CA1097946A - Variable pulley transmission - Google Patents

Abstract

ABSTRACT

A variable pulley transmission especially adaptable for use in a passenger vehicle which comprises driver and driven pulleys connected by a flexible belt, the spacing between the pulleys and thus the drive ratio being controlled by a hydraulic control arrangement which is both engine speed and torque responsive.

Description

~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.

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 .~

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~

- 10 ~

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 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 ' ~.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 --.

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.

., ~

.~ ,

Claims (8)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A variable pulley transmission for a vehicle comprising:
a driver shaft;
a driven shaft;
a rotatable driver pulley connected to said driver shaft;
driving means for rotating said driver shaft;
said driver and driven pulleys each comprising an axially fixed flange and an axially movable flange;
belt means drivingly connecting said pulleys;
spring means operatively associated with said driver and driven axially movable flanges normally urging said movable flanges axially toward said driver and driven fixed flanges;
hydraulic control means operatively associated with said pulleys to provide an additional load to the load of said spring means to thereby change the relative positions of the flanges of said pulleys and thus change the speed ratio therebetween;
said hydraulic control means comprising:
a pair of fixed displacement pumps, one of which provides pressure responsive to the speed of said driving means and the other of which provides pressure responsive to the torque of said driving means;

a hydraulic cylinder and a piston in said cylinder;
said driver pulley movable flange being connected to said piston;

said cylinder being connected to said pump providing torque responsive pressure; and a speed and torque responsive valve in the connection between said pump providing said torque responsive pressure in said cylinder.

2. A variable pulley transmission as recited in claim 1 further comprising an engine vacuum responsive valve varying the pressure of the hydraulic fluid from said pump providing said torque responsive pressure to said cylinder.

3. A variable pulley transmission as recited in claim 1 in which said hydraulic control means comprises a shift spool, one side of which communicates with said pump providing said speed responsive pressure and the other side of which communicates with said pump providing said torque responsive pressure, said shift spool being connected to said valve to control the hydraulic pressure to said cylinder.

4. A variable pulley transmission as recited in claim 3 further including a spring means operatively associated with said shift spool and resiliently urging said shift spool in one direction.

5. A variable pulley transmission as recited in claim 3 wherein said valve comprises a block connected to said shift spool and a hollow valve member, said hollow valve member being connected to said piston connected to said axially movable pulley flange and having spaced ports therein, one port communicating with said hydraulic cylinder and the other port being connected with said pump providing said torque responsive pressure and said sump depending upon the axial position of said block relative to said hollow valve member.

6. A variable pulley transmission as recited in claim 3, further comprising means to control the pressure from said pump providing said speed responsive pressure, said means comprising an orifice and a metering pin for said orifice, and a temperature responsive means supporting said metering pin to compensate for temperature changes in hydraulic fluid.

7. A variable pulley transmission as recited in claim 6 in which said temperature responsive means is a bi-metal member.

8. A variable pulley transmission as recited in claim 3 further comprising a solenoid operated valve to control the pressure from said pump providing said speed responsive pressure, said solenoid operated valve comprising an orifice and a valve member normally seated on said orifice, said valve member being operatively associated with the core of a solenoid and means to energize said core and unseat said valve member from said orifice.