical chamber
136
and a bottom surface
132
.
A gerotor gear set assembly
120
including an inner toothed gear rotor
158
and an outer toothed gear rotor
162
, as is commonly known in the art, is seated within the inner cylindrical chamber
136
, encompassed by the axial wall
130
, and axially supported by the bottom surface
132
. A longitudinal, cylindrical drive shaft
172
is operatively connected in a manner commonly known in the art to the gerotor gear set assembly
120
for rotating the gerotor gear set assembly
120
within the inner chamber
136
to pump the fluid entering the chamber
136
from the inlet
112
to the outlet
114
.
The gerotor pump
110
further includes a cylindrical cover plate
124
recessed within and against the axial wall
130
and seated against the gerotor gear set assembly
120
for closing the pump housing opening
128
. The cover plate
124
includes a generally flat planar surface
164
in mating engagement with the gerotor gear set assembly
120
and a center bore
160
for receiving the drive shaft
172
therethrough for connection to and rotation of the gerotor gear set assembly
120
. The cover plate
124
also includes a peripheral lip
176
extending axially from the planar surface
164
which abuts and is in sealing and mating engagement with the axial wall
130
of the pump housing
116
for sealing and closing the pump housing opening
128
.
The gerotor pump
110
further includes a spring bias member generally indicated at
126
interconnected between the pump housing
116
and the cover plate
124
for continuously biasing the cover plate
124
axially against the gerotor gear set assembly
120
. The spring bias member
126
maintains axial bearing pressure between the cover plate
124
and the gerotor gear set assembly
120
to reduce the manufacturing tolerance typically required for proper sealing between the cover plate
124
, gerotor gear set assembly
120
and axial wall
130
forming the inner chamber
136
of the pump housing
116
.
Referring to
FIGS. 5 through 8
, the spring member
126
includes a plurality of flexible locking tabs
178
spaced circumferentially about the circumference of the cover plate
124
for engaging an outer portion of the pump housing
116
to bias the cover plate
124
against the gerotor gear set assembly
120
. Each flexible locking tab
178
includes a generally U-shaped base portion
180
formed integrally with the peripheral lip
176
and extending radially outwardly therefrom as shown in FIG.
7
. Each flexible locking tab
178
further includes a generally L-shaped snap lock portion
182
extending axially downwardly from the base portion
180
for engaging the outer portion of the pump housing
116
. Referring to
FIGS. 7 and 8
, the snap lock portion
182
includes a flat contact end
184
spaced from and planar to the planar surface
164
of the cover plate
124
. A U-shaped torsion bar portion
188
extends between the lock portion
182
and the contact end
184
for biasing the cover plate
124
against the gerotor gear set assembly
120
in the inner chamber
136
. The cover plate
124
and flexible locking tabs
178
may be an integral stamped steel solid body or solid molded plastic body.
The pump housing
116
includes a plurality of anti-rotation arms
186
formed integrally with and extending radially outwardly from the outer portion of the housing
116
for releasably locking with the respective flexible locking tabs
178
to spring bias the cover plate
124
against the gerotor gear set assembly
120
. More specifically, the contact end
184
of the snap lock portion
182
engages the surface of the anti-rotation arm
186
of the pump housing
116
to releasably lock the flexible locking tabs
178
to the pump housing
116
.
In assembly, the gerotor gear set assembly
120
is seated within the inner chamber
136
with the outer periphery of the gear set assembly
120
in mating engagement with a portion of the axial wall
130
of the pump housing
116
and supported by the bottom surface
132
as shown in FIG.
6
. The cover plate
124
is then recessed within the pump housing opening
128
such that the peripheral lip
176
matingly engages the remaining portion of the axial wall
130
to close the opening
128
and seal the gerotor gear set assembly
120
between the bottom surface
132
, axial wall
130
and planar surface
164
of the cover plate
124
. The cover plate
124
is initially aligned with the pump housing
116
with each of the flexible locking tabs
178
positioned between an adjacent pair of the anti-rotation arms
186
. The cover plate
124
is then rotated counterclockwise about the pump housing
116
until the contact ends
184
and torsion bar portions
188
extend over the surfaces of the anti-rotation arms
186
abutting against the leg portions
182
as shown in FIG.
8
. The flexible locking tabs
178
maintain a biasing force, or tension, and sealing engagement between the cover plate
124
and the gerotor gear set assembly
120
to prevent leakage of fluid during normal operating pressures. The flexible locking tabs
178
and cover plate
124
also afford increase prime-ability of the pump
110
due to the zero tolerance between the cover plate
124
, gerotor gear set assembly
120
and pump housing
116
. Still further, the flexible locking tabs
178
allow the cover plate to flex or move away from the gerotor gear set assembly
120
in response to an increased fluid pressure to allow leakage across the face of the gear set assembly
120
to regulate the output pressure of the pump
110
.
Referring to
FIG. 9
, an additional alternative embodiment of the present invention is shown wherein the spring bias member
126
includes a plurality of separate torsion bars
190
circumferentially spaced about the gerotor pump
110
and operatively connected between the pump housing
116
and the cover plate
124
. The torsion bars
190
include a thin metal plate having a first end
192
fixedly secured to the pump housing
116
by a fastener
194
and a second end
196
in mating engagement with the cover plate
124
for urging the cover plate
124
against the gerotor gear set assembly
120
in a manner similar to the embodiment shown in
FIGS. 5 through 8
.
The invention has been described in an illustrative manner. It is to be understood that the terminology that has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the invention may be practiced other than as specifically described.
Claims
- 1. A gerotor pump for pumping pressurized fluid between an inlet port and an outlet port, said gerotor pump including:a pump housing defined by a pump cover and a pump end plate, said pump cover defining an open end, an axial bore, a bottom end, and a central opening in said bottom end, said pump end plate adapted to matingly engage said open end of said pump cover thereby enclosing said axial bore of said pump cover and creating an inner cylindrical chamber within said pump housing; a wear plate having a central opening and operatively disposed within said inner cylindrical chamber of said pump housing; a gerotor gear set assembly disposed within said inner cylindrical chamber of said pump housing such that said gerotor gear set assembly is operatively supported between said wear plate and said pump end plate; a shaft operatively connected to said gerotor gear set assembly for rotating said gerotor gear set assembly within said inner cylindrical chamber of said pump housing; a biasing member formed as a resilient annular ring that is operatively disposed between said bottom end of said pump cover and said wear plate, only said resilient annular ring adapted to operatively bias said wear plate against said gerotor gear set assembly and said pump end plate to create an axial zero tolerance condition between said wear plate, said gerotor gear set assembly, and said pump end plate.
- 2. A gerotor pump as set forth in claim 1 wherein said wear plate includes an annular groove disposed in its bottom surface, said biasing member adapted to be received within said annular groove.
- 3. A gerotor pump as set forth in claim 1 wherein said bottom surface of said pump cover includes an annular groove, said biasing member adapted to be received within said annular groove.
- 4. A gerotor pump as set forth in claim 1 wherein said biasing member is made from at least one of a group comprising fluorocarbon rubber or highly-saturated nitrile compounds.
- 5. A gerotor pump as set forth in claim 1 wherein said annular ring is further defined as an o-ring.
- 6. A gerotor pump as set forth in claim 1 wherein said wear plate includes a plurality of retaining tabs extending outward from the circumference of said wear plate and parallel to its central axis, and said pump cover includes a plurality of retaining grooves disposed axially along said inner bore, said retaining tabs adapted to slidingly engage said retaining grooves such that said wear plate is free to move axially within said pump cover but is prevented from rotating.
- 7. A gerotor pump as set forth in claim 1 wherein said gerotor gear set assembly includes an inner pumping gear element having external teeth interposed in meshing relationship with an outer pumping gear element having internal teeth, said inner pumping gear element operatively disposed on a central pump axis defined by center axis of said pump housing, said outer pumping gear element operatively disposed on an axis that is offset relative to said central pump axis so that rotation of said inner and outer pumping gear elements, relative to one another, creates gaps between said internal and external teeth which define expanding and contracting pumping volumes.
- 8. A gerotor pump as set forth in claim 1 wherein said pump end plate includes a planar surface in contact engagement with said gerotor gear assembly, said planar surface including an inlet passage and an outlet passage in fluid communication with said pumping volumes of gerotor gear set assembly.
- 9. A gerotor pump as set forth in claim 1 wherein said pump end plate includes an inlet port in fluid communication with said inlet port and an outlet port in fluid communication with said outlet passage such that said inlet port delivers fluid media at a lower pressure to said gerotor gear set assembly and said outlet port receives fluid media at a higher pressure from said gerotor gear set assembly.
US Referenced Citations (12)
Foreign Referenced Citations (1)
Number |
Date |
Country |
57-76284 |
May 1982 |
JP |