U.S. patent application number 10/647557 was filed with the patent office on 2004-03-04 for long-piston hydraulic machines.
Invention is credited to Gleasman, Keith E., Gleasman, Vernon E., Wrona, Matthew R..
Application Number | 20040042906 10/647557 |
Document ID | / |
Family ID | 32179426 |
Filed Date | 2004-03-04 |
United States Patent
Application |
20040042906 |
Kind Code |
A1 |
Gleasman, Vernon E. ; et
al. |
March 4, 2004 |
Long-piston hydraulic machines
Abstract
Smaller and lighter hydraulic pump/motors are provided with
pistons having body portions substantially as long as the axial
length of the respective cylinders in which they reciprocate. A
plurality of respective lubricating channels, formed
circumferentially and radially transecting the walls of each
cylinder, is each positioned to be closed at all times by the axial
cylindrical body of each respective piston during its entire
stroke. Each lubricating channel is interconnected, one to another,
to form a single, continuous lubricating passageway entirely within
the cylinder block and not connected by either fluid "input" or
fluid "output" passageways, being replenished solely by blow-by
entering from the valve end of each cylinder. A plurality of
sealing members, each located near the open end of each cylinder,
substantially eliminates blow-by from this lubricating passageway,
thereby significantly increasing volumetric efficiency. The
resulting improved lubrication, in combination with unique
spring-biased hold-down assemblies, permits use of variable-angle
swash-plate arrangements that require neither dog-bones at the
outer ends of the pistons nor conventional nutating-only
wobblers.
Inventors: |
Gleasman, Vernon E.;
(Pittsford, NY) ; Gleasman, Keith E.; (Fairport,
NY) ; Wrona, Matthew R.; (Fairport, NY) |
Correspondence
Address: |
Morton A. Polster
Eugene Stephens & Associates
56 Windsor Street
Rochester
NY
14605
US
|
Family ID: |
32179426 |
Appl. No.: |
10/647557 |
Filed: |
August 25, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10647557 |
Aug 25, 2003 |
|
|
|
10229407 |
Aug 28, 2002 |
|
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|
Current U.S.
Class: |
417/222.1 ;
417/269 |
Current CPC
Class: |
F04B 27/109 20130101;
F04B 1/141 20130101; F04B 1/143 20130101; F04B 1/126 20130101 |
Class at
Publication: |
417/222.1 ;
417/269 |
International
Class: |
F04B 001/12 |
Claims
We claim:
1. In a hydraulic machine having a plurality of pistons
reciprocally mounted in respective cylinders formed in a cylinder
block and positioned circumferentially at a first radial distance
about the rotational axis of a drive element, each said piston
having a body portion and a head end and each respective cylinder
having a valve end and an open head portion beyond which said head
end of each said piston extends at all times, and said pistons also
having a stroke varying up to a predetermined maximum, the
improvement comprising: a respective lubricating channel formed in
the cylindrical wall of each said cylinder in said cylinder block;
all of said lubricating channels being interconnected to form a
continuous lubricating passageway in said cylinder block; and each
said respective lubricating channel being substantially closed by
the axial cylindrical body of each respective piston during the
entire stroke of each said piston, thereby substantially closing
said continuous lubricating passageway at all times.
2. The hydraulic machine of claim 1 wherein said closed continuous
lubricating passageway is formed entirely within said cylinder
block, transecting each said cylinder and being centered
circumferentially at substantially the same radial distance as said
cylinders are centered about the rotational axis of the drive
element.
3. The hydraulic machine of claim 1 further comprising a sealing
member located in proximity to said open head portion of each said
cylinder for substantially eliminating blow-by between each said
piston and said open head portion of each respective cylinder.
4. The hydraulic machine of claim 1 wherein said closed continuous
lubricating passageway is replenished solely by blow-by between
said body portion of each piston and said valve end of each
respective cylinder.
5. The hydraulic machine of claim 1 wherein the primary movement of
lubricating fluid in said closed continuous lubricating passageway
is the result of at least one of (a) piston motion, (b) changing
fluid pressures within said respective cylinders, and (c) blow-by
between each said piston and said valve end of each respective
cylinder.
6. The hydraulic machine of claim 5 in combination with a closed
loop of circulating hydraulic fluid and wherein said blow-by
between each said piston and said valve end of each respective
cylinder is immediately returned to the closed loop without
requiring the use of a charge pump.
7. The hydraulic machine of claim 1 further comprising a
swash-plate with a flat face, said swash-plate having an
inclination relative to said rotational axis of the drive element,
and wherein said head end of each piston is maintained in effective
sliding contact with said flat face of said swash-plate during all
relative rotary motions between said pistons and said swash-plate,
said stroke of said pistons being determined in accordance with the
inclination of said swash-plate, and said body portion of each
piston has an axial cylindrical length sufficient to be supported
within said respective cylinder to assure minimal lateral
displacement of said head end of said piston when in relative
sliding contact with said flat face at all times during said
stroke.
8. The hydraulic machine of claim 7 wherein said cylinder block is
fixed in a housing, said swash-plate rotates with said drive
element and includes a rotor that rotates and nutates, and said
flat face is located on said rotor.
9. The hydraulic machine of claim 8 wherein the inclination of said
swash-plate is variable, and the stroke of said pistons varies up
to said predetermined maximum in accordance with said
inclination.
10. The hydraulic machine of claim 7 wherein each piston has a
spherical head end connected to said piston body by a narrowed neck
portion, and said machine further comprises: a respective sliding
shoe pivotally affixed to said spherical head end of each said
respective piston and maintained in effective sliding contact with
said flat face of said swash-plate during all relative rotary
motions between said pistons and said flat face; and a hold-down
assembly for biasing said sliding shoes toward said flat face of
said swash-plate.
11. The hydraulic machine of claim 10 wherein said hold-down
assembly comprises: a hold-down element biased toward said sliding
shoes and having a plurality of respective openings, the boundary
of each said respective opening in said hold-down plate being
located in proximity to said narrowed neck portion of each
respective piston; and a respective washer fitted about said
narrowed neck portion of each piston between said hold-down plate
and each respective sliding shoe, each said respective washer
having an extension aligned cylindrically for circumferentially
contacting each said respective sliding shoe; said washers being in
sliding contact with said hold-down plate for movement relative
thereto in response to the changing relative positions of said
sliding shoes when said flat face of said rotor is inclined
relative to said rotational axis of the drive element.
12. The hydraulic machine of claim 11 wherein the boundary of each
said respective opening in said hold-down plate is designed to be
in contact with more than one-half of the outer circumference of
each said respective washer at all times during said relative
movements.
13. The hydraulic machine of claim 11 wherein said machine further
comprises a coil spring positioned circumferentially about the
rotational axis of said drive element at less than said first
radial distance for biasing said hold-down plate against said
washers.
14. The hydraulic machine of claim 10 wherein said hold-down
assembly comprises only: a minimal spring bias sufficient to
maintain said effective sliding contact between each said shoe and
said flat face of said swash-plate in the absence of hydraulic
pressure at said valve end of each respective cylinder.
15. The hydraulic machine of claim 10 wherein said minimal spring
bias is provided by a plurality of springs, each said spring being
positioned respectively between said body portion of each
respective piston and said valve end of each respective cylinder.
Description
RELATED APPLICATIONS
[0001] This application is a Continuation-In-Part of U.S. copending
parent application Ser. No. 10/229,407, filed Aug. 28, 2002, which
application is hereby incorporated by reference.
TECHNICAL FIELD
[0002] This invention relates to hydraulic pump/motor machines that
have elongated pistons reciprocating in cylinders and, more
particularly, to a system for lubricating such pistons while
maintaining contact between the heads of such pistons and the
swash-plate of the pump/motor.
BACKGROUND
[0003] Hydraulic pumps and motors are well known and widely used,
having reciprocating pistons mounted in respective cylinders formed
in a cylinder block and positioned circumferentially at a first
radial distance about the rotational axis of a drive element. Many
of these pump/motor machines have variable displacement
capabilities; and they are generally of two basic designs: (a)
either the pistons 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 generally split to
include a non-rotating (but nutating) 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.
[0004] While 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, the mounting and
support of the swash-plate wobblers has always been a major
problem. For high-pressure/high-speed service, the wobbler must be
supported in a manner that allows the relative motion between the
non-rotating pistons and the wobbler to follow varying non-circular
paths. 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 against the swash-plate wobbler. These just-mentioned
elements greatly increase the complexity and cost of building the
rotating swash-plates of these machines.
[0005] 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 having 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 pivotally-mounted
conventional shoe element) that effectively contacts the
non-rotating flat surface of the swash-plate. Such elongated
pistons are designed so that a significant portion of the axial
cylindrical body of each piston remains supported 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.
[0006] 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 flow 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 affects the volumetric efficiency of
the pump or motor machine. For instance, a 10 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 need for adequate
lubrication.
[0007] The invention disclosed below is directed to improving the
volumetric efficiency of such elongated-piston machines while, at
the same time, assuring (a) appropriate lubrication of the pistons
and (b) simplification of the apparatus used to maintain contact
between the pistons and the swash-plate.
SUMMARY OF THE INVENTION
[0008] The invention is disclosed on two different hydraulic
machines. Both have 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 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-plate of
the other disclosed machine has an inclination 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.
[0009] In each machine, each piston is elongated, having an axial
cylindrical body portion that preferably is substantially as long
as the axial length of the respective cylinder 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 maintained in effective sliding contact with a
flat 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, 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 when it is
in sliding contact with the rotating/nutating flat face of the
swash-plate.
[0010] According to the invention, each cylinder formed within the
cylinder blocks of each machine is provided with a respective
lubricating channel formed in the cylindrical wall 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 substantially
closed by the axial cylindrical body of the piston during its
entire stroke. Preferably, each respective lubricating channel is
formed circumferentially and radially transects each cylinder.
[0011] Also formed in the fixed cylinder block of each machine is 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.
[0012] [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.] 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 substantially closed off by the
cylindrical body portions of the pistons at all times during
operation of the machine. During operation, this lubricating
passageway almost instantly fills with initial blow-by 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
blow-by effectively maintains high pressure within the continuous
lubricating passageway at all times. A plurality of sealing
members, each located respectively near the open end of each
cylinder, provides 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.
[0013] 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 closed 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 each
cylinder experiencing such pressure reduction. However, this
secondary blow-by is not "lost", i.e., it does not return to the
sump to be replenished into the closed loop hydraulic system by the
charge pump. Instead, this secondary blow-by 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.
[0014] This just-described lubricating passageway provides
appropriate lubrication to 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 per minute, thereby remarkably
increasing the volumetric efficiency of the invention's hydraulic
machines.
[0015] 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 improved lubrication of the elongated pistons, the disclosed
invention makes it possible to use these smaller and lighter
designs to meet the high-speed/high-pressure specifications
required for automotive use.
[0016] 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 (a) omits 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 but (b) also omits the
nutating-only wobbler portion of a conventional rotating/nutating
swash-plate. Instead, a conventional shoe is mounted directly to
the spherical head of each piston and is maintained in effective
sliding contact with the flat face of the swash-plate's rotor
portion 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.
[0017] Two simplified support mechanisms are disclosed: The first
simplified support mechanism comprises a unique hold-down plate
assembly biased by a 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 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.
[0018] The important changes introduced by this invention not only
provide hydraulic machines that are lighter and smaller than
conventional machines having similar specifications but, further,
provide machines with greater volumetric efficiency while reducing
the weight and size of the machines as well as the cost of
manufacture and simplifying assembly.
DRAWINGS
[0019] 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 the invention incorporated in the cylinder block and at the
piston/swash-plate interface.
[0020] FIG. 2 is a partially schematic and cross-sectional view of
the fixed cylinder block of the hydraulic machines of FIGS. 1 and 3
taken along the plane 2-2 with parts being omitted for clarity.
[0021] 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 the invention incorporated in the
cylinder block and at the piston/swash-plate interface.
[0022] 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 when the swash plate is inclined at
+25.degree., 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; the
view in FIG. 4A is 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.
[0023] FIGS. 5A and 5B, 6A and 6B, and 7A and 7B are, respectively,
views of the same parts illustrated in FIGS. 4A and 4B when the
swash-plate is operating at three other inclinations, namely, at
+15.degree., 0.degree., and -25.degree..
[0024] FIG. 8 is an enlarged, partial, schematic and
cross-sectional view of only a single cylinder and piston for
another hydraulic machine similar to those shown in FIGS. 1 and 3
but showing a more simplified second embodiment of a spring-biased
hold-down assembly for the invention's piston shoes.
DETAILED DESCRIPTION
[0025] 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.
[0026] Hydraulic Motor
[0027] 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.
[0028] 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.degree.) to the
axis 32 of drive shaft 30, being supported by an appropriate thrust
bearing assembly 35.
[0029] 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 pressure fluid
is withdrawn from each respective cylinder through port 37 and
fluid outlet 39 as each piston returns to its fully retracted
position.
[0030] 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.
[0031] 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 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 has been exaggerated for
clarification.
[0032] During operation of hydraulic motor 10, all interconnected
lubricating channels 40 are filled almost instantly by blow-by of
high-pressure fluid from inlet 36 entering each cylinder 14 through
port 37 and being forced between the walls of the cylinders 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 "secondary" blow-by 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 fluid in
otherwise closed lubricating passageway 40, 42 is again driven
between the walls of each cylinder 14 and the outer circumference
of body portion 22 of each piston 16 into the valve end of each
cylinder 14 experiencing such pressure reduction.
[0033] However, special attention of persons skilled in the art is
called to the fact that this just-mentioned secondary blow-by 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 secondary blow-by 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 flow of high-pressure blow-by from the
valve end of each cylinder experiencing increased pressure.
[0034] 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 flow of
blow-by entering around the opposite end of each piston 16.
[0035] The just-described lubrication arrangement is not only
remarkably simple, but 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.
[0036] 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 invention's simplified pinion/swash-plate
interface assemblies are described in greater detail in a separate
section below.]
[0037] 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 element 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.
[0038] 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.
[0039] Variable Hydraulic Pump
[0040] 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 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.
[0041] 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.
[0042] 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 speed that varies with the volume (gallons per minute) of
high-pressure fluid being delivered in a manner well known in the
art.
[0043] 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 40' formed
circumferentially therein. A plurality of passageways 42'
interconnects all lubricating channels 40' 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.
[0044] 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 40', 42' in cylinder block 112 of hydraulic pump 110
shown in FIG. 3, including the minimization of loss of lubricating
fluid from each lubricating channel 40' by a surrounding seal 144
located near the open end of each cylinder 114. Similarly, the flow
of lubricating fluid in closed continuous lubricating passageway
40', 42' is moderate but continuous as the result of "secondary"
blow-by 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 fluid
pressure is present in each cylinder 114 when each piston 116 is
moving to an extended position, while the source of the
high-pressure 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).
[0045] However, once again special attention of persons skilled in
the art is called to the fact that this just-mentioned secondary
blow-by 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
blow-by 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 fluid flow that leaks from
closed continuous lubricating passageway 40', 42' past the seals
144 at the end of each cylinder 114, any such minimal blow-by is
instantly replenished by a similar flow of blow-by entering around
the opposite end of each piston 116 experiencing increased
pressure.
[0046] As discussed in the preamble above, the invention permits
the machine's swash-plate apparatus to be simplified by (a) 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) the omission of
the wobbler portion itself as well as the apparatus conventionally
required for mounting the non-rotating wobbler to the
rotating/nutating rotor portion of the swash-plate.
[0047] Rotor 128 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 0.degree. (i.e., perpendicular) to
.alpha.25.degree.. In FIG. 3, rotor 128 is inclined at +25.degree..
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.degree. inclination shown, back to 0.degree. (i.e.,
perpendicular), and then to -25.degree..
[0048] The axial movement of collar 180 is controlled 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 arm
188 is positioned external of housing 192.
[0049] It will also be noted that swash-plate rotor 128 is balanced
by a shadow-link 194 that is substantially identical to
control-link 182 and is similarly connected to collar 180 but at a
location on exactly the opposite side of collar 180.
[0050] Piston Shoe Hold-Down Assemblies
[0051] Fluid pressure constantly biases pistons 116 in the
direction of rotor 128, and a thrust plate 198 is provided to carry
that load. However, at the speeds of operation required for
automotive use (e.g., 4000 rpm), additional bias loading is
necessary to assure constant contact between piston shoes 124 and
flat surface 126 of rotor 128. In view of the invention's omission
of conventional dog-bones and omission of the conventional wobbler
as well as its required mounting assembly, the variable hydraulic
machines of this invention are able to provide such additional bias
by using either of two simple spring-biased hold-down assemblies,
the first being similar to that already described above in regard
to hydraulic motor 10 in FIG. 1.
[0052] (a) Hold-Down Assembly with Single-Spring Bias
[0053] 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.
[0054] The hold-down assembly for pump 110 includes a coil spring
150 that is positioned about shaft 130 and received in an
appropriate crevice 152 formed in cylinder block 112
circumferentially about axis 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 is 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.
[0055] The positions of the just-described parts of the swash-plate
and piston shoe hold-down assembly change relative to each other as
the inclination of rotor 128 is altered during machine operation.
These changes in relative position are illustrated at various
inclinations of rotor 128, namely, at +25.degree., in FIGS. 4A and
4B; at +15.degree. in FIGS. 5A and 5B; at 0.degree. in FIGS. 6A and
6B; and at -25.degree., 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.]
[0056] Referring to the relative position of these parts at the
0.degree. 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.degree., 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.
[0057] 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.degree.
inclination shown in FIG. 4A, if 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.
[0058] That is, at inclinations other than 0.degree. (e.g., at
-25.degree. 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.degree.; 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.
[0059] 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.
[0060] Finally, attention is called to the suggested manufacture of
each shoe 124 and its respective mating special washer 156 using
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.
[0061] (b) Hold-Down Assembly with Multiple-Spring Bias
[0062] 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".
[0063] 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.
[0064] 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.
[0065] 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.
[0066] 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.
[0067] 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.
[0068] 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.
* * * * *