U.S. patent application number 10/178873 was filed with the patent office on 2003-09-04 for charge pump and auxiliary pump for hydrostatic transmissions and integrated hydrostatic transaxles.
This patent application is currently assigned to Hydro-Gear Limited Partnership. Invention is credited to Hauser, Raymond, Smothers, Daryl.
Application Number | 20030166431 10/178873 |
Document ID | / |
Family ID | 27014603 |
Filed Date | 2003-09-04 |
United States Patent
Application |
20030166431 |
Kind Code |
A1 |
Smothers, Daryl ; et
al. |
September 4, 2003 |
Charge pump and auxiliary pump for hydrostatic transmissions and
integrated hydrostatic transaxles
Abstract
A hydrostatic transaxle having a housing forming a sump
containing hydraulic fluid, a charge pump or auxiliary pump in flow
communication with the sump for creating high pressure hydraulic
fluid from the hydraulic fluid, a center section having hydraulic
porting formed therein, a hydraulic pump and motor, connected to
the hydraulic pump through the hydraulic porting. A differential
and output axles are also mounted in the housing with a drive train
connecting the hydraulic motor output shaft and the differential.
The drive train comprises a counter shaft secured to the housing
and having a first gear engaged to the motor output shaft and a
second gear engaged to both the first gear and the
differential.
Inventors: |
Smothers, Daryl; (Sullivan,
IL) ; Hauser, Raymond; (Sullivan, IL) |
Correspondence
Address: |
ALTHEIMER & GRAY
TEN SOUTH WACKER DRIVE, SUITE 4000
CHICAGO
IL
60606-7482
US
|
Assignee: |
Hydro-Gear Limited
Partnership
1411 S. Hamilton Street
Sullivan
IL
60951
|
Family ID: |
27014603 |
Appl. No.: |
10/178873 |
Filed: |
June 24, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10178873 |
Jun 24, 2002 |
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09774754 |
Jan 30, 2001 |
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6427443 |
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09774754 |
Jan 30, 2001 |
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09170915 |
Oct 13, 1998 |
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6192682 |
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09170915 |
Oct 13, 1998 |
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08700933 |
Aug 23, 1996 |
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5819535 |
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08700933 |
Aug 23, 1996 |
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08451162 |
May 26, 1995 |
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5557931 |
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08451162 |
May 26, 1995 |
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08394144 |
Feb 24, 1995 |
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5555727 |
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Current U.S.
Class: |
475/83 |
Current CPC
Class: |
F16H 61/40 20130101;
B60K 17/105 20130101; F16H 61/4139 20130101 |
Class at
Publication: |
475/83 |
International
Class: |
F16H 047/04 |
Claims
What is claimed is:
1. An axle driving apparatus comprising: a housing; a hydrostatic
transmission disposed in said housing and forming a sump, said
hydrostatic transmission including a hydraulic motor having a motor
shaft; a charge pump disposed adjacent to the external surface of
said housing and hydraulically connected to said hydrostatic
transmission; axles disposed in said housing; a differential gear
unit disposed in said housing for differential connection of said
axles; and a drive train disposed in said housing between said
hydrostatic transmission and said axle, said drive train
comprising: a counter shaft supported at both ends in said housing
so as to be disposed between said motor shaft and said axles; a
first gear rotatable relative to and provided on said counter shaft
for driving said differential gear unit; and a second gear driven
by said motor shaft, said second gear not rotatable relative to and
mounted on said first gear, wherein said second gear engages with
teeth of said first gear.
2. An axle driving apparatus comprising: a housing; a hydrostatic
transmission disposed in said housing and forming a sump, said
hydrostatic transmission including a hydraulic motor having a motor
shaft; an auxiliary pump in flow communication with said sump
disposed adjacent to the external surface of said housing; axles
disposed in said housing; a differential gear unit disposed in said
housing for differential connection of said axles; and a drive
train disposed in said housing between said hydrostatic
transmission and said axle, said drive train comprising: a counter
shaft supported at both ends in said housing so as to be disposed
between said motor shaft and said axles; a first gear rotatable
relative to and provided on said counter shaft for driving said
differential gear unit; and a second gear driven by said motor
shaft, said second gear not rotatable relative to and mounted on
said first gear, wherein said second gear engages with teeth of
said first gear.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 09/774,754, filed Jan. 30, 2001, which is a continuation of
U.S. application Ser. No. 09/170,915, filed Oct. 13, 1998, now U.S.
Pat. No. 6,192,682, which is a continuation of application Ser. No.
08/700,933, filed Aug. 23, 1996, now U.S. Pat. No. 5,819,535, which
is a continuation-in-part of U.S. application Ser. No. 08/451,162,
filed May 26, 1995, now U.S. Pat. No. 5,557,931, which is a
continuation of U.S. application Ser. No. 08/394,144, filed Feb.
24, 1995, now U.S. Pat. No. 5,555,727.
BACKGROUND OF THE INVENTION
[0002] This invention relates to charge pumps and other auxiliary
pumps used on hydrostatic transmissions ("HST") for use in light
duty applications. Such HSTs can either have their own housing and
be attached to an axle driving apparatus, or can be incorporated
within a housing that includes the components of the axle driving
apparatus. A unit that contains an HST within the housing of an
axle driving apparatus is often referred to as a integrated
hydrostatic transaxle ("IHT"). The operation of such units are
described in U.S. Pat. Nos. 5,201,692 and 5,314,387, the terms of
which are incorporated by reference.
SUMMARY OF THE INVENTION
[0003] This invention presents a unique and novel manner of
providing and mounting charge pumps and auxiliary pumps for both
IHTs or stand-alone HSTs that are mounted to a separate
transmission. As described in the '692 patent, an HST generally
comprises a pump that receives and is rotated by an input shaft
driven by a vehicle engine. The pump includes a plurality of
pistons that contact a swashplate to cause axial movement thereof
when the pump rotates. The pump is hydraulically connected to a
motor, which is similar in construction to the pump. The motor
receives hydraulic fluid from the pump, and movement of the motor
pistons against a swashplate causes rotation of the motor, which is
connected to and drives an output shaft. The hydraulic connection
between the pump and motor is a closed circuit; however, in any
such circuit there will be deliberate and incidental leakage due to
lubrication requirements, the high pressure of the hydraulic fluid
and manufacturing tolerances. Thus, the HST requires a mechanism to
replace fluid leaked from the closed circuit. This replacement
fluid is commonly called make-up fluid.
[0004] In present HST designs, the pump and motor are often mounted
on a center section that includes the hydraulic circuit therein.
The hydraulic circuit includes two sides: a high pressure side and
a low pressure side. The low pressure side is sometimes referred to
as the vacuum side. These two sides are reversed when the vehicle
motion is changed from forward to reverse.
[0005] Typically, the center section is mounted in a housing, and
the housing provides a hydraulic fluid sump. Make-up fluid is
brought from the sump into the low pressure side of the hydraulic
circuit to replace fluid which is lost therefrom due to leakage.
Specifically, check valves mounted directly into the center section
or mounted in a separate plate that is in communication with the
center section, as shown in the '692 patent, provide a fluid flow
path between the sump and the hydraulic circuit. However, this
arrangement often does not provide sufficient fluid flow into the
low pressure side of the circuit to replace the lost fluid.
Therefore, a charge pump may be used to assist in this process. In
addition, the use of an auxiliary pump to supply pressurized
hydraulic fluid for various purposes is generally known. This
invention provides for an efficient manner of mounting a charge
pump and, in some cases, an auxiliary pump, external to the housing
but still in direct communication with the hydraulic circuit in the
center section.
[0006] The external charge pump confers significant benefits with
respect to the accessibility on the hydraulic system design and
configuration. The external nature of the charge pump allows direct
access via a simple hydraulic fitting to hydraulic fluid that can
be used for auxiliary functions. Internal charge pumps, in
comparison, generally require a complex series of chambers,
connections and fittings in order for fluid to be accessible
exterior to the housing. External pumps provide accessibility
without unit disassembly, thereby allowing replacement, addition or
upgrade of a charge or auxiliary pump. Previous configurations were
not accessible without disassembly of the HST or IHT.
[0007] Additional benefits and features of this invention will be
disclosed in the description of the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a sectional side view of a charge pump and IHT in
accordance with the present invention;
[0009] FIG. 2 is a sectional end view of the IHT shown in FIG.
1;
[0010] FIG. 3 is a partial sectional side view of the porting plate
and charge pump of the IHT shown in FIG. 1, with a typical
hydraulic fluid flow path shown;
[0011] FIG. 4 is a partial sectional bottom plan view of the IHT
shown in FIG. 1, with the lower housing and charge cover partially
cut away;
[0012] FIG. 5 is a sectional side view of the IHT shown in FIG.
1;
[0013] FIG. 6 is a sectional side view of another embodiment of an
IHT in accordance with the present invention, with the center
section enclosed in the housing and porting plate mounted to the
exterior of the housing;
[0014] FIG. 7 is a sectional side view of another embodiment of an
IHT in accordance with the present invention, with the porting
plate incorporated as a part of the lower housing;
[0015] FIG. 8 is an elevational end view of an HST incorporating a
charge pump in accordance with the present invention;
[0016] FIG. 9 is a further elevational end view of the HST shown in
FIG. 8;
[0017] FIG. 10 is a sectional side view of the HST shown in FIG. 9
along the line 10-10;
[0018] FIG. 11 is a partial elevational side view of the HST lower
housing, porting plate and charge cover shown in FIG. 8;
[0019] FIG. 12 is a sectional side view of another embodiment of an
HST with a charge pump in accordance with the present invention
incorporating the porting plate into the lower housing;
[0020] FIG. 13 is a partial, sectional side view of the lower
housing of the embodiment shown in FIG. 12;
[0021] FIG. 14 is a sectional side view of an IHT incorporating an
auxiliary pump in accordance with another embodiment of the present
invention;
[0022] FIG. 15 is a sectional end view of the IHT shown in FIG.
14;
[0023] FIG. 16 is a sectional side view of the auxiliary pump used
in connection with the IHT shown in FIG. 14 with a typical fluid
path shown;
[0024] FIG. 17 is a partial sectional bottom plan view of an IHT as
shown in FIG. 14, with the lower housing, porting plate and
auxiliary pump cover partially cut away;
[0025] FIG. 18 is a hydraulic schematic of the embodiment as shown
in FIG. 14;
[0026] FIG. 19 is a bottom plan view of an HST incorporating an
auxiliary and charge pump of the present invention, with a partial
sectional view of the auxiliary pump cover;
[0027] FIG. 20 is a sectional side view of an HST incorporating an
auxiliary and charge pump embodiment of the present invention;
[0028] FIG. 21 is a hydraulic schematic of an embodiment that
incorporates separate charge and auxiliary pumps;
[0029] FIG. 22 is a sectional side view of a further embodiment of
an IHT incorporating separate charge and auxiliary pumps;
[0030] FIG. 23 is a sectional side view of a further embodiment of
the invention incorporating a gallery forming manifold;
[0031] FIG. 24 is a top view of the manifold shown in FIG. 23;
[0032] FIG. 25 is a bottom view of the manifold shown in FIG.
23;
[0033] FIG. 26 is a sectional side view of a further embodiment of
the invention incorporating a gallery forming manifold; and
[0034] FIG. 27 is a sectional side view of a further embodiment of
the invention incorporating a gallery forming manifold.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0035] A charge pump embodiment of the invention incorporated in an
IHT will first be described in accordance with the accompanying
drawings. FIGS. 1 through 5 illustrate an IHT configured with a
horizontally split housing with upper housing 21 and lower housing
22. The invention does not require any specific housing
configuration, and all known configurations can be accommodated.
All specifics of an IHT are not shown in these figures as the
general operating of an IHT is known in the art.
[0036] Pump 24 is disposed on center section 26 and receives input
shaft 25, which communicates with and is driven by a vehicle engine
(not shown). Center section 26 includes internal porting 30 that
hydraulically connects pump 24 and motor 40. Pump pistons 23 engage
adjustable swashplate 27 to create pressure within a center section
internal porting 30. Housings 21 and 22 form a sump or reservoir 32
external to center section 26. Motor 40 is connected to and drives
output shaft 41, which in turn drives gear 42a, which is connected
to gear 42b mounted on counter shaft 48. Gears 42a and 42b do not
rotate with respect to one another; the teeth of gear 42b engage
with gear 42a. As shown most clearly in FIG. 4, counter shaft 48 is
mounted to lower housing 21 by means of screws 49 and is located
between motor shaft 41 and axles 45a and 45b. Gear 42b then drives
gear 43 and the remaining gears of differential 44. Differential 44
is in turn operatively connected to the output drive axles 45a and
45b of the vehicle. The specifics of the output gearing and
differential are not essential to this invention and are disclosed
in the '387 patent.
[0037] The charge pump includes an inlet porting plate 28 external
to the lower housing 22 at the external surface thereof, i.e.,
attached to the lower housing 22. Porting plate 28 is mounted so
that its interior surface is in close proximity to center section
26. Gerotor housing 29, which is also known as a charge cover, is
attached to the external surface c,f inlet porting plate 28, and
gerotor set 34 is held in position by the configuration of input
shaft 25. This embodiment also includes mounting the porting plate
28 on other housing elements, or parts that may be labeled by other
nomenclatures, that would perform functions similar to the
described upper and lower housings. Porting plate 28 includes an
inlet 36 that is connected to an external reservoir 50 that
contains hydraulic fluid and which is typically mounted on a
supporting member of the vehicle in which the IHT is mounted. Inlet
36 could also be in communication with and receive fluid from sump
32 instead of reservoir 50.
[0038] Input shaft 25 extends through pump 24 and center section 26
to drive gerotor set 34, which is of a standard design known in the
art. Rotation of gerotor set 34 by shaft 25 creates a low pressure
or suction at inlet 36 that remains constant regardless of the
forward or reverse status of the HST. The porting plate 28 also
includes fluid passage 31 in communication with gerotor set 34. The
action of the gerotor will cause fluid forced from the gerotor set
into passage 31 to become pressurized. Thus, fluid is drawn through
inlet 36 by the suction created by rotation of gerotor 34; the
pressurized fluid is then forced into passage 31 and then into
gallery 37. Gallery 37 is formed and defined by the interface
between the inlet porting plate 28 and the center section 26. In
the embodiment shown in FIG. 1, lower housing 22 includes an
opening for the bottom surface of center section 26 to be
approximately flush with the external bottom surface of lower
housing 22. The attachment location of center section 26 in upper
housing 21 establishes the position of the center section 26. Other
embodiments with different split lines to the housing elements
would have a similar opening. The positioning of the interface
between the center section and the porting plate is not critical.
In the embodiment shown in FIG. 1, the interface is flush with the
external housing, but may move from that position in other
embodiments.
[0039] In an alternative embodiment shown in FIG. 6, center section
26 could be mounted entirely within the IHT housing and inlet
porting plate 28 would then be mounted on the external surface of
lower housing 22. The charge pump is then connected to internal
porting 30 of center section 26 with a lower housing passage 96 and
a gallery formed inside the lower housing by a gallery housing
97.
[0040] FIG. 7 shows another embodiment of this invention, similar
to that shown in FIG. 6, wherein the porting plate has been
integrally formed with the lower housing 22. Center section 26 is
seated on internal surface 99 of lower housing 22. Gallery 37 for
the hydraulic fluid is formed and defined by the lower surface of
center section 26 and the internal surfaces of the integrally
formed porting plate, i.e., lower housing 22. An o-ring 73 is used
to aid in positioning and seating these elements and prevents
leakage of hydraulic fluid from gallery 37. The principal benefit
of this embodiment is the reduction in complexity by the
elimination of a separate porting plate. In the embodiment shown in
FIG. 1 o-ring 73 seals gallery 37 from the interface between
porting plate 28 and lower housing 22 as well as from sump 32. With
the integration of porting plate and lower housing 22 into a single
piece, the requirement to seal between these two is eliminated,
which thus increases the reliability of the IHT.
[0041] In the embodiment shown in FIGS. 1-5, check valves 39a and
39b are operatively connected to internal porting 30 of center
section 26. As shown in this embodiment, check valves 39a and 39b
may be included in plugs that are threaded directly into the
surface of center section 26. Alternatively, they may be located in
a separate plate that is then secured to center section 26.
[0042] The two check valves 39a and 39b each communicate with a
different side of the internal hydraulic porting 30. As previously
stated, the hydraulic circuit, including internal hydraulic porting
30, consists of a high pressure and a low pressure side, which are
reversed when the vehicle direction, of motion is changed. Thus,
while the HST is in the forward position, one side of the hydraulic
circuit is under high pressure and the corresponding check valve is
closed. At the same time the other side of the hydraulic circuit is
under low pressure and that corresponding check valve is open and
receives hydraulic fluid from gallery 37. When the HST is moved to
reverse, the two sides switch and the formerly low pressure side is
under high pressure and the corresponding check valve is now closed
and the high pressure side is now under low pressure, closing that
corresponding check valve.
[0043] When the HST is in the neutral position, there is no demand
for make-up fluid. However, since the rotational speed of input
shaft 25 does not vary, the fluid pressure supplied to gallery 37
from gerotor set 34 will remain constant, requiring fluid to be
diverted back to sump 32 through relief passage 38 formed into
center section 26. Relief valve 35, which may be located at any
point in passage 38, controls the flow through passage 38. While
the relief passage was selected to be through the center section in
this embodiment of the invention, alternative passages can be
formed through the porting plate 28 or through the housing 22; the
locations of the relief passage in other than center section 26 are
considered obvious variations of the invention. Also, relief valve
35 can be a variety of devices in configurations that are known in
the art, and would remain in communication with passage 38
regardless of the location of that passage.
[0044] A charge pump embodiment of the invention incorporated in an
HST will now be described in accordance with the accompanying
drawings. As discussed above, another embodiment of this invention
uses the charge pump in a stand-alone HST that is mounted within a
housing separate from that of the components that transfer power
from the HST to one or more axle shafts. In such an embodiment, the
specifics of the charge pump and related structures shown in FIG. 3
can remain the same. FIGS. 8-11 show such a stand alone HST unit
incorporating a charge pump embodiment of the invention. The
general operation of the HST is identical to that described above
and elements that are structurally identical to those described
above are given identical numerals.
[0045] As shown in FIGS. 9 and 10, HST 60 includes upper housing 61
and lower housing 62. In these figures, the rotation of motor 40
caused by action of the motor pistons 45 against fixed swashplate
46 drives output shaft 41. Output shaft 41 is supported by bearings
63, and extends through the transmission mounting plate 68 that is
integrally formed with upper housing 61 so as to engage a separate
axle driving apparatus (not shown).
[0046] As shown is FIG. 10, inlet 36 receives fluid from the
housing for the axle driving apparatus to which the HST 60 is
mounted. Fluid may also be received from a reservoir 50 that would
be mounted to the support structure of the vehicle in which the HST
and axle driving apparatus were attached. As in the IHT
configuration, inlet 36 could also be in communication with sump 32
formed by the upper housing 61 and lower housing 62.
[0047] Another embodiment of the charge pump and lower housing is
shown in FIGS. 12 and 13, wherein the inlet porting plate 28 is
integrally formed with the lower housing 62, similar to the
embodiment shown in FIG. 7. The explanation provided above for the
IHT version of this embodiment is applicable for the HST. The same
benefits that accrue to the IHT from this embodiment also accrue to
the HST.
[0048] An auxiliary pump embodiment of the invention incorporated
in an IHT or HST will be described in accordance with the
accompanying drawings. A further embodiment encompasses the use of
a pump that provides hydraulic fluid to power attachments and
implements, known in the art as an auxiliary pump, in addition to
the charge pump with an IHT or with a stand-alone HST that is
mounted with a separate axle driving apparatus. Auxiliary pumps for
use with HSTs are generally known in the art and are used to create
hydraulic fluid flow to power attachments and implements such as a
hydraulic mower deck lift. FIGS. 14 through 18 show an IHT 120 with
a charge pump and auxiliary pump mounted thereon in accordance with
this invention. The general operation of IHT 120 in this embodiment
is substantially identical to that of the IHT depicted in FIGS.
1-5, and similar parts are indicated with the same numeral preceded
by the numeral "1". For the sake of brevity, such parts will not be
discussed herein except as such specifically relates to this 20
embodiment of the invention,
[0049] As discussed above, the auxiliary pump and charge pump
combination disclosed herein can be used with an IHT, as shown in
FIGS. 12-17, and can also be used with an HST as shown in FIGS. 19
and 20 that has its housing attached to a separate axle driving
apparatus (not shown). The general operation of the auxiliary pump
and charge pump in FIGS. 19 and 20 is identical to that shown in
FIGS. 12-17 and the following discussion is applicable to both
applications of this embodiment. The mounting of the HST housing
through transmission mounting plate 168 is the same as was
described for FIG. 10 above.
[0050] As shown in FIG. 14, center section 126 is attached to upper
housing 121 such that the lower surface is generally at the same
level as the external surface of lower housing 122. The center
section 126 may be but need not be attached to the surface of lower
housing 122 in this embodiment, but is positioned by the hole in
the lower housing 122 through which the center section 126 extends.
Inlet porting plate 128 is attached directly to lower housing 122.
Center section 126 includes two check valves 138 that, as per the
preceding discussion, may be directly pressed into the bottom of
the center section or which may be incorporated in a separate
plate. Gerotor housing 129 is mounted to porting plate 128 and
houses gerotor set 134. Auxiliary pump cover 90 is then mounted to
gerotor housing 129. O-rings 91a and 91b are used to prevent
leakage of hydraulic fluid from the gerotor housing 129.
[0051] Rotation of gerotor set 134 created by rotation of input
shaft 125 creates a suction at inlet 136. The hydraulic fluid drawn
into gerotor set 134 is then forced into auxiliary outlet passage
92 under pressure to an implement circuit. The implement circuit
returns hydraulic fluid via the auxiliary inlet passage 93, and
then into gerotor housing 129. The gerotor housing provides a path
for the hydraulic fluid that is connected to fluid passage 131 in
the porting plate, and thus to gallery 137. The path that returns
fluid from the implement circuit is not critical, and may be
implemented in a variety of configurations that are well known in
the art. The direction of fluid flow is generally shown by the
arrows in FIG. 16.
[0052] As shown in FIG. 17, auxiliary pump cover 90 also includes a
charge relief valve 94 and a check valve 95. These valves can be
implemented in a variety of configurations that are well known in
the art, and are not unique to this invention. As the FIG. 17
hydraulic schematic indicates, charge relief 94 acts to maintain
hydraulic pressure in gallery 137. Excess fluid not demanded by
check valves 139a and 139b is diverted through charge relief valve
94 and returned to gerotor set 134, where it is again routed
through auxiliary outlet passage to the implement circuit 89. If
either the motor or pump requires more hydraulic fluid than is
available through implement circuit 89, then the suction caused in
gallery 137 when either check valve 139a and 139b opens will cause
check valve 95 to open to provide the additional hydraulic fluid
required.
[0053] Another embodiment shown in FIGS. 21-22 uses two completely
separate gerotor sets 98 and 134 to serve as auxiliary and charge
pumps, respectively. In this embodiment, the charge and auxiliary
circuits are independent of each other, as shown in the hydraulic
schematic in FIG. 21. An implementation of this embodiment is shown
in FIG. 22, where input shaft 25 has been lengthened to extend
through a modified charge cover 129, into the auxiliary pump 98.
The operation of this embodiment follows the description above
until return to the auxiliary cover 90, where flow is directed back
into the line that leads to reservoir 50 or sump 132. The operation
of the charge pump circuit follows the description provided in the
charge pump section above.
[0054] Turning now to FIGS. 23-26, there is illustrated two further
embodiments of the present invention. In particular, both of these
embodiments include a charge pump, comprising a gerotor 34 and
gerotor housing 29, which is externally mounted to a lower housing
cap 200. The lower housing cap 200 is, in turn, mounted over an
opening in a housing section 202. As described previously, the
gerotor 34 is drivingly engaged to the pump shaft 25 for creating a
quantity of high pressure hydraulic fluid. The high pressure
hydraulic fluid is stored in the gallery 37, which is disposed in
an area between the center section 26 and the charge pump, for use
in the hydraulic pump and motor circuit as needed.
[0055] More specifically, the gallery 37 is defined by a manifold
204 which is cooperably positioned between the center section 26
and the housing cap 200 such that the upper surface of the manifold
204 matingly engages the center section 26, opposite its pump
running surface, while the lower surface of the manifold 204
engages the interior surface of the housing cap 200. Preferably,
the manifold 204 is constructed from a generally resilient and high
pressure and heat resistant material, such as molded plastic or the
like, to allow the manifold 204 to be compressionally captured
between the center section 26 and the housing cap 200. To provide
further structural integrity to the manifold 204, the manifold 204
may be provided with a series of strengthening ribs. The
compressional capturing of the manifold 204 between the center
section 26 and the housing cap 200 is desirable as it functions to
minimize leakage from the gallery 37. To further assist in
preventing leakage of the high pressure fluid as it flows from the
charge pump to the gallery, an optional O-ring 205 may be
positioned between the manifold 204 and the housing cap 200 which
O-ring 205 seals the fluid flow path therebetween.
[0056] Also preferably supported between the center section 26 and
10 the housing cap 200 is an oil filter 206 which surrounds the
manifold 204. While not required in the preferred embodiment the
upper portion of the oil filter housing includes an extension 207
which is trapable between the manifold 204 and the center section
26 when the manifold 204 is secured hereagainst. This cooperation
between the housing extension 207, center section 26, and manifold
204 functions to further secure the oil filter 206 in its desired
position. A pair of optional O-rings 208, 210 are also preferably
positioned between the oil filter housing and the center section 26
and housing cap 200, respectively, to prevent the flow of hydraulic
fluid therebetween.
[0057] In a preferred embodiment of the invention, the manifold 204
is constructed to have a first generally circular upper portion
204a and a second generally circular lower portion 204b of smaller
diameter. It is to be understood that this configuration, of the
manifold 204 is not meant to be limiting and that the manifold 204
may be provided with other geometric arrangements while maintaining
its ability to form the gallery 37. Nevertheless, the circular
configuration provided to the upper portion 204a is desirable as it
is more economical to machine the portion of the center section
which preferably mates with the manifold 204 to prevent the side to
side motion thereof as a circle. Additionally, the differing
diameters of the upper portion 204a and the lower portion 204b is
preferred as it creates a storage area for unpressurized, filtered
fluid which area is in fluid flow communication with the charge
pump.
[0058] During operation, filtered hydraulic fluid will be drawn
into the charge pump through an inlet hydraulic passage 212 formed
in the lower housing 200. The resulting pressurized hydraulic
fluid, created by the action of the charge pump, will be forced
into the gallery 37 through an outlet hydraulic passage 214 formed
in the lower housing 200 and an opening 216 formed in the manifold
204. Check valves 39a, 39b mounted within the center section 26,
operatively connect the gallery 37 and the high pressure hydraulic
fluid stored therein with the hydraulic porting formed within the
center section 26.
[0059] A charge relief valve 35 may optionally be provided to allow
pressurized hydraulic fluid to be dumped from the gallery 37. In
particular, the charge relief valve 35 may be maintained in the
manifold 204 (FIGS. 23-25), in the center section 26 (FIG. 26), in
the housing cap 200, or in the charge cover 29 (not shown). When
the charge relief valve 35 is maintained in the manifold 204, it is
preferred that the valve body 218 be formed integrally with
manifold 204 itself, thus obtaining a valve body 218 at no
additional cost within the manifold 204. This embodiment is
particularly desirable since the elimination of the valve body also
reduces the number or parts and simplifies the assembly process to
the point where such assembly can occur at an original equipment
manufacturer. Specifically, the component parts constituting the
valve function are inserted into this body and retained therein by
a retaining ring or like type of securing device. Similarly, when
the charge relief valve 35 is maintained in the center section 26,
it is preferred that the center section 26 itself be used as the
valve body. This embodiment retains the advantages above-described
but at a slightly higher cost owing to the need to machine the
center section 26 to achieve the features required to maintain the
charge relief valve 35 therein.
[0060] Should the charge relief valve 35 not be utilized, it is
preferred that a fixed diameter bleed orifice be formed through the
manifold 204. Specifically, the manifold 204 may be provided with
an aperture of predetermined size which will allow the pressurized
hydraulic fluid to be dumped from the gallery 37 at a rate
dependent upon the viscosity thereof. Alternatively, while not
preferred, the manifold 204 could be captured between the center
section and the charge pump with an imperfect seal whereby the
pressurized hydraulic fluid may escape from the gallery 37
therethrough.
[0061] While the embodiments of the invention illustrated in FIGS.
23 and 26 have been shown with an externally mounted charge pump,
it is also contemplated that the charge pump could be internally
mounted within the housing without departing from the spirit of the
invention. Accordingly, in a further embodiment, it is contemplated
that the charge pump could be mounted to the internal surface of
the housing cap with the manifold being cooperably disposed between
the center section and charge pump cover.
[0062] It is to be understood that the above description should not
be read as limiting the scope of this invention, as further
features and benefits will be obvious to one skilled in the art.
This invention should be read as limited by the claims only.
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