Continuously variable belt-drive transmission

A continuously variable belt-drive transmission of the type having spaced apart sheaves each provided with a plurality of sheave segments which may be moved radially inwardly and outwardly. A novel control is provided for selectively moving the segments inwardly or outwardly while the sheaves are rotating, the control including a motor carried by the body of each of the sheaves, the motor being operatively interconnected with the associated sheave segments. Power is transmitted to the motor by electrical wires, slip rings and brushes.

FIELD OF THE INVENTION 
The present invention relates generally to continuously variable belt-drive 
transmissions, and more particularly to a continuously variable endless 
belt power transmission system of the type wherein the effective diameter 
of the sheaves which the belt(s) pass over are simultaneously adjusted. 
BACKGROUND OF THE INVENTION 
Transmissions of many differing types are well known in the art. Ideally, 
in a motor vehicle, the transmission should provide stepless adjustment 
from zero to maximum ground speed, should be easy for the operator to 
adjust - or even automatic in its performance, should not cause any power 
loss, and should be low in first cost. Unfortunately, these desired 
characteristics are not all obtainable and thus no manufacturer can ever 
introduce the perfect transmission. A continuously variable belt-drive 
transmission has been used in the past. In one form the effective diameter 
of one sheave is varied while the other sheave, which is spring loaded to 
its largest effective diameter position, may have its effective diameter 
changed by the tension of the belt reacting against the springs. The 
primary adjustable sheave is typically adjusted by movement of a single 
side of the sheave. This form of continuously variable belt-drive 
transmission has the disadvantage in that only a single belt can be 
utilized in the transmission, which single belt may not be suitable for 
transmitting the power requirements necessary for many of today's 
vehicles. U.S. Pat. No. 4,409,862 shows a multi-belt split drive 
transmission wherein the belts of the drive and driven sheaves of the 
variable speed portion are both supported by sheave segments, which 
segments are moved radially inwardly or outwardly by opposed scrolls 
disposed within the housing that supports the sheave segments, the scrolls 
in turn being caused to be rotated relative to the housing by a gear train 
which is interconnected to electrically operated actuators disposed at a 
location to one side of the transmission. While the design of the above 
patent overcomes some of the problems and disadvantages of the prior art, 
this design is relatively expensive due to the utilization of complex gear 
trains and opposed scrolls. 
OBJECTS AND SUMMARY OF THE PRESENT INVENTION 
It is an object of the present invention to provide a continuously variable 
belt-drive transmission which is capable of transmitting relatively high 
torques, the belt-drive transmission being of reasonably low cost, and 
which is easy to adjust when in operation. 
If such a transmission is utilized in a heavily loaded tractor trailer it 
is believed that it will lower driver fatique as all shifting will be 
easily accomplished by electrical control means, thus not requiring double 
clutching and movement of shift levers. It is also believed that such a 
transmission can be utilized to either obtain the highest possible speeds 
in hilly terrain or the most fuel efficient operation in relatively flat 
terrain. Thus, in hilly terrain the engine can be set to its highest 
torque performance when going up a hill and by properly adjusting the 
transmission of this invention to maintain desired engine rpm for maximum 
torque the greatest possible speed will be maintained when going up the 
hill. To achieve the most fuel efficient operation the engine is set to 
its most fuel efficient speed and the transmission is adjusted to the 
desired output speed. 
The foregoing is achieved by mounting a control motor, which is preferably 
a stepping electric motor, on the rotating body of the sheave and coupling 
the output shaft of the motor with a scroll mounted within one side of the 
sheave, which scroll when rotated relative to the sheave causes the 
effective diameter of the sheave to be incrased or decreased. The electric 
motor is in turn interconnected with controls and a souce of power by 
means of commutator rings. 
The foregoing will be understood more completely after a consideration of 
the following detailed description taken in conjunction with the 
accompanying drawings in which a preferred form of this invention is 
illustrated.

DETAILED DESCRIPTION 
Referring first to FIG. 1, the continuously variable belt drive 
transmission of this invention is indicated generally at 10. The 
transmission includes a support 12 upon which are mounted bearing blocks 
14.1 to 14.7. As best shown in FIGS. 2 and 3 each bearing block includes a 
flange 14a, an upright portion 14b and a bearing 14c. The bearing blocks 
14 are mounted on frame 12 by fasteners 15. Journalled within the bearings 
14c of the various bearing blocks are a plurality of shafts. Thus, 
journalled in bearing blocks 14.1 and 14.2 is an input or first shaft 16. 
An intermediate of second shaft 18 has an intermediate portion supported 
by bearing block 14.4 and ends supported by bearing blocks 14.3 and 14.5. 
Finally, an output or third shaft 20 is supported by bearing blocks 14.6 
and 14.7. 
At this point it should be noted that the continuously variable belt drive 
transmission of this invention as shown in FIG. 1 is shown as a 
multi-stage transmission. Thus, the speed of intermediate shaft 18 may be 
varied with respect to input shaft 16, and similarly, the speed of output 
shaft 20 may be varied with respect to intermediate shaft 18. While a two 
stage transmission is shown in FIG. 1, it should be appreciated that any 
number of stages may be utilized to produce the desired result. Thus, a 
single stage may be utilized if it is only necessary to vary the 
input/output ratio by a factor equal to or less than that available from 
the single stage, the ratio factor hereinafter being referred to as X. 
Alternatively, if it is necessary to vary the input/output ratio by a 
factor more than X, but less than X.sup.2, then two stages may be 
employed. Similarly, if it is necessary to vary the input/output ratio by 
a factor of greater than X.sup.2 but less than X.sup.3 a three stage 
transmission may be employed. Since all of the stages are essentially the 
same in the following description only the single stage shown in FIG. 2 
will be described in detail. 
Mounted on the first and second shafts 16, 18, are first and second 
substantially identical adjustable sheaves 22, 24, respectively, the 
sheaves being in parallel alignment with each other. One or more power 
transmitting belts 26 transmit the power from the first sheave 22 to the 
second sheave 24. Each of the adjustable sheaves 22, 24 includes a body 28 
secured to the associated shaft for rotation therewith and a plurality of 
sheave segments 30 mounted on the body for radial inward and outward 
movement. If the sheave segments 30 are all disposed inwardly as shown on 
the first adjustable sheave 22 and similarly, if the sheave segments on 
the second adjustable sheave 24 are all disposed outwardly, the second 
shaft 18 will be caused to be rotated at a slower speed than that of the 
first shaft 16. Similarly, if the diameter of the first adjustable sheave 
22 were incrementally expanded and the diameter of the second adjustable 
sheave 24 were correspondingly incrementally reduced by moving the sheave 
segments 30 inwardly, the output speed of the shafts could be varied. 
Thus, if the diameters of the sheaves 22, 24 were equal the output shaft 
18 would have the same speed as input shaft 16. Similarly, if the diameter 
of sheave 22 were greater than the diameter of sheave 24 the scond shaft 
18 would have a faster rotational speed than the first shaft 16. 
In order to provide for the adjustment of the sheaves 22, 24, control means 
are provided which are capable of adjusting the effective diameter of both 
sheaves 22, 24 simultaneously by selectively radially moving the sheave 
segments 30 either inwardly or outwardly while the associated body 28 is 
rotating with its associated shaft. The control means include motor means 
32 carried by the body of each of the first and second sheaves, power 
transmitting means indicated generally at 34, the power transmitting means 
extending to the motor means about a portion of each of the shafts from a 
source of power 36 external of the transmission, and operator control 
means 38 which are capable of causing the motor means to be operated in 
the proper manner. 
Referring now in detail to FIGS. 3 through 6, the body 28 of an adjustable 
sheave includes a main body portion 40 which is secured to an associated 
shaft for rotation therewith by key 42, which key is received in an 
appropriate groove or keyway 43. Secured to the main body portion 40 is a 
back plate 44 which is also part of the body 28, the back plate being held 
to the main body portion 40 by suitable fasteners 46. While only one of 
the fasteners 46 is shown, the fasteners may be equal in number to the 
number of sheave segments. The main body portion 40, adjacent the back 
plate 44, is provided with an annular groove 48, which groove receives an 
annular element 50. The annular element carries on one face scroll teeth 
52. Since the element 50 carries scroll teeth 52 it is frequently referred 
to as a scroll or scroll element. In order to impart rotation to the 
scroll element 50 with respect to the body portion 40, gear teeth 54 are 
provided on the side of the scroll element 50 opposite the scroll teeth 
52. 
It should be noted at this point that the adjustable sheaves of this 
invention to a certain extent correspond to conventional chucks. In 
conventional chuck design the scroll 50 would be rotated by a key inserted 
within a suitable aperture in a skirt portion of the main body portion, 
the key carrying a pinion which is capable of engaging the teeth 54 to 
cause them to rotate relative to the body portion 40 to cause the jaws 
carried by the body portion of the chuck to move radially inwardly or 
outwardly. Such a design would not be practical in the continuously 
variable belt drive transmission of this invention as it is necessary to 
provide an alternate form of control means which is capable of moving the 
sheave segments 30 radially inwardly or outwardly while the body 28 is 
rotating wiht its respective shaft, for example 16 as shown in FIG. 3. To 
this end, the present invention contemplates the utilization of control 
means which includes the electric motor indicated by its output shaft 32, 
the motor 32 being mounted within a housing 56 which is mounted in any 
conventional manner on the back plate 44. In order to suitably power the 
electric motor the power transmitting means 34, which includes lines or 
conductors 57, extend from the source of power 36 to spaced apart 
commutator or slip rings 58, 60, which rings are mounted upon a stationary 
sleeve 62 which is suitably supported about the associated rotatable shaft 
(16 in FIG. 3) by bearings at either end, only one of the bearings 64 
being shown in FIG. 3. It should also be noted that an exterior portion of 
the sleeve 62 is interconnected with an associated bearing block. The 
commutators 58 and 60 are in turn contacted by suitable brushes 66, 68, 
respectively, which brushes are mounted in any conventional manner on 
housing 58, the brushes in turn being in electrical contact by means of 
wires with the motor 32. The motor 32 is of the type whose rotational 
output can be strictly controlled by the input of electrical current, one 
such motor being commonly referred to as a stepping motor. While only two 
slip rings 58, 60 are shown, if desired, additional slip rings and brushes 
may be utilized. While the slip rings 58 and 60 are shown mounted upon a 
stationary sleeve 62 other designs may be utilized. Thus, the slip rings 
58 and 60 may be mounted on the rotating shaft (for example 16) at a 
location adjacent one of the bearing blocks 14, the rings in turn being 
connected by brushes which are in electrical contact with the source of 
power 36 and control 38. The rings 58 and 60 will then be interconnected 
with the motor by suitable wires. 
An output gear 70 is mounted on the output shaft 32 of the motor for 
rotation therewith, the output gear 70 meshing with an input gear 72 
secured to shaft 74, which shaft 74 passes through suitable apertures in a 
skirt portion 76 of the main body portion 40 and through a flange 78 on 
the back plate 44. A pinion 80 is carried by the other end of the shaft 74 
and engages the gear teeth 54 on scroll element 50. In order to properly 
position the shaft 74, input geat 72 and pinion gear 80, spacers 82, 84 
may be disposed about the shaft 74. 
Each of the radially adjustable sheave segments 30 include a base sheave 
portion 86 (FIG. 5) and a top sheave portion 88 (FIG. 6) which is secured 
to the base sheave portion by fasteners 90. The base sheave portion 86 
includes a main body portion 91 which is provided on one side with teeth 
92 which are engagable by the scroll 52. In addition, the main body 
portion 91 of the sheave base portion 86 is also provided with laterally 
outwardly extending ribs 94. The base sheave portion 86 is received within 
a radially outwardly extending slot 96 (FIG. 3) in the main body portion 
40, the ribs 94 being received within grooves 98. When six sheave segments 
30 are to be utilized the base portion 40 is provided with six radially 
outwardly extending slots, the base sheave portions being received 
therein. 
The top sheave portion is to a certain extent U-shaped in cross-section and 
includes a bight portion 100, an attaching leg portion 102 and a 
supporting leg portion 104. The bight portion 100 is provided with 
suitable grooves 106 for reception of the drive belts 26. The attaching 
leg portion 102 is provided with a centering projection 1085 which not 
only helps to radially center the top sheave portion 88 when mounted on 
the base sheave portion 86 but also transmits some of the loading from the 
portion 88 to the base portion 86, so that not all of the loading is 
carried by the fasteners 90 in shear. Finally, the supporting leg portion 
104 is provided with an extension or key 110 which is T-shaped in 
cross-section. 
A support member 112 is disposed about the associated shaft (16 in FIG. 3) 
and is keyed thereto for rotation with the shaft by a key 114. The support 
member is provided with a number of radially outwardly extending slots 116 
which are equal in number to the sheave segments 30, the slots 116 also 
being of a T-shape in cross-section and receiving the extension key 110 of 
the top sheave portion. 
The operator control means 38 includes manually engagable means 118, which 
may be a knob mounted upon an electrical device such as a potentiometer 
120. The manual control 118 and its associated electrical device 120 is in 
turn interconnected with a control module 122 by conductors 124. The 
control module 122 in turn may be a microprocessor based controller which, 
upon receipt of input signals will deliver specific output signals to each 
motor 32. In FIG. 1 separate controls are shown for each stage, there 
being a single manually engagable control 118 for the first stage, which 
control is linked with the control module 122. When the control module 122 
receives a signal for the first stage, it will in turn cause the motor 
associated with the first adjustable sheave to be driven in one direction 
and the motor associated with the second adjustable sheave 24 to be driven 
in the opposite direction thereby increasing the effective diameter of the 
sheave segments 30 for one of the adjustable sheaves while decreasing the 
effective diameter for the other adjustable sheave. While separate 
controls for each stage is shown, it should be appreciated that a single 
controller may be utilized for all the stages, the individual 
potentiometers 120 in turn being coupled to a single signal processor and 
control module (not shown) which would in turn be coupled with the various 
motors of the adjustable sheaves for each stage to provide effective 
control. 
While the continuously variable belt drive transmission of this invention 
may be used in various applications, its operation will be described below 
in connection with its utilization in a motor vehicle. Initially though it 
should be appreciated that when used in a motor vehicle the transmission 
will be associated not only with the output shaft of the motor engine and 
its drive shaft, but also with a gear box and clutch. Thus, in one typical 
situation the output shaft of the vehicle engine may be interconnected 
with the input shaft 16 by means of a clutch, and the output shaft 20 may 
be interconnected with the drive shaft of the vehicle by a speed reducing 
gear box. In operation, the operator will normally start the vehicle 
engine with the clutch depressed. If the variable speed transmission is 
not already in its low position, it will be shifted to its low position, 
the low position being illustrated in FIG. 1. After the clutch has been 
released it is only necessary to dial in the desired final speed. Assuming 
that the final speed is to be as fast as possible, then the control module 
122 for each stage will cause the input adjustable sheave to be expanded 
to its full amount and the output adjustable sheave to be reduced in 
diameter to its smallest possible amount thereby providing the greatest 
speed increase from the transmission. While the control of the 
transmission has been stated to be operator controlled, it should be 
appreciated that other controls may be utilized. Thus, a microprocessor 
based control system may be utilized which will not only vary the output 
of the transmission but also vary the fueling of the engine so that either 
the most efficient performance of the engine or the maximum torque output 
can be achieved. Thus, if the engine can be run at its most fuel efficient 
speed while maintaining the desired ground speed, which may be detected in 
any conventional manner, an overall efficiency of operation may be 
achieved, while yet permitting high torque performance characteristics 
when desired, and also operator overrides, as when braking. 
The proceeding specification described by way of illustration and not of 
limitation, a preferred embodiment of the invention. It is recognized that 
many other modifications of the disclosed embodiments will occur to those 
skilled in the art. Such modifications and equivalents are within the 
scope of this invention.