GB2139715A - Variable transmission system - Google Patents

Abstract

A transmission system having a steplessly variable transmission ratio comprises a rotary annulus member (2) with teeth (4a) on its radially inward surface. In meshing engagement with the teeth (4a) is at least one drive wheel (5) connected to a drive input or output member (6, 16). The member (2) is connected to a shaft (1) for the output or input of drive. Disposed around the member (2) is a ring member (9) which can be driven in rotation and which has a radially inward surface with at least one depression therein. Mounted in the member (2) and slidable in respective radial directions are pin members (13) which can be urged radially inwardly by the inward surface of the ring member (9) so as to impede meshing engagement between the drive wheel (5) and the teeth (4a). When the drive wheel (5) is aligned with the depression (12), the pin members (13) can be displaced outwardly so as not to impede such meshing engagement. The ring member (9), when rotated at a faster or slower speed than the member (2), thereby controls the meshing engagement of the drive wheel (5) and the teeth (4a), thus producing a selectively variably controlled planetary motion between the drive wheel (5) and the annulus member (2). <IMAGE>

Description

SPECIFICATION Variable transmission The present invention relates to a variabletransmis sion, for usefor example in a motor vehicle.

Since the energy crisis in the 1970s brought an increasing awarness ofthe consequences of profligate use of natural resources such as oil, attempts have been made to maximisethe efficiency with which such natural resources are used. With more specific reference to motor vehicles, besides engine developments directed at enhancing engine efficiency and the like, efforts have also been made to develop transmission systems which enable an internal combustion engine in a motorvehicle to operate more efficiently, for example by operating as much as possible in an engine speed range at which maximum engine efficiency and minimum fuel consumption can be more readily achieved.Thus, various transmissions have been proposed, comprising steplessly variable transmission arrangements which progressivelychangethetransmission ratio to maintain the internal combustion engine within a predetermined engine speed range, in spite of varying engine speeds.

It has been found howeverthat in many such transmission systems, the results achieved in practice are not as satisfactory as might otherwise have been expected from theoretical considerations, for example due to wear of the components, susceptibilityto fouling, and the like.

The invention seeks to provide a transmission system having a steplesslyvariabletransmission ratio with a high degree of control sensitivity.

According to the present invention, there is provided a variable transmission system comprising an annular member having e.g. a radially facing surface providing a toothed configuration; at least one drive wheel disposed eccentrically with respect to said annulus member and having a tooth configuration engaged with the tooth configuration of said annulus membertherebyto provideforplanetary motion between said drive wheel and said annulus member; an input memberforthe input of drive into the system; an output memberforthe outputof drive; and means for selectively variably arresting said drive wheel with respect to said annulus member, therebyto vary the ratio oftransmission between said input and said output members.

In a preferred aspect of the invention, the means for arresting said drive wheel comprise a ring member which is rotatably mounted around said annulus member and which has a radially inwardly facing surface closely adjacent a radiallyoutwardlyfacing surface on the annulus member, and a multiplicity of pin members which are mounted in substantially radially extending bores in said annulus member, a first end of each said pin member co-operating with the radially inward surface of the ring member and each pin member being displaceable in its said bore between a first position in which its second end is disposed within a respective recess defined by said tooth configuration of said annulus member and a second position in which it is removed from said respective recess, said radially inward surface ofthe ring member having a depression whereny, when said pin members are at said depression, said pin members can be displaced from said first position to said second position, so as not to impede planetary motion between said drive wheel and said annulus member.

The ring member is driven in rotation by any suitable means such as an electric motor, by a tapping of powertaken from the inputtothetransmission system, orthe like. When therefore the ring member is rotated in such a way that the depression in the radially inwardlyfacing surface thereof is out of alignment with the drive wheel,the pin members carried by the annulus member are held in theirfirst positions in which the second ends thereof project into the respective recesses of the tooth configuration ofthe annulus member.The pin members will thereforepreventthedrivewheelfrom engaging fully into the respective recess into which each said pin member projects, so that the drive wheel, and the output member connected thereto, wil I thus be entrained by the annulus member as it is rotated by the input of drive to the transmission system.

The depression in the radially inward surface of the ring member has smooth, inclined transitions between the depression and the adjoining generally annular portions ofthe radially inward surface ofthe ring member, and the speed of entrainment ofthe drive wheel by the annular member will depend on the angle of relative rotation as between the annulus member and the ring member. Thus, when the drive wheel is aligned with the portion ofthe depression which is of the greatest radial depth, no drive will be transmitted, whereas as the drive wheel becomes progressively misaligned with the depression in the ring member, the drive wheel and thus the output member will be entrained atan increasing speed, by virtue of the pin members applying a progressively increasing arresting action to the drive wheel.

It should be noted atthis point that, where reference is made herein to teeth or tooth configuration, that term isto be interpreted in a broad sense, and therefore includes not only for example a conventional spurgeartooth configuration of generally pointed shape, although preferably with an at least substan tiallyflattip surface, butalsotooth-likeconfigurations formed by lobes or rounded portions capable of meshing interengagement.

In a preferred embodiment ofthe invention, the transmission as generally defined above may include a sunwheel disposed concentrically with respect to the annulus member and in meshing engagement with the drive wheel. In that construction, the input drive to the transmission may rotate the sunwheel, thereby producing movement of the drive wheel and the annulus member, in the same manner as in a The drawing(s) originally filed were informai and the print here reproduced is taken from a later filed formal copy.

The claims were filed later than the filing date within the period prescribed by Rule 25(1) of the Patents Rules 1982. planetary gearing system.

Wherethetransmission system does not have a sunwheel as just referred to above, the input to the transmission rotates for example the annulus member.

However, it should be noted that, while, for automotive uses, the inputtothetransmission system will generally drive eitherthe annulus member, orthe sunwheel where provided, with a member carrying the one or more drive wheels constituting the output member, it would alternatively be possible to reverse the direction of drive, insofarasthe member carrying the one or more drive wheels could constitute the input member ofthe transmission system, with the drive output being taken off atthe annulus member, or the sunwheel where provided.

In a preferred embodiment, the transmission system will comprise at leastthree wheels to provide for satisfactory balance and smoothness of drive.

An embodiment of the transmission system according to the present invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows a side view of the transmission system, in cross-section taken along line I-I in Figure 2, Figure la shows a viewsimilarto that of Figure 1, of part of a modified construction, Figure 2 shows a front view of the transmission system shown in Figure 1, viewing from the righthand side in Figure 1, and Figure 3 shows an alternative form of tooth configuration forthe transmission system illustrated in Figures 1 and 2.

Referring first to Figures 1 and 2, shown therein is a diagrammaticviewofa steplesslyvariabletransmission system comprising an input shaft 1 which can be connected to any suitable power source such as an internal combustion engine, although otherforms of drive may be envisaged according to operating circumstances, such as an electric motor. The input shaft 1 is fixedly connected to a rotary annulus member generally indicated at 2 and comprising a disc portion 3 and an annular edge portion 4which extends substantially axially relative to the shaft 1 and thus relative to the axis of rotation ofthe annulus member 2.The radially inwardlyfacing surfaceofthe edge portion 4 has a plurality of recesses therein, defining atooth ortooth-like configuration 4a, the term tooth in this context being interpreted broadly, as referred to above. The edge portion 4 therefore generally corresponds to the annulus in a planetary gearing system. Disposed within the edge portion 4 of the annulus member 2 and adjacentthe disc portion 3 is at least one drive wheel 5, as shown two,which have a tooth configuration in meshing engagement with the tooth configuration on the radially inwardlyfacing surface ofthe edge portion 4ofthe annulus member 2.

In pracical use,thetransmission system will generally comprise at leastthree drive gears as at 5, and possibly more, depending on the operating conditions, loads to be carried, required smoothness of drive, and the like. The or each drive wheel 5 is rotatablycarried byanoutputmemberwhich is illustrated in the form of a disc 6 rotatably about an axis corresponding to the axis ofthe input shaft 1.

Although the input shaft 1 is illustrated as terminating at the disc portion 3 ofthe annulus member 2, the input shaft 1 could be extended axially further to the right in Figure 1 ,to provide a suitable mountingforthe disc 6 which would therefore be rotatably journalled thereon. The disc 6 will provide means for connecting an output shaft or the like thereto, to take the drive from the transmission system.

The transmission system further comprises an arran.gementforselectively variably arresting relative planetarytnotion as between the drive gears5 and the annulusmember2. In the embodiment illustrated, such means comprise a rotatablysupported ring memberg;enerallyindicated at 7 and again comprises ing a discffirtion 8 and an axially extending annular edge portibn'9 which therefore extends over and around the edge portion 4 ofthe annulus member2, as can be most dbaitly'seenfrom Figure 1.The disc portion 8 ofthenng.member7 has a central aperture 1 whereby the member 7 is rotatablyjournalled on the input shaft 1asby a ball bearing assembly.

The radially inward surface ofthe annular edge portion 9 ofthe ring member 7 provides a control track 11 which, when the transmission system has two drive gears 5, is ofthe general configuration illustrated in Figure 2. More specifically, the track 11 on the radially inwardlyfacing surface of the edge portion 9 is at least substantially circular over a substantial part of the peripheral extent of the edge portion 9, but also includes first and second diametricallyoppositely disposed depressions as indicated at 12 in Figure 2.

Wherethetransmision system has a different number of drive gears from that illustrated, the track 11 on the ring member7 will also have a corresponding number of depressions 12.

Itwill be noted from theview shown in Figure2that the drepressions 12 are each of a smoothly curved configuration, thus providing a gentle transition from the adjoining circular portions ofthe track 11 on the member 7, as will be clear hereinafter.

The meansforselectivelyvariably arresting the drive gear or gears 5 relativetothe annulus member 2 furthercomprises a plurality of pin or pin-like mem bers, only someofwliich are with illustrated at 13 in Figures 1 and 2. As will be seen more clearlyfrom Figure 2, each pin member 13 illustrated is of a headed.

configuration with a-eounded head, and is mounted slidably in a bore ofwhiehtwo are illustrated in broken lines in Figure 2, atT4 extending at leastsubstantially radially through the edge portion 4 ofthe annulus member 2. Each bore 14 opens, at its inwardend, at least substanUfyatThe bottom of a respective recess defined by thetooth configuration 4a on the radially- inward surfaceofthe edge portion 4. Eachrecess defined by the tooth configuration 4a may have apin member 13 associated therewith, although it may be found satisfactory for example for everyother recess to have a pin member 13 or for each third recessto have a pin member 13, orthe like, dependingon the operating conditions and requirements of thetrans mission system.

It will be seen from Figure 2 thatthe pin members 13 are of such a length that, when the heads thereof rest against the radially outward peripheral surface ofthe edge portion 4, the other, inward, ends ofthe pin members 13 project into the respective recesses defined bythetooth configuration 4a on the edge portion 4. It will be seen therefore that, with the pin members 13 in that position, the associated drive gear 5 ca n not come into meshing engagement with the tooth configuration 4a on the annulus member 2, being prevented from doing so by the inwardly projecting portions of the pin members.

Looking still at Figure 2, it will be seen that, at positions adjoining the respective depressions 12 in the ring member,the pin members 13 are illustrated in positions in which the heads thereof are moved away from the radially outward surface of the annulus member 2, byvirtue ofthe pin members 13sliding radially outwardly in their respective bores, as their heads move into the respective depressions 12. In operation of the system, it will be appreciated that the pin members 13 will tend to move intotheirradially outwardly displaced position by virtue of centrifugal force, as the annulus member2 rotates.

The mode of operation of the above-described transmission system is as follows: When the shaft 1 is set in rotation by a suitable drive means, it rotates the annulus member2 within the ring member 7 and around the assembly comprising the drive gears Sand the output member 6carrying the drive gears 5. In the position shown in Figure 2, with the drive gears 5 aligned with the respective depressions 12 in the member 7, the pin members 13 are free to be displaced outwardly into the respective depressions 12 and therefore do not impede engagementals between the teeth of the annulus member 2 and the drive gears 5.The drive gears Swillthus rotate freely abouttheirspindles mounting them on the output member 6, and the output member 6 will therefore generally not rotate, anytendencyto rotation thereof due to friction in the various components being resisted by the load to which the output member 6 is connected. Thattherefore represents the idle condition ofthe transmission system.

In order now to cause the drive to the input shaft 1 to be transmitted through the transmission system to the output member 6, the ring member 7 is driven in rotation, and is thus displaced relative to the annulus member 2, by any suitable means, such as an electeic motor, as diagrammatically indicated at 15 in Figure 1, with drive shaft and pinion. Such rotary movement causes the ring member7 to move its depressions 12 partially out of alignment with the respective drive gears 5. That means that, although the pin members 13 can still be displaced outwardly into the respective depressions 12, the positions, in regard to the peripheryoftheannulus member 2, atwhich such outward movement ofthe pin members 13 occurs, are displaced relativetothe gears5.In consequence, as some pin members 13, at positions corresponding to the positions of the drive gears 5 in the annulus member 2, are held in an inwardly displaced position in which their inward ends project inwardly into the recesses defined by the tooth configuration 4a of the annulus member 2, the drive gears 5 are prevented from moving into full meshing engagementwiththe respective recesses of the tooth configuration 4a, and will thus be entrained by the annulus member 2 as it is rotated by the input shaft 1.It will be seen therefore thatthespeed atwhichthe ring member7 is rotated and thus its rotational position relative to the annulus member 2 will govern the extent to which the drive gears 5 are prevented from freely meshing with the tooth configuration 4a on the annulus member 2, until, in the limit position, when the ring member 7 is rotating at the same speed as the annulus member 2 but with the respective depressions 12 in the control track 11 totally out of alignment with the drive gears 5, the drive gears Sand thus the output member 6will be rotated, as a unit, atthe same speed as the annulus member 2 and the input shaft 1. The transmission ratiowill be 1:1 in that condition ofthetransmission system.It will be seen therefore that the transmission system can be steplessly adjusted to give a steplessly variable transmission ratio, by virtue of controlling the relative positions of the respective depressions 12, with respectto the adjoining drive gears 5.

In an alternative embodiment, as shown in Figure 1a,the input shaft 1, instead of being connected directly to the annulus member 2, could be connected to a sunwheel 16 which is therefore disposed within and operatively engaged with the drive gears 5. The annulus member 2 could then be suitablyjournalled on the input shaft 1, in the same mannerasthe ring member7 is journalled on the input shaft 1.The transmission system in this modified form wouldthen operate in substantially the same manner as described above, with the rotary input movement ofthe drive shaft 1 being transmitted through the rotating sunwheel 1 6to the drive gears 5 and thus to the annulus member 2, with the transmission ratio being suitably controlled by relative rotary displacement of the ring member 7.

It should be noted here that the above-described transmission system is 'self-starting', insofar as the pin members 13 are automaticallythrown outwardly into contact with the track 11 defined by the radially inwardly facing surface of the edge portion 9 ofthe ring member7, by centrifugal force as soon as the annulus member 2 begins to rotate. The transmission will only become operativeto transmitdrive however, when the ring member 7 is rotated, as referred to above.

In practice, the entire assembly illustrated will generally be surrounded by a suitable casing and the assembly would preferably run in a suitable oil bath in the casing, to minimise wear and also noise. The ring member7 may be driven in rotation by an electric motor 15, as referred to above, controlled for example by a rheostat or other suitable control means, to provide progressive and controlled variation in the speed of rotation of the electric motor and thus the ring member7, to give control of the transmission ratio ofthesystem. In an automotive use however, the driveforthe ring member7 or control member could be taken from the drive input, as at the input shaft 1, with a suitable control arrangement interposed between the input shaft 1 and the actual drive on the member 7, controlled for example by the driver ofthe vehicle. Alternatively, the drive to the ring member 7 could be controlled in dependence on the speed of engine rotation, as by a governor arrangement orthe like, to ensure that the transmission ratio ofthe system is always so set as to permit the internal combustion engine to operate at its most effective speed or at least in its most effective engine speed range.

Itwould be possible, in a similar manner to a planetary gearing, Cor the transmission system to be designed to be operated in the reverse manner two that described above, in which casethe member6would constitute the input member and the drive would be taken off atthe shaft 1. In other respects, the mode of operation ofthe transmission system in that situation would bethe same as described above with reference to the drawings.

The illustrated construction has the advantage of simplicity in regard to the manner of mounting and the mode of operation of the pin members 13 insofar as they are simply mounted displaceably in suitable bores in the annulus member 2, the head on the radially outward end of each pin member 13 preventing the pin member from dropping into the centre of the assembly and the pin members being displaced outwardly by centrifugal force as the assembly ofthe annul us member2 and the pin members is rotated.It would alternatively be possible however to provide a form of spring means, as indicated in highly diagrammaticform in Figure 2 bya spring ring portion 17, for urging the pin members radially outwardly into their positions of co-operation with the track 11 1 on the radially inwardly facing surface ofthe edge portion 4 ofthering member7althoughthatwould beatthe cost of complicating the assembly.

Referring now to Figure 3, shown therein is an alternative form of the tooth configuration 4a for constituting the recesses and projections on the radially inward surface of the annulus member2 and on the gears 5. The tooth configuration illustrated would tend to be smoother in operation than a conventional involute-type gear configuration, and the lobar-type configuration shown in Figure 3 could be even more rounded, with the radially outwardly disposed portion of each tooth on the gearwheel 5 being even more enlarged, in the peripheral direction, thantheform shown in Figure 3. Itwill be appreciated thatthe precise nature and configuration ofthe teeth ofthe respective tooth configurations will be adapted to the conditions of operation ofthe systems.

Similarly, the precise configuration of each of the depressions 12 will be adapted to the conditions of operation ofthe system, for example the depression may have a gently inclined surface at its entry end, being the surface which leads the pin members 13 into the deepest part of the depression 12, and a more abrupt exit surface, or equally inclined surfaces on both sides of the depression, with a smooth transition between the depression and the adjoining circular portions ofthe track 11 defined by the radially inward surface ofthe ring member 7. Purely by way of example, an angle of inclination ofthe entry surface, relative to the peripheral direction ofthetrack 11, of around 8 , has been found to give satisfactory drive results, in a small-scale assembly constructed as a test model.It is thought, although this is not a definitive view at this time, thatthe sine ofthe angle of the entry ramp surface govern the power required to control the transmission system by the rotary motion ofthe ring member 7.

In a modified embodiment, instead of the pin members 13 projecting through the annulus membere 2 in such a way asto engage intothe bottom of the respective recesses of the tooth configuration 4a, the pin members could emerge at, or at least substantially at, the crown of the respective teeth 4a, to produce the same operational effect as described above.

In yetanother modified embodiment, itwouldbe possible forthe annulus member which is disposed around the outside of the drive gears 5 in the illustrative embodiments to be disposed at a position in which it is within the drive gears 5,therefore having its tooth configuration on its radially outwardly facing surface and engaging the drive gears attheir radially inward portions. ltwouldappearhoweverthatsuch an assemblywould be additionally complicated, by virtueoftheneedtoprovidespring meansorsuitable guide means for displacing the pin members radially inwardly into co-operation with the track defined by the ring member7, which would equally have to be disposed inside the tooth annulus member. While such a construction is thought to be theoretically viable, it might encounter difficulties in practical execution.

Various modifications and alterations may be made in the constructions described above and illustrated by way of example; thus, the tooth configuration on the annulus member need not be on a radiallyfacing surface, but could be onforexample an axiallyfacing surface, with suitable consequential design alterations in the other components.

Claims (16)

1. Avariabletransmission system comprising an annulus member having a surface providing a tooth configuration; at least one drive wheel disposed eccentrically with respect to the annul us member and having a tooth configuration engaged with the tooth configuration ofthe annulus membertherebyto providefor planetary motion between the drive wheel and the annulus member; an input memberfor the input of drive into the system; an output memberfor the output of drive; and means for selectively variably arresting said drive wheel with respect to said annulus memberthereby to vary the ratio oftransmission between said input and output members.

2. A system according to claim 1 wherein said means for selectively variably arresting said drive wheel includes a ring memberwhich is rotatable around said annulus member and which has a radially inwardly facing surface adjacent a radially outwardly facing surface of the annulus member, and a multiplicits or arresting means co-operable with the radially inward surface ofthe ring member and capable of being selectively displaced radially inwardly into a position such asto impede full engagement between the tooth configurations of said annulus member and said drive wheel, said radially inward surface ofthe ring member having a depression therein whereby, when said arresting means are at said depression, said arresting means are displaceable outwardly so as notto impede said full engagement between the tooth configurations of said annulus member and said drive wheel.

3. Asystem according to claim 1 wherein said means for selectively variably arresting said drive wheel includes a ring member which is rotatable around said annulus member and which has a radially inward surface adjacent a radially outward surface of the annulus member, and a multiplicity of pin members mounted in respective substantially radially extending bores in said annulus member, a first end of each said pin member being co-operable with the radially inward surface of the ring member and each pín member being displaceable in its said bore between a first position in which its second end is capable of impeding full engagement between the tooth configurations of said drive wheel and said annulus member and a second position in which it is not capable of impeding saidfull engagement, said radially inward surface of the ring member having a depression therein whereby, when said pin members are at said depression, said pin members are capable of being displaced from said first position to said second position.

4. Asystem accordingtoclaim 20rclaim3 wherein said ring member is rotatable by power drive means.

5. Asystem according to claim4whereinsaid drive means comprises an electric motor.

6; System according to claim 4wherein said drive means includes a meansfortapping power from the input to the transmission system.

7. A system according to anyone of the preceding claims wherein said tooth configurations are of a spur gear-like configuration.

8. Asystem according to anyone of claims 1 to 6 wherein said tooth configurations comprise lobes or rounded portions capable of meshing interengagement.

9. A system according to any one ofthe preceding claims and including a sunwheel disposed concentrically with respectto the annulus member and in meshing engagement with the drive wheel.

10. A system according to any one ofthe preced- ing claims wherein said input member is connected to the annulus memberfor producing rotary drive movement thereof.

11. A system according to any one ofthe preceding clairns and including a pluralityofsaid drive wheels;

12. Asystem accordingto claim 11 and including at leastfourdrive wheels.

13. Asystem according to cilaim 2 orclaim 3 or any claim.appendantto claim 2 or claim 3 wherein the or eachsaid depression has inclined surface portions at its respective ends at which it has the transition to the adjoining portions ofthe radially inward surface of the ring member, the angles of inclination of said inclined surface portions being adapted to the conditions of operation of the system.

14. A system according to claim 1 wherein said surface of said annulus memberthat provides said tooth configuration is an at least substantially axially facing surface.

15. Avariabletransmissionsystem substantially as hereinbefore described with referenceto Figures 1 and 2, or Figure 1 a, or Figures 1 and 2 or Figure 1a as modified by Figure 3.

16. In a motor vehicle, a variable transmission system according to any one of the preceding claims.