Note: Descriptions are shown in the official language in which they were submitted.
~7~9~6
This invention relates to a variable pulley
transmission for a vehicle.
This is a division of copending Canadian Patent
Applicatîon Serial number 296t975 filed on February 15, 1978.
Variable pulley transmissions are well known in
the art. Because of the present energy crisis, coupled
with the high price of fuel, emphasis is being placed on
~elatively low-powered, small, low-cost passenger vehicles
which are capable of obtaining high mileage per gallon of
fuel~ For such usage, the variable pulley transmission
is ideal. Additionally, such à transmission offers an
unlimited numher of speed ratios throughout its range.
The invention to be described relates to a variable
speed belt drive system, especially constructed for a
passenger car. It can, however, be adapted for other types
of vehicles.
According to the present invention, there is
provided a variable pulley transmission for a vehicle
including a driver shaft, a driven shaft, ~ rotatàble driver
pulley connected to the driver shaft and driving means ~or
rotatins the driver shaft. The driver and driven pulleys
each lnclude an axially fixed flange and an axially movable
flange with belt means drivingly connecting the pulleys.
Spring means is operatively associated with the driver and
driven axially ntovable flanges and normally ur~e the movable
flanges axially toward the driver and driven fixed flanges.
Hydraulic control means is operatively associated with the
pulleys to provide an additional load to the load of the
spring means to thereby change the relative positions of the
flanges of the pulleys and thus change the speed ra-tio
therebetween. The hydraulic control means includes a pair
of fixed displacement pumps, one of which provides pressure
. i
Sb/J ~
responsive to the speed of the driving means and the o-ther
of which provides pressure responsive to the tor~ue of the
driving means. There is provided a hydraulic cylinder with
a piston in the cylinder, the driver pulley movable flange
being connected to the pis~on and the cylinder being connected
to t~e pump providing torque responsive pressure. A speed
and torque responsive valve is provided in the connection
between the pump providing the torque responsive pressure
in the cylinder.
In a specific embodiment of the invention, there is
provided an engine vacuum responsive valve varying the
pressure of the hydraulic fluid from the pump providing the
torque responsive pressure to the cylinder. The hydraulic
control means may include a shift spool, one side of which
communicates with the pump providing the speed responsive
pressure and the other side of which communicates with the
pump providing the torque responsive pressure, the shift
spool being connected to the valve to control the hydraulic
pressure to the cylinder. A spring means may be operatively
associated with the shift spool, which spring resiliently
urges the shift spool in one direction.
In the accompanying drawings:
FIG. 1 is a schematic illus-tration of a variable
pulley transmi~,sion in low drive ratio or idle position;
FIG. 2 is a schematic illustration of a variable
pulley transmission in high drive ratio position;
FIGS. 3 and 3A, when placed one above the other,
illustrate, schematically the transmission and hydraulic
control system of this invention;
FIG. 4 is a plan view oE a disc spring-finger
assembly of this invention illustrating its a-ttachment to
other parts of the transmission.
-- 2 --
sb/~J~,
FIG, 5 is a curve of the output of one of ~he
pumps of the hydraulic control system plotted against engine
FIG~ 6 is a family of curves of the output of ~h~
.
other of the pu~ps of the hydraulic control system plotted
against engin2 P~;
FIG. 7 is a schematic of a torque responsive
pressure con~rol assembly;
FIGS. 8, 9 ~nd 10 are details of the driving
connection o~ the disc spring-finger assembly and a pulley;
and
FIG. 11 is a detail of a valve plunger in the
pressure control assembly.
Looking at FIGS. 3 and 3A, there is illustrated
schematically a variable pulley tr2nsmission assembly which
comprises a oriver pulley 1~, a driven pulley 14 and a
c`ontrol sysLe~ ~6.
The driver pulley 12 comprises a fixed flange 18
connected to ~ drive shaft 20 by a key 22 received in a
ke~ay 24 in the shaft 20, and snap rings 26, 28 recelved in
grooves 30, 32, respectively, in the sha~t 20. Because of
the connection, the fixed flange 18 rotates with the shaft
. 076204 BI~L
.
20. The shaft 20 îs connected ~o a main drive shaft 34
driven b~ a prime mover, such as an internal combustion
engine 36. The shaft 34 is connected to a starting clutch
38 which in turn is connected by a shaft 40 to a forward-
reverse mechanism 42 of any desirable construction. The
fo~ard-reverse mechanism 42 is connected to the shaft 20.
l~e driver pulley 12 further comprises an axially
movable flange 44 having a hub portion 46 surrounding the
shat 20, which hub portîon 46 has a cylindrical piston
port.ion 48 received in a cylindrical member 50 closed by an
end member or cover 52 to define a chamber 54 co3municating
via passages S5 and slots 56 in the shaft 20 with a centxal,
open-ended bore 58 also in the shaft 20D The piston 48 has
a terminal end 59 which abuts the cover 52 when the driver
flange is in low ratio position.
A disc spring 60 (see also FIG. 4) is drivingly
connected adjacent the outer rim 62 of ~he movable flange 44
b~ spaced connecting means 64; the 5pring 60 has radially
inwardly projecting fingers 66, some of which are connected
by pins 68 and the like to a portion of the me~ber 50.
One ~nd of a hollow ~ube 70 is received in the
open-ended bore in the shaft 20 and is connected by a pin 72
to a portion of the hub 46 of the movable flange 44. The pin
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.~
07~204-BT~L
7 passes through opposite slots in the shaft 20, permittîng
the tube 70 to be axially movable~ Because of the pin
connection, the hollow tube 70 as well as the entire movable
flange asse~bly is rotatable with the shaft 20. The opposite
end o the ~ollow tube 70 is slidably received in the block.
74 of a follow-up valve 76 and is closed by a flanged plug
78. One or more (usually a plurality) ports 80 communîcate
the outside to the interior of -the hollow tube 70.
The block 74 has a first a~nular groove 8~ connec~ed
to a drain conduit 84 opening to a sump 86, i.e., a supply
of hydraulic Sluid, such as oil, and a seco~d annular groo~e
88 connect~d to a conduit 90. The flanged plug 78 is received
in an enlarged cavity 92 in the block 74; the flange limiting
~he relative t-avel be~een the hollow tube 70 and the block
74.
A shift spool 94 is connected wlth the bloc~ 74
and is received in a stationar~ block 96 of a shift spool
means 97. rne spool 94 deines cavities 98 and 99 on the
opposite sides thereo~ as shown. A coil spring 100 surrounds
the connecting stem 102 of the spool 94, and the opposite
ends of the block 96 are connected to conduits 104 and 106,
respectively. The conduit 104 communicates with the cavit~
98 and the conduit 106 communicates with the cavity 106.
The driven pulley 14 comprises a fixed flange 108
connected to a driven or output shaL t 110 ~y a key 112
received in a key~7ay 114 in the shaft 110, and snap rings
116, 118 received in grooves 120, 122, respectively, in the
snalt 110~ and an axially movable ~lange 124 having an
076204-BI~L
a~lally extending hub 126 surroundlng the shaft 110. The
shaft 110 is provided with a radially extending flange 128
tn ~hich is connected a cylindrical member 130 surrounding
the hub 126 and defining therewith a cavity 132~ A disc
spring 133 similar in cons~ruction ~o the spring 60 is
drivingly connected at its periphery to the flange 124 and
is fingers 133a engage the member 130. In order to provide
suficient loading of the flange 124, a double or triple
parallel stacked spring may be used. The ~erminal end 134
of the hub 126 is exposed ~o the cavity 132, so that the h~b
126 acts as a piston when fluid is introdueed into the
~avity 132. To in~roduce fluid into the cavity 132, the
shaft 11~ is a~ially bored at 136 and transversely bored at
138 and 13g. The bore 136 is plugged at its terninal end
and a conduit 140 is connected to a non-rotatable delivery
sleeve 142 surrounding the shaft 110. An annular groove 143
in the sleeve 142 provides comm~nication between the conduit
140 and the bores 136, 138 and 139.
A flexible belt 144 eonnects the driver pulley 12
and ~he driven pulley 14. The belt 14~ can be constructed
o metal or an elastomeric material reinforced with iber
glass or other cord tension members. The belt may be covered
with a nylon or other cloth. Other belt constructions may
be used, if desired. The flanges 108 and 124 of the driven
pulley never abut one another because there must always be
2 load on the belt 144 which is prov;ded by the spring-
finger arrangement 133 and 133a and hydraulic pressure in
the cavity 132.
076;~U4-~WL
The hydraulic control system 16 comprises a ~air
of positive displacement pumps 150, 152, preferably of the
type known as internal-external gear pumps. One such known
variety is sold under the Tradename "Gerotor". Other types
of positive displacement pu~ps may be substituted without
departing fro~ the spirit of the invention. ~le pumps 150
and 152 are connected to and drî~en by a common drive shat
154 which in turn is driven from the engine 360 ~e pump
150 delivers hydraulic ~luid ~mder a pressure which is
engine torque responsive and will be referred to as "P"
while the pu~ 152 delivers a hydraulic flui~ under a
pressure which is en~ine speed responsive and will be
referred to 2S "G". The suction or inlet ports 156, 158 and
160A o the pumps 150, 152 are both connected by a conduit
160 to the s~p 86. The outlet of the pump 150 is connected
by a conduit L62 to the conduits 90, 104, and 140, pre-
viously ment~oned. An engine manifold vacuum connected and
torque responsive pressure control assembly 164 is associated
with the con~uit 162 and thus the pressure P is controlled
by engine vacuum. As the vacuum increases, the assembly 164
varies the p~essure at which hydraulic fluid is bypassed to
the intake p~rt 160A.
The pump 152 delivers hydraulic fluid under a
pressure rela,ed to the engine speed by the conduit 106,
previously described. A metering pin 168 registering with a
metering ori ice 169 is in the conduit 106~ The pin 168 is
supported by a cantllevered bi-metallic arm 17C. The travel
o the arm 170 is limited by stops 172 and 174. A kickdown
076204-BI~L
~ 7 ~6
apparatus, generally identified as 176, is also associated
with the conduit 106 and thus with the output o~ the pump
152. The kickdown apparatus 176 cornprises a normally closed
valve member 178 registering ~L~h an orifi~e 179 in the
conduit 106. The valve member 178 ig supported ~y a cantilevered
bi-metallic arm 180. The valve membPr ~78 is resiliently
urged toward the vaLve orifice 179 by a coil spring 186, and
thus is nor~ally closed until the core 182 of a solenoid 184
is energized by energizing the solenoid coil 188 by a kickdown
switch ~not sho~n) under the control o the driver of the
vehicle.
The pressure control assembly ~64J see especially
FIG. 7, comprises a multiple part housing 200 comprising a
first cup-shaped part 202, a second part 204, and a closure
par~ 206, the part 206 being a support casting. The parts
204 alld 206 are bolted together by headed bolts 210 while the
part 202 to which is connected a hose or conduit 218. The
conduit 218 is connected at its opposite end to the fuel
intake manifold 220 o the engine 36.
.
Within the part 202 and retained in position by
~he 1anges 212 and 214 is a diaphragm 222 connected by a
rivet 224 at its center to a cup-shaped spring retainer 226.
The rivet 224 bears against a valve operating rod 227. A
second spaced spring retainer 228 is connected at the opposi~e
end of the part 202 and a coll spring 230 is positioned
between the retainers 226 and 228. The spring 230 urges the
diaphragm 222 and the rivet 224 against the rod 227. The
valve o?erating rod 227 is slidably received in an in~7ardly
extending neck 232 of the part 204.
076204-BWL ~0~ 7 946
,
~ second diaphragm 236 is fixedly positioned
between the parts 204 and 206 and is connected to a spring
retainer 238 by a rivet ~35. The ri.ve~ 239 bears against
the r~d 227. A coil spring 240 is posi~ioned between the
retainer 238 and the part 204. The interior of the part 204
~s provided with a tube ~itting 242 to which is connected a
hose or conduit 244. The hose or conduit 244 is connected
to a solenoid operated valve 246 associated with the forward-
reverse shit mechanism 42.
A valve plunger 248 which seats on a valve seat
250 is associa~ed with the assembly 164 and controls the
pressure in the output or outlet conduit 162 from the pump
150, which conduit 162 also connects with a conduit 252 (see
FIG. 3) a star~ing clutch engaging servo (not sho~rn) as is
known in the ar~. The valvc plunger 248 is also provided with
an orifice 254 2nd a cross passage 255 into ~ich the orifice
254 opens (see detail FIG. 11). The rivet 239 bears against
the valve pluncer 248 and thus the plunger 248 is always
urged toward the seat 250 by the spring 240 tthe plunger
ac~îng as a poppet type relief valve un~er certain conditions)
except when the fo~Jard and reverse mechanism is energizing
the solenoid 2L6 admitting vacuum into the member 204 the~eby
o~ercoming the 102d on the spring 240. (~ile this indicates
a hydraulic clu,ch, other types of clutches May be used
within the scope o the invention.) The part 206 has a vent
255a to vent one side of the diaphra~m 236. In t'ne conduit
162 (see FIG. 3) is also an orifice 256 and a metering pin
258 controlled by a temperature resporlsive bi metalllc arm
260. One side of the metering pin 258 and the valve 248 is
07620~-B~.JL
in ~ conduit 160A leading to the input of the pump 150. The
combin~tion of the orifice 254 and the oriice 256 generates
the initial rise in the P curve of FI~ 6, which may be used
to control a hydrauli~ally controlled starting clutch as in
the prior ar~.
FIG. 4 illustrates the spring 60 for the driver
pulley 12 with its radially inwardly direc~ed fingers 66.
The spring 60 is drivingly connected at spaced locations to
the ri~ 6~ or the pulley flange 44 by connecting means 64.
The means 64 is also illustrated in FL~S. 8, 9 and 10 and
each co~Drises a ront member 262 spaced rom a rear me~ber
264, tne members being suitably spaced and connected together.
The front member 262 has a threaded opening 266 to
receive a set screw 268 and also an extension 270 which
engages a member 272 having a project;on 274 passing through
an opening 276 in the rim 62. To avoid drilling holes ln
~he ~ingers 66, the means 64 is slipped over a ~inger, moved
outwardly to the position shown and the set screw 268 is
tightened to effectively connect the disc spring 60 to the
rim 62.
The disc spring 133 fo~ the driven pulley 14 ~th
fingers 133a is essentially the same constructîon as the
spring 60 and is connected in a similar fashion to the
flange 12L; however, because it must exert a load on the
flance t?4 and thus the belt 144 in excess of that pro~lded
by the driver pulley 12, the spring 133 may be stacked, .or
exam~le, it may be constructed with a plurality of disc
springs, each having inwardly directed fingers~
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076204-Bl~ 10~7946
As illustrated in the drawings but not specifically
described are suitable O-ring seals. These are provided
where necessary and desira~le.
OPERATION
With the engine 36 idling and ~e clutch 38
released, the dri~e shafE will be at rest 2nd the pulleys 12
and 14 will be in the positîons of FIG. 1.
The pump 150 will be operating ~ut due to the
ori~îces 254 and 256 bypassing fluid to ~he intake port 156
the pressure will be at a very low value. IL this pressure
is used in a hydraulically controlled starting clutch, the
pressure will be insufficient to overcome the retractor
sprin~s in the clutc'n which maintain the clutch in the
re.lease position. The pump 1S2 will also be operating but
due to the fluid bypassing orifiees 169 and 179, this
pressure will also be at a very low value in the passage 106
an~ will be unable to overcome the r~tractive load of ~he
spring 100 i~ the shifL spool 97.
Therefore, the shift spool piston 94 and ~he
follow-up valve 76 will be at the ~ully retracted position
(to the right as sho~n in the drawings) ~hich opens the
passages 80 directly to the sump 86 via the groove 82 and
the passage 84, thus maintaining zero pressure in the cavity
54 and on the driver pulley piston 48. At this time, the
piston 48 abuts the closure 52 to provide a reaction for the
-- 11 --
076204-BT~
~ 7 ~
be_~ 102ding forces developed at the dri~en pulley 14 (as
beforP stated, a load is always main~ained on ~he belt 144
by the driven pulley 14).
To start the vehicle moving, the throttle of the
engine (not shown~ is opened and the engine rpm increase~.
The pump 1~0 delivers fluid pressure P in the manner indicated
along the let portion of the curve (FIG. 6) which causes ~he
clutch 38 to ~ngage so a~ to connect th~ shafts 34 and 40.
This causes the pulleys 12 and 14 to rotate and the driven
shaft 110 is rotated which starts the vehicle moving. The
pump 152 delivers even a 10~7er pressure at ~his stage of
operation ~nd the pressure is still insufficien~ in the
passage 106 to start moving the shaft spool piston 94 ~o tne
left (as viewed in the drawings). Therefore, the driver
piston cavity 54 remains at zero pressure and connec~ed to
; the su~p 86 until some higher rpm is reached. The engine 36
and drive shaft 40 continue to turn together in the low
drive ratio until the pressure G (see ~he rising portion oI
the pressure curve G, FIG. 5) becomes sufficient to initiate
movement oî the shit spool piston 94 and ollow-up valve 7
to admit pressure into the driver p;ston chamber 54.
Movement o the piston 94 and the pressure in the
driver piston chamber 54 on the piston 48 initiates ~oveme~t
of the driver pulley flan~e 44 toward the flange 18. Move-
ment of the flange 44 toward the flange :l8 transmits additi.onal
tension ~o the belt 144 and forces the driven flange 124 to
move to the left, thereby changing the drive ratio between
the pulleys. The resulting drive ratio will cause a feed-
back signal ~incremental change in engine RPM and G pressure
- 12 -
' ~.J / V~.U'~--DWl.
:`
.ich changes the Lorce on the shif~ spool 94) which will
correct ~or any dri~t in RPM during the spee~ ratio change
at a giYen torque level as additional load is ~laced on the
engine. This results in the maintenance of a constan~ engine
speed for a given to-que level until ~he ratio change has
been completed to the end of the travel of ~he driver
pulley piston 48 a~ which time ~he dr~ver flange 44 but~s
against the driver pu~ley flange 18.
Continued o?eration at this torque le~el results
in a constant overdrive ratio and varying engine speeds
related directly to .~e vehicle speed. It will be seen from
the curves of FIG. 6 th~t if this operation is at a 50%
torque level, the opposing pressures (P) on the lef~ hand
sid~ of the shift spool piston 94 will be moderate and
consequently only a ~oderate RPM will be required to attain
sul~ficient pressure i~ the passage 106 to balance the
pressure on the oppos-Le side of the shift spool piston 94
wnich results in 2 mocerate engine ~PM and constant engine
soeed operation throu~n the ratio change phase. With increasing
torque, higher values o, G and higher RPM of .ne engine will
be required to induce the ratio change, such that in additIon
to the increased torque provided at higher throttle openings~
increased RPM is also provided, so that considerable fle~ibility
in the power output is available.
Turning now ~o the follow-up valve, Lhe annular
groove 82 is connected to the sump 86 by the conduit 84 and
,he groove 88 is connected to the pump 150. The land between
- ~3 -
~ v ~ ~ ~ v~--D~`~L
~roove 82 and groove 88 straddles the delivery ports 80 into
the delivery tube 70. The amoun~ of pressure in the passage
90 which actually is delivered to the cavi~y 54 and the
driver piston 48 is the result of minute shifts in the
position of the follow-up valve body 74 in relation to the
movemen~ o~ the pis~on 94 of the shift spool 97. A slight
movement of the driver pulley p;s~on 48 to the left which
tends to increase the efective diameter of the driver
pulley 12 and the position of the belt 144 will tend to dump
pressure in.o the sump 86 through the passage 84 and communicate
the openings 80 with the groove B2 and thereby nullify this
i.nitial movement. Conversely~ any tendency of the belt 144
to move do~m to a smaller driving diame~er (with the flanges
18 and 44 ~oving apart) will tend to admit more line pressure
to the driver piston cavity 54 and correct for this motion~
so that the result is that the pressure in chamber 54 is
regulated at all times at some value less than the available
pressure in the lîne 162, ~hereas the pressure on the driven
assembly piston 134 is always directly connected to this
source of pressure, i.eO, line 162; thus a load is always
maintained on the belt 144 by the driven pulley.
.. . .
The configuration of the metering pin 168 (in
conduit 106) and the deflection rate of the ~i-metallic leaf
spring 170 is developed to produce the desired shape of
pressure G (pump 152~ versus engine RPM. The action of the
bi-metal spring 170 with changes in o;l temperature com-
pensates.for the change in o;l viscosity, such that the
curve remains substantially the same over the operating
range of oil ternperatures. ~t higher temperatures the
076204-BI~L
~ ~ 7 ~ ~
l metal spring 170 reaches ~he 5~0P 174 after which the
e~fective free length of the cantilever a~m is reduced7 so
that the amount of compensa~ion at higher temperatures is
reduced in accordance with the smaller changes in oil vis
eosi~y encountered at higher temperatures. In other words,
the ~;scosity of the oil changes quite rapidly from room
tem~erature to 140 bu~ from 140 ~o 200 it doesn~t change
nearly as much. On the opposite side of the bl-metal
spring 170, the stop 172 shortens the eff ctive cantilever
length of the bi~metal spring 170 to cause the governor
curve G to flex upward near the higher Pnd of the engine
operating speed range, s~ that a strong change in governor
signal is provided near the top d~sired operating range o~
the engine to avoid the possibility of o~erspeeding the
engine. The secondary cantilever spring 180 and metering
pin 178 is normally held closed by the solenoid plunger 182
and its spring 186 but when maximum performance is desired,
a kickdo~n switch (not shown) in the throttle linkage (no~
shown) closes at the full throttle position or just beyond
the full throttle position to energize the ~olenoid windings
188 and retract the plunger 182 thereby allowing the canti-
lever/bi-metal spring 180 to provide an additional or
auxiliary orifice and a maximum performance governor cuxve
~ho~n dotted in FIG. 5~ The ~luid then passes through both
OL the orifices 169, 179, and thereby increases the speed
required at the pump 152 to reach the governor pressure
which forces the belt 144 into the top overdrive ratio (FIG.
2). Tf at a given speed and torque condition, the follow-up
va~ve 176 and the position of the belt 144 is in a certain
- 15 -
--.
U4 ~IL
F ition, oper2tion of the Xickdown switch will reduce the
pressure from a solid curve to ~he level shown ~y the dotted
curve thereby reducin~ the force on the right hand side of
shift spool piston 94. The follow-up valve 76 will move to
the right and relieve pressure in`the cham~er 54 causing the
1ange 44 o ~he dri~er pulley to move to the right. The
belt 144 then moves towards the bottom of the driver pulley,
changing the ratio of the drive toward low drive ratio. The
spring 60 always provides a bias load on the flange of the
driver pulley ~2 to squeeze the belt 1~4 but the bias load
is insu~ficient by itself to overcome ~he tension of the
belt produced by the driven flange assembly 14.
Assuming the driver of the vehicle has been
cruising at a certain speed at part throttle and wishes ~o
accelerate by opening the throttle but not to the extent of
~oing through the kickdo~n. Instead oi changing the pressure
G at the pump 152, the increase throttle causes a decrease
in vacuum in t-ne pressure control valve 164. This per~its
more of the spring pressure to be applled to that valvel
thereby increasing the pressure to a higher level in the
conduit 162 and on the le~t hand side o~ the shift spool
piston 94 (in the cavity 98). This will cause the follow~up
valve 76 to move to the right and the ports 80 will commu-
nicate to some e~tent with the groove 82 and thus the
conduit 84 and the sump 86.
Some of the pressure in the chamber 54 will be
relieved causir.g a shift in the belt position towards the
lo~er drive r2tio position.
- 16 -
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