USRE31361E - Variable pulley transmission - Google Patents

Abstract

A power transmission adapted to be connected between a prime mover and a driven means which comprises a variable pulley drive comprising drive and driven pulleys connected by a belt, each having at least one flange axially movable with respect to the other. The pulleys continously rotate when the prime mover is operational. The output of the prime mover is directly connected to the pulley drive. The prime mover may be an automobile engine, the driven means may include the wheels of an automobile. A speed-responsive friction starting device with means to shift between neutral, forward and reverse is connected between the driven pulley and the driven means. Shifting of a dry, i.e, non-lubricated, belt on the pulleys when the speed ratio is changing is enhanced because of the continuous driving of the pulleys. Also, because the direction of the rotation of the pulleys is always the same, shifting between forward and reverse is enhanced, this being true for any type of belt. The drive ratio between the pulleys is controlled by a hydraulic control arrangement which is both engine speed and torque responsive and the drive to the vehicle wheels may be through a synchronizer or a planetary gear arrangement to a differential.

Description

BACKGROUND OF THE INVENTION

The prior art is replete with examples of power transmissions using variable pulley devices comprising a pair of pulleys connected by a belt. The generally accepted variable pulley transmission for automobile use has a clutch and a forward-reverse-neutral mechanism between the prime mover and the transmission. The rate at which the belt can be shifted diminishes as the pulley speed decreases, and in the usual arrangement when the starting mechanism is located between the motor and the drive pulley, the pulley speed decreases rapidly to zero when the vehicle is brought to a stop. It is desirable to maintain the belt in high ratio over a wide range and steady state vehicle speeds, but if a sudden stop is made from say 20 MPH, it is difficult to return the belt to the starting or low ratio before the pulleys stop rotating. With the usual arrangement, a compromise is made to maintain the belt in lower ratios below about 25 MPH, which adversely affects fuel economy. Also, with the usual arrangement, it is necessary to bring the vehicle and pulleys to a complete stop before engaging reverse gear which reverses the direction of rotation of the pulleys; in such case, it is difficult to rock the vehicle out of snow or mud.

THE INVENTION

The apparatus according to this invention comprises a variable pulley drive connected between a prime mover and a driven means. Each pulley has at least one axially movable flange, the spacing between the flanges determining the speed ratio therebetween, the drive between the pulleys being by a flexible belt. Such belts are known in the art and may be constructed of an elastomer with tension members such as cords of metal, fiberglass and the like or of connected metal sections. The apparatus is suitable for automotive uses, the prime mover being the automotive engine and the driven means being a differential and ultimately to either the front or rear wheels of the vehicle.

In the invention described herein, the driver pulley is connected to the drive shaft, so that the pulleys are continuously rotated when the engine is running; starting of the vehicle can be accomplished by a speed-responsive friction starting device, such as a clutch, either automatic or manual, a brake band or disc packs on a reaction member and the like. The starting device will also generally include a forward-reverse-neutral selector mechanism. Starting devices of the type noted and directional selector mechanisms are well known in the art.

One of the main objectives of this invention is to continuously rotate the pulleys during motor operation so that shifting the belt between ratios can be easily accomplished, especially when the vehicle is brought to a rapid stop from a moderate speed and the belt must be returned to the starting or low ratio from a high ratio.

A second objective accomplished by this invention is to permit the pulleys to continuously rotate in the same direction as the prime mover during forward to reverse shifts, so that the inertia of these parts do not have to be synchronized.

There is also provided a hydraulic control system for the pulley assemblies which is both engine speed and engine torque responsive.

The final drive arrangement is controlled by an automatic starting clutch through a forward-reverse mechanism, such as a gear set. The axially movable driveR flange is preloaded with a disc spring and finger structure which connects the rim of the movable flange to a hydraulic cylinder to carry torque between the flange and the cylinder. The hydraulic piston of the cylinder is fed with hydraulic pressure by a follow-up valve controlled by a shift spool or plunger.

The three devices, i.e., the hydraulic cylinder, the follow-up valve, and the shift spool control the axial position of the movable driveR flange and thereby the drive ratio of the transmission.

The driveN assembly comprises a disc spring with fingers which preloads the axially movable flange of the driven pulley and which, together with a fluid or hydraulic pressure, maintains the movable flange against the belt, so that the pulley carries the torque. The spring and fingers connect the movable flange to a driveN shaft, i.e., the shaft for the final drive assembly for driving the wheels of the vehicle. The hydraulic pressure and the load of the spring control the flange loading of the driveN assembly and thus control the torque capacity thereof.

Another of the objectives of this invention is to control the flange loading on the driveN pulley in such a manner that it closely matches the torque requirements of the belt connecting the driveR and the driveN pulleys in the various drive positions and at the various input torque levels of the engine. The variation in flange loading with respect to flange position or belt ratio is controlled by the shape of the load deflection curve of disc spring, such that when the belt is in the low ratio position, a relatively high spring load is exerted, and as the belt moves to the high drive ratio position, the load diminishes in a pronounced manner. In the preferred embodiment of this invention, the spring load in the high drive ratio position is less than half of the spring load in the low drive ratio position. The change in load with reference to input or engine torque is accomplished on the driveN pulley by variations in the hydraulic pressure applied to the piston connected to the movable flange of the driveN pulley. The combined force of the spring and the hydraulic pressure give a family of curves for each torque level of the drive.

SUMMARY OF THE INVENTION

A power transmission apparatus constructed in accordance with this invention is effective to transmit rotary motion between an engine output shaft and some driven means, such as the driving wheels of a vehicle. The apparatus includes a variable rotary pulley driving unit, having a driver pulley and a driven pulley interconnected by a suitable belt. Each pulley has a pair of flanges, of which at least one is axially movable with respect to the other flange to change the spacing between the flanges of a single pulley. The flange walls are tapered so that changes in the flange spacing in each pulley can effect a corresponding change in the speed ratio between the driver and driven pulleys. Means is provided to operate, responsive at least to the speed of the engine output shaft, to change the spacing of the pulley flanges and thus correspondingly modify the speed ratio.

Particularly in accordance with the present invention, the engine shaft is connected to the driver pulley so that the pulleys are continuously rotated only in one direction whenever the motor is operating. Such pulley rotation enhances the shifting movement of the belt on the pulley flanges as the speed ratio between the pulleys is changed. A speed-responsive friction starting device is provided, to effect a driving connection between the driven pulley and the driven means. A selection means is incorporated to select the direction of rotation of the driven means. Such selection means may comprise a forward-reverse-neutral shifting assembly.

THE DRAWINGS

FIG. 1 is a schematic of a variable pulley drive in a low drive or idle condition;

FIG. 2 is a schematic of a variable pulley drive in a high drive condition;

FIG. 3 is a schematic of a variable pulley drive according to this invention showing its relation to the engine and the driven means;

FIGS. 4 and 4A, when placed one above the other, illustrate the transmission and hydraulic control system of this invention;

FIG. 5 is a plan view of a disc spring-finger assembly of this invention illustrating its attachment to other parts of the transmission;

FIG. 6 is a curve of the output of one of the pumps of the hydraulic control system plotted against engine RPM;

FIG. 7 is a family of curves of the output of the other of the pumps of the hydraulic control system plotted against engine RPM;

FIGS. 8 and 9 are enlarged illustrations of follow-up valve ports;

FIG. 10 is a schematic of a torque responsive pressure control assembly;

FIGS. 11, 12 and 13 are details of the driving connection of the disc spring-finger assembly and a pulley;

FIG. 14 is a detail of a valve plunger in the pressure control assembly; and

FIGS. 15 and 16 are illustations of alternative forms of final drive arrangements.

DETAILED DESCRIPTION

Attention is invited to the drawings and especially FIGS. 1 and 2 which show a variable pulley drive in two conditions, i.e., idle or slow speed condition (FIG. 1) and high speed condition (FIG. 2). The variable pulley drive designated at 20 comprises adriveR pulley 22 and adriveN pulley 24, each associated with ashaft 26, 28 respectively, and connected by a power transmission belt means 30. The belt means 30 can be a belt of an elastomer reinforced with tension members, a metal belt of connected sections, a combination metal-elastomer belt and/or the like.

ThedriveR pulley 22 comprises a pair offlanges 32, 34; one of which is drivingly connected to theshaft 26 and the other of which is arranged for limited longitudinal or axial movement with respect to the other and theshaft 26. In a like manner, thedriveN pulley 24 comprises a pair offlanges 36, 38; one of which is drivingly connected to theshaft 28 and the other of which is arranged for limited longitudinal or axial movement with respect to the other end and theshaft 28.

As will be observed from FIG. 1 of the drawings, every revolution of thepulley 22 corresponds to a partial revolution of thepulley 24 when the pulley drive is operational and in idle or low speed condition. Similarly, in the FIG. 2 showing, every revolution of thepulley 22 corresponds to multiple revolutions of thepulley 24.

FIG. 3 illustrates the transmission of this invention and its relationship to other parts of a complete drive for an automobile. The transmission comprises thevariable pulley drive 20, a prime mover ormotor 40, and avibration damper 39 of known construction located between the motor and thedriveR pulley 22 to damp out torsional vibration from themotor 40, a speed-responsive friction starting device 42 which may be a clutch either manual or automatic, a brake band or disc packs on a reaction member and the like withmeans 44 to select neutral, forward and reverse drives, and adifferential 46 through which the wheels 48 (either front or rear) of a vehicle are driven. A typical starting clutch is described in U.S. Pat. No. 3,263,782. As will be noted, theshaft 50 of themotor 40 is directly drivingly connected, through thevibration damper 39, to theshaft 26 of thedriveR pulley 22; thus when themotor 40 is operational and itsshaft 50 is rotating, thepulleys 22, 24 will also be rotating. Theshaft 28 is connected to the starting device 42 and the direction selector which in turn is connected by ashaft 52 to the differential 46. To start the vehicle, the drive from the driveN pulleys must be transmitted to thewheels 48. This is accomplished by the speed-responsive friction starting device and the direction is selected by themeans 44. In this drawing, the hydraulic control system is indicated by the numeral 52 while the final drive arrangement is noted at 54. The details of thesystem 52 and thedrive arrangement 54 will follow.

Various means may be used to bias the movable flange of each pulley toward the fixed flange thereof to ensure belt contact; for example, springs, such as disc springs and coil springs. Hydraulic means may also be used with the mechanical biasing means. The flanges can be constructed as part of a hydraulic piston and cylinder arrangement and hydraulic control means can be provided to maintain or vary hydraulic pressures. It is common practice to construct a variable pulley with centrifugally responsive weights and the like in order to change drive ratios between the pulleys as the rotational speed of the driving shaft changes. Such devices may be used in the pulley drive of this invention.

When shifting between forward and reverse, the pulleys continuously rotate in the same direction as the prime mover, so that the inertia of these parts do not have to be synchronized.

Contrast the above with the more conventional arrangement with the clutch and selector mechanism positioned between the engine and the driveR pulley. When shifting between forward and reverse drive, the direction of rotating the pulleys must be reversed and the rotation of the pulleys must be stopped to effect the reversal of the drive.

Looking at FIGS. 4 and 4A, there is illustrated the variable pulley transmission assembly which comprises thedriveR pulley 22, a driveNpulley 24 and thehydraulic control system 52.

ThedriveR pulley 22 comprises a fixedflange 32 connected to thedrive shaft 26 by a key received in a keyway 58 in theshaft 26, and snap rings 60, 62 received in grooves in theshaft 26. Because of the connection, the fixedflange 32 rotates with theshaft 26. Theshaft 26 is connected to thedrive shaft 50 of a prime mover, such as aninternal combustion engine 40. Thevibration damper 39 is connected between theshafts 50 and 26.

ThedriveR pulley 22 further comprises the axiallymovable flange 34 having ahub portion 68 surrounding theshaft 26, whichhub portion 68 has acylindrical piston portion 70 received in acylindrical member 72 closed by an end member or cover 74 to define a chamber 76 communicating viapassages 78 andslots 80 in theshaft 26 with a central, open-endedbore 82 also in theshaft 26. Thepiston portion 70 has a terminal end 84 which abuts thecover 74 when the driveR flange is in low ratio position.

A disc spring 86 (see also FIG. 5) is drivingly connected adjacent theouter rim 88 of themovable flange 34 by spaced connectingmeans 90; thespring 86 has radially inwardly projectingfingers 92, some of which are connected bypins 94 and the like to a portion of themember 72.

One end of ahollow tube 96 is received in the open-ended bore in theshaft 26 and is connected by apin 98 to a portion of thehub 68 of themovable flange 34. Thepin 98 passes throughopposite slots 80 in theshaft 26, permitting thetube 96 to be axially movable. Because of the pin connection, thehollow tube 96 as well as the entire movable flange assembly is rotatable with theshaft 26. The opposite end of thehollow tube 96 is slidably received in the block orbody 100 of a speed-responsive follow-upvalve 102 and is closed by aflanged plug 104. One or more (usually a plurality)ports 106 communicate from the outside to the interior of thehollow tube 96. Theports 106 are elongated and of varying widths; as illustrated in FIGS. 8 and 9, a preferred configuration is pear-shaped (FIG. 8); the ports can also be essentially diamond-shaped (FIG. 9) or can be provided with a tapering defining wall, to ensure a gradual flow of fluid without a surge.

Theblock 100 has a firstannular groove 108 connected to adrain conduit 110 opening to asump 112, i.e., a supply of hydraulic fluid, such as oil, and a second annular groove 114 connected to aconduit 116. Theflanged plug 104 is received in anenlarged cavity 118 in theblock 100, theflanged plug 104 limiting the relative travel between thehollow tube 96 and theblock 100. Thecavity 118 is open to thesump 112 by thedrain conduit 110.

Ashift spool 120 is connected with theblock 100 and is received in astationary block 122 of a shift spool means 124. Thespool 120 definescavities 126 and 128 on the opposite sides thereof as shown. Acoil spring 130 surrounds the connectingstem 132 of thespool 120, and the opposite ends of theblock 122 are connected toconduits 134 and 136, respectively. Theconduit 134 communicates with thecavity 126 and theconduit 136 communicates with thecavity 128.

The driveNpulley 24 comprises the fixedflange 38 connected to a driven oroutput shaft 28 by a key 142 received in akeyway 144 in theshaft 28 and snap rings 146, 148 received ingrooves 150, 152, respectively, in theshaft 28, and an axiallymovable flange 36 having an axially extendinghub 156 surrounding theshaft 28. Theshaft 28 is provided with aradially extending flange 158 to which is connected acylindrical member 160 surrounding thehub 156 and defining therewith acavity 162. Adisc spring 164 similar in construction to thespring 86 is drivingly connected at its periphery to theflange 36 and itsfingers 166 engage themember 160. In order to provide sufficient loading of theflange 36, a double or triple parallel stacked spring may be used. Theterminal end 168 of thehub 156 is exposed to thecavity 162, so that thehub 156 acts as a piston when fluid is introduced into thecavity 162. To introduce fluid into thecavity 162, theshaft 28 is axially bored at 170 and transversely bored at 172 and 174. Thebore 170 is plugged at its terminal end and aconduit 176 is connected to anon-rotatable delivery sleeve 178 surrounding theshaft 28. Anannual groove 180 in thesleeve 178 provides communication between theconduit 176 and thebores 170, 172 and 174.

Theflexible belt 30 connects thedriveR pulley 22 and the driveNpulley 24. Thebelt 30 can be constructed of metal or an elastomer material reinforced with fiberglass or other cord tension members. The belt may be covered with a nylon or other cloth. Other belt constructions may be used, if desired. Theflanges 36 and 38 of the driveNpulley 24 never abut one another because there must always be a load on thebelt 30 which is provided by the spring-finger arrangement 164 and 166 and hydraulic pressure in thecavity 162.

Thehydraulic control system 52 comprises a pair ofpositive displacement pumps 190, 192, 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 pumps may be substituted without departing from the spirit of the invention. Thepumps 190 and 192 are connected to and driven by acommon drive shaft 194 which in turn is driven from theengine 40. Thepump 190 delivers hydraulic fluid under a pressure which is engine torque responsive and will be referred to as "P", while thepump 192 delivers a hydraulic fluid under a pressure which is engine speed responsive and will be referred to as "G". Thepump 190 has suction orinlet ports 196 and 198 while thepump 192 has an inlet orsuction port 200. The suction orinlet ports 196 and 200 of thepumps 190, 192, respectively, are connected by aconduit 202 to thesump 112. The outlet of thepump 190 is connected by aconduit 204 to theconduits 116, 134 and 176, previously mentioned. An engine manifold vacuum connected and torque responsivepressure control assembly 206 is associated with theconduit 204 and thus the pressure P is controlled by engine vacuum. As the vacuum increases, theassembly 206 varies the pressure at which hydraulic fluid is bypassed to theintake port 198.

Thepump 192 delivers hydraulic fluid under a pressure related to the engine speed to theconduit 136, previously described. Ametering pin 208 registering with ametering orifice 210 is in theconduit 136. Thepin 208 is supported by a cantileveredbi-metallic arm 212. The travel of thearm 212 is limited bystops 214 and 216. A kickdown apparatus, generally identified as 218, is also associated with theconduit 136 and thus with the output of thepump 192. The kickdown apparatus 218 comprises a normally closed valve member 220 registering with anorifice 222 in theconduit 136.

The valve member 220 is supported by a cantileveredbi-metallic arm 224. The valve member 220 is resiliently urged toward thevalve orifice 222 by acoil spring 226, and thus is normally closed until thecore 228 of asolenoid 230 is energized by energizing thesolenoid coil 232 by a kickdown switch (not shown) under the control of the driver vehicle.

Thepressure control assembly 206, see especially FIG. 10, comprises amultiple part housing 240 comprising a first cup-shapedpart 242, asecond part 244, and aclosure part 246, thepart 246 being a support casting. Theparts 244 and 246 are bolted together by headedbolts 248 while thepart 242 is connected to a hose orconduit 250. Theconduit 250 is connected to its opposite end to theair intake manifold 252 of theengine 40.

Within thepart 242 and retained in position by theflanges 254 and 256 is adiaphragm 258 connected by arivet 260 at its center to a cup-shapedspring retainer 262. Therivet 260 bears against avalve operating rod 264. A second spacedspring retainer 266 is connected at the opposite end of thepart 242 and acoil spring 268 positioned between theretainers 262 and 266. Thespring 268 urges thediaphragm 258 and therivet 260 against therod 264. Thevalve operating rod 264 is slidably received in an inwardly extendingneck 270 of thepart 244.

Asecond diaphragm 272 is fixedly positioned between theparts 244 and 246 and is connected to aspring retainer 274 by arivet 276. Therivet 276 bears against therod 264. A coil spring 278 is positioned between theretainer 274 and thepart 244. The interior of thepart 244 is provided with a tube fitting 280 to which is connected a hose orconduit 282. The hose orconduit 282 is connected to a solenoid operatedvalve 284 associated with the forward-reverse shift mechanism 44.

Avalve plunger 286 which seats on avalve seat 288 is associated with theassembly 206 and controls the pressure in the output oroutlet conduit 204 from thepump 190, whichconduit 204 also connects with a conduit 290 (see FIG. 4), to a starting clutch engaging servo (not shown) as is known in the art. Thevalve plunger 286 is provided with anorifice 292 and a cross-passage 294 into which theorifice 292 opens (see detail FIG. 14). Therivet 276 bears against thevalve plunger 286, and thus theplunger 286 is always urged toward theseat 288 by the spring 278 (the plunger acting as a poppet-type relief valve under certain conditions), except when the forward and reverse mechanism is energizing thesolenoid 284 admitting vacuum into themember 244, thereby overcoming the load on the spring 278. (While this indicates a hydraulic clutch, other types of clutches may be used within the scope of the invention). Thepart 246 has avent 296 to vent one side of thediaphragm 272. In the conduit 204 (see also FIG. 4) is also anorifice 298 and ametering pin 300 controlled by a temperature-responsivebi-metallic arm 302. One side of themetering pin 300 and thevalve 286 are in theport 198 leading to the input of thepump 190. The combination of theorifice 292 and theorifice 298 generates the initial rise in the P curve of FIG. 6, which may be used to control a hydraulically controlled starting clutch as in the prior art.

FIG. 5 illustrates thespring 86 for thedriveR pulley 22 with its radially inwardly directedfingers 92. Thespring 86 is drivingly connected at spaced locations to therim 88 of thepulley flange 34 by connectingmeans 90. The means 90 is also illustrated in FIGS. 11, 12 and 13 and each comprises afront member 304 spaced from arear member 306, the members being suitably spaced and connected together.

Thefront member 304 has a threadedopening 308 to receive aset screw 310 and also anextension 312 which engages amember 314 having aprojection 316 passing through anopening 318 in therim 88. To avoid drilling holes in thefingers 92, themeans 304 is slipped over a finger, moved outwardly to the position shown and theset screw 310 is tightened to effectively connect thedisc spring 80 to therim 88.

Thedisc spring 164 for the driveNpulley 24 withfingers 166 is essentially the same construction as thespring 86 and is connected in a similar fashion to theflange 36; however, because it must exert a load on theflange 36 and thus thebelt 30 in excess of that provided by thedriveR pulley 22, thespring 164 may be stacked; for example, it may be constructed with a plurality of disc springs, each having inwardly directed fingers.

As illustrated in the drawings but not specifically described are suitable O-ring seals. These are provided where necessary and desirable.

The final drive arrangements can be as illustrated in FIGS. 15 and 16; FIG. 15 illustrating the use of asynchronizer 350 and FIG. 16 illustrating the use of a planetary gear set 352. The drive between the synchronizer and the planetary gear set and the diffeerential can be with gear trains or chains or combinations of gear trains and chains and the like.

Looking at FIG. 15, there is illustrated thesynchronizer 350. Thesynchronizer 350 comprises ashaft sleeve 354 connected to the starting clutch 42, thesleeve 354 surrounding and being connected to theshaft 28. Thesleeve 354 is provided with a central hub 356. The central hub 356 is formed with axially orientedteeth 358 engaginginternal teeth 360 of an axially shiftableclutch sleeve 362. Acircular groove 364 in theclutch sleeve 362 receives a shift fork (not shown) to axially shift theclutch sleeve 362. Surrounding theshaft sleeve 354 is a reverse gear 366 and aforward gear 368. The revese gear 366 is connected by achain 370 to agear 372 fixed to astub shaft 374 suitably supported by spacedbearings 376, 378, while theforward gear 368 meshes with agear 380 connected to thestub shaft 374. Thestub shaft 374 has agear 382 connected by achain 383 to agear 384 to drive the differential 46.

The drive between thegears 366 and 372 can be by an intermediate gear and thegears 382 and 384 can be constructed to mesh with one another if desired.

Synchronizer rings 386 and 388 are provided which frictionally engageareas 390 and 392 of therespective gears 366 and 368. Thegears 366 and 368 haveclutch teeth 394 and 396, respectively, adapted to be engaged by the teeth of theclutch sleeve 362 to provide a positive driving connection between the hub 356 and gear 366 orgear 368. Synchronizer rings 386 and 388 havegear teeth 398 and 400 thereon which are functional in the synchronizing operations as known in the art.

When forward motion is desired, theclutch sleeve 362 is moved by the shift fork, so that itsteeth 360 engage theteeth 400 of thesynchronizer ring 388 and theteeth 396 of thegear 368, thus providing a connection between theforward gear 368 and theshaft 28.

When reverse motion is desired, theclutch sleeve 362 is moved by the shift fork, so that itsteeth 360 engage theteeth 398 of the synchronizer ring 386 and theteeth 394 of the gear 366, thus providing a connection between the reverse gear 366 and theshaft 28.

Looking now at FIG. 16, planetary gear set 352 comprises ahousing 450 of multiple part construction which at one end supports theshaft 28 in abearing 452. Theshaft 28 is formed or provided with a pair of spaced sun gears 454 and 456, thesun gear 454 forming withplanet gears 458 and aring gear 460, a forward reduction drive, and thesun gear 456 forming withplanet gears 462 and aring gear 464, a reverse reduction drive. The outer perimeter of thering gear 460 receives abrake band 466 operated by the forward-reverse shift mechanism which has been omitted from FIG. 16 for the sake of clarity. When theband 466 engages thering gear 460, rotation is transmitted to anannular support 468 for the planet gears 458. A forwardly extending sleeve-like portion 470 of thesupport 468 surrounds theshaft 28 and is relatively rotatable therearound. Thesleeve 470 is formed or provided with asprocket 472 which meshes with adrive chain 474. Thechain 474 also meshes with asprocket 476 in the differential 46. A rearwardly extendingextension 478 of thesupport 468 forms thering gear 464. Asupport 480 for theplanet gear 462 has anannular surface 482 to be engaged by areverse brake band 484. Thesupport 480 also has a sleeve portion 486 surrounding theshaft 28 and relatively rotatable therearound. When the reverse band is energized, the planet gears 462 are held stationary, so that thering gear 464, the plane gears 458 and thesleeve 470 rotate in a direction reverse to that previously described. The sleeve andsprocket 470 and 472 rotate in the opposite direction than previously described so that the differential is also reversely driven.

OPERATION

With theengine 40 idling, thedriveR pulley 22 will be in the FIG. 1 relationship and rotating. The driveNpulley 24 will also be rotating, as will theshaft 28.

Thepump 190 will be operating, but due to theorifices 292 and 298 bypassing fluid to theintake ports 196 and 198, the pressure will be at a very low value. (If this pressure is used in a hydraulically controlled starting clutch, such as in U.S. Pat. No. 3,263,782, the pressure will be insufficient to overcome the retractor springs in the clutch which maintain the clutch in the release position). Thepump 192 will also be operating, but due to thefluid bypassing orifices 210 and 222, this pressure will also be at a very low value in thepassage 136 and will be unable to overcome the retractive load of thespring 130 in theshift spool 124.

Therefore, theshift spool piston 120 and the follow-upvalve body 100 will be at the fully retracted position (to the right as shown in the drawings) which opens thepassages 106 directly to thesump 112 via thegroove 108 and thepassage 110, thus maintaining zero pressure in the cavity 76 and on thedriveR pulley piston 70. Because of its hydraulic and mechanical connections, the follow-upvalve 102 is both speed and torque responsive. At this time, the piston surface 84 abuts theclosure 74 to provide a reaction for the belt loading forces developed at the driveN pulley 22 (as before stated, a load is always maintained on thebelt 30 by the driveN pulley 22).

To start, the throttle of the engine (not shown) is opened and the engine RPM increases. Thepump 190 delivers fluid pressure P in the manner indicated along the left portion of the curve (FIG. 6) which activates the automatic starting device 42. When the direction of movement of the vehicle is selected by the shift lever, theshaft 28 is connected to thedrive shaft 26 and to thefinal drive assembly 54. The vehicle then starts to move. Thepump 192 delivers even a lower pressure at this stage of operation and the pressure is still insufficient in thepassage 136 to start moving theshift spool piston 120 to the left (as viewed in the drawings). Therefore, the driveR piston cavity 76 remains at zero pressure and connected to thesump 112 until some higher RPM is reached. Theengine 40 and theshafts 26 and 28 turn together in the low drive ratio until the pressure G (see the rising portion of the pressure curve G, FIG. 7) becomes sufficient to initiate movement of theshift spool piston 120 and the follow-upvalve body 100 to admit pressure into the driveR piston chamber 76.

Movement of thepiston 120 and the pressure of the driveR piston chamber 76 on thepiston 70 initiates movement of thedriveR pulley flange 34 toward theflange 32. Movement of theflange 34 toward theflange 32 transmits additional tension to thebelt 30 and forces thedriveN flange 36 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 which changes the force on the shift spool 120) which will correct for any drift in RPM during the speed ratio change at a given torque level as additional load is placed on the engine. This results in the maintenance of a constant engine speed for a given torque level until the ratio change has been completed to the end of the travel of thedriveR pulley piston 70 at which time thedriveR flange 34 butts against thedriveR pulley flange 32.

Continued operation at this torque level results in a constant overdrive ratio and varying engine speeds related to the vehicle speed. It will be seen from the curves of FIGS. 6 and 7 that if this operation is at a 50% torque level, the opposing pressures (P) on the left-hand side of theshift spool piston 120 will be moderate and consequently only a moderate RPM will be required to attain sufficient pressure in thepassage 136 to balance the pressure on the opposite side of theshift spool piston 120 which results in a moderate engine RPM and constant engine speed operation through the ratio change phase. With increasing torque, higher values of G and higher RPM of the 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 flexibility in the power output is available.

Turning now to the follow-up valve, theannular groove 108 is connected to thesump 112 by theconduit 110 and the groove 114 is connected to thepump 190. The land betweengroove 108 and groove 114 straddles thedelivery ports 106 into thedelivery tube 96. The amount of pressure in thepassage 116 which actually is delivered to the cavity 76 and thedriveR piston 70 is the result of minute shifts in the position of the follow-upvalve block 100 in relation to the movement of thepiston 120 of theshift spool 124. A slight movement of thedriveR pulley piston 70 to the left which tends to increase the effective diameter of thedriveR pulley 22 and the position of thebelt 30, will tend to dump pressure into thesump 112 through thepassage 110 and communicate theopenings 106 with thegroove 108 and thereby nullify this initial movement. Conversely, any tendency of thebelt 30 to move down to a smaller driving diameter (with theflanges 32 and 34 moving apart) will tend to admit more line pressure to the driveR piston cavity 76 and correct for this motion, so that the result is that the pressure in cavity 76 is regulated at all times at some value less than the available pressure in theline 204, whereas the pressure on thedriveN assembly piston 168 is always directly connected to this source of pressure, i.e.,line 204, thus a load is always maintained on thebelt 30 by the driveN pulley.

The configuration of the metering pin 208 (in conduit 136) and the deflection rate of thebi-metallic leaf spring 212 is developed to produce the desired shape of pressure G (pump 192) versus engine RPM. The action of thebi-metal spring 212 with changes in oil temperature compensates for the change in oil viscosity, such that the G curve remains substantially the same over the operating range of oil temperatures. At higher temperatures thebi-metal spring 212 reaches thestop 216 after which the effective free length of the cantilever arm is reduced, so that the amount of compensation at higher temperatures is reduced in accordance with the smaller changes in oil viscosity encountered at higher temperatures. In other words, the viscosity of the oil changes quite rapidly from room temperature to 140°, but from 140° to 200° it doesn't change nearly as much. On the opposite side of thebi-metal spring 212, thestop 214 shortens the effective cantilever length of thebi-metal spring 212 to cause the governor curve G to flex upward near the higher end of the engine operating speed range, so that a strong change in governor signal is provided near the top desired operating range of the engine to avoid the possibility of overspeeding the engine. Thesecondary cantilever spring 224 and metering pin 220 is normally held closed by thesolenoid plunger 228 and itsspring 226, but when maximum performance is desired, a kickdown switch (not shown) in the throttle linkage (not shown) closes at the full throttle position or just beyond the full throttle position to energize thesolenoid windings 232 and retract theplunger 228, thereby allowing the cantilever/bi-metal spring 224 to provide an additional or auxiliary orifice and a maximum performance governor curve shown dotted in FIG. 7. The fluid then passes through both of theorifices 210, 222, and thereby increases the speed required at thepump 192 to reach the governor pressure which forces thebelt 30 into the top overdrive ratio (FIG. 2). If at a given time speed and torque condition the follow-upvalve body 100 and the position of thebelt 30 is in a certain position, operation of the kickdown switch will reduce the pressure from a solid curve to the level shown by the dotted curve, thereby reducing the force on the right-hand side of theshift spool piston 120. The follow-up valve body will move to the right and relieve pressure in the chamber 76 causing theflange 34 of the driveR pulley to move to the right. Thebelt 30 then moves towards the bottom of the driveR pulley, changing the ratio of the drive toward low drive ratio. Thespring 86 always provides a bias load on the flange of thedriveR pulley 22 to squeeze thebelt 30, but the bias load is insufficient by itself to overcome the tension of the belt produced by thedriveN flange assembly 24.

Assuming the driver of the vehicle has been cruising at a certain speed at part throttle and wishes to accelerate by opening the throttle but not to the extent of going through the kickdown, instead of changing the pressure G at thepump 192, the increase throttle causes a decrease in vacuum in thepressure control valve 206. This permits more of the spring pressure to be applied to that valve, thereby increasing the pressure to a higher level in theconduit 204 and on the left-hand side of the shift spool piston 120 (in the cavity 126). This will cause the follow-upvalve body 100 to move to the right and theports 106 will communicate to some extent with thegroove 108 and thus theconduit 110 and thesump 112.

Some of the pressure in the chamber 76 will be relieved causing a shift in the belt position towards the lower drive ratio position.

TECHNICAL ADVANTAGES

An important component of the inventive combination is a speed-responsive friction starting device, positioned to effect a driving connection between the driven pulley and the driven means. One such automatic clutch control arrangement is disclosed in the above-identified Patent No. 3,263,782. With the disclosed arrangement the input pulley is always driven at the engine speed, and both pulleys turn in the same direction. Thus pulley inertia is not a problem in the forward-reverse shift. By providing a speed-responsive friction starting device, the operational benefits of a lockup torque converter are obtained without the necessity for inserting a torque converter and a lockup clutch, but only the friction device or clutch of this invention.

While only particular embodiments of the invention have been described and illustrated, it is manifest that various alterations and modifications can be made therein. It is therefore the intention in the appended claims to cover all such modifications and alterations as may fall within the true spirit and scope of the invention.

Claims (12)

I claim:

1. In a power transmission apparatus adapted to transmit rotary motion between an engine with an engine shaft and a driven means such as the driving wheels of a vehicle and the like and having a variable rotary pulley drive unit with a driver pulley and a driven pulley connected by a belt means, each pulley having a pair of flanges, at least one flange of which is axially movable with respect to the other flange to change the spacing between the flanges and thus the speed ratio between the pulleys, and means responsive at least to the speed of the engine shaft to change the spacing of the pulley flanges and thus the speed ratio, the improvement which comprises:

means connecting said driver pulley directly to the engine shaft so that the pulleys are continuously rotated only in one direction when the motor is operating and its shaft is rotating, the continuous rotation of said pulleys when said engine is operating enchancing the shifting of the belt means on said pulley flanges when the speed ratio between the pulleys is changed;

means comprising a speed-responsive friction starting device .Iadd.responsive to the speed of the engine .Iaddend.drivingly connecting said driven pulley and said driven means; and

means to select the direction of rotation of said driven means.

2. A power transmission apparatus as recited in claim 1, where said speed-responsive friction starting device comprises a clutch.

3. A power transmission apparatus as recited in claim 2, where said means to select the direction of rotation of said driven means comprises a forward-reverse-neutral shifting device operatively associated with said starting device.

4. A power transmission apparatus as recited in claim 3, where said drivingly connecting means further comprises a synchronizer means.

5. A power transmission apparatus as recited in claim 3, where said drivingly connecting means further comprises a planetary gear set.

6. In a power transmission apparatus .[.adapted to be connected between a prime mover and a driven means, having

a variable rotary pulley drive unit and a forward-reverse gear means,

said pulley drive unit comprising a driver pulley and a driven pulley each having a pair of flanges axially movable with respect to one another to change the speed ratio between the pulleys, and a belt means connecting the driver and driven pulleys for transmitting power therebetween, the improvement comprising:

means connecting said driver pulley directly to said prime mover so as to be continuously rotated only in one direction by said prime mover during its operation;.]. .Iadd.as recited in claim 1 further comprising .Iaddend.

control means operatively associated with said .[.prime mover.]. .Iadd.motor .Iaddend.and said pulley drive unit and responsive to the operation of the .[.prime mover.]. .Iadd.motor .Iaddend.for changing the speed ratio between the pulleys.[.;.].

.[.means connecting said driven pulley to said gear means;

means connecting said gear means to said driven means; and

means to select forward, reverse and neutral drives through said gear means.]..

7. A power transmission apparatus as recited in claim .[.6.]. .Iadd.13.Iaddend., and further comprising chain means connecting said gear means to said driven means.

8. A power transmission apparatus as recited in claim .[.6.]. .Iadd.13.Iaddend., in which said gear means comprises at least one planetary gear set.

9. A power transmission apparatus as recited in claim .[.6.]. .Iadd.13.Iaddend., in which gear means comprises a synchronizer.

10. In a power transmission apparatus having a drive pulley and a driven pulley, each pulley having a pair of tapered flanges, at least one of which is axially movable relative to the other to regulate the flange spacing and correspondingly to modify the speed ratio between the pulleys, the drive pulley being driven by an engine and the pulleys being drivingly connected by a belt with the spacing between the pulley flanges of each pulley being variable to provide a variable speed drive, and a hydraulic control system operatively associated with the pulleys to vary the spacing of the flanges and including a pump providing an engine torque responsive hydraulic fluid, the improvement comprising:

a follow-up valve in said hydraulic system having a movable block to control the flow of hydraulic fluid to a piston connected to a flange of the drive pulley and connected piston operator to control the spacing of the drive pulley flanges;

an opening in said piston operator through which said hydraulic fluid flows;

said block being movable relative to said opening to control the amount of fluid to said piston;

said opening having an elongated shape with a leading portion being smaller than a trailing portion to ensure gradual flow of fluid to said piston and to reduce surges in said flow.

11. In a power transmission apparatus as recited in claim 10, in which said opening is pear-shaped.

12. In a power transmission apparatus as recited in claim 11, in which said opening is essentially diamond-shaped. .Iadd. 13. A power transmission apparatus as recited in claim 6 where said means to select the direction of rotation of said driven means comprises gear means connected to said driven pulley and to said driven means and further comprising means to select forward, reverse and neutral drives through said gear means. .Iaddend.

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