Note: Descriptions are shown in the official language in which they were submitted.
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FTFLD OF THE INVENTION:
The present invention relates to a hydraulic propulsion
system for a human powered vehicle of the type in which the
vehicle operator provides the power for propulsion by charging
an accumulator and controlling flow of hydraulic fluid to one
or more motors.
I~ArKOROUND TO THE INVENTION:
There is a need for a human powered urban vehicle as an
alternative vehicle that fills the gap between the bicycle and
the automobile. Such a vehicle is of great utility in urban
and third world environments where, due to population and
space reasons, automobiles are not universally utilized. In
such environments there is also a consumer demand for an
alternative that provides a good ride, weather protection, and
ease of use in crowded cities.
In the past, many attempts to replace the bicycle have
resulted in vehicles which suffer from numerous disadvantages.
So called recumbent bicycles wherein the rider is seated in a
position part way between sitting upright and reclining have
disadvantages in that the very low seated position of such
vehicles reduces visibility and increases the likelihood of
accident or injury. Such vehicles have not gained acceptance
among conventional bicycle riders and therefore have a very
limited market.
A preferred type of human powered vehicle features a
chassis on which are mounted three independently sprung wheels,
two in the rear and one steerable front wheel. The suspension
allows the vehicle to lean like a bicycle around corners, yet
remains upright when stopped or moving slowly. The vehicle
avoids a low seating position. Careful design has also
facilitated a number of features found to be desirable in such
vehicles through a consumer preference survey. Such features
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include a comfortable seat. The rider's legs project somewhat
forward, allowing a bucket-type seat to be used, which allows
the rider to push on pedals as hard as desired against the seat
back rather than being limited by his body weight. Hill
climbing is accordingly easier. A step through frame is also
provided so the rider can easily mount and dismount. Weather
protection is also provided by an optional weather protection
shell which completely protects the rider from rain and cold
when needed. Equally a rear carrier storage area is also
protected to keep the cargo dry. An enclosed carrier may be
located behind the seat and between the rear wheels easily to
carry packages. Carrying loads at a lower level improves
stability of the vehicle when carrying substantial loads.
SttrrfNtARV OF THE INVENTION
The present invention provides a hydraulically operated
propulsion system for such a vehicle, replacing conventional
chain and sprocket drives currently used in bicycles, which
system has numerous advantages over conventional bicycle
operating mechanisms. The drive system is inherently low
maintenance, since all drive components are sealed in oil.
Further, a hydraulic drive system includes an accumulator in
which pressurized oil may be stored which allows car-like
acceleration when required. During braking, the hydraulic
drive system has the ability to capture otherwise wasted brake
energy by pumping up the pressure in the accumulator, thus
allowing the vehicle start up again from stop without pedaling.
In accordance with an embodiment of the invention, a
hydraulic propulsion system for a human powered vehicle
comprises: a reservoir, a treadle pump having dual treadles,
an accumulator, a hydraulic variable ratio pressure transducer,
and at least one hydraulic motor. The reservoir is connected
to the pump, the pump is connected to the accumulator, or
motor and valve means connects the accumulator to the motor.
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The hydraulic variable ratio pressure transducer is in circuit
between the accumulator and the motor. The motor is connected
to said reservoir, also pressurized hydraulic fluid is supplied
to the accumulator from the pump, and pressurized hydraulic
fluid is provided from the accumulator to the motor, and
hydraulic fluid is returned to the reservoir from the motor or
to the variable pressure ratio transducer.
In accordance with another embodiment, the variable
pressure ratio hydraulic transducer comprises a vane type
armature which freely rotates within a cam ring. The armature
includes a radially extending passage intermediate each pair
of vanes, the armature rotates about a porting ring having
ports for communication with the armature passages, and
including a centrally mounted control vane having passage means
therein, port means for connects the transducer to a source of
pressure and to an outlet in pressure ratio relationship to the
source of pressure. Means are provided for manually
controlling the position of the control vane for varying the
pressure ratio of the transducer.
BRIEF DESCRIPTION OF THE DRAWINGS
A better understanding of the invention will be obtained
by a consideration of the detailed description below of a
preferred embodiment, with reference to the following drawings,
in which:
Figure 1 is a simplified view of a hydraulically operated
human powered vehicle of the invention:
Figure 2 is a schematic diagram of the hydraulic circuit
of the vehicle:
Figure 3 is a physical layout illustrating the controls
and principle components of the hydraulic propulsion system;
Figure 4 is a schematic view of one side of the treadle
operated hydraulic pump of the hydraulic system
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Figure 5 is a top view of the pump with the treadles
removed;
Figure 6 is a side view of the linkage for controlling the
variable stroke connection between the treadle and connecting
rod of the piston;
Figure 7 is a section through a wheel motor in accordance
with the present invention;
Figure 8 is a mechanical schematic of the bidirectional
clutch, shown linearly for simplicity;
Figure 9 is a detail of Figure 8;
Figure 10 is a view on the line 8-8 of Figure 7;
Figure 11 is a cross-section through the control valve of
Figure 2;
Figure 12 is a cross-section through the 1, 2, 3 valve of
Figure 2;
Figure 13 is a schematic diagram of the valve 24 of Figure
2;
Figure 14 is a section through the hydraulic variable
transducer of Figure 2;
Figure 15 is a plan view of the porting ring of Figure 19;
Figure 16 is an elevational view of the porting ring of
Figure 14;
Figure 17 is a plan view of the control vane of Figure 14;
Figure 18 is an elevation view of the control vane of
Figure 14;
Figure 19 is an axial view of the armature of the pressure
transducer;
Figure 20 is an end view of the armature of Figure 19;
Figure 21 is a plan view of an end plate of the transducer
of Figure 14;
Figure 22 is a schematic view of a four chamber
transducer, and
Figure 23 is a view of the central control shaft and
porting of Figure 22.
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~ETATLED DESCRIPTION OF THE DRAWINGS:
Figure 1 illustrates a human power driven vehicle
incorporating continuous power input and energy storage and
recapture via a self-contained hydraulic system having an
accumulator, a constant displacement vane motor, a variable
stroke piston pump, and other components. The vehicle 10
consists of a chassis 11, a steerable front wheel 12 and a pair
of independently suspended rear wheels 13. A seat 14 is
provided for the rider, and a steering mechanism 15 operated
by the rider controls the position of the independently sprung
front wheel.
The rider is positioned in a semi-upright position with
hands grasping steering handlebars 15 and feet positioned on
treadle pedals 16. Treadle pedals 16 operate a pair of
variable stroke, variable displacement piston pumps 20 as a
component of the hydraulic propulsion system.
Referring to Figure 2, the vehicle power input consists
of suitable exertion by the operator against the treadles which
operate the variable stroke piston pumps 20. Dynamically,
variable stroke length is accomplished by a manually controlled
linkage described hereinafter connected to conventional piston
pumps. Check valves (not shown) are included in the pumps in
the normal fashion for pumping hydraulic fluid from a low
pressure reservoir 21 to the high pressure side 22 of the
hydraulic circuit. In a preferred embodiment, two hydraulic
motors 30 are provided at the rear of the vehicle, each driving
one rear wheel. These motors are constant displacement vane
type motors which operate as a motor upon start up and during
cruise operation and can be operated as pumps to provide
regenerative braking during deceleration. A control system is
provided as discussed hereinafter which controls operation of
the vehicle during all phases from stationary to accelerating,
constant speed, decelerating, and braking. The vehicle is also
provided with secondary brakes which are preferably internal
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expanding drum brakes to supplement the regenerative braking
when required.
In accordance with the invention a hydraulic variable
pressure ratio transducer 25 is included in the hydraulic
circuit which greatly improves the efficiency of vehicle
operation.
Referring to Figure 2, there is disclosed schematically
a hydraulic operating system of the vehicle of Figure 1. A
double piston treadle pump 20 draws fluid from a reservoir 21
and delivers this fluid to the high pressure line 22. There
the fluid is subsequently routed to valve 24 or valve 23.
Valve 24 feeds the hydraulic fluid to a hydraulic variable
pressure ratio transducer 25 and through a control valve 26 to
an accumulator 27. Consequently, the wheel motors 30 can
receive fluid under pressure from the transducer 25 via the
valve 23,24, and 26 directly from the treadle pump 20 via valve
23, or any desirable combination thereof. Under the
regenerative braking, all of the flow from the wheel motors 30
is combined with any oil flow in pipe 22 and passes via valve
24 to the transducer 25. Relief valves 28 and 29 return fluid
from the high pressure side of the hydraulic circuit to the
reservoir 21 in the event there is an over-pressure in the high
side of the hydraulic circuit. Consequently, wheel motors 30
under the control of valve 23 provide propulsion to the vehicle
and during regenerative braking charge the accumulator 27.
Reservoir 21 may preferably be an air-over-oil reservoir
provided with a diaphragm to retain cleanliness in the
hydraulic circuit and accumulator 27 may also be an air-over-
oil accumulator with a diaphragm.
As mentioned above, the two wheel motors 30 are provided
which are constant displacement vane motors that can also be
reversed to pump fluid to the accumulator 27 for regenerative
braking. The motors 30 are mounted coaxially with the wheels
and the motor bearings also serve as wheel bearings. All
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energy to and from the wheels passes through the wheel motors
and there are no chains, gears, belts, sprockets or other
mechanical drive components. Details of the individual wheel
motors will be discussed below in relation to Figures 7 and 10.
Each of these motors 30 is also provided with a bi-directional
clutch which is integrated with the wheel motor that serves to
disconnect the motor armature from the wheel shaft and removes
drag when coasting and allows the vehicle to achieve a coasting
performance comparable with a bicycle. The clutch re-engages
automatically when the motor 30 is driving a wheel, and is
manually engaged for regenerative braking.
The accumulator 27 is a pressure storage system of about
4 litres in volume which uses the spring force of compressed
air behind a diaphragm to store energy in the form of
pressurized oil. Either by itself or in combination with the
treadle pump, it allows the delivery of energy at much higher
rates than the rider can deliver, facilitating rapid
acceleration. For deceleration, it can accumulate braking
energy regeneratively. Control valve 26 controls oil flow to
the accumulator and to the transducer 25. The control valve
is intended to prevent or extend the leak down of the
accumulator and is shown in Figure 11. The control valve 26 can
also serve as a flow limiter or governor for wheel speed.
Figure 3 which is a physical layout illustrating the
controls and principles of the hydraulic propulsion system
shows the piston pump 20, drawing oil from the reservoir 21 and
delivering pressurized oil to the high pressure side of the
hydraulic system 22. Pressurized oil is then directed by the
energy control module 34, either to the accumulator 27 or the
wheel motors 30. The energy control module 34 includes valve
mechanisms 23, 24 and 26 (Fig.2) together with a hydraulic
variable pressure ratio transducer 25. Right and left hand
grips 31 and 32 which are of a conventional rotary type well
known in the field of motorcycle controls and brake levers 35
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and 33 are provided on the handlebars (not shown). The right-
hand grip controls forward acceleration (f.a.), detent center
(d.c.) and regenerative braking (r.g.). The left-hand grip 32
controls pedal displacement in the treadle pump 20 as disclosed
hereinafter. The energy control module 34 also receives motor
disconnect control m.d. from the left-hand grip 32 mounted
lever and forward acceleration, detent center, and regenerative
braking control from the right-hand grip 31. The energy
control module 34 in turn controls regenerative braking
clutches of the wheel motor 30, as will be detailed
hereinafter.
When the right-hand grip 31 is in the detent center (d. c.)
position operation of the pedal pump 20 can be used to
pressurize wheel motors and propel the vehicle. Turning the
right-hand grip 31 in the forward acceleration (f. a.) position
will connect the accumulator 27 to the wheel motors 30
providing acceleration to the vehicle and if wanted in excess
of the acceleration capabilities of a convention bicycle, and
more nearly in line with the capabilities of an internal
combustion engine automobile. Sustained pumping of the pump
20 will continue to provide hydraulic fluid to the accumulator
and to the wheel motors as necessary. Turning the right-hand
control 31 to the regenerative braking (r. g.) position will
actuate the regenerative braking clutches of the motors 30, and
changes valuing causing the motors to deliver oil to the
accumulator 27. As shown in Figure 2, relief valves 28 and 29
prevent over pressure in the high side of the hydraulic system
or in the accumulator 27.
The details of the pedal pump 20 are shown in Figures 4,
5, and 6 of the drawings. In order to provide the best pump
for the hydraulically operated vehicle, several factors were
considered: (1) cost effectiveness, (2) efficiency, (3)
variable displacement, (4) treadle design for reducing area
required by the feet and reduce height knees had to come,
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ground clearance, and at the same time allowing for partial
treadle strokes, and (5) low force needed to change
displacement of pump.
In accordance with the invention, it is important to avoid
a rotary pump with crank pedals, such as conventional gear,
vane, or axial piston pumps would constitute, as this would
provide even resistance to rotation throughout the entire
rotation when the accumulator is engaged with the circuit, even
when the pedals are in the top and bottom dead center
positions. In a conventional bicycle, one can exert as much
or as little force as desired during pedal crank rotation,
since the pedal crank will rotate easily as long as the bicycle
is in motion. This allows the pedals to pass bottom dead
center and top dead center easily where it is difficult to
apply much force. A constant resistance rotary pump would be
difficult to get past these points if the accumulator was
engaged in the circuit, particularly when pedaling at high
force.
The near linear motion of a treadle pedal is well suited
to avoiding this problem. A rotary pedal is not suitable
unless the problems discussed above are avoided. The treadle
pump shown in the drawings is, of course, the preferred pump
for operating the hydraulic system.
Referring to Figure 4, each drive arc 40 is pivoted on
pivot 41 and is provided with an arcuate surface 42 having
serrations for connecting to the foot 46 on the connecting rod
43 of the piston pump 49. Foot pressure on the arc 40 causes
the arc to move in the direction to drive the connecting rod
43 and cause the piston 45 to pressurize oil in the cylinder
44 which is subsequently pumped to the high side 22 of the
hydraulic circuit. The foot 46 on the connecting rod 43 is
connected to the arc 40 by the interlocking teeth illustrated
in Figure 4. The curvature of the surface 42 and of the foot
96 have the same center of curvature which is the pin 47. Both
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the foot 46 and the surface 42 have interlocking teeth capable
of preventing slippage under load.
The arc 40 is shown at the end of travel, and at this
point a small gap is created between the foot 46 and the
surface 42 due to a piston travel stop, which may provided for
example by a pin 48 reaching the end of the slot in arm 49 as
shown in Figure 5. It will also be appreciated that a piston
stop can also be built into the end of the cylinder bore. Foot
46 can pivot around pin 48 but a detent-to-center spring and
ball tries to place it as shown to match its arc with surface
42. Slotted arm 49 holds con rod 43 in its position by wrist
pin 47. Slotted arm 49 pivots around pin 50 which is shown
concentric with wrist pin 47 when piston 45 is at the bottom
of its stroke. This slotted arm also has a detent-to-center
mechanism, not shown, which the operator can reposition. Thus
if the pump 20 were operating in the configuration shown and
the operator wished to increase the displacement, the slotted
arm detent mechanism would be shifted. When treadle 40 reaches
the bottom of its stroke, the slotted arm 49 will move the
connecting rod 43 and foot 46 to its new position. The foot
46 detent-to-center will ensure that the interlocking teeth on
the foot 46 and the surface 42 match in order to accomplish
this. While a single pedal 40 has been shown, a two cylinder
pump with two pairs of slotted arms 49 would be present, one
for each of the two cylinders. In a two cylinder pump, each
pedal is connected to drive one piston and an interconnecting
mechanism, not shown, can be provided to ensure that pedal
movements are equal and opposite.
The piston return spring 51 and both detent-to-center
mechanisms resist pedal force during travel. These are steel
springs and efficiently return this energy later in the stroke.
It should be noted that the operator must use full strokes
in order to effect a displacement change. When partial
stroking occurs, which a treadle design can allow, the foot 46
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never leaves the surface 42 and the slotted arm 49 cannot
effect movement.
Oil enters and leaves the cylinders 44 by check valves
which are self-actuating which eliminates the need for valve
control mechanisms. Such check valves are inexpensive and
prevent any downstream feedback from the rest of the circuit
affecting pump operation.
Figure 7 is an axial section of a wheel motor 30. The
motor consists of a shaft 60 having a distal end 61 provided
with a threaded hole for securing a wheel thereto. The shaft
60 is mounted on bearings 67 and 62, bearing 67 being a roller
bearing and 62 a ball bearing. A clutch pack 63 is fixed to
the end of shaft 61 and connects torque tube 64 to shaft 61.
The wheel motor rotor 68 is fixed to torque tube 64 and rotates
therewith. An oil seal 65 is provided at the wheel end of
shaft 60 in accordance with normal hydraulic motor
construction. Wheel motor rotor 68 revolves on torque tube 64
and interfaces with cam ring 66 as detailed in Figure 10.
For the sake of simplicity, hydraulic connections to the
motor have not been illustrated, but these will be evident to
persons skilled in the art from the description which follows.
The motor is completed by end plates 69 and 70, between
which the steel cam ring 66 is fastened.
It will be noted that the shaft 60 would normally be
formed from mild stainless steel, the end plates 69 and 70
would be formed from aluminum, and the cam ring 66 and rotor
68 would be formed from steel. A single bolt and bevel gear,
spline, or other type of keying can be used for fastening the
wheel, and a single bolt provides for relatively rapid wheel
change.
It should be noted that rotor 68 does not ride on the
wheel shaft 60 but rather rides on the torque tube 64, which
is connected by the clutch 63 during operation of the vehicle
as detailed below. This arrangement completely isolates the
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rotor 68 from forces arising from shaft 60 moving during
cornering loads and flexing due to cantilever loads. Ball
bearing 62 is provided to counteract thrust on the wheel shaft
60.
Figure 10 is a cross-section on the line 8-8 on Figure 7.
The rotor 68 is shown in the steel cam ring 66. The rotor 68
is connected to the torque tube 64, for example by a crown
spline 30~ of rotor width. As illustrated, the rotor 68
includes a plurality of slots 71 in which are positioned pairs
of pressure balanced dual vanes, and the cam ring 66 is
provided with constant radius sections 72 and 73. Accordingly
vane slot losses due to friction are eliminated by the constant
radius sections in areas where vanes have a differential
pressure across them. By virtue of the lower pressure design,
small clearances and wide area of rotor end eliminates the need
for pressure balanced end plates. It should also be noted that
this design can make use of a constant radius section due to
its relatively low speed. Conventional pump and rotor designs
usually make use of constant vane acceleration profiles in
order to allow higher rpm. Typical characteristics of the
wheel motor for a one person vehicle would be 34.41 ml/rev. and
at a pressure of 68.05 atm, 237.27 Newton-metres rev. or 37.76
Newton-metres torque with a 7.62 cm rotor with 1.91 by 0.366
cm travel vane.
Operation of the bidirectional clutch 63 of Figure 7 is
explained below in relation to Figures 8 and 9. In order to
explain the operation of the bidirectional clutch, it is shown
for simplicity sake as a linear arrangement rather than as a
circular arrangement. However the principles of operation are
defined. Referring to Figure 8 and Figure 9, a grooved roller
80 occupies most of the pockets 81 in race 82. Springs 83 in
slot 84 push rollers 80 to center bottom of pockets 81. This
action moves retainer 85 to the position shown in Figure 9.
Ratchet pawl 86 is attached to retainer 85 by a slot 87, and
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is pushed to the right as illustrated in Figure 8 in the slot
by springs (not shown). In the "passive" direction, the pawl
86 is spring loaded to enter pockets 88 in race 89 as race 89
travels in the direction of arrow 89A. During regenerative
braking, another pocket 81 contains another pawl (not shown)
which points in the opposite direction. Means are also
provided for raising the pawl manually. Thus regenerative
braking can be disabled if not required. The regenerative
braking pawl would not be raisable while under load, but a
brief motor direction pulse will cause it to release. If the
race 89 moves to the direction of arrow 89A, pawl 86 will
engage pocket 88 and cause retainer 85 to also move left. Slot
spring for pawl 86 is strong enough to override all the roller
springs 83 at once. This action also moves rollers 80 to the
left and out into pockets 88 and 81. Roller pin slots in
retainer 85 permit this. Rollers engage pockets 88 and 81
simultaneously transmitting the load. Pawl slot 87 and springs
(not shown) prevent any significant load from being transmitted
by pawl 86. Similarly when the reverse pawl is lowered the
clutch will engage in the opposite direction. This type of
clutch could also be built with two active pawls or two passive
ones. A clutch with two passive pawls however would serve no
purpose since it would resemble a solid connection and
function. The groove in rollers 80 could be eliminated by
providing a second spring slot in race 89.
This clutch has several benefits. First of all, the
rollers 80 have a large load carrying capacity combined with
the light engagement pawl 86, means that the clutch can be
small as well as having a small coasting friction. The simple
parts are easy to construct or obtain. Rollers for instance
can be modified rollers from roller bearings. In addition,
since the rpm of the wheels of the vehicle is relatively low,
the small size of the clutch permits engagement of the
regenerative braking without damage to the clutch.
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Figure 11 is a section through the control valve 26 of
Figure 2. This control valve is a pilot operated valve that
has three purposes, firstly to prevent accumulator leak down.
Without valve 26 the accumulator could leak down in as little
as 10 minutes, but with the valve in the circuit the charge in
the accumulator could last up to a month. This valve also
prevents unintended reverse operation of the vehicle and
prevents accidental over speed of wheel motors when in the free
wheel mode or where a governor is present prevents excess in
wheel speed in drive.
The valve 26 as illustrated includes a port A connected
to the accumulator, a port B connected to the motors and a port
R connected to the reservoir. The special features of the
valve are illustrated in words on the drawing. During
operation the valve has four possible conditions as follows:
1. The vehicle is stopped, the accumulator is charged
and the brake signal is effected.
There is no pilot operation and the valve remains closed.
2. The vehicle is stopped or moving, the accumulator is
charged.
A set of pilot valves makes use of the higher pressure of the
accumulator compared to port B to cause the control valve to
open rapidly. The port cuts off about 95~ of travel to cushion
valve travel. The remaining oil goes through small port or a
groove. This action all occurs with the operator's forward
acceleration signal.
3. Vehicle coasting, some accumulator charge, operator
signals regenerative braking.
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There is no pilot valve signal, but instead pressure build-up
at port B forces valve open, oil over valve will port to A via
passage 1. Once open, the valve remains open unless signaled
to close, and only if the pressure at A and B is at least 600
psi above R, the reservoir.
4. System discharged.
The spring will open the valve, readying the vehicle for
pedaling via A or regenerative braking via B.
Figure 12 illustrates the operation of valve 23 of Figure
2. Figure 13 is a schematic diagram of the valve 29 of Figure
2. Referring to Figure 2, it will be noted that the wheel
motors 30 are shown with ports X and Y which are connected to
X and Y of valve 23. As illustrated the valve also includes
ports 1, 2, 3 and 4 and a connection leading to the reservoir
21. The valve is shown in the rest or motor position. When
the valve moves from the rest position to the non-rest position
it redirects the motor port X from port 2 to port 1 and blocks
off the Y motor port from port 3. The Y motor port can still
exit to port 4 through a check valve. Similarly with valve 29
of Figure 13, the valve is shown in the open position, not the
rest position and moving the spool to the rest position blocks
off the pedal pump P port from the accumulator circuit.
Figure 14 is a schematic diagram of the construction of
the hydraulic variable pressure ratio transducer 25 of Figure
2. As illustrated the transducer consists of an ellipsoid cam
ring 90, a freely rotating armature 91, a porting ring 92 and
a control vane 93. The end plates of the transducer are
connected as shown in Figure 21 so that an external port 94 is
connected to the wheel motors. Ports 95 and 96 are connected
to the accumulator and the central opening in control vane 93,
port 97 connects to the return to the reservoir.
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As detailed in Figures 19 and 20, the armature 91 which
rotates freely about the porting ring 92 is provided with a
plurality of radial vanes and radial holes positioned between
the vanes for communication with the interior of the porting
ring 92.
Figure 15 is an axial view of the porting ring 92 showing
ports 95 and 96 for connection to the accumulator and
illustrating openings 99 and 100.
Figure 16 is a view of the porting ring 92 at right angles
to Figure 15 showing the port 99 in phantom, the port 100 and
the connections from the ports 95 and 96 to the opening 99 and
100 in phantom.
Figure 17 illustrates the control vane 93 with control
vane oil entrance and exit 97 to the reservoir. Additionally
there are shown oil ports 101 and 102 which are positioned in
openings 99 and 100 of the porting ring 92 and receive oil from
the radial holes in the armature 91 as detailed in Figures 19
and 20.
Figure 18 illustrates a view at right angles to Figure 17
of the control valve 93 showing the control shaft 103 which is
connected by means not shown to a control mechanism not
illustrated for varying the position of the vane and thereby
varying the pressure ratio of the hydraulic variable ratio
transducer 25.
Figure 19 is an axial view of the armature 91 which
includes a plurality of slots 110 carrying dual pressurized
vanes 111. In accordance with standard high pressure vane
technology, the vanes 111 can be pressurized from the bulbous
portion at the inner end of each slot 110 to cause the vanes
to extend to the cam ring 90 as shown in Figure 14. The
armature includes radially drilled holes 112 between adjacent
pairs of vanes.
It would be appreciated by those skilled in the art that
the control vane is mounted inside the porting ring which in
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turn is mounted inside the freely rotating armature, and in
turn the armature being mounted inside the cam ring is all
positioned between end plates, one of which permits the shaft
103 to extend external to the transducer and the other of which
is illustrated in Figure 21. The porting ring 92 is fixed
immobile between the end plates, with ports 95 and 96 aligned
with end plate connections 105 and 106. Port 94 is of course
aligned with opening 109 in end plate 115, and opening 107 is
in line with opening 97 of control vane 93. Port 104A is also
provided in end plate 115 and is connected to port 104 and the
transducer is therefore a two chamber mechanism. The
characteristics of the transducer are that it is a variable
flow constant pressure ratio device, the ratio being set by the
position of the control vane 93 under the control of the
operator.
This is in contrast to a flow control valve which is a
constant volume device that throttles the flow, all of the
throttled energy being wasted. The transducer is relatively
simple having one rotor, one control valve shaft, two chambers,
three ports and twelve vanes in the embodiment illustrated in
Figure 19. Since there is no throttling of the flow the energy
efficiency of the device is extremely high, there being
virtually no loss in the transducer.
Figure 22 illustrates a four chamber version of the
transducer, with the armature removed for clarity. As before,
the armature consists of slotted vanes with radial holes
drilled between each pair of vanes similar to the armature of
Figures 19 and 20.
Figure 23 illustrates the center control porting ring and
the rotary control section to control pressure area of
accumulator section.
The transducer as illustrated in Figures 14 through 21
inclusive is a hydraulic variable transformer that performs
this function as a free turning armature with no drive shaft.
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The armature is a standard vane type as seen in vane pumps and
motors commonly available, except that a hole has been drilled
radially in between each pair of vanes to the center.
The transducer is ported conventionally in zone A
illustrated in Figure 14, which is connected only to the wheel
motor and pedal pump circuit and allows oil in and out of zone
A. The armature rides on the porting ring which is stationary
at all times and has an oil entrance-exit at its stationary
vanes. The control vane can rotate approximately 90° and its
position determines the pressure ratio between zone A and zone
B. The control vane position is controlled through the shaft
103 as illustrated in Figure 18.
The armature 91 will rotate as fast as necessary to cause
the pressure balance to be re-established and can reverse
direction. Direction reversal is invisible to the operator.
As the armature rotates, oil in zone A cannot exit via radial
holes since they are blocked by parts of the stationary porting
ring. Once in zone B or zone C, oil can only exit or enter via
radially drilled armature holes because the end porting is not
present in these areas. There is a reaction torque on the
control vane which can be used for control feedback to the
operator.
A four chamber variation of the transducer is illustrated
in Figures 22 and 23 and accomplishes the same task as the two
chamber version of Figures 14 through 21. The rotary control
section E of Figure 23 ports oil through radial armature holes
to effect a pressure distribution in the cam ring. Oil which
flows out of zone A via radial holes would return via radial
holes from area F to zone B when the armature is turning
counterclockwise. If the armature is turning clockwise, zone
A oil enters zone X and then exits via end ports C in the end
plate. Stationary segment D of the porting ring prevents oil
from returning via radial holes in zones X and Y.
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If rotary segment E is rotated counterclockwise from the
position shown in drawing, then zone A would also move
counterclockwise in the cam ring. Zone B being
counterclockwise from zone A would shrink while a new zone B
clockwise from zone A would develop. This has the effect of
reducing displacement of zone A. When zone A is centered
around line P of Figure 22, it has zero displacement.
Continuing to move zone A counterclockwise will again increase
displacement but in the opposite direction. Eventually zone
A and zone B will have exchanged positions. If the transducer
is in a position as shown, accumulator oil could exit into zone
A causing armature to rotate clockwise and pressurize zone X,
delivering power through port C. Motor return oil would enter
in port C in zone Y and exits zone B through radial holes to
area F (Figure 23). Oil could also be delivered to zone X by
a pump causing counterclockwise armature rotation delivering
oil to accumulator via zone A. Oil would be entering zone B
from the reservoir and returning via zone Y back to the
reservoir along with any oil exiting the motor if present. The
transducer would change rotational direction as needed, and
this would be invisible to the operator.
Rotating control section E counterclockwise to the area
shown on zone B would allow zone Y oil to cause a clockwise
rotation charging the accumulator.
As with the mechanism of Figures 14 to 21, there is a
finite number of vanes and some cogging action may result in
certain conditions, particularly at low delivery. A small fast
rotating design would, of course, reduce this effect.
The hydraulic circuit of a vehicle in which this
transducer of Figures 22 and 23 would be used is required to
be modified for this transducer. The main difference is that
the rotary control section reverses pressure direction so that
a motor reversing valve would not be required in a typical
hydraulically actuated vehicle.
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Since rotary control section E is in hydraulic balance,
both radially and circumferentially, there are therefore no
control forces. Operator feedback is therefore not available
but could be supplied by a spring or other similar device.
Area F in Figure 23 is connected to the reservoir and
changes in size as needed. There would be four area F's if the
rotary control section is not at an end travel point. Area F
always has a corresponding zone B in the cam ring. With more
high and low pressure interfaces than the device of Figures 14
to 21, there would be more hydraulic leakage losses when
compared to that device in the mechanism of Figures 14 to 21.
As seen from the explanations of the two embodiments, the
transducers are two basic approaches to the design, and it is
important to realize that these two designs can each have other
numbers of chambers. The difference in approach is really of
a three port device and four port device.
