Continuously-variable transmissions are useful for reducing the energy
consumption and/or simplifying the control of land vehicles and some machinery.
However, mechanical transmissions of this type generally require friction wheels,
chains, or belts which are less efficient, durable, and compact than conventional
geared transmissions. Continuously-variable electrical, hydraulic, or pneumatic
transmissions also encounter losses because of the conversions from mechanical to
the other forms of energy and back again.
Energy consumption can be reduced by using flywheels to store and
release energy. Flywheel energy storage can allow an engine to operate intermittently
at favorable loads and allow recovery of energy that would otherwise be dissipated
by braking. Continuously-variable transmissions have been necessary to match the
speed of such flywheels with the required output speed.
Torque transmission devices sometimes are controlled by or employ
movable flyweights. The inertia generated by the flyweights is controlled strictly
by the speed of a rotating shaft and is thus predetermined for any speed of the
shaft. Any energy storage in the flyweights is incidental and cannot be used as
a controllably variable source of rotational energy or momentum.
As used herein, a variable inertia flywheel is one including a mass-carrying,
rotating member which undergoes controlled and controllable changes in rotational
moment of inertia by radial movement of mass supported on the rotating member, the
addition or removal of mass from the rotating member or both.
It is an object of the invention to provide a flywheel energy storage
system with improved versatility.
In one aspect, the invention is an energy storage apparatus including
a pair of variable inertia flywheels and an output shaft. This aspect of the invention
is characterized by control means for selectively equalizing the angular momentums
of the flywheels and varying the angular momentums of the flywheels from one another
during rotation of the flywheels.
It is yet another object of the invention to provide transmission
type gearing for obtaining a wide range of output speeds from a flywheel energy
It is yet another object to provide a flywheel energy storage system
with paired flywheels for load balancing.
It is yet another object of the invention to provide a pair of variable
inertia flywheels for flywheel energy storage and a control system for varying
the moments of inertia of the two flywheels to add and remove energy from the system.
It is a further object of the invention to use gearing to add and
remove energy from the flywheel energy storage system so as to reduce conversion
In another aspect the invention is a mechanical transmission which
preferably combines flywheel energy storage with a continuously-variable output
over several overlapping speed ranges. The output is infinitely-variable in the
lowest speed range. Power is efficiently transmitted through conventional gears
and clutches, not through special friction or gripping elements.
Many component arrangements, methods of varying and controlling flywheel
inertia, and gearing the flywheels are possible with this invention. The illustrated
embodiments provide a direct connection between a flywheel and output shaft in
the highest speed range for minimum gearing losses, uses bevel gearing only where
pitchline velocities and loads are relatively low for minimum cost, and has no
bearings that are heavily loaded by flyweights. The last feature and a favorable
stress distribution permits a reasonably high energy storage capacity for a given
weight and volume.
The described embodiments disclose two methods for varying flywheel
inertia: one for the main flywheels, the other for the control system. The latter
method is somewhat less efficient, but is itself well-suited to this application
(variable energy storage) and causes only a minor energy loss.
Brief Description of the Figures
The invention is shown in the following figures in which:
Detailed Description of the Invention
- Figure 1 is a longitudinal section of the transmission in plane I of Figs.
4-8, passing axially through two main flywheels used for energy storage, two liquid-weighted
flywheels used for control, and through shafts, clutches, and gearing for power
- Figure 2 is a longitudinal section in plane II of Figs. 4-8, showing shafts
and gearing for driving and controlling the main flywheels by the liquid-weighted
control flywheels, low-pressure pumps and piping for the control flywheel liquid,
and a higher-pressure pump for lubrication and for operating the clutches and brakes
- Figure 3 is a broken longitudinal half-section in plane III of Figs. 4 and
8, intersecting the flywheel axis that is at a different angle than Fig. 1, illustrating
a shaft, clutch, and gearing for transmitting power in the lowest speed range between
the main flywheel at the input end and the sun gear in a planetary gearing unit.
- Figure 4 is a transverse cross-section in plane IV of Figs. 1-3 and shows the
pitch lines of the gears in a train at the input end of the transmission.
- Figure 5 is a transverse cross-section in plane V of Figs. 1 and 2 passing
through a main flywheel.
- Figure 6 is a transverse cross-section in plane VI of Figs. 1 and 2 showing
- Figure 7 is a transverse cross-section in plane VII of Figs. 1 and 2 passing
through a liquidweighted control flywheel and illustrating a special differential.
- Figure 8 is a transverse cross-section in plane VIII of Figs. 1-3 and shows
the pitch lines of gears in a train and in a planetary unit at the output end
of the transmission.
- Figure 9 depicts in block diagram form an automatic system for controlling transmission
shifting and engine operation.
- Figure 10 depicts diagrammatically another variable inertia flywheel strip
- Figure 11 depicts diagrammatically in block form, the major subsystems of the
transmission of Figures 1 through 9.
In the figures, joints required for assembly of the rotating parts
are omitted for clarity, along with any associated keys, splines, screws, or bolts.
Plain bearings are shown for the same reason. Ball or roller bearings can obviously
be substituted where advantageous.
It is convenient to use two main flywheels of the same size and two
control flywheels of the same size.
The outer housing of the transmission is divided into an input end
cap 1, a central shell 2, and an output end cap 3, held together by bolts 4. These
parts are aligned by two fitted bolts 5, with nuts 6, at each end, or by dowels
or keys. Mounting lugs 7 are provided for bolting to a foundation.
A series of cups, 8 to 15, with a plurality of extending transverse
ribs 16 and a lug 17 comprise the major non-rotating internal parts. The cups reduce
flywheel windage losses. For maximum strength, the flat ends of the cups are extended
to form the ribs, but some additional ribs may be necessary. The parts are held
in alignment by fitting notches 18 in ribs 16 and lug 17 on longitudinal ribs
19 on shell 2. Outlet end cap 3 and cups 8 to 15 are held together by tie bolts
20, supported by ribs 16 and threaded into lugs 21 on cup 8. With this construction,
most of the internal parts and end cap 3 can be assembled on a fixture, stacking
from the output end, and piping can be connected with easy accessibility. The
assembly can then slide into shell 2 and end cap 1 can be installed.
The operation and organization of the disclosed preferred embodiment
transmission/energy storage apparatus may be better understood with an initial
reference to Fig. 11 depicting in block diagram form the major operating subsystems
of the device. The preferred embodiment energy storage/continuously variable transmission
includes an input shaft 27 and an output shaft 44. It comprises variable inertia
flywheels A and B and output means, indicated generally at 300, which permits
selective individual or simultaneous coupling of either flywheel A and B in a forward
or reverse direction and at various degrees of reduction with the output shaft
44. Each flywheel A and B preferably includes a drum 23 or 24, a spool 25 or 26
rotatable with respect to the drum, and one or more radially movable flyweights,
preferably in the form of flexible strips 22 which are wound many times around
the spool in a space provided between an inner periphery of each drum and outer
periphery of each spool. The strips 22 are moved radially between the two peripheries
in a manner to be described for selectively varying the moment of inertias of
the flywheels. The output means 300 disclosed preferably includes output clutches
37, 38 for selectively coupling either one or both of the flywheels A and B in
a "forward" rotational direction with the output shaft 44 through the intermediate
shaft 39. The output means 300 further includes reversing gearing 301 and reversing
gearing 302. Each permits "reverse" rotational coupling of flywheels A and B,
respectively, with the output shaft 44. The reversing gearing 301 and 302 are selectively
engaged with the output shaft 44 through an output differential 303 by means of
a clutch 56 and brake band 52, respectively. The reversing gearing 301 and 302
permit with the output clutches 37 and 38 selective rotational coupling of either
flywheel A or B with the output shaft 44 in either rotational direction of the
output shaft. The output means 300 of the preferred device further includes output
differential means 303 which permits simultaneous coupling of the output shaft
44 with both of the pair of flywheels A and b in selectable rotational directions.
Reverse gearing 301 includes gears 56 and 59 while reverse gearing 302 includes
a planetary differential formed by sun gear 47, planet gears 48 and 49, planet
carrier 50 and internal gear 51. The output differential includes internal gear
40 coupled with intermediate shaft 39, sun gear 41 coupled with gears 51 and 59,
planetary gears 42 and planetary gear carrier 43 coupled directly with the output
shaft 44. The gearing and clutch coupling of the output means 300 permit the transmission
of torque and energy from the flywheels A and B to the output shaft and from the
output means to the flywheels.
At an opposite end of the device, an input shaft 27 and input means
indicated generally at 304 are provided for coupling the input shaft with the flywheels
A and B. The input means 304 is characterized in com prising input clutches 29
and 30 for selectively coupling the input shaft 27 with either (or both) of the
pair of flywheels A and B.
Although not seen in Fig. 11 the intermediate shaft is coaxial with
the flywheels A and B extending through each of the spools 25 and 26. The input
means 304 and output means 300 are configured to couple the input shaft 27 and
output shaft 44 together only through the drum members 23 and 24 of the pair of
flywheels A and B.
Control of the angular momentum and of the moments of inertia of
each of the flywheels A and B is through a control means 305 which comprises control
flywheels C and D which are geared to each of the main variable flywheel spools
25 and 26, respectively. Scoops 95 are driven radially in opposite directions in
each of the control flywheels C and D by racks 125 and 126 to assure that when
fluid is removed from one control flywheel it may be added to the other in a manner
to be described. Actual fluid transfer between the control flywheels is accomplished
by pump means 311 provided by pumps 109, 110 and 116 in a manner to be described.
Averaging differential means 306 is coupled with each of the drums 23 and 24 while
reversing differential means 307 is coupled with each of the spools 25 and 26.
The two differentials 306 and 307 are coupled together by a pinion carrier 69.
The averaging and reversing differentials together couple the drum members 23, 24
and spool members 25, 26 of the variable inertia flywheels A and B for causing
the spool members 25 and 26 to rotate at an average speed equal to the average
speed of rotation of the drum members 23, 24 and for causing relative rotation
between the drum and spool members 23, 25 of one of the pair of flywheels to be
exactly opposite a relative rotation between the drum and spool members 24, 26 of
the remaining one of the pair of flywheels. Averaging differential means 306 comprises
bevel gearing 71 and 72, coupled with the drums 23 and 24 and pinions 75. Reversing
differential means 307 comprise bevel gearing 73 and 74 coupled to the spools
25 and 26 through shafts 83 and 84, respectively and pinions 76. Pinion carrier
69 supports both sets of pinions 75 and 76.
Position indicator means 308 provides an output through swivel block
157 of the relative degree of wrap of the flexible strip member 22 of flywheel
A around spool 25. The swivel block 157 acts through pawls 61 on control shaft
129, controlling racks 125 and 126, to prevent movement of the racks 125 and 126
in a direction which would cause overtravel of the drum member 23, 24 of either
variable inertia flywheel A, B, respectively with respect to its spool member 25,
26. Position indicator means 308 comprises, in addition to swivel block 157, a
gear train comprising components 141 through 146 and 148 through 156 and related
components 158 through 164. Controller means 309 is provided for automatically
selecting one of the pair of variable inertia flywheels A and B for coupling with
the output shaft 44. The components of controller means 309 are depicted in detail
in Fig. 9. The controller means 309 is externally controlled through control shaft
140. Controller means 309 operates through switch means 310 comprising components
134 through 139, which are also partially controlled through the control shaft
140 in a manner to be described.
The preferred relocatable flyweights of the main flywheels A and
B consist of flexible strips 22 attached at one end to the inner circumferential
periphery of the main flywheel rotor drums 23 and 24 and at the other end to the
outer circumferential periphery of main flywheel spools 25 and 26 respectively.
Two strips 22 with ends attached 180 degrees apart along drum inner periphery
and spool outer periphery are used in each flywheel A and B to balance the flywheels.
The strips 22 are interleaved with one another. Centrifugal loading will force
each strip 22 outward against the drum inner circumferential periphery until the
portions of the strips remaining on the spools are wound tight. The strips will
form skewed catenary curves between the layers on the drums and the layers on the
spools, as indicated in Fig. 5. The spools are turned relative to the drums to
vary the amount of strip at the different radii, thus varying the moments of inertia.
Winding more strip on a spool reduces the moment of inertia and tends
to increase the rotational speed of a flywheel. If the flywheel is delivering a
net output torque, its speed may not increase, but will fall more slowly than
if inertia remained constant.
The spools 25 and 26 of the two flywheels A and B are geared in such
a manner that a flexible strip 22 is wound on the spool of one flywheel as a like
strip 22 is unwound from the spool of the other flywheel. This reduces the net
load on the control system. The speed of one flywheel will thus tend to rise while
that of the other tends to fall.
If the strips are made of a material such as flat spring steel, with
a Young's modulus comparable to or higher than the drum material, the drum will
not have to carry all of the centrifugal load of the strips lying against it.
To move outward and burst the drum, the layers of strip must slide on each other.
However the very high centrifugal loads will cause so much pressure between the
layers that friction will prevent such sliding.
The only load on the control system is produced by the centrifugal
load of the lengths of strip bridging the distance between the outer layer on the
spool and the inner layer on the drum. If the strip is thin, this load will be
a small fraction of the load that would be produced if the flyweight mass were
concentrated in a few solid bodies. However, the energy required to shift the flyweight
is the same because the great length of strip which must be moved offsets the
Whenever the momentum of either flywheel becomes too low, it can be
restored by an input shaft 27 with splines 28, keys, or other devices for coupling
to an engine output shaft. The input shaft 27 is geared to flywheels through clutches
29 and 30, gear teeth 31 and 32 on the clutch peripheries, idler gears 33 and 34,
and gear teeth 35 and 36 on the drums 23 and 24, respectively. The flywheels turn
in the same direction with this gearing.
Clutches 29 and 30 would not both be engaged at the same time in
normal operation and both would be disengaged to utilize the energy stored in the
flywheels or to so store energy from braking.
Flywheel speed does not necessarily have to increase to absorb energy.
Energy can be absorbed at a constant or a decreasing speed if the inertia of that
flywheel is increasing.
Idler gears 33 and 34 could be omitted and other parts could be enlarged
so that gear teeth 31 and 32 meshed directly with teeth 35 and 36, respectively.
The purpose of using idlers is to avoid excessive pitchline velocities in the gearing
and to reduce the overall size of the transmission.
These gear trains could readily be designed to make the flywheels
turn faster or slower than the engine, if appropriate.
The rotation of flywheel drums 23 or 24 in a "forward" direction
is transmitted through clutches 37 or 38 and intermediate shaft 39 to internal
gear 40 in a planetary output differential unit 303 including sun gear 41 and
planet gears 42 on a planet carrier 43. Carrier 43 is connected to the output shaft
44, which has splines 45, keys, or other devices for coupling to the driven mechanism.
Clutch 46 allows the intermediate shaft 39 and the output shaft 44 to be directly
The rotation of drum 24 is transmitted in a reversed direction to
sun gear 41 through reversing gearing 302 comprising a planetary unit consisting
of sun gear 47, planet gears 48 and 49 on planet carrier 50, and internal gear
51. The reverse rotation is transmitted when brake band 52 is applied to planet
carrier 50 by actuator 53.
The rotation of drum 23 is transmitted in a reversed direction to
sun gear 41 through clutch 56 and reverse gearing 301 comprising rotor drum gear
teeth 35, idler gear 33, gear teeth 31, gear 54, reverse transmission shaft 55,
clutch 56, gear teeth 57 on the periphery of clutch 56, idler gear 58, and gear
59 (Figs. 3, 4, and 8).
An intermediate output speed range is obtained by applying brake
band 60 to internal gear 51 with actuator 61 preventing the rotation of that gear
(Figs. 1 and 8). Alternatively, the brake band 60 can be located to be applied
to intermediate shaft 39 so as to prevent the rotating of internal gear 40.
Output Speed Maximum Drum Speed
Forward Driving Drum
-0.1 to 0.4
0.3 to 0.6
0.5 to 1.0
Table 1 shows which clutches and brakes are engaged (designated by
"E") to obtain various ratios of output speed to the maximum speed of flywheel
drums 23 or 24. Other clutches and brakes are disengaged. Numerical values of
the ratios are for the case where gear proportions are such that planet carrier
43 rotates at 0.6 of the speed of internal gear 50 and 0.4 of the speed of sun
gear 41, where the transmission ratio between either drum and gear 41 is -1.0, and
where the speed of each flywheel can be varied between 0.5 of the maximum drum
speed and the maximum.
The ratios in Table 1 are not proportional to the absolute speeds
that can be obtained when using stored energy. The energies in the flywheels and
the maximum speeds that are obtained from each flywheel are continually changing
in this situation.
The reciprocal speed ratio in mode 1A, Table 1, is infinitely variable.
The reason for adding any other modes is that only a relatively small amount of
the total stored energy can be utilized in this mode. The flywheels would have
to be excessively heavy if this were the only mode.
A forward output torque in mode 1A is split by planet gears 42 between
drums 23 and 24. The torque on the forward driving drum 23 tends to lower its speed,
but the torque on the reverse drum 24 tends to raise its speed. The result is
that the control limits are reached and a forward output speed can no longer be
maintained when there may still be much energy remaining in the flywheels.
The forward and reverse drums in mode 1B are interchanged from those
in mode 1A. Most of the stored energy can be used by alternating between modes
1A and 1B. However, the fraction of the energy that can be used for acceleration
from a stop or that can be stored when braking to a stop is not much different
than in either mode alone.
The addition of speed ranges 2 and 3 and the associated modes allows
most of the energy to be used for acceleration to an output speed equal to flywheel
drum speed and allows storage of the energy from braking to a stop from such speeds.
Thus flywheels for stop and go service can be reasonably light.
A planetary reduction gear is formed in speed range 2. When internal
gear 51 and coupled sun gear 41 are held stationary by brake band 60, the forward
rotation of one of the flywheels is transmitted to internal gear 40, and the planet
carrier 43 and output shaft 44 rotate at reduced speeds. A direct drive from one
of the flywheels is obtained in speed range 3 by engaging clutch 46. In both of
these ranges, the unconnected flywheel idles, but it balances a major portion of
the loads on the control system and transfers energy through that system.
Clutches 37, 38, and 46 are shown as hydraulically-operated multiple-disk
friction clutches of conventional design, like those used in automatic automotive
transmissions. The internal construction of clutches 29, 30 and 56 would be similar.
Automatic shifting would generally be necessary because of the number of clutches
There will usually be times at which the output speeds will be the
same in two modes. Shifts are then possible with no slipping of clutches and brakes
and should be made at these times. If necessary, flywheel speeds could be adjusted
during shifts to eliminate slipping. Two shifts, using one mode in each speed range,
should usually be sufficient when accelerating directly from a stop to a maximum
speed or when braking to a stop from such a speed.
The hydraulic pressure on an annular piston 62 forces multiple disks
63 into frictional contact during engagement of the clutches. Splines 66 and 67
allow axial movement of the disks, but prevent rotation of disks relative to the
hub 64 and the rotation of alternate disks relative to the drum 65. A clutch release
spring 68 relieves contact loads when the hydraulic pressure is released for disengagement.
Positive engagement splined clutches could be used instead, reducing
space requirements and frictional and windage drags, but introducing a risk of
clashing during shifts. Two frictional clutches would still be desirable: one
to unload the input shaft and another to unload the output shaft during shifts
involving the respective shafts.
The averaging and reversing differentials 306 and 307 are preferably
combined in a special bevel gear differential seen in Figs. 2 and 7, consisting
of bevel gears or teeth 71, 72, 73, and 74 and a carrier 69 with pinions 75 and
76. This special differential forces the spools 25 and 26 to rotate at the same
average speed as the rotor drums 23 and 24. It also causes the relative rotation
between drum 23 and spool 25 of one of the pair of flywheels (e.g. the inlet end
flywheel) to be exactly opposite that between drum 24 and spool 26 of the remaining
one of the flywheels (e.g. in the output end flywheel). Pinions 75 and 76 are on
the same carrier 69, but pinions 75 mesh only with bevel gears 71 and 72 and pinions
76 mesh only with bevel gear 73 and bevel teeth 74.
Rotor drum 23 is geared to bevel gear 71 through gear teeth 35, idler
33, gear teeth 79 on wheel 77, and shaft 83. Rotor drum 24 is geared to bevel gear
72 through gear teeth 36, idler 34, gear 80, and hollow shaft 84. Spool 25 is
geared to bevel gear 73 through gear 87, idler gear 89, gear teeth 81 on wheel
78, and hollow shaft 85. Spool 26 is geared to bevel gear teeth 74 on wheel 70
through gear 88, idler gear 90, and teeth 82 on wheel 70. The gear ratio for each
of these trains is identical.
Housings 91 and 92 of control variable inertia flywheels C and D
are attached to spools 25 and 26, respectively (Figs. 1 and 7). Liquid 93 is removed
from a control flywheel C or D that is coupled to a main flywheel A or B to be
accelerated trough a scoop 95 and added to the other flywheel through channels
94 to produce rotation of spools 25 and 26 relative to drums 23 and 24, respectively.
Strip 22 is thus wound on one of the spools and unwound from the other.
Transmission oil, such as that used in automatic automotive transmissions,
would be a suitable liquid 93 for the control flywheels, for operating clutches
and actuators, and for lubrication.
Preferably, a major portion of the kinetic energy in the liquid 93
entering a scoop 95 is recovered in a turbine 97 or 98 with buckets 99 before the
liquid leaves the flywheel. For example, liquid is conveyed by a scoop 95 from
the periphery of housing 92 into turbine 98, attached to that housing. The turbine
discharge is contained by a stationary cone 102, falls through a port 100 in cup
15 into discharge chute 104, and flows through pipe 106 to the inlet chamber 107
of pump 109. The liquid is then pumped through pipe 111 into the inlet chamber
113 of the other control flywheel. It flows through channels 94 to the periphery
of housing 91, slowing it. Paddles 115 keep the liquid rotating with the flywheel.
Scoops 95 project through openings in cones 101 and 102 where necessary. (Figs.
1, 2, 6 and 7).
Strip 22 is wound in such a direction that any rotation of a control
flywheel that is faster than that of its main flywheel will cause strip to be wound
on the spool, tending to increase the speed of the main flywheel. Thus, any friction
between the rotating parts will accelerate the speed change in the main flywheel.
The energy absorbed by pumps 109 and 110 is insignificant, as only
a small head is required. For convenience, these pumps are driven by shaft 84,
geared to flywheel drum 24.
If it is ever necessary to continue main flywheel inertia adjustments
after one control flywheel housing has been filled with liquid 93, slowing of the
control flywheel can be continued by adding liquid from the main hydraulic pump
116 through pipe 119 (Figs. 2, 6, and 7) and a valve 118 (Fig. 6). When a rack
126 is in its extreme radially-inward position, a rod 117 pushes the spring-loaded
stem 166 of the valve 118, opening it and admitting liquid into pipe 112 (or 111).
Pipe 119 is branched to supply valves 118 for each of the pipes 111 and 112. With
scoop 95 in a position radially inward from lip 120 on the control flywheel (Fig.
1), the overflow spills over the lip and drains to the bottom of shell 2 and end
cap 3 through holes 121 in the bottoms of cups 10 or 11 (Fig. 7). It then returns
to pump 116 through inlet 122 (Fig. 8). This procedure is inefficient because
the kinetic energy in the overflow is wasted, but should be acceptable if done
A small continuous leakage through valves 118 replenishes losses
and maintains proper liquid levels in the control flywheels. The excess would normally
be removed by scoops 95.
Pressure from the main hydraulic pump 116 must be high enough to
operate any hydraulically-operated clutches, such as 29, 30, 37, 38, 46, or 56,
and brake actuators, such as 53 and 61. The pump also maintains lubricant flow.
Torque for driving this pump is divided among all flywheels through pinions 75
and 76 on carrier 69, connected to the pump by shaft 123 (Fig. 2). The pump 116
is powered by means of a shaft 86 extending from the carrier 69.
Scoops 95 are connected to racks 125 and 126 by bars 96 projecting
through slots 124 in cups 14 and 15. Upper racks 125 and lower racks 126 mesh with
gear teeth 127 and 128, respectively, on shaft 129 (Figs. 1 and 6). Scoops 95
are contained in a streamlined fairing 130 (Fig. 7) and the slots are covered by
streamlined shields 131 (Fig. 1) to minimize windage losses of the control flywheels.
The power required to rotate shaft 129 would generally be low enough to permit
A switch means 310 is desirable for preventing speed controls from
being reversed when shifts are made that interchange the forward-driving flywheels.
Referring to Fig. 6, a coupling 132 transmits rotary motion of shaft 129 (see also
Fig. 1) to a shaft 133 while permitting a piston 134 in a hydraulic actuator cylinder
135 to move shaft 133 along its own axis, thus engaging a double-acting toothed
clutch collar 136 on shaft 133 with either of the two bevel gears 137 or 138. The
speed control shaft 140 turns an attached bevel gear 139 which meshes with gear
137 and 138, turning them in opposite directions. Connecting the hydraulic system
to produce the same pressure on one side of the piston 134 as in the clutch 37
and the same pressure on the other side as in clutch 38 would cause clutch 136
to engage the proper gear to turn shafts 133 and 129 in the correct direction (Fig.
Position indicator means 308 is provided for preventing overtravel
in the rotations of drums 23 and 24 relative to spools 25 and 26, respectively,
to prevent damage to strips 22 from excessive tension. Details are shown in Figs.
2 and 5. Gear wheels 77 and 81 have internal teeth 141 and 142, respectively. Teeth
141 mesh with planet gears 143 on a carrier 144 attached to a hollow shaft 145
with worm teeth 146. Planet gears 143 also mesh with sun gear teeth 148 on gear
wheel 147. Teeth 142 drive wheel 147 through gears 150 and 151, attached to a shaft
152, where gear 151 meshes with teeth 149 on wheel 147. Teeth 141 have the same
pitch diameter as teeth 142, planet gears 143 have the same diameter as gears 150
and 151, and teeth 148 have the same pitch diameter as teeth 149. The rotation
of planet carrier 144 and shaft 145 is proportional to the difference between the
rotations of gear wheels 77 and 78 and hence the difference between the rotations
of drum 23 or 24 and spool 25 or 26, respectively.
The rotation of shaft 145 is reduced by worm teeth 146 meshing with
a worm wheel 153 attached to shaft 154, which has worm teeth 155 meshing with teeth
156 on a block 157. Block 157 swivels on pins 158 and bears on plates 159 above
and 160 below. Pawls 161 are connected to swiveling block 157 by pins 162 and are
held against the block by tension spring 163.
When one of the pawls 161 engages ratchet teeth 164 on shaft 129,
it prevents rotation of the shaft and motion of scoops 95 in one direction and
further winding of strip 22 on one of the spools 25 or 26, but it allows scoop
motion in the other direction, with consequent unwinding. To restore full speed
control, it is necessary to apply engine power to one of the main flywheels through
clutches 29 or 30 or to shift to a different mode. Block 157 could be connected
to hydraulic valves as a component of the engine throttle control and the clutch
Sectors 156 and 158 slide on flat plates 162 and 163 above and below.
Lugs 160 extend downward sufficiently to bear on plate 163 and the wide end of sector
158 is thick enough to bear on both plates.
The transmission can easily be adapted to use continuously-variable
mechanical drives for control. The control device is only required to produce a
variable difference in the speeds of two members, such as drum 23 and spool 25,
rotating at high speed in the same direction. A 50 percent difference would be
ample and could readily be obtained from continuously-variable traction or belted
devices. Such a device would be well-suited to the light loads and high rotational
speeds required for control, but would be less suited for the higher powers and
greater speed range required if used as the complete transmission.
Intermittently-operated clutches and brakes could be used for control.
Efficiency losses and wear problems would probably be small because of the light
Although flywheels C and D are added for speed control, the energy
which they store adds to the capacity of the transmission. Their energy can reach
the output both through their effects on the inertias of the main flywheels and
through the gearing used to drive them. Alternatively, the liquid variable inertia
flywheels C and D can be enlarged and substituted for the main flywheels A and
B. Such a system would not have equivalent energy storage flywheels of equal volume
due primarily to the lower mass of liquid. Such a system would be further subject
to energy losses in fluid transfer. However, at least differentials 306 and 307
and one of the pairs of flywheels (A, B) can be eliminated.
Figure 9 is a diagram of the components of a controller system 309
of Fig. 11 for shifting the transmission and for operating the engine. The transmission
controller 167 and the engine controller 168 could operate mechanically, hydraulically,
electronically, or by a combination of methods.
The essential inputs to the transmission controller 167 are obtained
from sensors indicating the speeds of drums 23 and 24, the position of flywheel
control block 157, and the rotation of speed control shaft 140, which is controlled
by the operator and is an indication of the desired changes in output speed. The
position of block 157 is a function of the amount of strip 22 wound on spools
25 and 26 and hence the inertia associated with each of the drums 23 and 24. The
angular momentum of each flywheel is computed from the product of the inertia and
the drug speed. Whether either flywheel requires engine power or whether a shift
is necessary to prevent overwinding of strip 22 or to control output speed is determined
from the position of block 157, the momentums, the desired changes in output speed,
and the current output speed. The latter is determined from the drum speeds and
the current shift mode.
If engine power is required, a signal selecting the proper input clutch,
29 or 30, travels from transmission controller 167 to servovalve 170 and to engine
controller 168. Controller 168 determines the throttle setting produced by throttle
actuator 169. The clutch signal causes controller 168 to accelerate the engine
from idle speed, until an engine speed signal into the controller matches a signal
sent from controller 167 that is proportional to the speed of the selected drum.
Controller 168 sends a signal to servovalve 170 and the clutch is engaged with
little or no slipping. Controller 168 then adjusts the throttle for optimum fuel
economy in accordance with engine speed, which is equal or proportional to drum
speed when the clutch is engaged. The application of engine power continues until
the termination of the clutch signal from controller 167 indicates that a limit
has been reached. The clutch disengages and the engine returns to idle speed.
It would generally be economical to use a relatively small engine
operating at high loads. However, the engine would have to be large enough to maintain
the maximum continuous load imposed on the vehicle or machine.
Transmission controller 167 determines shift modes. There are certain
ratios of drum speeds at which shifts can be made without changing drum speeds
or output speeds. Shifts made at these times would cause the least slipping in
clutches and brakes and the least interruption in power delivered to the output.
whether a shift should be made or suppressed when such a ratio occurs would be
determined from the same information used to start and stop the application of
Although it would be simple to produce a signal to the operator when
drum speeds were suitable for a shift, manual shifting would be undesirable because
an operator could not react fast enough to insure a smooth shift. However, a skilled
operator might improve performance by anticipating forthcoming conditions more
accurately than a computing device could predict from the input information. The
operator could select the speed range and possibly the driving flywheel in advance,
as indicated by the dashed arrows into controller 167 in Fig. 9. The shift would
be delayed until the ratio of drum speeds reached the proper value and would then
be performed automatically.
A signal from controller 167 indicating the driving drum travels
to servovalve 171, which engages the corresponding clutch 37 or 38. A signal indicating
the speed range travels to servovalve 172, which operates clutches 46 and 56 and
actuators 53 and 61 for brake bands 52 and 60, respectively. Hydraulic lines from
servovalve 171 to clutches 37 and 38 are also connected to servovalve 172. The combination
of the pressure inputs from these lines and the speed range selection produces the
proper outputs from servovalve 172.
The transmission would function as an ordinary geared transmission
if clutches 29 and 30 were both engaged in speed range 1, if clutch 29 were engaged
in modes 2A or 3A, if clutch 30 were engaged in modes 2B and 3B, and if the flywheel
inertias were held constant (Table 1). The overall transmission ratios for the
gear ratios corresponding to Table 1 and to the drawings would be 0.2, 0.6, and
1.0 in speed ranges 1, 2, and 3, respectively. However, flywheel inertias would
cause a very sluggish response to engine throttle changes. A faster response could
be obtained in speed ranges 2 and 3 by setting the driving flywheel for minimum
A directly-geared reverse transmission ratio (-0.4) could be obtained
by adding a brake on the input end of intermediate shaft 39 and engaging brake
band 52 or clutch 56.
In some applications, it would be possible to carry only a small
electric motor with the transmission or to carry no motor. For example, the transmission
could be used instead of rechargeable batteries for energy storage and instead
of an electric motor for driving some vehicles and high-powered portable tools
and machinery. Advantages would be the elimination of chemical hazards and of
the costs and difficulties of replacing spent or damaged batteries, rapid charging
and rapid energy release without damage, ability to operate in explosive atmospheres,
and a possibly higher efficiency and lighter weight.
Energy would be stored while the vehicle or machine was out of service
by plugging into an electric outlet if there was a self-contained motor for accelerating
the flywheels or by coupling a shaft to a stationary motor. Energy could be stored
at an essentially constant motor speed by driving the output shaft of the transmission
and operating its speed controls automatically. The situation would be similar to
that occurring during the storage of braking energy. Input shaft 27 and clutches
29 and 30 would be unnecessary.
To store energy for long periods, it would be necessary to evacuate
the air surrounding the parts rotating at high speed. A continuously-variable traction
device or intermittently-operated clutches and brakes would be more suitable for
speed control than liquid-weighted flywheels in this situation.
Very high strength materials would be required in the flywheels for
low weight when no engine is carried.
Loads on the control system depend on the speeds and inertias of
each flywheel. For a specified variation of output torque and speed, it is possible
to calculate the variation in the flywheel inertias which will eliminate the load
on the control system. Although the solution is different in every case, the results
are similar for many cases and differ substantially from the inertia variation
obtained by winding uniform strips 22 in one flywheel and unwinding at the same
rate in the other flywheel. Therefore, control loads can generally be reduced
by using non-uniform strips to obtain the most suitable inertia variation.
The simplest method of producing non-uniform strips is to vary the
width so as to provide opposing sides tapering between the ends of the strip. This
is indicated in great exaggeration in Fig. 11. The appropriate inertia variation
requires the narrowest portions of the strips 22 in the outer layers around spools
25 and 26. Drums 23 and 24 could be designed to fit such strips. Axial displacements
of strips tightly wound on spools 25 and 26 would be resisted by friction. However,
there is some danger that the strips could become axially misaligned while the
transmission is idle and then be damaged when put into operation.
This problem can be avoided by cutting holes in strips 22&min; of
uniform width. A series of aligned slots 173 would be cut in the strip 22&min;
as depicted in Fig. 10 to leave adequate radial support for the wound layers.
Both the numbers and the widths of the slots 173 could be varied to obtain the
proper inertias. Although the slots 173 could be cut so that the remaining bridges
174 are radially aligned on the drum layers initially, the widest slots should be
narrow enough to keep bending stresses in the bridges at a safe level if they
do not remain aligned and are unsupported radially.
Parts are depicted and numbered as follows in one or more of the
- 1 input end cap;
- 2 central shell;
- 3 output end cap;
- 4 bolts;
- 5 fitted bolts;
- 6 nuts;
- 7 mounting lugs;
- 8,9 main flywheel cover cups;
- 10,11 control flywheel cover cups;
- 12,13,14,15 spacer cups;
- 16 transverse ribs;
- 17 lug;
- 18 locating notches in ribs 16 and lug 17;
- 19 longitudinal ribs on shell 2;
- 20 tie bolts;
- 21 lugs on cup 8 threaded for tie bolts 20;
- 22 flexible strip(s) flyweight, in each main variable inertia flywheel;
- A,B main variable inertia flywheels;
- 23,24 main flywheel rotor drums;
- 25,26 main flywheel spools extending into the hollow interior of each drum
23 and 24, respectively;
- 27 input shaft;
- 28 splines for coupling engine to input shaft 27;
- 29,30 clutches for connecting input shaft 27 to rotor drums 23 and 24, respectively;
- 31,32 gear teeth on clutches 29 and 30, respectively;
- 33,34 idler gears meshing with teeth 31 and 32, respectively;
- 35,36 gear teeth on rotor drums 23 and 24, meshing with idler gears 33 and
- 37,38 clutches for connecting rotor drums 23 and 24, respectively, to intermediate
- 39 intermediate shaft;
- 40 internal gear at end of intermediate shaft 39;
- 41 sun gear;
- 42 planet gears;
- 43 planet carrier mounted to output shaft 44;
- 44 output shaft;
- 45 splines for coupling driven mechanism to output shaft 44;
- 46 clutch for connecting intermediate shaft 39 to output shaft 44;
- 47 sun gear on drum 24;
- 48,49 planet gears meshing with sun gear 47 and internal gear 51, respectively;
- 50 planet carrier;
- 51 internal gear meshing with planet gear 49;
- 52 brake band for planet carrier 50;
- 53 actuator for applying brake band 52;
- 54 gear meshing with gear teeth 31;
- 55 reverse transmission shaft mounting gear 54;
- 56 clutch for connecting shaft 55 to sun gear 41;
- 57 gear teeth on clutch 56;
- 58 idler gear meshing with gear 57;
- 59 gear meshing with idler gear 58;
- 60 brake band for internal gear 51;
- 61 actuator for brake band 60;
- 62 annular piston in clutch 46;
- 63 friction disks of clutch 46;
- 64 hub of clutch 46;
- 65 drum of clutch 46;
- 66 splines extending radially out from clutch hub 64;
- 67 splines extending radially in from clutch drum 65;
- 68 clutch release spring between hub 64 and inner periphery of piston 62;
(Parts 62 to 68 are also designated on Fig. 1 for clutch 37.)
- 69 carrier for pinions 75 and 76;
- 70 gear wheel, geared to spool 26;
- 71,72 bevel gears, geared through shafts 83 and 84 to rotor drums 23 and 24,
- 73 bevel gear, geared to spool 25;
- 74 bevel gear teeth on gear wheel 70;
- 75 pinions, meshing with bevel gears 71 and 72;
- 76 pinions, meshing with gear 73 and bevel teeth 74;
- 77 gear wheel, geared to rotor drum 23;
- 78 gear wheel, geared to spool 25;
- 79 external helical or spur teeth on gear wheel 77, meshing with idler 33;
- 80 gear joined with gear 72 and meshing with idler 34;
- 81,82 external helical or spur teeth on gear wheels 78 and 70, respectively;
- 83 shaft connecting bevel gear 71 and gear wheel 77;
- 84 hollow shaft concentric with shaft 86 and connecting gear wheel 72 and gear
80 and driving pumps 109 and 110;
- 85 hollow shaft concentric with shaft 83 and connecting bevel gear 73 and gear
- 86 shaft connecting pinion carrier 69 and hydraulic pump 116;
- 87,88 gears attached to spools 25 and 26, respectively;
- 89,90 idler gears meshing with gear teeth 81 and 82, respectively, and with
gears 87 and 88, respectively;
- C,D control variable inertia flywheels attached to spools 25 and 26, respectively;
- 91,92 substantially toroidal liquid support housings of flywheels C and D,
- 93 liquid for weighting control flywheels C and D;
- 94 channels in control flywheel housings 91 and 92;
- 95 scoops for removing liquid from control flywheel housings 91 and 92;
- 96 support bars for scoops 95;
- 97,98 hydraulic turbines in and attached to control flywheel housings 91 and
- 99 turbine buckets;
- 100 port openings in cups 14 and 15;
- 101,102 cones for containing discharge of turbines 97 and 98, respectively;
- 103,104 turbine discharge chutes from control flywheel housings 91 and 92,
- 105,106 pipes carrying liquid from chutes 103 and 104 to pump inlet chambers
108 and 107, respectively;
- 107,108 inlet chambers of pumps 109 and 110, respectively;
- 109,110 pumps for control flywheels;
- 111,112 pipes carrying liquid from pumps 109 and 110 to control flywheel inlet
chambers 113 and 114, respectively;
- 115 paddles in control flywheel housings 91 and 92, to keep liquid 93 rotating
with the flywheels;
- 116 main hydraulic pump;
- 117 rods projecting from racks 126 (only one depicted);
- 118 valves (only one depicted);
- 119 pipe connected to discharge of pump 116;
- 120 lips in control flywheel housings 91 and 92;
- 121 holes in bottom of cups 10 and 11;
- 122 inlet to pump 116;
- 123 shaft connecting pinion carrier 69 to pump 116;
- 124 slots in cups 14 and 15 for scoop support bars 96;
- 125 upper racks;
- 126 lower racks;
- 127,128 gear teeth on shaft 129 meshing with racks 125 and 126; respectively;
- 129 shaft in control system;
- 130 streamlined fairings for scoops 95;
- 131 streamlined shields covering slots 124;
- 132 coupling between shafts 129 and 133;
- 133 second shaft in control system;
- 134 piston on shaft 133;
- 135 actuator cylinder;
- 136 toothed clutch collar on shaft 133;
- 137,138,139 bevel gears in control system;
- 140 speed control shaft;
- 141,142 internal teeth in gear wheels 77 and 78, respectively;
- 143 planet gears in control system, meshing with internal teeth 141 and sun
gear teeth 148;
- 144 carrier for planet gears 143;
- 145 hollow shaft attached to planet carrier 144;
- 146 worm teeth on shaft 145;
- 147 gear wheel;
- 148 sun gear teeth on wheel 147;
- 149 gear teeth on wheel 147;
- 150,151 gears in control system, meshing with teeth 142 and 149, respectively;
- 152 shaft connecting gears 150 and 151;
- 153 worm wheel, meshing with teeth 146;
- 154 shaft attached to worm wheel 153;
- 155 worm teeth on shaft 154;
- 156 worm wheel teeth, meshing with teeth 155;
- 157 swiveling block with worm wheel teeth 156;
- 158 pin on which block 157 swivels;
- 159,160 bearing plates for block 157;
- 161 pawls on either side of block 157;
- 162 pins holding pawls 161 on block 157;
- 163 tension spring acting on pawls 161;
- 164 ratchet teeth on shaft 129;
- 165 shaft for idler gear 34;
- 166 spring-loaded stem on each valve 118;
- 167 transmission controller;
- 168 engine controller;
- 169 throttle actuator
- 170,171,172 servovalves;
- 173 slots in strip 22&min;;
- 174 bridges between ends of slots 173.