Note: Descriptions are shown in the official language in which they were submitted.
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DUAL HYDRAULIC MACHINE TRANSMISSION
FIELD OF THE INVENTION
This invention relates to hydraulic transmissions used for vehicle locomotion
and
to liquid hydraulic pump/motor machines appropriate for relatively "heavy
duty"
automotive use. More particularly, the invention pertains to an all-hydraulic
transmission
for an automobile.
BACKGROUND OF THE INVENTION
All-hydraulic transmissions are known in the prior art. In U.S. Patent
3,199,286
"HYDROSTATIC DRIVE" to Anderson, issued August 10, 1965, a modular hydraulic
drive uses a sirigle pump driving separate motors for each of four wheels to
provide
step-less acceleration. The hydraulic drive includes control valves at each
wheel and
recharging of low fluids. In U.S. Patent 3,641,765 "HYDROSTATIC VEHICLE
TRANSMISSION" to Hancock et al., isstied February 15, 1975, the four-wheel
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hydrostatic drive has special sets of one-way valves and restrictive
coimections to
perinit differentiation and provide traction control between the front and
rear axles.
There is a need in the art for a transmission that permits a return to the
proven
but considerably lower speed engines with reduced torque loss in order to
iizcrease
gasoline engine vehicle efficiency and reduce the weight and cost of
manufacture of
cars. There is also a need in the art for a transmission that allows a car to
change
speeds, while the engine operates at a more constant speed. Although the
transmissions
in current use in most automobiles require the engine to cycle between low
speeds and
very high speeds during acceleration, an engine is much more fuel-efficient
when
running at a constant speed.
All-hydraulic transmissions have been used effectively in slow-moving heavy
machinery such as tractors and lightweigllt vehicles such as golf carts and
all-terrain
vehicles (ATV's). Although all-hydraulic transmissions have been contemplated
for
automobiles, the inefficiency of hydraulic transmissions in the prior art has
made them
impractical for use in automobiles. Scaling a hydraulic transmission of the
prior art for use
in an automobile would produce an unacceptably large, heavy, and noisy
transmission, and
such transmissions would be larger, heavier, and noisier than the
transmissions currently
used in automobiles.
Although an internal combustion engine is the industry standard for
automobiles in the United States, several major automobile manufacturers are
researching a homogeneous-charge-compression-ignition (HCCI) engine. In a
conventional gasoline engine, the air-fuel mixture is ignited by a spark plug
to create
power. In an HCCI engine, similar to in a diesel engine, a piston compresses
the air-
fuel mixture to increase its temperature until it ignites. It is estimated
that an HCCI
engine is capable of a 30% increase in fuel economy over a standard gasoline
internal
combustion engine. However, a major hurdle for implementation of HCCI
technology
in automobiles is a difficulty in controlling the combustion both at low and
at high
engine speeds.
There is a need in the art for a transmission, which provides the necessary
power to run an automobile while allowing its engine speed to remain in a
relatively
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narrow low-to-moderate range where the combustion in HCCI engines is more
easily
controlled. Such a transmission allows implementation of more fuel efficient
HCCI
engines on gasoline-powered vehicles.
Hydraulic pumps and motors are also well known and widely used, having
reciprocating pistons mounted in respective cylinders fonned 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 inachines have variable displacement
capabilities,
and they are generally of two basic designs. In the first basic design, the
pistons
reciprocate in a rotating cylinder block against a variably inclined, but
otherwise fixed,
swash plate. In the second basic design, 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, 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.
The pumps and motors utilized in the invention and described herein are liquid-
type hydraulic inacllines and it should be understood that the terms fluid and
pressurized
fluid as used herein throughout, are intended to identify incompressible
liquids rather than
compressible gases. Because of the incompressibility of liquids, the pressure
and load duty
cycles of 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 reinarks 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 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 be supported in a manner that allows for the relative motion
between the
heads of the non-rotating pistons and a mating surface of the rotating and
nutating swash
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plate. Such prior art swash plates have often been split into a
rotating/nutating rotor
portion and a nutating-only wobbler portion, the latter including poclcets
that mate with the
heads of the non-rotating pistons through connecting "dog-bones".
That is, such fixed-cylinder-block inachines have heretofore used a"dog-bone"
extension rod (i.e., a rod witli two spherical ends) to interconnect one end
of each piston
with the 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 otlier
spherical end is
usually held at all times in a pocket of the swash plate wobbler during all
relative motions
between the heads of the non-rotating pistons and the pockets of the nutating
swash plate.
As is well known in the art, these relative motions follow varying non-
circular paths that
occur at all inclinations of the swash plate away from 0 . These dog-bones
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 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.
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 circuxnference 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
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machine can use as much as 4 gallons of fluid per ininute 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 blow-by is accomplished by using fluid
that would
5 otherwise be used to drive or be driven by the pistons to accomplish worlc,
Therefore, in
the example just given above, the 4 gallons of fluid per minute used for blow-
by
lubrication, reduces the volunletric efficiency of the machine.
The invention disclosed below is directed to improving the volumetric
efficiency
of such elongated-piston machines while, at the same time, assuring
appropriate
lubrication of the pistons and sinlplification of the apparatus used to
maintain contact
between the pistons and the swash plate.
SUMMARY OF THE INVENTION
Certain exemplary embodiments can provide a modular transmission adaptable for
use in
a vehicle having an engine, an accelerator for indicating desired variations
in vehicle velocity, a
brake for indicating desired reductions in vehicle velocity, and an output
drive for driving the
wheels of the vehicle, said transmission comprising: a plurality of hydraulic
machines, each
having a rotating shaft, elongated pistons that reciprocate within cylinders
formed in a stationary
cylinder block, and an angularly adjustable swash plate, said pistons having a
stroke that is
variable up to a predetermined maximum by angular adjustment of said swash
plate; said
hydraulic machines, respectively, being (a) operable as a hydraulic pump with
said respective
hydraulic pump shaft being rotatable by the engine of said vehicle, (b)
operable as a hydraulic
motor with said respective hydraulic motor shaft being operatively connected
to rotate said output
drive of the vehicle, and (c) interconnected in a hydraulic closed loop; a
controller for
determining the relative speed of said output drive of the vehicle, said
controller being operable
following the initiation of operation of said vehicle engine and being
responsive to: the speed of
said hydraulic pump shaft; the speed of said hydraulic motor shaft; and
desired variations in
vehicle velocity as indicated by operation of said accelerator and said brake;
and said controller
determining: said angular adjustment of the swash plate of said hydraulic
pump; said angular
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adjustment of the swash plate of said hydraulic motor; and the speed of said
engine; said
controller modifying the operation of said vehicle in accordance with said
desired variations in
vehicle velocity as indicated by operation of said accelerator and said brake
while compensating
for changes in vehicle load and variations in the terrain being traversed by
the vehicle and
automatically adjusting the speed of said engine to maximize predetermined
parameters related to
fuel economy.
Certain exemplary embodiments can provide a method of controlling power to a
wheel
drive shaft of an automobile having an engine, a drive mode selector, an
accelerator pedal, a
brake pedal, and a transmission comprising a hydraulic pump having an
adjustable pump swash
plate angle and a hydraulic motor having an adjustable motor swash plate
angle, the method
comprising the steps of: a) measuring a drive mode selector position, an
accelerator pedal
position, and a brake pedal position; b) measuring an engine speed and an
automobile speed; and
c) controlling the pump swash plate angle and the motor swash plate angle
based on the drive
mode selector position, the accelerator pedal position, the brake pedal
position, the engine speed,
and the automobile speed while maintaining a constant engine speed within
predetermined values
of the pump swash plate angle and the motor swash plate angle.
The modular transmission uses only a pair of small and light hydraulic
machines of
remarkably improved volumetric efficiency with pistons having body portions
substantially as long as the axial length of the respective cylinders in which
they
reciprocate. The two hydraulic machines operate in a closed loop, one being
used as a
pump driven by the vehicle's engine, and the other used as a motor. Each
machine has a
fii11y articulatable swash plate. By coinputer control, the angles of the
swash plates of the
two machines are infinitely varied to provide an appropriate optimum ratio of
engine/wheel speed for all conditions from start-up, city driving, hill
climbing varied
according to load and steepness, and over-drive for highway. This complete
vehicle
operation is attained while the vehicle's engine continues to operate at
relatively constant
speeds and relatively low RPM.
The modular transmissions are described using various einbodiments of hych-
aulic
machines, all of which share a novel combination of simple structural features
including
elongated pistons reciprocating in a fixed cylinder block, cylinders provided
with unique
lubrication recesses, and shoes directly attached to each piston (without dog-
bones) that
malce sliding contact with a rotating and nutating swash plate or, preferably,
with the
nutating-only wobbler portion of a split swash plate. Testing has verified
that these simple
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structural features have synergistically resulted in a remarkably increased
volumetric
efficiency and such increased mechanical efficiency that even the drive shafts
of machines
as large as 12-cubic inch capacity can be easily turned by hand when the
machine is fully
assembled. Each disclosed machine can operate as eitlier a pump or a motor.
These fixed-cylinder-bloclc hydraulic machines can be built smaller and
lighter
than conventional rotating block hydraulic machines having similar
specifications. Wit11
the improved lubrication of their elongated pistons, it is possible to use
these smaller and
lighter hydraulic machines to meet the high-speed/high-pressure specifications
required
for automotive use as an infinitely-variable automatic transmission.
Each machine has a fully articulatable swash plate, and by means of a computer
program, variations in the angles of the swash plates of the two machines are
infinitely
varied to provide an appropriate optimum ratio of engine/wheel speed to
provide the
equivalent of infinitely variable gear ratios for all conditions from start-
up, city driving,
hill climbing varied according to load and steepness, and over-drive for
higllway.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 shows a partially schematic and cross-sectional view of a hydraulic
machine with a
variable swash plate angle.
Fig. 2 shows a partially schematic and cross-sectional view of the hydraulic
machine of
Fig. 1 taken along the plane 2-2 with parts being omitted for clarity.
Fig. 3A shows a partially schematic view of a hold-down plate, when the swash
plate is
inclined at +25 , as seen from the plane 3A-3A of Fig. 1.
Fig. 3B shows a partially cross-sectional view of the swash plate and piston
hold-down
assembly, the view being taken in the plane 3B-3B of Fig. 3A.
Fig. 4 shows a cross-sectional view of a single cylinder with a long spring.
Fig. 5 shows a partially schematic and cross-sectional view of a hydraulic
machine with a
split swash plate.
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Fig. 6 shows a view of a "closed loop" arrangement of two hydraulic machines
as known
in the prior art.
Fig. 7A shows a schematic view of a pump and motor combined in an end-to-end
embodiment of a hydraulic module of the inventive transmission.
Fig. 7B shows a schematic view of the same pump and motor combined in a side-
by-side
embodiment to form another hydraulic module of the inventive transmission.
Fig. 8A shows a schematic and relatively to scale representation of the
hydraulic module
of Fig. 7A, showing it being used as a transmission in a front-wheel-drive
vehicle.
Fig. 8B shows a schematic and relatively to scale representation of the
hydraulic module
of Fig. 7A, showing it being used as a transmission in a rear-wheel-drive
vehicle.
Fig. 9A is a schematic and relatively to scale top view of the hydraulic
module of Fig. 7B,
showing it being used as a transmission in a more conventional rear-wheel-
drive
vehicle.
Fig. 9B is a schematic and relatively to scale end view of the hydraulic
module of Fig. 9A.
Fig. 10 is a bloclc diagram of the preferred inputs and outputs of the
computer controller in
an embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Initially, the following key features of the invention are described:
To meet the world's needs for oil conservation while, at the same time, not
requiring changes that will cause a significant disturbance in the world's
present allocation
of fuels, the invention provides an all-hydraulic, gearless, infinitely
variable
transmission that uses known and tested hydraulic and electronic coinponents.
Since the hydraulics of a transmission of the present invention provide
working
torque at very low engine RPM's, a gasoline engine vehicle incorporating the
present
invention in place of the vehicle's original torque converter transmission
operates at
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much lower engine speeds. This feature is due to the remarkable efficiencies
that are
achieved by using hydraulic machines having stationary cylinder blocks and
rotating
swash plates that vary through a wide continuum of angles, preferably from -25
to
+250.
A transmission of the present invention is directly coupled without reduction
of
speed to the engine of a gasoline-powered vehicle. A transmission of the
present
invention completely replaces the existing transmission of the vehicle,
fitting into the
same space but having substantially less volume and less weight than the
original
transmission. No clutches or torque converters are required between the
vehicle engine
and the present invention, which includes two hydraulic machines operated
respectively as a pump and a motor connected in a "closed loop" hydraulic
flow. The
pump, driven directly by the vehicle's engine, produces a swash plate-
controlled flow
of hydraulic fluid that is sent directly into the accompanying znotor. The
motor is
directly coupled to the drive shaft for the vehicle's wheels and, by selective
positioning
of its respective swash plate, produces the torque called for by the driver in
reaction to
the drive wheel resistance torque.
That is, the inventive transmission fundamentally changes the way the
automobile responds to driver inputs. In an automobile with either a manual or
automatic geared transmission, when the driver calls for acceleration by
pressing on
the gas pedal, power is increased to the wheel drive shaft by increasing the
speed of
the engine. Upon continued acceleration, when the engine reaches a certain
high speed,
the trarisinission shifts to a higher gear, either automatically or through
the clutch by
driver input, and the engine speed drops. With the inventive gearless
transmission,
when the driver calls for acceleration by pressing on the gas pedal, power is
increased
by changing the swash plate ratio in the transmission, and the engine speed
remains
relatively constant. Upon continued acceleration, only when the swash plate
ratio
reaches a certain value, is the engine speed increased to a new, slightly
higher level, to
provide the required additional power.
The transmission's electronic controls are remarkably simple. Engine speed and
output drive shaft speed are monitored along with fuel consumption and
driver's throttle
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and bralce indications, and the only variables that are controlled are the
angle of the swash
plates in the hydraulic pump/motors and, less often, engine RPM.
With a prototype of the present invention, the hydraulic transmission provided
enough power to the wheel drive shaft of a sport utility vehicle (weighing
5575
pounds) to accelerate the automobile rapidly on a dynamoineter-simulated flat
roadway
to 30 MPH while maintaining an engine speed of 860 RPM. This preliminary test
operated the vehicle through infinitely variable transmission ratio limits of
25:1 to over
0.67:1. As the automobile accelerates to higher speeds, it is possible to make
gradual
step increases in the engine speed in order to maximize the time that the
engine is
maintained at constant speeds and improve fuel efficiency. The prototype
hydraulic
transmission was capable of providing enough power to accelerate the
automobile to
highway speeds while never increasing engine speed beyond 2200 RPM. Also, the
inventive transmission was able to start up and maintain a stable vehicle
speed at 2
RPM (i.e., a speed of only 16 feet per minute), and it achieved acceleration
rates
pealcing greater than 10 MPH/second with a 50% reduction in fuel consumption
during
such acceleration as measured by positive displacement flow meters. Further,
satisfactory deceleration was achieved at 20 MPH/second to bring the vehicle
to a
complete stop without using the vehicle's brakes.
A transmission of the present invention is capable of varying the speed of the
drive shaft with minimal changes to engine speed. Thus, the present invention
allows
engine speed to remain in a relatively narrow low-to-moderate range where the
combustion in recently proposed HCCI engines is predicted to be more easily
controlled. A transmission of the present invention is highly compatible with
implementation of more fuel efficient HCCI engines on gasoline-powered
vehicles.
Further, the present invention opens the possibility of the auto industry
being
able to return to proven lower speed/higher torque engines, allowing even
greater
efficiency improvements to be achieved with lighter, lower cost engines.
While the operation of hydraulic machines of the type that may used to create
the
hydraulic portion of the inventive transmission are well known, a prefeiTed
pair of such
hydraulic machines will next be described in some detail. As indicated above,
it can be
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assumed that each disclosed machine is connected in a well known "closed loop"
hydraulic system with an appropriately mated pump or motor. Both hydraulic
machines in
the transmission of the preserit invention are preferably identical in
structure, one being
used as a pump and the other as a motor.
5 In a preferred embodiment, a transmission of the present invention is used
in
combination with an accumulator to improve fuel economy.
Long-Piston Hydraulic Machine
Referring to Fig. 1, a variable hydraulic machine 110 includes a modular fixed
cylinder block 112. Cylinder block 112 has a plurality of cylinders 114 (only
one shown)
10 in which a respective plurality of mating pistons 116 reciprocate 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 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
fonned on the
surface of a rotor 128 that is pivotally attached to a drive element, namely,
shaft 130 that is
supported on bearings within a bore in the center of cylinder block 112.
Hydraulic machine 110 is provided with a modular valve assembly 133 that is
bolted as a cap on the left end of modular cylinder block 112 and includes a
plurality of
spool valves 134 (only one shown) that regulate the delivery of fluid into and
out of
cylinders 114.
The machine 110 can be operated as either a pump or as a motor. For operation
as
a motor, during the first half of each revolution of drive shaft 130, high
pressure fluid fiom
an inlet 136 enters the valve end of each respective cylinder 114 through a
port 137 to
drive each respective piston from its retracted position to its fitlly
extended position.
During the second half of each revolution, lower pressure fluid is withdrawn
from each
respective cylinder through port 137 and fluid outlet 139 as each piston
returns to its fully
retracted position.
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For operation as a pump, 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 higli
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
machine, e.g., hydraulic machine 110 discussed above, causing the pistons of
the mating
machine to move at a speed that varies with the volume (gallons per minute) of
high
pressure fluid being delivered in a mamler well known in the art.
The cylindrical wall of each cylinder 114 in modular cylinder block 112 is
transected radially by a respective lubricating chaimel 140 foimed
circumferentially
therein. A plurality of passageways 142 intercoimect all lubricating channels
140 to form a
continuous lubricating passageway in cylinder block 112.
Each respective lubricating channel 140 is substantially closed by the axial
cylindrical body 122 of each respective piston 116 during the entire stroke of
each piston.
That is, the outer circumference of each cylindrical body 122 acts as a wall
that encloses
each respective lubricating channel 140 at all times. Thus, even when pistons
116 are
reciprocating through maximum strokes, the continuous lubricating passageway
interconnecting all lubricating channels 140 remains substantially closed off.
Continuous
lubricating passageway 140, 142 is simply and economically formed within
cylinder block
112.
During operation of hydraulic machine 110, all interconnected lubricating
channels
140 are filled almost instantly by a minimal flow of high-pressure fluid from
inlet 136
entering each cylinder 114 through port 137 and being forced between the walls
of the
cylinders and the outer circumference of each piston 116. Loss of lubricating
fluid from
each lubricating channel 140 is restricted by a surrounding seal 144 located
near the open
end of each cylinder 114. Nonetheless, the lubricating fluid in this closed
continuous
lubricating passageway of lubricating chantiels 140 flows moderately but
continuously as
the result of a continuous minimal flow of fluid between each of the
respective cylindrical
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walls of each cylinder and the axial 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
130 as the pistons reciprocate. As the pressure in each cylinder 114 is
reduced to low
pressure on the return stroke of each piston 116, the higher pressure fluid in
otherwise
closed lubricating passageway 140, 142 is again driven between the walls of
each cylinder
114 and the outer circumference of body portion 122 of each piston 116 into
the valve end
of each cylinder 114 experiencing such pressure reduction.
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
respoilse to
piston motion and to the changing pressures in each half-cycle of rotation of
drive shaft
130 as the pistons reciprocate.
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 is preferably variable from 0
(i.e.,
perpendicular) to 25 . In Fig. 1, 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 linlc 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 180 is moved to the right in Fig. 1, the
inclination of rotor 128
varies throughout a continuum from the +25 inclination shown, back to 0
(i.e.,
perpendicular), and then to -25 .
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. While the remaining 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 extenlal of
housing 192.
Swash plate rotor 128 is balanced by a shadow link 194 that is substantially
identical to
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control link 182 and is similarly connected to collar 180 but at a location on
exactly the
opposite side of collar 180.
Referring to both Fig. 1 and Fig. 2, the cylindrical wall of each cylinder 114
is
transected radially by a respective lubricating channel 140 fonned
circumferentially
therein. A plurality of passageways 142 interconnect all lubricating channels
140 to form a
continuous lubricating passageway in cylinder block 112. Each respective
lubricating
channel 140 is substantially closed by the axial cylindrical body 122 of each
respective
piston 116 during the entire stroke of each piston. That is, the outer
circumference of each
cylindrical body 122 acts as a wall that encloses each respective lubricating
channel 140 at
all times. Thus, even wllen pistons 116 are reciprocating through maximum
strokes, the
continuous lubricating passageway interconnecting all lubricating channels 140
remains
substantially closed off. Continuous lubricating passageway 140, 142 is simply
and
economically formed within cylinder block 112 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 machine 110, all interconnected lubricating
channels
40 are filled almost instantly by a minimal flow of high-pressure fluid from
inlet 36
entering each cylinder 114 through port 137 and being forced between the walls
of the
cylinders and the outer circumference of each piston 116. Loss of lubricating
fluid from
each lubricating channel 140 is restricted by a surrounding seal 1441ocated
near the open
end of each cylinder 114. Nonetheless, the lubricating fluid in this closed
continuous
lubricating passageway of lubricating channels 140 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 the axial 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
130 as the pistons reciprocate. As the pressure in each cylinder 114 is
reduced to low
pressure on the return stroke of each piston 116, the higher pressure fluid in
otherwise
closed lubricating passageway 140, 142 is again driven between the walls of
each cylinder
114 and the outer circumference of body portion 122 of each piston 116 into
the valve end
of each cylinder 114 experiencing such pressure reduction.
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Referring to Fig. 3A and Fig. 3B, a hold-down assembly for a hydraulic machine
includes a hold-down element 154 with a plurality of circular openings 160,
each of wllich
surrounds the neck 120 of a respective piston 116. The swash plate is at +25
angle in Fig.
3A and Fig. 3B. Fig. 3A shows the hold-down plate 154 from the perspective of
looking
down the shaft of the rotor 128, or from plane 3A-3A of Fig. 1. 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. Each respective shoe cavity is comlected through an appropriate shoe
chaiinel 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.
Fluid pressure constantly biases pistons 116 in the direction of rotor 128,
and the
illustrated 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 loading
is necessary
to assure constant contact between piston shoes 124 and flat surface 126 of
rotor 128. The
variable hydraulic machines provide such additional bias by using one of three
simple
spring-biased hold-down assemblies.
The first hold-down assembly, for hydraulic machine 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.
The positions 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.
Referring to the relative position of these parts at 0 inclination, each
piston channel 164
has the same radial position relative to each respective circular opening 160
in hold-down
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element 154. At all inclinations other than 0 , the relative radial position
of each piston
clianne1164 is different for each opening 160, and the relative positions of
each special
washer 156 is also different. The different relative positions at each of the
nine openings
160 are themselves constantly-changing as rotor 128 rotates and nutates
through one
5 complete revohition at each inclination. For instance, at the 25
inclination shown in Fig.
3A, 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 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.
10 At inclinations other than 0 , 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. 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. Each follows a cyclical path (that appears to trace a
lemniscate, i.e., a
15 "figure-eight") that varies in size with the angular inclination of swash
plate rotor 128 and
the horizontal position of each piston 116 in fixed cylulder block 112. To
assure proper
contact between each respective shoe 124 and flat surface 126 of rotor 128, a
size is
preferably 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 for all inclinations of rotor 128.
A second hold-down assembly is shown schematically in Fig. 4 in an enlarged,
partial, and cross-sectional view of a single piston of a hydraulic machine
210. Each piston
216 is positioned in the modular fixed cylinder block 212 within a cylinder
214, the latter
being transected radially by a respective lubricating channe1240 formed
circumferentially
therein. In the same manner as described in relation to the other hydraulic
machines
already detailed above, each lubricating channel 240 is interconnected with
similar
channels in the machine's other cylinders to forin a continuous lubricating
passageway in
cylinder bloclc 212. An optional surrounding sea1244 may be located near the
open end of
each cylinder 214 to minimize further the loss of lubricating fluid from each
lubricating
channe1240.
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Fixed cylinder block 212 includes neither a large axially circumferential coil
spring
nor an axially circumferential crevice for holding same. The modular fixed
cylinder block
212 of hydraulic machine 210 can be connected to either a modular fixed-angle
swash
plate assembly or a modular variable-angle swash plate assembly, but in either
case,
hydraulic machine 210 piovides a much siinpler hold-down assembly. Namely, the
hold-
down assembly of this embodiment includes 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.
Each piston shoe 224 is similar to the conventional shoes shown in the first
hold-
down assembly and is inounted 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.
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.
Eacli 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 232. 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 minimal but
sufficient to
maintain effective sliding contact between each shoe 224 and flat face 226 in
the absence
of 1lydraulic pressure at the valve end of each respective cylinder 214. The
minimal bias of
springs 250 not only facilitates assembly but also prevents entrapment of tiny
dirt and
metal detritus encountered during assembly and occasioned by wear.
Referring to Fig. 5, a third hold-down assembly for a hydraulic machine 310
includes an improved conventional split swash plate arrangement. A plurality
of pistons
316, each including a respective sliding shoe 324, reciprocates in respective
cylinders 314
fonned in cylinder block 312 that is identical to cylinder block 112.=Each
shoe 324 slides
on the flat face 326 formed on a wobbler 327 that. is mounted on a mating
rotor 328 by
appropriate bearings 372, 374 that permit wobbler 327 to nutate without
rotation while
rotor 328 both nutates and rotates in a manner well known in the art. The
inclination of
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wobbler 327 and rotor 328 about axis 329 is controlled by the position of a
sliding collar
380, a controllink 382, and a balancing shadow link 394.
Shoes 324 are held down by a hold-down assembly substantially identical to the
first hold-down assembly, however, the large single coil spring 150 is
replaced by a
plurality of smaller individual coil springs.
A hold-down plate 354 is fixed to wobbler 327. Each shoe 324 receives the
circuinfere.ntial extension of a respective special washer 356, and the neck
of each piston
316 is positioned within one of a corresponding plurality of respective
openings 360
formed through hold-down plate 354. While wobbler 327 does not rotate with
rotor 328,
the nutational movement of wobbler 327 is identical to the nutational movement
of rotor
328 and, therefore, the relative motions between shoes 324 and the flat
surface 326 of
wobbler 327 are also identical to those in the first hold-down assembly.
A plurality of individual coil springs 350 provides the minimal spring bias to
maintain effective sliding contact between each shoe 324 and flat face 326 of
wobbler 327
in the absence of hydraulic pressure at the valve end of each cylinder 314.
Each coil spring
350 is positioned circuinferentially about each shoe 324, being captured
between each
special washer 356 and a collar formed just above the bottom of each shoe 324.
Referring to Fig. 6, each hydraulic machine, whether a motor or a pump, is
preferably paired with another hydraulic machine, a mating pump or motor, in a
well
known "closed loop" arrangement. For exainple, the high-pressure fluid exiting
from the
outlet 139 of hydraulic machine 110 is directly delivered to the input 136' of
a mating
hydraulic machine 110', while the low-pressure fluid exiting from the outlet
139' of
hydraulic machine 110' is directly delivered to the input 136 of mating
hydraulic machine
110. Hydraulic inachine 110 and hydraulic machine 110' may be identical in
structure
except that hydraulic machine 110 is used as a pump and hydraulic machine 110'
is used
as a motor. 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 to maintain a predetermined volume of fluid in the closed
loop system
at all times.
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Hydraulic Transmission
In one embodiment, the dual hydraulic machines are arranged end-to-end, as
shown in Fig. 7A, and in another embodiment the dual hydraulic machines are
arranged side-by-side, as shown in Fig. 7B. In the end-to-end embodiment, the
pump
400 includes a pump shaft 402 driving the pump swash plate 404, which drives
the
long pistons in the pump cylinder block 406. A hydraulic circuit 408 connects
pump
400 to the motor 410. Hydraulic circuit 408 provides fluid communication
between
pump cylinder block 406 and the motor cylinder block 412. Pressurized
hydraulic fluid
from pump 400 drives the motor pistons, which drive the motor swash plate 414
to turn
the motor drive shaft 416. In the side-by-side embodiment, the hydraulic
circuit 418 is
reconfigured to connect the two cylinder blocks 406, 412, which sit next to
each other.
In this embodiment, pump 400 and motor 410 may be structurally connected along
their common side to provide stability to the pump-motor unit.
While the end-to-end arrangement is simpler and lighter, requiring fewer parts
to
connect the pump to the motor, the side-by-side arrangement is significantly
shorter in
length. An end-to-end 12-cubic inch prototype is 25 inches in length and 10
inches in
diameter and weighs 150 pounds. A side-by-side 12-cubic inch prototype is 17
inches in
length and 20 inches across. Both prototypes pump 12 cubic inches of
pressurized liquid
per revohztion at full pump swash. Both prototypes are so efficient that very
little energy is
lost as heat. Throughout operation, the cylinder block remains comparatively
cool to prior
art hydraulic machines. Both prototypes are remarkably quiet during operation
as well.
As indicated earlier, the transmission's electronic controls are remarkably
simple.
Engine speed, working fluid pressure, and output drive shaft speed are
monitored along
with fuel consumption and the driver's throttle and brake indications, and the
only
variables that are controlled are engine RPM and the angles of the swash
plates in the
hydraulic pump and hydraulic motor. Further, after reaching highway speeds,
the motor
swash plate is varied to provide a continuously variable overdrive from 1:1
through about
0.5:1.
In an embodiment of the present invention, the hydraulic transmission is
modular.
The term "modular", as used herein, is specifically intended to describe a
unit that can be
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used "as is" to replace the existing transmission of a presently operating or
designed
vehicle. A modular transmission according to the present invention malces it
possible
to allow a present gasoline engine vehicle to operate with an increase in fuel
efficiency
comparable to what could be achieved by a similarly sized diesel engine
vehicle.
Fig. 8A is a schematic, and relatively to scale, illustration of a front-wheel-
drive automobile, showing the "east-west" engine 401 located between the front
tires
405a, 405b and in front of the rear tires 405c, 405d. The vehicle's
transmission has
been removed and replaced with the end-to-end modular embodiment of the
invention
illustrated in Fig. 7A, namely, hydraulic pump 400 is connected to hydraulic
motor
410 througll hydraulic circuit 408. This module is shown in one possible
position
relative to engine 401, with pump shaft 402 being connected by a belt 411 to
the
auxiliary component drive shaft 403a of engine 401. A connection mechanism 424
connects the output of the hydraulic module from motor drive shaft 416 to the
front
wheel drive shaft 422.
Preferably, the output is connected to the vehicle's front wheels through the
same mechanism that received the output of the vehicle's original
transmission. In one
embodiment, connection mechanism 424 is a mechanical coupling of only motor
output shaft 416 to front wheel drive shaft 422. In another embodiment,
connection
mechanism 424 involves meclZanically combining motor output 416 with engine
output
403b to provide power to front wheel drive shaft 422. In both embodiments, the
power
supplied to wheel drive shaft 422 is varied primarily by varying the hydraulic
settings
to vary the output of the hydraulic module. In both embodiments, the power
supplied
to wheel drive shaft 422 may be varied secondarily by varying the speed of
engine
401. In the second embodiment, connection mechanism 424 may include a single
orbiter to combine the power output from motor shaft 416 with the output from
engine
drive shaft 403b.
Fig. 8B is a schematic, and relatively to scale, illustration of a rear-wheel-
drive
automobile, showing the "north-south" engine 401 a located between the front
tires
405a, 405b. The vehicle's transmission has been removed and replaced with the
end-to-
end modular embodiment of the invention illustrated in Fig. 7A, namely,
hydraulic
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pump 400 is connected to hydraulic motor 410 through hydraulic circuit 408.
This
module is shown in one possible position relative to engine 401, with pump
shaft 402
being connected by a belt 411 to the auxiliary component drive shaft 403a of
engine
401. A connection mechanism 428 connects the output of the hydraulic module
from
5 motor drive shaft 416 to the rear wheel drive shaft 426.
Preferably, the output is connected to the vehicle's rear wheels through the
same mechanism that received the output of the vehicle's original
transmission. In one
embodiment, connection mechanism 428 is a mechanical coupling of only motor
output shaft 416 to rear wheel drive shaft 426. In another embodiment,
connection
10 mechanism 428 involves mechanically combining motor output 416 with engine
output
403b to provide power to rear wheel drive shaft 426. In both embodiments, the
power
supplied to wheel drive shaft 426 is varied primarily by varying the hydraulic
settings
to vary the output of the hydraulic module. In both embodiments, the power
supplied
to wheel drive shaft 426 may be varied secondarily by varying the speed of
engine
15 401. In the second embodiment, connection mechanism 428 may include a
single
orbiter to combine the power output from motor shaft 416 with the output from
engine
drive shaft 403b.
Similarly, Fig. 9A and Fig. 9B are schematic, and relatively to scale, top and
end view illustrations of the front end of a conventional rear-wheel-drive
vehicle,
20 showing a conventional "north-south" engine 401 a located between the
vehicle's front
tires 405c, 405d. Again, the vehicle's transmission has been removed and
replaced, but
in this instance with the side-by-side modular embodiment of the invention
illustrated
in Fig. 7B. While hydraulic pump 400 is still connected to liydraulic motor
410
through hydraulic circuit 408 at the rear of the module, the front of the
module
includes a connection box 407 with a mounting plate 419. The module is bolted
to the
fly-wheel casing 409 at the rear of engine 401 a. The pump shaft of hydraulic
pump 400
is connected by conventional ineans to the main drive shaft of engine 401 a
(not
shown); and the output of the hydraulic module is also connected by
conventional
means (not shown) within connection box 407 to an output shaft 417 that
comlects to
the vehicle's wheels through the saine mechanism that received the output of
the
vehicle's original transmission. In the second einbodiment, connection box 407
may
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include a single orbiter to combine the power output from motor shaft 402 (see
Fig.
7B) with the output from the engine drive shaft.
Vehicle Operation
The vehicle engine operation is started in a conventional manner, with the
vehicle's shift lever in "Park". (NOTE: The vehicle's shift lever is
hereinafter referred
to as the "drive mode selector".) When the engine is running normally at idle,
e.g.,
approximately 750 RPM and the vehicle is still in "Park", the transmission and
its
computer controller are in standby mode. The engine can be raced in neutral by
operation of the gas pedal. As soon as the drive mode selector is moved out of
"Park",
the computer controller begins controlling both engine speed and vehicle speed
based
on the following real-time inputs:
a) position of the drive mode selector
b) position of the accelerator pedal
c) position of the brake pedal
d) vehicle speed based on engine output shaft and wheel drive shaft speeds
e) fuel flow rate to the engine
f) positions of the swash plates on the pump-motors
g) hydraulic circuit pressure.
The computer controller uses these inputs to produce real-time outputs to the
following components:
a) high-pressure hydraulic safety valves on the pump-motors
b) swash plate servo position valves on the pump-motors
c) engine throttle to adjust to an optimum engine speed.
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The communications between the computer controller and the various components
of the automobile are showif schematically in Fig. 10. Whenever the vehicle's
engine is
turned on, the coinputer controller 450 continually monitors the inputs from
the driver,
namely the position of the drive mode selector 452, the position of the brake
peda1454,
and the position of the gas peda1456. The computer controller also monitors
the speed of
the engine drive shaft 458 to determine whether adjustments need to be made to
change
the speed of the drive shaft 458. When the driver inputs 452, 454; 456
indicate a desired
change in drive shaft speed 458, the computer controller determines (a) the
rate of fuel
flow to the engine 460 as an indirect measure of engine speed, (b) the value
of hydraulic
pressure 462 in the pump and motor and the positions of (c) the pump swash
plate 464a
and (d) the motor swash plate 464b.
Computer controller 450 then uses a predetermined algorithm to achieve the
desired change in drive shaft speed 458 most efficiently. This 'is
accoinplished by making
one or more of the following changes: computer controller 450 may adjust the
engine
tlirottle 466 to change the rate of fuel flow to the engine 460, and/or may
adjust the swash
plate servo valves 470 to adjust the positions of one or both the pump and
motor swash
plates 464a, 464b.
A vehicle incorporating a transmission of the present invention preferably has
the
following features:
1. When the drive mode selector is moved from "Park" to "Drive" or "Neutral"
but
the brake is still being applied, the system avoids any build-up of hydraulic
pressure in the
closed-loop system by maintaining the pump swash plate in the 0 position.
2. When the drive mode selector is moved from "Park" to "Drive" or "Neutral"
and
pressure is removed from the brake pedal, the pump swash plate still remains
at 0 , and the
motor swash plate remains at +25 . As long as the pump swash plate remains at
0 , all
fluid in the closed loop remains in a "no flow" condition. This maintains the
wheel drive
shaft in a"locked" position, providing a "hill holding" feature. Should the
vehicle be in an
extreme uphill or downhill condition, where the vehicle is moved by gravity in
spite of the
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23
locked rear drive shaft, the pump swash plate is commanded to increase the
flow of fluid
slightly in either a + or - direction to maintain 0 MPH vehicle speed.
3. When the drive mode selector is in "Drive" and the brake is not being
applied,'as
long as the accelerator is being depressed, calling for more hydraulic
pressure/torque than
is required to overcome tractive resistance torque, the angle of the pump
swash plate is
steadily increased in the + direction, moving fluid to the motor and
increasing its rotation
and the rotation of the vehicle drive shaft, accelerating the vehicle. Under
these conditions,
the vehicle continues to accelerate until the hydraulic presssure/torque is
equal to the
tractive resistance torque of the vehicle's wheels on the terrain. If the
pressure on the
accelerator is decreased, calling for a lower pressure set point, the angle of
the pump
swash plate is reduced to slow the acceleration of the vehicle until that set
point is reached.
A transmission of the present invention fundamentally changes the way the
automobile responds to driver inputs. In an automobile with either a standard
or
automatic geared transmission, when the driver calls for acceleration by
pressing on
the accelerator, power is increased to the wheel drive shaft by increasing the
speed of
the engine. Upon continued acceleration, when the engine reaches a certain
high speed,
the transmission shifts to a higher gear, either automatically or through the
clutch by
driver input, and the engine speed drops. In an automobile with a gearless
transmission
of the present invention, when the driver calls for acceleration by pressinng
on the gas
pedal, power is increased by changing the swash plate ratio in the
transmission, and the
engine speed remains constant. Upon continued acceleration, only when the
swash
plate ratio reaches a certain value, is the engine speed increased to provide
more
power.
Since the hydraulics of a transmission of the present invention provide
working
torque at very low engine RPM's, a gasoline engine vehicle incorporating the
present
invention in place of the vehicle's original torque converter transmission
operates at
much lower engine speeds. This feature is due to the remarkable efficiencies
that are
achieved by using hydraulic machines having stationary cylinder bloclcs and
rotating
swash plates that vary through a preferable continuum of at least -25 to +25
.
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A transmission of the present invention is capable of varying the speed of the
drive shaft with minimal changes to engine speed. Thus, the present invention
allows
engine speed to remain in a relatively narrow loW-to-moderate range where the
combustion in HCCI engines is more easily controlled. A transmission of the
present
invention is highly coinpatible with implementation of more fuel efficient
HCCI
engines on gasoline-powered vehicles.
The pump-motors of the present invention preferably use no "dog bones". They
preferably have minimal "blow-by", which is preferably less than.1 gallon per
minute. They are preferably connected in a"closed loop". The puinp-motors ,
preferably have a traditional split swash plate, modified by adding bearings
to support the
nutating-only wobbler portion on the nutating/rotating rotor member. In one
embodiment
of the present invention, these bearings are needle bearings. They preferably
have a
mechanical valve system. Each pump-motor preferably includes a hold-down plate
biased
by a plurality of springs, each spring being positioned, respectively,
circumferentially
about the sliding shoe associated with the head of each piston. This
combination of a split
swash plate and a hold-down element significantly reduces the surface speed of
the
relative motion between the shoes and the swash plate and, thereby, results in
reduced
wear and costs and in a significant increase in machine efficiency.
Example: 2004 Chevy Tahoe All-Hydraulic Transmission Installation and
Evaluation
To demonstrate the modular nature and to quantify the fuel efficiency of an
all-
hydraulic transrim.ission of the present invention, the automatic transmission
of a 2004
Chevrolet Tahoe was removed and a transmission of the present invention was
installed in
its place.
The vehicle powertrain consisted of a GM 5.3L V8 engine directly coupled
through a non-reduction gear to the infinitely variable transmission. The
transmission
consisted of a hydraulic puinp and motor coupled only by the hydraulic flow.
The pump,
driven by the engine, produced the necessary swash plate-controlled flow that
was directed
to the hydraulic motor. The motor, by the position of its swash plate and
being directly
coupled to the drive shaft for the vehicle's drive wheels, produced the
necessary torque in
reaction to the drive wheel resistance torque.
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The following inputs from the vehicle control modules to the infinitely
variable
transmission controller were used:
1. The drive mode selector with Park, Reverse, Neutral, Drive and Parlc
Lock.
5 2. The accelerator pedal position sensor for driver indication of desired
power.
3. Off idle switches for redundant control with the driver pedal at full off
position.
4. Brake pedal sensor for driver indication of accelerated reduction of
10 speed.
The following transmission components were installed for inputs to the
computer
controller:
1. Tliree hydraulic pressure transducers to monitor the higli pressure pump,
motor, and charge circuit pressure.
15 2. Two speed sensors to monitor the transmission input from the engine and
output speeds to the rear driveshaft.
3. Two fuel flow meters for engine supply and return.
4. Two pump and motor swash plate positions LVDT.
5. Hydraulic charge circuit flow meter.
20 Outputs from the computer controller:
6. High pressure hydraulic safety solenoid valve.
7. Two high pressure pump and motor swash plate servo valves.
The various accelerator pedal/swash plate angle setting ratios calculated by
computer controller are all initially calculated and, thereaffer, tested with
dynamometer
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26
data. For the prototype, initial calculations set system pressure at 200 PSI
for engine idle
conditions, building to a maximum of 3,800 PSI, with 167 lb-ft torque per each
1,000 PSI
variation in differential pressure. For the prototype Tahoe vehicle,
preliminary calculations
indicate engine RPM range limits of 750 to 2,200, with transmission ratio
limits of 25:1
(low-low) to 0. 67: 1 (overdrive). The intent of this prototype design is to
keep the engine
operating at its lowest RPM while maintaining adequate torque for all EPA
tests. Since,
for a given amount of torque required, the engine can produce that amount over
a range of
RPM and fuel delivery values, the computer controller algorithms are selected
to attain
highest fuel economy.
It should be indicated that, while it is intended that this invention.be used
modularly to replace existing transmissions in gas-engine vehicles, it is
useable as a
factory-installed unit and in diesel engine vehicles as well:
In this regard, should the invention be used with a vehicle that already has,
or can
modularly replace, its present high speed gasoline engine witli a lower
speed/higher torque
engine such as that prevalent in the 1960-70's, the increase in gas efficiency
will be
markedly greater.
Thus, a transinission of the present invention is not only lighter in weight,
simpler,
and less expensive to build, but it also permits the world to retain its huge
gas engine
infrastructure, while improving fuel consumption coinparable to that which
inight be
achieved with diesel engines, thereby achieving much needed energy
conservation
without concomitant disruption in world fuel allocation.
The present invention opens the possibility of the auto industry to return to
proven lower speed/higher torque engines, allowing the resulting efficiency
improvements to be achieved with lighter, lower cost engines.
Accordingly, it is to be understood that the embodiments of the invention
herein
described are merely illustrative of the application of the principles of the
invention.
Reference herein to details of the illustrated embodiments is not intended to
limit the
scope of the claims, which themselves recite those features regarded as
essential to the
invention.
