Note: Descriptions are shown in the official language in which they were submitted.
CA 02494996 2005-02-07
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TITLE
LONG-PISTON HYDRAULIC MACHINES
TECHNICAL FIELD
This invention relates to liquid hydrauiic pump/motor machines
appropriate for relatively "heavy duty" automotive use, e.g., for
hydraulic transmissions used for vehicle locomotion and/or for the
storing and retrieval of fluids in energy-saving accumulator systems.
[Note: the term "liquid" is used to distinguish from "gas" hydraulic
pumps, e.g., pumps for compressing air and/o r other gases which,
while using somewhat similar-looking parts, have remarkably less
demanding pressure andr load duty cycles and, therefore, are generalfy
considered by hydraulic experts as being incorporated in a different
technical field having relatively few compatible design parameters.]
BACKGROUND
Hydraulic pumps and motor are well known and widely used,
having reciprocating pistons mounted in respective cylinders formed in
a cylind'er bl'ock and. positioned circumferentiall'y at a first radial
distance about the rotationa.l, axis of a drive, el'errment. Many of these
pu ~ ~ p/motor machines have variabfe dispPacement capabilities, and'
they are g,enerally of two basic designs: (a)'~ either the pistons
~=~'f.~;+ . .. . .
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reciprocate in a rotating cylinder block against a variably inclined, but
otherwise fixed, swash-plate; or (b) the pistons reciprocate in a fixed
cylinder block against a variably inclined and rotating swash-plate that
is often split to include a non-rotating (i.e.,nutating-only) "wobbler"
that slides upon the surface of a rotating and nutating rotor. While
the invention herein is applicable to both of these designs, it is
particularly appropriate for, and is described herein as, an improvement
in the latter type of machine in which the pistons reciprocate in a fixed
cylinder block.
As indicated above, this invention is directed to "liquid" (as
distinguished from "gas") type hydraulic machines. Because of the
incompressibility of liquids, the pressure and load duty cycles of the
these two different types of hydraulic machines are so radically
different that designs for the gas compression type machines are
inappropriate for use in the liquid-type machines, and visa versa.
Therefore, the following remarks should all be understood to be
directed and applicable to liquid-type hydraulic machines and, primarily,
to such heavy duty automotive applications as those identified in the
Technical Field section above.
Hydraulic machines with fixed cylinder blocks can be built much=
lighter and smaller than the machines that must support and protect
heavy rotating cylinder blocks. However, these lighter machines
require rotating, and nutating swash-plate assemblies that are difficult
to mount and support. For high-pressure/high-speed service, the
swash-plate assembly must besupporteda in a manner that allows for
the relative motion, between the heads of the non-rotating pistons and'
: -, ~ ~ :-_ -=:-; ~;l~s,,~ . ,. ,,_. ~
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a mating flat surface of the rotating and nutating swash-plate. As just
indicated above, such prior art swash-plates have often been split into
a rotating/nutating rotor portion and a nutating-only wobbler portion,
the latter including the flat surface that mates with the heads of the
non-rotating pistons. As is well known in the art, this relative motion
follows varying non-circular paths that occur at all inclinations of the
swash-plate away from 00
.
Also, such fixed-cylinder-block machines have heretofore used a
"dog-bone" extension rod (i.e., a rod with two spherical ends) to
interconnect one end of each piston with the flat surface of the
nutating-but-not-rotating wobbler. One spherical end of the dog bone
is pivotally mounted into the head end of the piston, while the other
spherical end is usually covered by a pivotally-mounted conventional
"shoe" element that must be held at all times in full and flat contact
against the flat surface of the swash-plate wobbler. These just-
mentioned elements greatly increase the complexity and cost of
building the rotating swash-plates of these lighter machines.
Dog-bone rods are also sometimes used to interconnect one end
of each piston with, the inclined (but not rotating) swash-plates of
hydraulic machines with rotating cylinder blocks. However, more often
this latter type of machine omits such dog-bones, using instead
elongated pistons, each having a spherical, head at one end; (again,
usually covered, by a pivotalfy-mounted conventional shoe element)
that effectively contacts the non-rotating, f[atsurface of the swash-
pl'ate. Such, elongated pistons are designedi sa that a sig-nificant
portion of the, axial= cylindrical, body of each, piston, remains supported!
CA 02494996 2005-02-07
4 f ij
- -
by the walls of its respective cylinder at all times during even the
maximum stroke of the piston. This additional support for such
elongated pistons is designed to assure minimal lateral displacement of
each spherical piston head as it slides over the inclined-but-not-
rotating swash-plate when the pistons rotate with their cylinder block.
Generally, these elongated pistons are primarily lubricated by
"blow-by", i.e., that portion of the high pressure fluid that is forced
between the walls of each cylinder and the outer circumference of
each piston body as the reciprocating piston drives or is driven by high
pressure fluid. Such blow-by provides good lubrication only if
tolerances permit the fiow of sufficient fluid between the walls of the
cylinder and the long cylindrical body of the piston, and blow-by
sufficient to assure good lubrication often negatively effects the
volumetric efficiency of the pump or motor machine. For instance, a
cubic inch machine can use as much as 4 gallons of fluid per minute
for blow-by. While smaller tolerances can often be used to reduce
blow-by, the reduction of such tolerances is limited by the needs for
adequate lubrication that increase with the size of the pressure and
duty loads of the machine. Of course, such bl'ow-by is accomplished
by using. fluid that would otherwise be used to drive or be driven by
the pistons to accomplish work. Therefore, in the exarnple j,ust given
above, the 4 gallons of fluid per minute used for blow-by lubrication,
reduces the volumetric efficiency of the machine.
The invention disclosed, bel'ow is d'irected, to improving the
volumetric efficiency of such! el'ong;ated'-piston, machines while, at the,
same time, assuring, (a); appropriate lubrication~ of the, pistons and, (b)
~t,~F.. i
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simplification of the apparatus used to maintain contact between the
pistons and the swash-plate.
SUMMARY OF THE INVENTION
The invention is disclosed on various embodiments of hydraulic
machines, all of which are designed with the preferred format of fixed
cylinder blocks and rotating/nutating swash-plates. [However, persons
skilled in the art will appreciate that the invention is equally applicable
to hydraulic machines with rotating cylinder blocks and swash-plates
that do not rotate with the drive elements of the machines.] Each
disclosed machine can operate as either a pump or a motor. One
embodiment has a swash-plate that, while rotating, at all times with the
drive element of the machine, is fixed at a predetermined inclined
angle relative to the axis of the drive element so that the pistons
move at a maximum predetermined stroke at all times. The swash-
plates of the other disclosed machines have inclinations that can be
varied, throughout a range of angles in a manner well known in the art
to control the stroke of the pistons throughout a range of movements
up to a maximum in each direction.
In each machine according to the invention, each piston is
elongatedi, having an axial' cylindrical body portion that preferably is
substantially as long as the axial length of the respective cylind'er in
which, it reciprocates. Preferably, each piston also has a spherical head
end that, by means of a conventionally pivoted' shoe and relatively
simple apparatus, is ma=intained, in; effective sfid'ing contact with a flat
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face of the machine's swash-plate. The axial length of each cylindrical
piston body is selected to assure minimal lateral displacement of the
spherical first end of the piston at all times. Therefore, the preferable
piston for this invention is "elongated", that is, even when each piston
is extended to its maximum stroke, that portion of the piston body
which is still supported within its respective cylinder is sufficient to
assure a minimal lateral displacement of the extended spherical end of
the piston at all times during machine operation.
[NOTE: To facilitate explanation of the invention, each piston is
described as having an axial cylindrical body portion and a spherical
head end, while each respective cylinder has a valve end and an open
head portion beyond which the spherical head end of each piston
extends at all times. Further, for all preferred emodiments, it is
assumed that each disclosed hydraulic machine (e.g., whether motor
or pump) is paired with a similar hydraulic machine (e.g., a mating
pump or rriotor) in a well known "closed loop" arrangement wherein
the high-pressure fluid exiting from each pump is directly delivered to
the input of the related motor, while the low-pressure fluid exiting
from each motor is directly delivered to the input of the related pump.
As understood in the art, a portion of the fluid in this closed loop
system is continually lost to "blow-by" and is collected: in a sump; and
fluid is automatically delivered from the sump back into the closed
loop, by a charge pump, ta maintain a predetermined volume of fluid in
the cl'osed loop system at all times.]
According to the inventioa, each, cylinder forrnedl within the,
cylinder blocks of each machine is provided with: a, respective
~- =~~gV, '.~::~
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lubricating channel formed in the cylindrical wail of each cylinder. This
lubricating channel is positioned so that at all times during
reciprocation of the piston within its respective cylinder, each
respective lubricating channel remains almost completely closed by the
axial cylindrical body of the piston during its entire stroke. [The '
movement of fluid in these lubricating channels is discussed in greater
detail beginning two paragraphs below.] Preferably, each respective
lubricating channel is formed circumferentially and radially transects
each cylinder.
Also formed in the fixed cylinder block of each machine are a
plurality of further passageways that interconnect each of the just-
described lubricating channels. The interconnection of all of the
lubricating channels, one to another, forms a single, continuous
lubricating passageway in the cylinder block. This continuous
lubricating passageway is formed entirely within the cylinder block,
preferably transecting each cylinder and, being centered
circumferentially at substantially the same radial distance as the
cylinders are centered about the rotational axis of the drive element.
Special attention is called to the fact that, in the preferred
embodiments disclosed, the continuous lubricating passageway just
described above is not connected by either fluid "input" or fluid
"output" passageways but instead is almost completely closed off by
the cylindrical body portions of the pistons at all times during
operation of the machine. Therefore, the only source of Iubricating,
fluid suppl'ying; this continuous lubricating; passageway is a secondary
minimal: flow of ffuidl between each of the respective cyl'ind'rical~ walls of
rfR',~~
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CA 02494996 2005-02-07
i?:. } '.6 ii,; i?
- 8
us
each cylinder and the axial cylindrical body of each respective piston.
During operation, this lubricating passageway almost instantly fills with
an initial minimal flow of high-pressure fluid that enters at the valve
end of each cylinder and then passes between the walls of each
cylinder and the outer circumference of the body portion of each
driven piston. This secondary minimal flow effectively maintains high
pressure within the continuous lubricating passageway at all times. If
necessary, a plurality of sealing members, each located respectively
near the open end of each cylinder, can optionally provide a relatively
tight seal for substantially eliminating blow-by between the body
portion of each piston and the open head portion of each respective
cylinder, thereby allowing the escape of only minimal blow-by from this
lubricating passageway past the open end of the cylinders. However,
in actual practice it has been found that only a relatively minimal blow-
by from the open end of the cylinders moves past the elongated -
pistons of the invention and, since a small amount of blow-by mist is
required for adequate lubrication of the drive shaft bearings, etc., such
optional sealing members may not be necessary.
Nonetheless, the lubricating fluid in this closed continuous
lubricating passageway moves constantly as the result of the ever-
changing. pressures in each of the respective cylinders as the pistons.
reciprocate. That is, as the pressure in each cylinder is reduced to low
pressure on the return stroke of each piston, the high pressure fluid in
the otherwise cl'osed lubricating, passageway is again driven between
the walls of each cylinder and the outer circumference of the body of
each~ piston~ into the valve end~ of eachi cylinder experiencing such'
pressure reductiom However, the lubricating fluid that is driven toward'
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low pressure is not "lost", i.e., it is not "blow-by" and is not returned
to the sump to be replenished into the closed loop hydraulic system by
the charge pump. Instead, this low pressure lubricating fluid is
immediately returned to the closed loop without requiring the use of a
charge pump, and the closed continuous lubricating passageway is
immediately replenished by the entrance of a similar flow of high-
pressure blow-by from the valve end of each cylinder experiencing
increased pressure.
The just-described lubricating passageway provides appropriate
lubrication for the high-speed reciprocation of the pistons while
substantially reducing blow-by. During successful operation of
commercial prototypes built according to the invention, blow-by was
reduced by 90%. That is, the blow-by experienced by conventional
commercial hydraulic machines of comparable specifications generally
ranges between 4-5 gallons per minute, while the blow-by experienced
by the invention's prototypes ranges between 0.5-0.7 gallons aer
minute, thereby remarkably increasing the volumetric efficiency of the
invention's hyd'raulic machines.
As indicated above, fixed-cylinder-block hydraulic machines can
be built smaller and, lighter than conventional, rotating block hydraulic
machines having similar specifications. As a result of the irnproved,
lubrication of the elongated pistons, the disclosed invention makes it
possibfe to use these smaller and lighter d'esigns to meet the high-
speed/high, pressure specifications required, for automotive use.
,.a,
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Further, special attention is called to the invention's significantly
simplified support assemblies for the variable rotating swash-plates of
the invention's disclosed hydraulic machines. Each of the invention's
support assemblies disclosed herein omits the dog-bones that
normally are mounted between the outer end of each piston and the
nutating-only wobbler portion of a conventional rotating/nutating
swash-plate, and a conventional shoe is mounted directly to the
spherical head of each piston and is maintained in effective sliding
contact with the flat face portion of the swash-plate by means of a
minimal spring bias sufficient to maintain such effective sliding contact
in the absence of hydraulic pressure at the valve ends of the pump's
cylinders.
Two simplified support mechanisms are disclosed: The first
simplified support mechanism comprises a unique hold-down plate
assembly biased by a single coil spring positioned circumferentially
about the rotational axis of the pump's drive element. The invention's
second support mechanism is even simpler, comprising nothing more
than a conventional shoe mounted directly to the spherical head of
each piston, with the minimal bias being supplied by a plurality of
springs, each spring being: positioned respectively within the body
portion of each respective pistoa between the body portion of each,respective
piston and the valve end of each respective cylinder. While
the second support mechanism is a little more difficult to assemble
than the first, the latter is considerably simpler, lighter, and cheaper to
manufacture.
~.:
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- 9b
The important changes introduced by this invention provide
hydraulic machines that are lighter and smaller than conventional
machines having similar specifications. Further, as indicated above,
actual testing of working prototypes have proven that this invention
provides machines with significantly increased volumetric and
mechanical efficiency. In short, the invention disclosed herein provides
machines having remarkably greater efficiency while significantly
reducing the weight and size of the machines as well as the cost of
manufacture and simplifying assembly.
DRAWINGS
FIG. 1 is a partially schematic and cross-sectional view of a
hydraulic machine with a fixed cylinder block and a rotating/nutating
swash-plate having a fixed angle of inclination, showing features of the
invention incorporated in the cylinder block and at the piston/swash-
plate interface.
FIG. 2 is a partially schematic and cross-sectional view of the
fixed: cylinder block of the hydraulic machine of FIG. 1, taken along, the
plane 2-2 with parts being omitted for clarity.
FIG. 3 is a partially schematic and cross-sectional, view of a
hydraulic machine with, a fixed cylinder block and: a rotating/nutating
swash-plate having, a variable angle of inclination, again showing,
features of the invention~ incorporated' in. thecytind'er block and at the,
piston/swash-plate interface.
CA 02494996 2005-02-07
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FIGS. 4A and 4B are partially schematic and cross-sectional
views of the swash-plate and piston shoe hold-down assembly
disclosed in FIGS. 1 and 3, with parts removed for clarity, showing
relative positions of the head ends of the pistons, shoes, and special
washers, as well as the spring-biased hold-down element that biases
each sliding shoe against the flat face of the swash-plate when the
swash plate is inclined at +25 , the view in FIG. 4A being taken in the
plane 4A-4A of FIG. 3 in the direction of the arrows, while the view in
FIG. 4B is taken in the plane 4B-4B of FIG. 4A.
FIGS. 5A and 5B, 6A and 6B, and 7A and 7B are views of the
same parts illustrated in FIGS. 4A and 4B when the swash-plate is
inclined, respectively, at +15 , 0 , and -25 , the respective views in
FIGS. 5B, 6B, and, 7B being taken in the respective planes 5B-5B, 6B-
6B, and 7B-7B of FIGS. 5A, 6A and 7A.
FIG. 8 is an enlarged, partial, schematic and cross-sectional view
of only a single cylinder and piston for another hyd'raulic machine
similar to those shown in FIGS. land 3 but showing, a more simplified
second embodiment of a spring-biased hold-down assembly for the
invention's piston shoes.
,7 õ=a! ,~sr=:-... ~
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DETAILED DESCRIPTION
The operation of hydraulic machines of the type to which the
invention may be added is well known. Therefore, such operation will
not be described in detail. As indicated above, it can be assumed that
each disclosed machine is connected in a well known "closed loop"
hydraulic system with an appropriately mated pump or motor.
CA 02494996 2005-02-07
WO 2004/020827 PCT/US2003/026707
Hydraulic Motor
[25] Referring to FIG. 1, hydraulic motor 10 includes a fixed cylinder
block 12 having a plurality of cylinders 14 (only one shown) in which a
respective plurality of mating pistons 16 reciprocates between the
retracted position of piston 16 and the extended position of piston 16'.
Each piston has a spherical head 18 that is mounted on a neck 20 at
one end of an elongated axial cylindrical body portion 22 that, in the
preferred embodiments shown, is substantially as long as the length of
each respective cylinder 14.
[26] Each spherical end 18 fits within a respective shoe 24 that slides
over a flat face 26 formed on the surface of a rotor 28 that, in turn,
is fixed to a'drive element, namely, shaft 30 of the machine. Shaft 30
is supported on bearings within a bore 31 in the center of cylinder
block 12. Flat face 26 of fixed rotor 28 is inclined at a predetermined
maximum angle (e.g., 25 ) to the axis 32 of drive shaft 30, being
supported by an appropriate thrust bearing assembly 35.
[27] A modular valve assembly 33, which is bolted as a cap on the left
end of cylinder block 12, includes a plurality of spool valves 34 (only
one shown) that regulates the delivery of fluid into and out the
cylinders 14. As indicated above, each of the machines disclosed can
be operated as either a pump or as a motor. For this description of a
preferred embodiment, the fixed-angle swash-plate machine shown in
FIG. 1 is being operated as a motor. Therefore, during the first half of
each revolution of drive shaft 30, high-pressure fluid from inlet 36
enters the valve end of each respective cylinder 14 through a port 37
to drive each respective piston from its retracted position to its fully
extended position; and during the second half of each revolution, lower
CA 02494996 2005-02-07
WO 2004/020827 PCT/US2003/026707
11
pressure fluid is withdrawn from each respective cylinder through port
37 and fluid outlet 39 as each piston returns to its fully retracted
position.
[28] In a manner well known in the art, fluid inlet 36 and outlet 39 are
preferably connected through appropriate "closed loop" piping to a
mating hydraulic pump (e.g., pump 110 shown in FIG. 3 and discussed
below) so that, at all times, fluid pressure biases spherical ends 18 and
respective shoes 24 against flat face 26. The serial extension and
retraction of each respective piston causes rotor 28 to rotate,
thereby driving shaft 30. Flat face 26 is fixed at the maximum angle
of inclination so that, when the flow rate of hydraulic fluid being
circulated in the closed loop through inlet 36 and outlet 39 is relatively
small, pistons 16 reciprocate relatively slowly, resulting in a relatively
slow rotation of drive shaft 30. However, as the flow rates of fluid
circulation in the closed loop increase, the reciprocation of the pistons
increases accordingly and so does the speed of rotation of drive shaft
30. When operated at automotive speeds or pressures (e.g., up to
4000 rpm or 4000 psi), lubrication of the pistons becomes critical, and
blow-by losses can also greatly increase. Cylinder block 12 is modified
by the invention to address such lubrication needs and to reduce such
blow-by losses.
[29] Referring now to both FIGS. 1 and 2, the cylindrical wall of each
cylinder 14 is transected radially by a respective lubricating channel 40
formed circumferentially therein. A plurality of passageways 42
interconnect all lubricating channels 40 to form a continuous
lubricating passageway in cylinder block 12. Each respective
lubricating channel 40 is substantially closed by the axial cylindrical
body 22 of each respective piston 16 during the entire stroke of each
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- 12
piston. That is, the outer circumference of each cylindrical body 22
acts as a wall that encloses each respective lubricating channel 40 at
all times. Thus, even when pistons 16 are reciprocating through
maximum strokes, the continuous lubricating passageway
interconnecting all lubricating channels 40 remains substantially closed
off. Continuous lubricating passageway 40, 42 is simply and
economically formed within cylinder block 12 as can be best
appreciated from the schematic illustration in FIG.2 in which the
relative size of the fluid channels and connecting passageways and has
been exaggerated for clarification.
During operation of hydraulic motor 10, all interconnected
lubricating channels 40 are filled almost instantly by a minimal flow of
high-pressure fluid from inlet 36 entering each cylinder 14 through
port 37 and being forced between the walls of the cyiinders and the
outer circumference of each piston 16. Loss of lubricating fluid from
each lubricating channel 40 is restricted by a surrounding seal 44
located near the open end of each cylinder 14. Nonetheless, the
lubricating fluid in this closed continuous lubricating passageway of
lubricating channels 40 flows moderately but continuously as the
result of a continuous minimal flow of fluid, between each of the
respective cylindrical, walls of each cylinder and~ theaxial cylindrical;
body of each respective piston in response to piston motion and to
the changing pressures in each half-cycle of rotation of drive shaft 30
as the pistons reciprocate. As the pressure in each cylinder 14 is
reduced to. low pressure on the return stroke of each piston 16, the
higher pressure fluidi in- otherwiseclosed'Iubricating+ passageway 4G, 421
is again, driven between the walls of each cylinder. 14 and the. outer
;~.
,yimv s~~f r; ~~i?:L }
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- 13
circumference of body portion 22 of each piston 16 into the valve end
of each cylinder 14 experiencing such pressure reduction.
However, special attention of persons skilled in the art is called
to the fact that this just-mentioned minimal flow of fluid back into
cylinder 14 is not "lost". Instead, it is immediately returned to the well
known closed hydraulic fluid loop that interconnects the pump and
motor. Further, this minimal flow of fluid does not return to a sump
and, therefore, does not have to be replenished into the closed loop
hydraulic system by a charge pump. Finally, closed continuous
lubricating passageway 40, 42 is immediately replenished by the
entrance of a similar minimal flow of high-pressure fluid from the valve
end of each cylinder experiencing increased pressure.
As mentioned above, there is minimal blow-by loss from closed
continuous lubricating passageway 42 that interconnects all lubricating
channels 40. That is, there may be a minimal fluid flow that leaks from
this closed continuous lubricating passageway past the seals 44 at the
end of each cylinder 14. However, any such minimal blow-by is
instantly replenished by a similar minimal flow of high pressure fluids
entering around the opposite end of each piston 16.
The just described lubrication, arrangement is not onl'y
remarkably simple, and it also permits a similar simplification of the
pinion/swash-plate interface apparatus of the hydraulic machine to
further reduce the cost of manufacture and' operation.
CA 02494996 2005-02-07
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z
To complete the description of hydraulic motor 10, the
pinion/swash-plate interface apparatus shown in FIG.1 comprises only
(a) rotor 28 mounted on drive shaft 30 using conventional needle and
thrust bearings and (b) a simple spring-biased hold-down assembly for
maintaining piston shoes 24 in constant contact with the rotating and
nutating flat surface 26 of rotor 28. [Note: Two embodiments of the
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14
invention's simplified pinion/swash-plate interface assemblies are
described in greater detail in a separate section below.]
[35] The first embodiment of the invention's hold-down assembly, as
shown in FIG. 1, includes a coil spring 50 that is positioned about shaft
30 and received in an appropriate crevice 52 formed in cylinder block
12 circumferentially about axis 32. Spring 50 biases a hold-down
eleme.nt 54 that is also positioned circumferentially about shaft 30 and
axis 32. Hold-down element 54 is provided with a plurality of openings,
each of which surrounds the neck 20 of a respective piston 16. A
respective special washer 56 is positioned between hold-down element
54 and each piston shoe 24. Each washer 56 has an extension 58 that
contacts the outer circumference of a respective shoe 24 to maintain
the shoe in contact with flat face 26 of rotor 28 at all times.
[36] The just-described hydraulic motor, with its remarkable
simplification of both lubrication and the piston/swash-plate interface,
is efficient, easy to manufacture, and economical to operate.
Variable Hydraulic Pump
[37] A second preferred embodiment of a hydraulic machine in
accordance with the invention is illustrated in FIG. 3. A variable
hydraulic pump 110 includes a modular fixed cylinder block 112 which is
identical to cylinder block 12 of hydraulic motor 10 shown in FIG. 1 and
described above. Cylinder block 112 has a plurality of cylinders 114
(only one shown) in which a respective plurality of mating pistons 116
reciprocates between the retracted position of piston 116 and variable
extended positions (the maximum extension being shown in the position
of piston 116'). Each piston has a spherical head 118 that is mounted
on a neck 120 at one end of an elongated axial cylindrical body portion
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122 that, in the preferred embodiment shown, is substantially as long
as the length of each respective cylinder 114. Each spherical piston
head 118 fits within a respective shoe 124 that slides over a flat face
126 formed on the surface of a rotor 128 that, as will be discussed in
greater detail below, is pivotally attached to a drive element, namely,
shaft 130 that is supported on bearings within a bore 131 in the
center of cylinder block 112.
[38] In a manner similar to that explained above in regard to hydraulic
motor 10, variable pump 110 is also provided with a modular valve
assembly 133 that is bolted as a cap on the left end of modular
cylinder block 112 and, similarly, includes a plurality of spool valves
134 (only one shown) that regulates the delivery of fluid into and out
of cylinders 114.
[39] As indicated above, each of the machines disclosed can be
operated as either a pump or as a motor. For the description of this
preferred embodiment, the variable-angle swash-plate machine 110
shown in FIG. 3 is being operated as a pump, and drive shaft 130 is
driven by a prime mover (not shown), e.g., the engine of a vehicle.
Therefore, during the one-half of each revolution of drive shaft 130,
lower pressure fluid is drawn into each respective cylinder 114
entering a port 137 from a "closed loop" of circulating hydraulic fluid
through inlet 136 as each piston 116 is moved to an extended position.
During the next half of each revolution, the driving of each respective
piston 116 back to its fully retracted position directs high-pressure
fluid from port 137 into the closed hydraulic loop through outlet 139.
The high-pressure fluid is then delivered through appropriate closed
loop piping (not shown) to a mating hydraulic motor, e.g., motor 10
discussed above, causing the pistons of the mating motor to move at a
CA 02494996 2005-02-07
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nft Iuit Rnn i tt
.,,t, vv, d,,:,, r õq' .~ ri !T ~. .'1 I~ ~}, ,,,, . .., }~..,~! t }4wt' , ,
i~,,, .t }t,,,1} f , õ }l..,~l }l}t ' =t{..
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- 16
speed that varies with the volume (gallons per minute) of high
pressure fluid being delivered in a manner well known in the art.
Once again referring to modular cylinder block 112, it is
constructed identical to cylinder block 12 which has already been
described. That is, the cylindrical wall of each cylinder 114 is
transected radially by a respective lubricating channel 140 formed
circumferentially therein. A plurality of passageways 142 interconnect
all lubricating channels 140 to form a continuous lubricating
passageway in cylinder block 112. A cross-section of cylinder block
112 taken in the plane 2-2 looks exactly as the cross-sectional view of
cylinder block'12 in FIG. 2.
In effect, almost all, of the discussion above relating to the
invention's continuous lubricating passageway 40, 42 with reference
to the apparatus of hydraulic motor 10 shown in FIGS. 1 and' 2, applies
equally to the operation of continuous lubricating passageway 140,
142 in cylinder block 112 of hydraulic pump 110 shown in FIG. 3,
including the fairly extreme minimization of loss of lubricating fluid
from each lubricating channel 140 by optionally including a surrounding
seal 144 located near the open end' of each cylinder 114. Similarly,
the flow of lubricating fluid in closed continuous lubricating,
passageway 140. 142 is moderate but continuous as the result of a
secondary minimal fluid flow in response to piston motion and to the
changing pressures in each half-cycle of rotation of drive shaft 130 as
the pistons. reciprocate. Of course, as is different in pump 110, lower
fiuid' pressure is present in each cylind'er 114 when each piston 1.16 is
moving to an, extended' position, whil'e the source, of the high~ pressure
CA 02494996 2005-02-07
;,,, r e,,,:, ,,,; rõti, r= a u
-17 - WEPU'US
fluid that is forced between the walls of the cylinders and the outer
circumference of each piston 116 occurs as each piston 116 is being
driven from its extended position to its fully retracted position by the
rotation of drive shaft 130 by the prime mover (not shown).
However, once again special attention of persons skilled in the
art is called to the fact that this just-mentioned secondary minimal
fluid flow back into each cylinder 114 is not "lost". Instead, it is
immediately returned to the well known closed hydraulic fluid loop that
interconnects the pump and motor. That is, this secondary fluid flow
does not return to a sump and, therefore, does not have to be
replenished into the closed loop hydraulic system by a charge pump.
Also, while there may be a minimal blow-by that leaks from closed
continuous lubricating passageway 140, 142 past the seals 144 at the
end of each cylinder 114, any such minimal blow-by is instantly
replenished by a similar minimal fluid flow entering around the opposite
end of each piston 116 experiencing increased pressure.
As discussed in the preamble above, the invention permits the
machine's swash-plate apparatus to be simplified (a) by the omission
of the dog-bones that normally are mounted between the outer end of
each piston and a nutating-only wobbler portion, of a conventional,
rotating/nutating swash-plate and, (b) in the embodiments illustrated
in FIGS. 1 and 3, by the omission of the wobbler portion itself as well'
as the apparatus conventionally req,uired, for mounting: the non-rotating
wobbler tothe. rotating/nutating rotor portion of the swash-plate.
~t'i: = _.
CA 02494996 2005-02-07
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aõ õi:t,~õ. : < ::,, = t == r'' ai:: :. ': ' :,;%~ ' , };;,.;: , ., .,Ih.
,-" {!,=õ ~! , i1,.,l~ õ~7~ ~i,,,!',=.;;!' : li;;,. ,.;~E ~. ~.,:.'.;3 t+ .
.A''=.i: . . iF:;'=~.
ta ~~
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Still referring to FIG. 3, rotor 128 of pump 110 is pivotally
mounted to drive shaft 130 about an axis 129 that is perpendicular to
axis 132. Therefore, while rotor 128 rotates with drive shaft 130, its
angle of inclination relative to axis 130 can be varied from 00 (i.b.,
perpendicular) to 25 . In FIG. 3, rotor 128 is inclined at +25 . This
variable inclination is controlled as follows: The pivoting of rotor 128
about axis 129 is determined by the position of a sliding collar 180
that surrounds drive shaft 130 and is movable axially relative thereto.
A control-link 182 connects collar 180 with rotor 128 so that
movement of collar 180 axially over the surface of drive shaft 130
causes rotor 128 to pivot about axis 129. For instance, as collar 128
is moved to the right in FIG. 3, the inclination of rotor 128 varies
throughout a continuum from the +25 inclination shown, back to 00
(i.e., perpendicular), and then to -25 .
The axial movement of collar 180 is controiled by the fingers
184 of a yoke 186 as yoke 186 is rotated about the axis of a yoke
shaft 190 by articulation of a yoke control arm 188. Yoke 186 is
actuated by a conventional linear servo-mechanism (not shown)
connected to the bottom of yoke arm 188. In this preferred'
embodiment, while the remainder of the elements of yoke 186 are all:
enclosed within a modular swash-plate housing 192 and, yoke shaft
190 is supported in bearings fixed to housing 192, yoke control arrn,
188 is positioned, external of housing 192.
It will, also be noted~ that swash-plate rotor 128 isbal'ancedi by a
shad,ow-li,nk 1,94 that is substantial6y identicalf to control'-lin,k 182 and!
A~r~l'.
~.L1~ i~n F'.rsi' y
CA 02494996 2005-02-07
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:=;: r tt ji:~pw 4 ~6d
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19
is similarly connected to collar 180 but at a location on exactly the
opposite side of collar 180.
Piston Shoe Hold-Down Assemblies
Fluid pressure constantly biases pistons 116 in the direction of
rotor 128, and the illustrated conventional thrust plate assembly is
provided to carry that load. However, at the speeds of operation
required for automotive use (e.g., 4000 rpm) additional bias toading is
necessary to assure constant contact between piston shoes 124 andr
flat surface 126 of rotor 128. In view of the invention's omission of
conventional dog-bones, the variable hydraulic machines of this
invention provide such additional bias by using one of three simple
spring-biased hold-down assemblies, the first being similar to that
already described above in regard to hydraulic motor 10 in FIG. 1.
(a) Hold-Down Assembly with Single-Spring Bias
The following description of the invention's first embodiment for
a hold-down assembly continues to refer to FIG. 3, but reference is
now also made (a) to FIG. 4A, which shows an enlarged'view taken in
the plane 4A-4A of FIG. 3 when viewed in the direction of the arrows,
and (b) to FIG. 4B, which shows an enlargement of the same view of
shown in FIG. 1 with parts removed for clarity.
The hol'd-downassembly for pump 110 includes a coil spring.
1150 that is positioned about shaft 130, and received in, an appropriate
crevice! 1:52 forrned" in, cylinder block 112 circum#erentially about axis
!r, t4y 1-:
CA 02494996 2005-02-07
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132. Coil spring 150 biases a hold-down element 154 that is also
positioned circumferentially about shaft 130 and axis 132. Hold-down
element 154 is provided with a plurality of circular openings 160, each
of which surrounds the neck 120 of a respective piston 116. A
plurality of special washers 156 are positioned, respectively, between
hold-down element 154 and each piston shoe 124. Each washer 156
has an extension 158 that contacts the outer circumference of a
respective shoe 124 to maintain the shoe in contact with flat face 126
of rotor 128 at all times.
The positions of the just-described parts of the swash-plate and
piston shoe hold-down assembly change relative to each other as the
inclinations of rotor 128 is altered during machine operation. These
Deg
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changes in relative position are illustrated at various inclinations of
rotor 128, namely, at +25 , in FIGS. 4A and 4B; at +15 in FIGS. 5A and
5B; at 0 in FIGS. 6A and 6B; and at -25 , in FIGS. 7A and 7B. [NOTE:
Persons skilled in the art will appreciate that each piston shoe 124 has
a conventional pressure-balancing cavity centered on the flat surface
of shoe 124 that contacts flat face 126 of rotor 128, and that each
respective shoe cavity is connected through an appropriate shoe
channel 162 and piston channel 164 to assure that fluid pressure
present at the shoe/rotor interface is equivalent at all times with fluid
pressure at the head of each piston 116. Since piston channel 164
passes through the center of spherical head 118 of each piston 116,
the position of channel 164 can be used to facilitate appreciation of
the relative movements of the various parts of the hold-down
assembly.]
[52] Referring to the relative position of these parts at the 0
inclination shown in FIGS. 6A and 6B, each piston channel 164 (at the
center of each spherical head 118 of each piston 116) has the same
radial position relative to each respective circular opening 160 in hold-
down element 154. As can be seen from the views in the other
illustrated inclinations of swash-plate rotor 128, at all inclinations
other than 0 , the relative radial position of each piston channel 164 is
different for each opening 160, and the relative positions of each
special washer 156 is also different.
[53] It must be appreciated that, at each of these illustrated swash-
plate inclinations, the different relative positions at each of the nine
openings 160 are themselves constantly changing as rotor 128 rotates
and nutates through one complete revolution at each of these
inclinations. For instance, at the 25 inclination shown in FIG. 4A, if
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21
during each revolution of rotor 128, one were to watch the movement
occurring through only the opening 160 at the top (i.e., at 12:00
o'clock) of hold-down element 154, the relative position of the parts
viewed in the top opening 160 would serially change to match the
relative positions shown in each of the other eight openings 160.
[54] That is, at inclinations other than 00 (e.g., at -25 shown in FIG.
7A), during each revolution of rotor 128, each special washer 156 slips
over the surface of hold-down element 154 as, simultaneously, each
shoe 124 slips over the flat face 126 of rotor 128; and each of these
parts changes relative to its own opening 160 through each of the
various positions that can be seen in each of the other eight openings
160. These relative motions are largest at 25 ; and each follows a
cyclical path (that appears to trace a lemniscate, i.e., a "figure-eight")
that varies in size with the angular inclinations of swash-plate rotor
128 and the horizontal position of each piston 116 in fixed cylinder
block 112.
[55] Therefore, to assure proper contact between each respective
shoe 124 and flat face 126 of rotor 128, in preferred embodiments, a
size is selected for the boundaries of each opening 160 so that the
borders of opening 160 remain in contact with more than one-half of
the surface of each special washer 156 at all times during each
revolution of rotor 128 and for all inclinations of rotor 128, as can be
seen from the relative positions of special washers 156 and the
borders of each of the openings 160 in each of the drawings from FIG.
4A through FIG. 7A. As can be seen from the drawings, a circular
border is preferred for each opening 160.
[56] Finally, attention is called to the suggested manufacture of each
shoe 124 and its respective mating special washer 156 using
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22
reinforced thermoplastic resin materials. These mating parts can also
be combined to form a single thermoplastic shoe/washer combination,
with the shoe portion being manufactured so that it is formed about
the spherical head 118 of each piston 16', 22. Similarly, the cost and
complexity of thrust bearing assembly 35 can be significantly reduced
by the use of reinforced thermoplastic resins.
[57] (b) Hold-Down Assembly with Multiple-Spring Bias
[58] The second embodiment of the invention's hold-down assembly,
while slightly more difficult to assemble, is considerably simpler and
less expensive. This second embodiment is shown schematically in FIG.
8 in an enlarged, partial, and cross-sectional view of a single piston of a
further hydraulic machine 210 according to the invention. Piston 216
is positioned in modular fixed cylinder block 212 within cylinder 214,
the latter being transected radially by a respective lubricating channel
40" formed circumferentially therein. In the same manner as
described in relation to the other hydraulic machines already detailed
above, lubricating channel 40" is interconnected with similar channels
in the machine's other cylinders by a plurality of passageways that
forms a continuous lubricating passageway in cylinder block 212; and,
similarly, a surrounding seal 244 is located near the open end of each
cylinder 214 to minimize the loss of lubricating fluid from each
lubricating channel 40".
[59] The only difference between fixed cylinder block 212 and the
modular cylinder blocks disclosed in FIGS. 1 and 3 is that fixed cylinder
block 212 includes neither a large axially circumferential coil spring nor
an axially circumferential crevice for holding the same.
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[60] While not shown, the modular fixed cylinder block 212 of
hydraulic machine 210 can be connected to either a modular fixed-
angle swash-plate assembly (as shown in FIG. 1) or a modular variable-
angle swash-plate assembly (as shown in FIG. 3); but in either case,
hydraulic machine 210 provides a much simpler hold-down assembly.
Specifically, the hold-down assembly of this embodiment comprises
only a respective conventional piston shoe 224 for each piston 216 in
combination with only a respective coil spring 250,'the latter also being
associated with each respective piston 216.
[61] Each piston shoe 224 is similar to the conventional shoes shown
in the first hold-down assembly just discussed above and, similarly, is
mounted on the spherical head 218 of piston 216 to slide over the flat
face 226 formed on the surface of the machine's swash-plate rotor
228 in a manner similar to that explained above. Each coil spring 250
is, respectively, seated circumferentially about hydraulic valve port
237 at the valve end of each respective cylinder 214 and positioned
within the body portion of each respective piston 216.
[62] Again, in the manner just explained above, each shoe 224 slips
over flat face 226 of rotor 228 with a lemniscate motion that varies in
size with the horizontal position of each piston '216 and the inclination
of rotor 228 relative to axis 230. During normal operation of hydraulic
machine 210, shoes 224 are maintained in contact with flat face 226
of the swash-plate by hydraulic pressure. Therefore, the spring bias
provided by coil springs 250 is only minimal but still sufficient to
maintain effective sliding contact between each shoe 224 and flat face
226 in the absence of hydraulic pressure at the valve end of each
respective cylinder 214.
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[63] It has been found that the just-described minimal bias of springs
250 not only facilitates assembly but is also sufficient to prevent
entrapment of tiny dirt and metal detritus encountered during
assembly and occasioned by wear. Further, special attention is again
called to the fact that this second embodiment provides this necessary
function with only a few very inexpensive parts.
[64] The just-described pump/motor as well as the invention's other
hydraulic machines described earlier, all provide both lubrication and a
piston/swash-plate interface that are remarkably simple and relatively
inexpensive to manufacture and provide further economies by reducing
the number of parts required for efficient operation and increasing
volumetric efficiency.
