Drive system

A drive system especially adapted for driving accessories associated with the engine of a vehicle and controlled essentially by the speed of the engine crankshaft. The drive system comprises a pair of variable pulleys interconnected by a flexible belt, one pulley being driven from the engine crankshaft and the other pulley being associated with one or more accessories.

BACKGROUND OF THE INVENTION 
Modern vehicle engines have been called upon to drive an increasing number 
of accessories as the sophistication of modern vehicles increases, which 
accessories include many convenience items demanded by the customer. 
Generally, the accessory drive provides at least a linear ratio between the 
speed (rpm) of the engine and the speed (rpm) of the accessory driven 
shaft. At low engine speeds, no serious problems exist; but at high engine 
speeds serious problems exist. Because of this relationship, it is 
imperative to construct the accessory with proper bearings, so that it can 
operate at elevated speeds without an undue limitation on its life. The 
strength and size of rotating parts must be such that extremely high 
speeds do not rupture them. In addition, the wide variation in operating 
speed of an accessory at times creates a demand for sophisticated control 
systems. Such construction makes the accessory more expensive than 
necessary or desirable both as original equipment (OEM) parts and as 
replacement parts. Driving the accessories at very high speeds results in 
a substantial decrease in the efficiency of the vehicle because a 
substantial percentage of the output is required for the accessory drive. 
This is extremely wasteful because the present fixed ratio drives result 
in accessory speeds which are not required for proper operation of the 
accessories. 
This problem becomes even more severe in some modern engines which are of 
relatively low horsepower and which operate at relatively high speeds. 
Further, the lack of efficiency of the system requires the use of more 
gasoline--a needless and serious waste of energy. In addition, each 
accessory normally has a most efficient or optimum RPM range and with 
normal systems the accessory is not within this range due to wide 
variation in the input speed. 
Various energy saving types of accessory drives have been proposed. For 
example, the drive between the engine and the fan for cooling the radiator 
has been thermostatically controlled. This type of drive is temperature 
dependent and has no relation to engine shaft speed. Such a drive is not 
suitable for alternator or generator drive because these accessories must 
be driven continuously when the engine is operating. Other types of drives 
employ slipping friction clutches; while they may be successful, they have 
not found acceptance because of the cost of the drive and energy losses 
during operation. 
For an accessory drive system to meet requirements for use in modern 
vehicles, it should be small enough to fit in present-day engine 
compartments without any substantial modifications, it should be 
relatively inexpensive, it should be susceptible of mass production and 
adjustable to modern assembly techniques, it should have long life, and it 
should produce a drive from the engine to the accessories which increases 
their speeds in approximately a linear relation with increasing engine 
speed at low RPM but which produces relatively constant accessory speeds 
as the engine speed increases about a predetermined point throughout the 
normal vehicle driving range. The present invention meets all these 
criteria. 
The drive of this invention is to be distinguished from the conventional 
variable pulley transmission as is presently used in, for example, 
off-the-road vehicles or has been proposed for the transmission for 
transmitting power from an engine to the driving mechanism of a vehicle, 
whether they are wheels, lugs or other devices. In such prior 
transmissions, the engine rpm is increased and, at the same time, the rpm 
of the driven mechanism is increased at an even faster rate. 
THE INVENTION 
This invention relates to a drive system especially constructed for 
transmitting rotary motion to accessories associated with a prime mover. 
The drive system is also adaptable for transmitting rotary motion between 
a driven and a driving means where similar drive characteristics are 
required or desired. 
The drive comprises a relatively inexpensive assembly of variable diameter 
pulleys which can be constructed largely of stamped metal parts and which 
are connected by a belt. The belt is generally the only part which will 
require replacement even after a considerable length of operating time. 
More specifically, the drive system of this invention comprises a pair of 
variable pitch diameter pulleys, one a driveR associated with the drive or 
crankshaft of an engine, and the other, a driveN associated with a driven 
shaft and pulleys for driving the accessories, either individually or as a 
package. Each of the variable pulleys has an axially fixed flange and an 
axially movable flange, the change in pitch diameters of the pulleys being 
responsive to the speed of the crankshaft. 
The driveR assembly includes a torque cam-follower means to transmit torque 
between the crankshaft and the axially movable pulley flange and a spring 
with centrifugally actuated weights is associated with the driveR axially 
movable pulley flange. The spring and weights thereon operate on the 
sliding flange of the driveR pulley and determine shift points. The spring 
and therefore the sliding flange are deflected as a function of input 
speed only, making the drive speed and not torque responsive; the 
cam-follower means prevents shifting of speed ratios due to torque 
variations. 
The driveN assembly also comprises a torque cam-follower connecting the 
pulley flanges and a torsion spring so arranged to maintain the follower 
in engagement with the cam. The spring also functions to initially load 
the axially movable pulley flange so as to maintain the belt contact with 
the flanges. 
In the specific embodiment described herein, the driveR and driveN pulleys 
rotate at a fixed ratio at low engine or crankshaft speeds, as for 
example, a ratio of 1 to 1.41, when the accessory drive pulley is rotating 
at approximately 1700 rpm and the engine crankshaft is rotating at 
approximately 1200 rpm, centrifugal force acting on the weights connected 
to the driveR spring causes movement of the weights resulting in the 
driveN pulley being substantially locked at the same rpm while the 
crankshaft speed can attain much higher speeds. When the weights can no 
longer move, the drive again becomes fixed in a drive ratio of 1.41 to 1. 
The much higher crankshaft speed is generally one which corresponds to a 
vehicle speed above the national limits. Thus in the driving range of, for 
example, an engine speed of 1200 to about 2400, which for domestic 
automobiles in the range of 30 mph to about 55 mph, the driveN shaft from 
which the majority of accessories are driven is rotating in the embodiment 
being described at approximately 1700 rpm. 
Each of the accessories can be driven at substantially its optimum speed 
from the driven shaft at least over the major driving speed of the 
vehicle, it being recognized that the optimum speed of each accessory may 
be different and can be achieved by providing various drive ratios between 
the driven shaft and the particular accessory.

DETAILED DESCRIPTION 
Looking now at FIGS. 1 and 2 which show the drive in different operating 
conditions, there is a driveR assembly 10 and a driveN assembly 12, each 
having a variable pulley 14 and 16, respectively, drivingly connected by a 
belt 18. 
The driveR assembly 10 includes the variable pulley 14 which comprises a 
fixed flange 20 and a movable flange 22. The fixed flange is bolted to the 
crankshaft 24 of a prime mover by means of a bolt 25. A sleeve member 26 
with an axially extending flange 28 surrounds the bolt 25. A pin 27 is 
received in a slot 29 in the sleeve 26 and prevents relative rotation of 
the flange 20 and the shaft 24. Surrounding the sleeve member 26 is a 
sleeve bearing 30 and surrounding the sleeve bearing 30 is an axially 
extending sleeve 32 integral with the movable flange 22. This construction 
permits relative rotation, as necessary, between the fixed and movable 
flanges 20 and 22, respectively. 
The assembly 10 also comprises a torque cam-follower means 34 comprising a 
torque cam member 36 having a plurality of cams 38, which member is 
connected to the flange 28 of the sleeve member 26. The cam member 36 is 
axially and rotationally fixed with respect to the sleeve member 26. The 
means 34 also comprises a torque follower member 40 having a plurality of 
followers 42, which member is connected to the sleeve 32 of the movable 
flange 22. A pad 44 of low friction material such as a plastic, is 
attached to each follower 42 to contact the respective cam 38. The member 
36 is essentially a disc with extending cams 38 and the follower member 40 
is also essentially a disc with extending followers 42. A typical torque 
cam-follower means is illustrated in FIG. 5. In the embodiment being 
described, there are three cams 38 and three followers 42 in the torque 
cam-follower means 34. The main consideration is to provide a cam for each 
follower. 
Also connected to the flange 28 of the sleeve member 26 is a cup-shaped 
spring retainer 46 having a rim 48 with a groove 50 therein. A spring 52 
is received in the rim 48 and is retained therein by means of a snap ring 
54 received in the groove 50. The spring 52 is illustrated in FIG. 3 and 
comprises a disc portion 56 with radially inwardly extending fingers 58. 
The spring 52 is pre-loaded to a first deflection position (FIG. 1) such 
that at idle and low shaft speeds it urges the movable flange 22 toward 
the fixed flange 20. 
The terminal ends of the fingers 58 are received between fulcrum members 60 
and 62, the noses of each being rounded as illustrated. The members 60 and 
62 are ring-like, surrounding the sleeve 32 of the movable flange. A 
ring-like thrust bearing 64 is located between the fulcrum 62 and the 
follower member 40 being axially positioned by a snap ring 65, and a 
ring-like thrust bearing 66 is positioned between the fulcrum 60 and a 
ring-spacer 68 which surrounds the sleeve 32. One end of the spacer 68 
abuts the movable flange 22. The thrust bearings 64 and 66 permit relative 
rotation between adjacent parts. 
A plurality of weights 70 are attached to the spring 52 and move generally 
outwardly under the influence of centrifugal force. These weights are 
responsive to the speed of the crankshaft 24 and as they move outwardly, 
cause the spring to move toward the position illustrated in FIG. 2. The 
terminal ends of the spring fingers 58 roll or rock on the rounded noses 
of the fulcrums 60,62. Movement of the spring causes axial movement of the 
sleeve 30 and thus of the flange 22. When the weights "bottom" on the 
retainer 46, no further axial movement of the flange 22 can occur. The 
drive ratio between the pulleys 14 and 16 is then fixed. 
For accessories whose speed must be fixed with the crank-shaft speed, a 
pulley may be provided on the outside of the retainer 46. Such a pulley is 
not illustrated herein. 
The driveN assembly 12 comprises the pulley 16 having an axially fixed 
flange 74 and an axially movable flange 76. The flange 74 is provided with 
an axially extending sleeve portion 78, the terminal end of which abuts 
the defining walls of a recess 80 in a plate 82. The flange 74 also has a 
web portion 84. The engine fan 88 and the assembly 12 have fasteners 92 
passing through suitable openings in the web portion 84 and the plate 82. 
The flange 74 also has a rearwardly extending grooved member 93 which is 
adapted to receive belts driving various accessories for the vehicle. 
The axially movable flange 76 has a forwardly extending sleeve portion 96 
surrounding but spaced from the sleeve 78 of the fixed flange 74 by a 
sleeve bearing 97. A cam-follower means 98 is positioned between the plate 
82 and the flange 76 and comprises a plurality of cams 100 on a cam ring 
102 and a follower ring 104 having a plurality of followers 106. The 
follower ring 104 is connected to the flange 76. Pads 108 of plastic or 
other low friction material are carried by each follower 106 to ride on 
the respective cams 100. In the embodiment illustrated, there are three 
cam lobes and followers. The torque cam-follower is similar to that 
illustrated in FIG. 5. A torsion, coil spring 110 surrounds the sleeve 
portion 96. One end of the spring has a tang 112 received in an opening in 
the plate 82 and the other end is connected to the follower means 102 by a 
bolt 113 received in an opening 114. A flexible dust cover 116 is 
positioned around the torque cam-follower means, as illustrated to prevent 
entry therein of dust and dirt. 
In operation, the driveR and driveN pulleys will be in the drive condition 
as illustrated in FIG. 1 up to the shifting speed, i.e., in the embodiment 
being described, a crankshaft speed of approximately 1200 rpm. As the 
crank-shaft speed increases, the weights begin to move outwardly by 
centrifugal force toward the spring retainer 46 which acts as a stop 
means. The position of the driveR spring means toward that shown in FIG. 2 
and the movable flange 22 (because of the construction of the assembly) 
moves axially away from the fixed flange 20 permitting the belt 18 to ride 
lower in the pulley 14. The followers 42 ride downwardly on the cams 38. 
With the belt tension reduced, the flange 76 of the driveN pulley moves 
axially toward the flange 74, the spring 110 assisting the movement. The 
followers 106 ride higher on the cams 100. 
The changing ratio of the drive allows the driveN shaft 90 (and the fan 88) 
to rotate at an essentially constant speed. In this embodiment, about 1700 
rpm, the same speed as when the weights 70 started moving. 
When the weights 70 bottom on the spring retainer 46, the drive again 
becomes locked in a certain drive ration. 
A typical shift curve is shown in FIG. 4 in which output (driveN) rpm is 
plotted against input (driveR) rpm. As can be seen, the speed relationship 
between the driveR and driveN pulleys is a fixed ratio A to a certain 
value, at which time the weights 70 move outwardly resulting in the axial 
movement of the driveR pulley flanges away from each other. At this time 
the driveN pulley flanges axially move toward each other. The drive ratio 
during this time is shown on the curve as B. The continued movement of the 
weights 70 eventually brings about the pulley relationship of FIG. 2 where 
the weights 70 have bottomed on the retainer 46 and the drive is then 
again in a fixed drive ratio C. Because the drive mechanism of this 
invention is speed responsive, the curbe B has no sharp dips when an 
accessory, such as air conditioning, is activated.