U.S. patent number 3,907,465 [Application Number 05/502,109] was granted by the patent office on 1975-09-23 for hydraulic power translating device.
This patent grant is currently assigned to Hydraulic Products Incorporated. Invention is credited to Donald R. Dorff, Joseph A. Santi.
United States Patent |
3,907,465 |
Dorff , et al. |
September 23, 1975 |
Hydraulic power translating device
Abstract
A bi-directional hydraulic power translating device of the
gerotor type having inner and outer rotatable partial meshing gear
elements rotatably mounted in a casing with a clearance space
surrounding the outer gear element and with fluid passage structure
and valve means providing for a fluid flow through said clearance
space in either direction of operation of the device for obtaining
radial balance of the outer gear element in start-up operation and
also during rotation by hydrodynamic effects.
Inventors: |
Dorff; Donald R. (Union Grove,
WI), Santi; Joseph A. (Racine, WI) |
Assignee: |
Hydraulic Products Incorporated
(Sturtevant, WI)
|
Family
ID: |
23996377 |
Appl.
No.: |
05/502,109 |
Filed: |
August 29, 1974 |
Current U.S.
Class: |
418/71;
418/171 |
Current CPC
Class: |
F04C
15/0042 (20130101) |
Current International
Class: |
F04C
15/00 (20060101); F04C 015/00 () |
Field of
Search: |
;418/71,72,171,32
;417/315 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Freeh; William L.
Assistant Examiner: Smith; Leonard
Attorney, Agent or Firm: Wegner, Stellman, McCord, Wiles
& Wood
Claims
We claim:
1. A bi-directional power translating device of the gerotor type
having a casing with a cylindrical chamber, inner and outer gerotor
elements rotatably positioned in said chamber with a clearance
space between the chamber wall and the outer periphery of the outer
gerotor element, a pair of casing ports connectable to pressure and
tank respectively, passage means in said casing interconnecting
said casing ports and including flow passages to fluid ports
associated with the gerotor elements, means for delivering a flow
of fluid to said clearance space in either direction of operation
including a fluid inlet to said clearance space and generally in
line with a line through the axis of rotation of the inner gerotor
element and the pivot axis of the outer gerotor element, a fluid
outlet from the clearance space through which fluid passes and
which is diametrically opposed to said fluid inlet, each of said
fluid inlet and outlet being connected to said passage means, and
means to connect the fluid inlet to whichever of the casing ports
that receives pressure fluid and the fluid outlet to the other
casing port.
2. A bi-directional hydraulic motor of the gerotor type comprising,
a casing having a pair of ports, an inner gear element and an outer
gear element rotatably mounted in said casing with said outer gear
element eccentrically mounted relative to the inner gear element
whereby a series of fluid chambers are defined between said gears
and with said gears having their teeth interrelated at two
cross-over areas wherein fluid communication is blocked between
said fluid chambers at either side of said cross-over areas, a pair
of kidney-shaped fluid ports intermediate said cross-over areas,
and means subjecting the exterior of said outer gear element where
the outer gear element is a minimal distance from the casing to a
fluid pressure to obtain radial balance thereof upon start-up to
free the outer gear element for rotation relative to the case and
to balance said outer gear element during rotation, said means
including a single fluid pressure inlet and a diametrically opposed
single fluid outlet externally of the outer gear to provide a
restricted fluid flow path with flow in the direction of outer gear
element rotation to said fluid outlet and extending around the
exterior or the outer gear element from a location in advance of
said point where the outer gear is a minimal distance from the case
to a location beyond said point, and means connecting said fluid
pressure inlet to both of said casing ports with flow communicating
only to the casing port receiving pressure fluid.
3. A bi-directional hydraulic motor as defined in claim 2 wherein
said last mentioned means includes a pair of check valves
positioned in the flow path to either side of the fluid inlet.
4. A bi-directional power translating device comprising, a casing
with a cylindrical chamber, partially meshing inner and outer gear
elements rotatably mounted in said chamber with a clearance space
between a wall of said chamber and the outer periphery of said
outer gear element, said gear elements being eccentrically related
to define a series of fluid chambers and with said gear elements
having their teeth interrelated at two cross-over areas wherein
fluid communication is blocked between said fluid chambers at
either side of the cross-over areas, a pair of kidney-shaped fluid
ports in said casing intermediate said cross-over areas, a pair of
flow passages connected to respective ones of said ports, a fluid
pressure inlet to said clearance space circumferentially located
intermediate said fluid ports and connected to said flow passages,
a fluid pressure outlet from said clearance space diametrically
opposed to said pressure inlet and connected to said flow passages,
and valve means for placing only one of said flow passages in
communication with said fluid pressure inlet and the other flow
passage in communication with said fluid pressure outlet.
5. A power translating device as defined in claim 4 wherein said
valve means is pressure responsive.
6. A power translating device as defined in claim 5 wherein said
valve means includes first and second pairs of check valves with
one pair of preventing flow from said clearance space and between
said flow passages and the other pair permitting flow from said
clearance space but blocking flow between said flow passages.
7. A bi-directional hydraulic motor of the gerotor type comprising,
a casing, an inner gear element and an outer gear element rotatably
mounted in said casing with said outer gear element eccentrically
mounted relative to the inner gear element whereby a series of
fluid chambers are defined between said gears and with said gears
having their teeth interrelated at two cross-over areas wherein
fluid communication is blocked between said fluid chambers at
either side of said cross-over areas, a pair of kidney-shaped fluid
ports intermediate said cross-over areas, a pair of flow passages
connected one to each of said fluid ports, and means subjecting the
exterior of said outer gear element where the outer gear element is
a minimal distance from the case to a fluid pressure whereby the
outer gear element is supported for rotation relative to the case,
said means including a single fluid pressure inlet and a
diametrically opposed single fluid outlet externally of the outer
gear element to provide a restricted fluid flow path with flow in
the direction of outer gear element rotation to said fluid outlet
and extending around the exterior of the outer gear element and
with both said fluid inlet and fluid outlet connected to said flow
passages, and valve means to connect the flow passage having
pressure fluid to said fluid pressure inlet and the fluid pressure
outlet to the other flow passage.
8. A bi-directional hydraulic motor as defined in claim 7 wherein
passage means including said flow passages extend through said
casing between casing ports connectable to a source of pressure and
to tank, and the valve means includes a pair of pressure responsive
check valves positioned in said passage means to either side of
said fluid inlet and responsive to pressure whereby either of said
casing ports may supply pressure fluid and provide by-directional
operation.
9. A bi-directional hydraulic motor as defined in claim 8 wherein
said valve means includes a second pair of check valves to connect
said fluid outlet to whichever of the casing ports is connected to
tank.
Description
BACKGROUND OF THE INVENTION
This invention pertains to bi-directional power translating devices
of the gerotor type and more particularly to such a device
functioning either as a hydraulic motor or a pump.
The prior art discloses power translating devices of the gerotor
type in which radial balancing of the outer element is attempted as
shown, for example, in Brundage U.S. Pat. No. 3,427,983. The
inadequacies thereof are listed in a later Brundage U.S. Pat. No.
3,680,989. In a gerotor type device, the forces generated are
variable both in magnitude and in direction because the area of
operation on the internal part of the outer gear element is based
on two shifting seal points and the timing with respect to the
fluid port supplying the space between the gear elements. This area
varies in frequency and magnitude with the frequency being a
function of the number of teeth on the inner gear element times the
speed of rotation thereof and with the magnitude being a function
of the geometry of the inner and outer gear elements. Further, the
force acting on the outer gear element results in a pivoting of the
outer gear element relative to the casing about a generally fixed
point which establishes a minimum space in the clearance area
surrounding the outer gear element. This location varies with the
variation in magnitude and direction of the forces created by
operation of the device.
The prior art referred to above attempts to balance the outer gear
element by porting operating pressure to a plurality of locations
externally of the outer gear element. These attempts do not
recognize the variation in the magnitude and direction of the
forces.
A solution to the aforesaid problems is disclosed in the pending
application of the applicants, Ser. No. 205,164, filed Dec. 6,
1971, now U.S. Pat. No. 3,834,842. The prior application of
applicants discloses a solution to providing radial balance for the
outer gear element by utilizing a hydrodynamic sleeve bearing
effect wherein fluid may flow in the clearance space between the
outer gear element and the casing and in the same direction as the
rotation of the outer gear element and with a build-up in pressure
resulting from the forces urging the outer gear element toward the
casing. Applicant's prior device was constructed for operation in
one direction.
SUMMARY OF THE INVENTION
A primary feature of the invention disclosed herein is to provide a
bi-directional power translating device wherein an outer gear
element of a gerotor type device is radially balanced by a
hydrodynamic sleeve bearing effect in either direction of rotation
of the device.
In carrying out the invention disclosed herein the outer gear
element of the gerotor type device is mounted within a casing and
with a clearance space therebetween and with a fluid inlet
connected to said clearance space along a line coinciding generally
with the axis of rotation of the inner gear element and the pivot
point for the outer gear element along with a fluid outlet from the
clearance space diametrically opposite from the fluid inlet and
with valve means operable in response to fluid pressure to connect
the fluid inlet to either of the two casing ports for the device
which is receiving the fluid pressure and for connecting the fluid
outlet to the other of the casing ports that is connected to
tank.
With the location of a fluid inlet and a fluid outlet relative to a
clearance space in the casing surrounding the outer gear element of
the power translating device, it is possible to establish a
hydrostatic pressure gradient on initial start-up of the device as
a motor and with a hydrodynamic pressure established during normal
operation of the device as a pump or motor to obtain radial balance
of the outer gear element and to absorb varying loading resulting
from a shifting resultant of forces acting about the pivot point of
the outer gear element and also to resist deflections of the shaft
mounting the inner gear element, particularly at higher operating
pressures. It is contemplated that the operating pressure could be
as high as 5,000 psi.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan central section of the bi-directional power
translating device taken along the line 1--1 in FIG. 2;
FIG. 2 is a vertical section taken generally along the line 2--2 in
FIG. 2;
FIG. 3 is a graph showing the relation of hydrostatic pressures at
different points about the outer gear element and at two different
values of supply pressure;
FIG. 4 is a graph similar to FIG. 3 showing the relation of
hydrodynamic pressures at two different supply pressures;
FIG. 5 is a schematic view of the power translating device as a
motor at stall;
FIG. 6 is a schematic view of the power translating device as a
motor in operation in one direction of rotation; and
FIG. 7 is a view similar to FIG. 5 with the device as a pump.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The bi-directional power translating device is shown in FIGS. 1-6
as a motor and has a casing indicated generally at 10 with a
central part 11 defining a cylindrical chamber 12 and with a pair
of cover blocks 14 and 15 positioned to either side of the plate 11
and with the casing secured by a series of bolts 16. The power
translating device is of the gerotor type wherein an inner gear
element 20 is positioned within an outer gear element 21. The inner
gear element 20 is mounted on a shaft 22 for rotation therewith,
with the shaft being supported in the casing by bearings 23 and 24.
The cylindrical chamber 12 has its internal wall offset
eccentrically from the axis of rotation of the shaft 22 and the
inner gear element 20. This is conventional in a gerotor type
hydraulic power translating device. With the six teeth 25 on the
inner gear element 20 and the seven internal teeth 26 on the outer
gear element 21, there is thus established a plurality of fluid
chambers in spaces between the gear elements.
The casing 10 has a pair of opposed casing ports 30 and 31 for
connection to a supply of pressure fluid and to tank with the
connections being reversible because of the power translating
device being bi-directional in operation. For the schematic views
of FIGS. 5 and 6, it is assumed that the casing port 30 is
connected to a source of pressure fluid and that the casing port 31
is connected to tank. The casing ports 30 and 31 are interconnected
by passage means including a flow passage 40 which terminates in a
kidney-shaped fluid port 41 whereby fluid under pressure is
delivered to fluid chambers defined between the inner and outer
gear elements. The passage means includes a second flow passage 42
extending from the casing port 31 and terminating in a
kidney-shaped fluid port 43 whereby fluid delivered from certain of
the fluid chambers between the inner and outer gear elements may
flow to the casing port 31.
As shown in FIG. 5, a tooth 25 of the inner gear element meshes
with two teeth 26 of the outer gear element to define one
cross-over area between the pressure and tank sides of the device
with a second cross-over area being defined by surface engagement
between the tip of a tooth 25 of the inner gear element and a tip
of a tooth 26 of the outer gear element. The kidney-shaped fluid
ports 41 and 43 are positioned intermediate said cross-over
areas.
The outer gear element 21 has a diameter less than that of the
cylindrical chamber 12 whereby there is a clearance space 45
therebetween. For the device to have operating characteristics of
high starting torque as well as radial balance during operation,
fluid is supplied to the clearance space 45 for flow around the
outer gear element and exhaust from the clearance space to tank.
This is accomplished by having a fluid inlet 46 to the clearance
space defined by a groove in the casing plate 11 which communicates
with a groove 47 on a face of the casing plate 11 and which extends
to upper and lower valve bores 48 and 49 connected to the flow
passages 40 and 42 to thereby define passage means interconnecting
the casing ports 30 and 31. A pair of pressure responsive valves
are positioned in the valve bores 48 and 49 and specifically
comprise a pair of check valves 50 and 51 which are spring-loaded
by springs 52 and 53, respectively, to seat against associated
valve seats and open in response to fluid pressure. As seen in the
schematic view of FIG. 5 the check valve 51 opens in response to
pressure at casting port 30 and in flow passage 40 to deliver
pressure fluid to the fluid inlet 46 while the assocaited check
valve 50 prevents communication of the fluid inlet with the casing
port 31. With the pair of check valves 50 and 51, it is possible to
have bi-directional operation of the power translating device with
either of the casing ports 30 and 31 connected to a source of fluid
under pressure and to have fluid pressure conducted to the fluid
inlet 46 to supply pressure fluid to the clearance space 45.
Fluid is exhausted from the clearance space 45 through a fluid
outlet 60 formed as a groove in the casing plate 11 and which
connects by a passage 61 to a space 62 in the casing block 15
surrounding the shaft 22. This space communicates with the flow
passages 40 and 42 through a pair of passages 63 and 64 (FIG. 2)
each of which have associated therewith a pressure responsive valve
in the form of check valves 65 and 66 which are urged by their
respective springs 67 and 68 in a direction to close the space 62
from communication with the flow passages 40 and 42. The back side
of the check valve 65 and 66 are exposed to the flow passages 40
and 42 whereby existence of fluid under pressure in one of said
flow passages will maintain the associated check valve seated. In
the direction of operation referred to herein, there is fluid
pressure in the flow passage 40 whereby check valve 66 is
maintained closed while the pressure of fluid exhausted from the
clearance space 45 is sufficient to unseat the check valve 65 and
permit fluid to flow to the flow passage 42 which is connected to
tank.
The hydrostatic and hydrodynamic pressures involved in the device
in obtaining good start-up characteristics and radial balancing
during operation are shown in the graphs of FIGS. 3 and 4. In each
of FIGS. 3 and 4, a pressure curve is shown in full line for
operating at a relatively high pressure and a pressure curve shown
in broken line for operating at a lower supply of pressure and with
the points along the abscissa of the graph identified from A to H
corresponding to the circumferential locations identified in FIGS.
5 and 6. The hydrostatic pressures are shown in FIG. 3 which when
delivered to the fluid inlet 46 are at a value shown at point A.
The pressure progressively drops to point C and continues at a
relatively low value until a point shortly prior to point H. The
hydrostatic pressure results from the flow of oil under pressure to
fluid inlet 46 and then in both directions, as indicated by the
arrows in FIG. 5, toward points C and G. The amount of this flow is
a function of clearance, system pressure and capacity. As the outer
gear element 21 begins to rotate it first climbs the wall of the
cylindrical chamber 12 in a direction opposite to the clockwise
rotation of FIGS. 5 and 6. This restricts the clearance on one side
of the outer gear element thus causing a greater flow from A to G
than from A to C. This differential flow rate will cause the
pressure gradient between A and B to be greater than between A and
H due to variance of flow and this will balance the outer gear
element.
In considering the hydrodynamic pressures, it should be noted that
forces resulting from pressure acting in the fluid chambers of the
device act generally in the direction of the arrow 70 in FIG. 6 but
with variations in the direction thereof as previously explained.
This force causes a pivoting of the outer gear element 21 about a
point 72 which is fixed relative to the casing in all rotative
positions of the gear elements with the result that the outer gear
element is urged toward the wall of the cylindrical chamber 12 in a
direction generally indicated by the arrow 74 in FIG. 6. The fluid
inlet 46 to the clearance space lies along a line which includes
the pivot point 72 and the rotational axis of the shaft 22 to
provide the maximum bearing area in either direction of rotation of
the device and well in advance of the minimum clearance space
between points B and C of FIG. 6 and generally in the area of the
arrow 74.
In the opposite direction of rotation the minimum clearance area
would be between the points G and H. For the direction of rotation
shown in FIG. 6, it will be seen from the graph of FIG. 4 that
there is a build-up of pressure between points B and C which
counteracts the forces tending to pivot the outer gear element 21
toward the cylindrical chamber wall. Thus the hydrodynamic pressure
radially balances the outer gear element while the hydrostatic
pressure is diminishing. With the hydrodynamic sleeve bearing
effect, it is inherent that the peak pressure as illustrated
between B and C in the graph of FIG. 4 will vary peripherally of
the cylindrical chamber 12 as the location of the arrow 74
representing the direction of pivoting varies. Thus the
hydrodynamic bearing effect inherently provides radial balance even
though the resultant of the forces indicated by arrow 70 varies as
is inherent in a gerotor type device. The curves of FIG. 4 will
vary dependent upon viscosity of the fluid, clearance and speed of
rotation of the device.
The pressure peak will move toward point C as viscosity increases
and clearance decreases. With a speed increase the pressure peak
will widen because of a greater flow through the clearance space
resulting from the carrying of fluid around the outer gear element
as the outer gear element rotates.
It is believed obvious from the foregoing that if the casting port
31 is connected to pressure and the casing port 30 connected to
tank, then the check valve 50 will open to deliver fluid under
pressure to the fluid inlet 46 with the check valve 51 being closed
to block communication with the casing port 30. The check valve 65
will be held closed by pressure in the flow passage 42 and the
check valve 66 will open to permit fluid to flow from the fluid
outlet 60 to the casing port 30.
With this construction, a bi-directional power translating device
is provided wherein, in either direction of operation, fluid is
delivered to the clearance space to obtain hydrostatic pressure at
stall and start-up of the device and to obtain hydrodynamic
balancing pressure for operation at various speeds and loads and
with a shift in the maximum pressure location responsive to the
shift in the forces acting on the outer gear element.
The previous description of the structure shown in FIGS. 1-6 has
been of a motor which is one form of a bi-directional power
translating device. The desirability of obtaining radial balance of
the outer gear element is equally applicable to a pump of the
gerotor type. Generally, in the description and in the claims,
reference to a power translating device is intended to be generic
to both motors and pumps. In a pump there are no adverse forces in
start-up operation since there is no initial loading of the gear
elements. There is, however, the same reactive force on the outer
gear element during normal rotation which is balanced by the
hydrodynamic bearing effect.
FIG. 7 is a view similar to FIG. 5 and schematically showing the
power translating device with valving associated therewith for pump
operation. In FIG. 7, parts corresponding to those shown in FIG. 5
have been given the same reference numeral with a prime affixed
thereto. It will be noted that the direction of rotation of the
unit is the same as FIG. 5, with the casing port 30' being
connected to a supply of fluid and the casing port 31' being the
pressure outlet port. There has been a reversal of location of the
two pairs of check valves with the check valves 50' and 51' acting
in opposition to pressure conditions at casing ports 30' and 31'.
With the direction of operation shown in FIG. 7, check valve 50'
opens to permit flow of fluid to the groove 60' which now functions
as a fluid inlet. In the other direction of operation as a pump,
the check valve 51' opens to permit flow to the groove 60' from the
casing port 30'.
The second pair of check valves 65' and 66' function to permit flow
from the groove 46' to the casing port 30' or 31' which is at the
lower pressure.
Another way of adapting the disclosed structure to bi-directional
pump operation would be a change in eccentricity of the outer gear
element 21. Specifically referring to FIG. 2, the point M
identifies the center of rotation of the outer gear element within
the casing for operation as a motor. With the valving unchanged and
as disclosed in FIGS. 1-6, the chamber 12 in the central part 11 of
the casing could be changed to provide for a center of rotation of
the outer gear element 21 about point P in pump operation.
It should be recognized that there are several different designs
for a power translating device of the gerotor type. In the specific
embodiment disclosed, reference has been made to a 6-7 teeth
relation. It is also known to have teeth relationships of 8-9,
10-11 and 12-13, and there are possibly other variations. The key
principle common to these devices is the lower relative velocity
between the coacting surfaces of the inner and outer gear
elements.
Also contemplated within the invention in referring to inner and
outer gear elements are structures of the type shown in U.S. Pat.
No. 3,623,829, wherein the inner gear element has external teeth
which are in the form of spherical elements.
* * * * *