GB2373034A - Pressure chamber seal for a cone pulley gearbox - Google Patents

Abstract

A cone pulley belt contact gearbox with a first pair 1 of cone pulleys 1a, 1b and a second pair 2 of cone pulleys 2a,2b each with an axially displaceable 1a,2a and an axially fixed 1b,2b cone pulley and a contact means 3 mounted for torque transfer between these pairs of cone pulleys. A pressure chamber 110 is sealed by a seal which has an elastic sealing ring 401 and a substantially shape stable ring element 402. The elastic sealing ring 401 may be positioned both inside or outside the substantially shape stable ring element 402. A coil spring that tapers and widens is also disclosed (figs 2-4).

Description

GEARBOX

The invention relates to a gearbox such as an infinitely variable cone pulley belt contact gearbox with a first pair of cone pulleys and a second pair of cone pulleys each with an axially displaceable and an axially fixed cone pulley and a belt contact means mounted for torque transfer between these pairs of cone pulleys, with at least one energy accumulator mounted actively between an axially fixed element and an axially displaceable cone pulley.

Gearboxes of this kind are known for example from DE OS 195 44 644. With these gearboxes a coil spring such as a compression spring is used for example to produce pretension between an axially fixed element and an axially displaceable cone pulley.

With these types of gearboxes when fitting a cylindrical spring it can often lead to individual windings of the spring escaping radially outwards through the high axial biasing of the spring and to these individual windings jamming between the axially movable cone pulley and the axially fixed element. This leads to a considerable impairment in the functioning of the gearbox.

According to the invention there is provided a continuously variable cone pulley belt contact gearbox with a first pair of cone pulleys and a second pair of cone pulleys each with an axially displaceable and an axially fixed cone pulley and a contact means mounted for

torque transfer between these pairs of cone pulleys, with at least one pressure chamber, characterised in that the pressure chamber is sealed by a seal which has an elastic sealing ring and a substantially shape stable ring element.

It is advantageous if the elastic sealing ring is mounted radially inside the substantially shape stable ring element, but it can also be mounted radially outside of the substantially shape stable ring element.

An energy accumulator can be mounted actively between an axially fixed element and an axially displaceable cone pulley, which energy accumulator has a cross-section which deviates from a cylindrical shape and has a cross-section which tapers in a first axial area and widens out again in a second axial area.

In the event of severe axial biasing of the energy accumulator, the energy accumulator is deformed so that the windings are placed radially inwards against an attachment of the axially displaceable cone pulley and do not move radially outwards and jam or block individual component parts of the gearbox.

It is expedient if the energy accumulator is a compression spring or coil spring with individual windings wherein at least the axially outer windings have a larger radius in the radial direction than at least individual windings mounted axially further inwards.

It is likewise advantageous if the cross-section of the energy accumulator has a double cone like contour. The cross-section can also have a double frusto-conical shape.

It is also expedient in a further embodiment if the axially fixed element and/or the axially movable cone pulley has a socket in which windings in the end areas of the energy accumulator are housed and supported radially outwards.

It is advantageous if the socket is formed in the axially displaceable cone pulley as a circumferential groove which is enclosed radially by an attachment and in which at least one winding in the end area of the energy accumulator is housed whereby the winding is supported radially outwards on the attachment and is supported in the axial direction on the cone pulley.

It is expedient if the socket of the axially fixed element supports at least one winding of the energy accumulator in the end area of the energy accumulator in the radial direction outwards and in the axial direction.

The invention will now be further explained by way of example with reference to the accompanying drawings, in which: Figure 1 is a sectional view through a gearbox, such as a cone pulley belt contact gearbox, shown in part;

Figure 2 is a section of a pair of cone pulleys ; Figure 3a shows a cut our section of Figure 2 ; Figure 3b shows a cut out section of Figure 2; Figure 4 shows a cut out section of an energy accumulator Figure 5a shows an illustration of a sealing ring and Figure 5b shows an illustration of a sealing ring.

The variation of an embodiment of a cone pulley belt contact gearbox shown in part in Figure 1 has a pair 1 of pulleys on the drive side mounted rotationally secured on the drive shaft A and a pair 2 of pulleys mounted rotationally secured on the output shaft B. Each pair of pulleys has an axially movable disc part la and 2a and an axially fixed disc part Ib and 2b. A belt contact means in the form of a chain 3 is provided between the two pairs of pulleys for torque transfer.

In the upper halves of the relevant illustration of the corresponding pairs of pulleys 1, 2 is shown the relative axial position between the corresponding disc parts la, Ib and 2a, 2b which corresponds to the maximum transmission ratio in underdrive whilst in the lower halves of these illustrations is shown the relative position between the correspondingly associated disc parts la, Ib and 2a, 2b respectively which corresponds to the maximum transmission

ratio in overdrive.

The pair of pulleys 1 can be axially rensioned through a setting member 4 which is formed as a piston cylinder unit. The pair 2 of cone pulleys can be tensioned axially against the chain 3 in a similar way through a setting member 5 which is likewise formed as a piston cylinder unit. An energy accumulator 7 which is formed by a coil spring is provided in the compression chamber 6 of the piston cylinder unit 5 and urges the axially movable disc part 2a in the direction of the axially fixed disc part 2b. If the chain 3 is located on the output side in the radially inner area of the pair 2 of pulleys 2 then the tensioning force applied by the energy accumulator 7 is greater than if the chain 3 is located in the larger diameter range of the pair 2 of pulleys. This means that as the gear transmission ratio increases into overdrive the pretensioning force applied by the energy accumulator 7 also increases. The coil spring 7 is supported on one side directly on the axially movable disc part 2a and on the other side on a pot-shaped component 8 which defines the pressure chamber 6 and is rigidly connected to the output shaft 3.

A further piston/cylinder unit 10,11 is provided each time in active parallel connection with the piston cylinder uniras 4,5 to serve to change the transmission ratio of the gearbox. The pressure chambers 12,13 of the piston cylinder units 10,11 can be filled with pressurised medium or emptied alternately according to the transmission ratio required. To this end the pressure

chambers 12, 13 can according to requirements etcher be connected to a pressurised medium source, such as a pump or however to an outlet pipe. with a change in. the transmission ratio one of the pressure chambers 12,13 is filled with pressurised medium, thus its volume is increased, whilst the other pressure chamber 13,12 is emptied at least in part, thus its volume is reduced.

This alternate pressure biasing and emptying of the pressure chambers 12,13 can be carried out by means of a corresponding valve. With regard to the design and functioning of a valve of this kind reference is made in particular to the prior art already quoted. Thus for example with DE OS 40 36 683 a valve 36 is provided which is designed as a square slider and is fed with a pressurised medium source 14 formed as a pump.

In order to produce a pressure which is at least dependent on moment a torque sensor 14 is provided which is based on a hydro-mechanical principle. The torque sensor 14 transfers the torque introduced through a drive gearwheel or drive pinion 15 to the pair 1 of cone pulleys. The drive gearwheel 15 is mounted by a rolling bearing 16 on the drive shaft A and is connected rotationally secured through keyed connection or teething 17 to the cam disc 18 of the torque sensor 14 which is also supported axially on the drive gearwheel 15. The torque sensor 14 has the axially fixed cam disc 18 and an axially displaceable cam disc 19 which each have run-up ramps between which expanding bodies are provided in the form of balls 20.

The cam disc 19 is axially displaceable on the drive shaft A but is rotationally secured relative to same. To this

end the cam disc 19 has a radially outer area 19a pointing away axially from the balls 20 and supporting teething 19b which interact with counter teething 21a of a component part 21 which is connected to the drive shaft A both axially and circumferentially fixed. The teeth 19b and counter teeth 21a are formed relative to each other so that an axial displacement between the component parts 19 and 21 is possible.

The component parts of the torque sensor 14 define two pressure chambers 22,23. The pressure chamber 22 is restricted by a ring-shaped component part 24 rigidly connected to the drive shaft A and by areas or component parts 25,26 formed or supported by the cam disc 19. The ring-shaped pressure chamber 23 is mounted practically radially outside of the ring-shaped pressure chamber 22 but axially off-set relative to the latter. The second pressure chamber 23 is likewise defined by the ring-shaped component part 24 and by the sleeve-like component part 21 fixedly connected to the latter and further by the ringshaped component part 25 fixedly connected to the cam disc 19 and which is axially displaceable and acts like a piston. The ring-shaped component part 24 is connected rotationally secured to the shaft by internal teeth and external teeth on the shaft A and is supported in the axial direction of the nut 90.

The input shaft A supporting the torque sensor 14 and the pair 1 of cone pulleys is mounted in a housing 30 on the torque sensor side through a needle bearing 27 and on the side of the pair 1 of cone pulleys remote from torque

sensor 14 through a ball bearing 28 taking up the axial forces and a roller bearing 29 provided for the radial forces. The output shaft B holding the pair 2 cf output pulleys is mounted in the housing 30 at its end adjoining the setting members 5 and 11 through a double cone roller bearing 31 which absorbs both radial forces and the axial forces which occur in both axial directions, and on the side of the pulley pair 2 remote from the setting members 5,11 through a roller bearing 32. The output shaft B supports at its end remote from the setting members 5, 11 a bevel gear wheel 33 which is in active connection for example with a differential.

In order to produce the pressure which is modulated at least in dependence on moment through the torque sensor 14 and which is required for tensioning the cone pulley belt contact gearbox a pump 34 is provided which is connected to the pressure chamber 22 of the torque sensor 14 through a central channel 35 formed in the drive shaft A and opening into at least one radial channel 36. The pump 34 is further connected by a connecting pipe 37 to the pressure chamber 6 of the piston cylinder unit 5 on the second pair 2 of pulleys. The connecting pipe 37 opens into a central channel 38 which is provided in the output shaft B and which is connected to the pressure chamber 6 in turn through at least one radially aligned channel 39.

The pressure chamber 22 of the torque sensor 14 is connected to the pressure chamber 9 of the piston cylinder unit 4 through the channel 40 which is circumferentially off-set relative to the section according to Figure 1 and

is therefore shown in broken lines. The channel 40 is formed in the ring-shaped component part 24 which is rigidly connected to the shafu A. Thus a connection is always provided through the channel 40 between the first pressure chamber 22 and the pressure chamber 9. Furthermore at least one outflow channel 41 is provided in the drive shaft A and is or can be brought into connection with the pressure chamber 22 whereby its outflow crosssection can be changed in dependence on at least the torque transferred. The outflow channel 41 opens into a central bore 42 of the shaft A which can be connected in turn with a pipeline through which the oil flowing out of the torque sensor 14, e. g. for lubricating the component parts can be directed to the corresponding spot. The axially movable ramp or cam disc 19 which is mounted axially displaceable on the drive shaft A forms with the inner area 26a a closing area which interacts with the outflow channel 41 and which can close the outflow channel 41 more or less in dependence on at least the ensuing torque. The closing area 26a thus forms in connection with the outflow channel 41 a valve or throttle point. The outflow opening or outflow channel 41 is opened or closed accordingly at least in dependence on the torque ensuing between the two discs 18,19 through the disc 19 which acts as a control piston whereby a pressure corresponding at least to the ensuing moment and applied by the pump 34 is produced at least in the pressure chamber 22. Since the pressure chamber 22 is connected to the pressure chamber 9 and also through the channels or pipelines 35, 36, 37, 38 and 39 to the pressure chamber 6 a corresponding pressure is also produced in these

chambers 9, 6.

As a result of me parallel connection between the piston cylinder units 4,5 and the piston cylinder units 10, 11 the forces produced by the pressure supplied by the torque sensor 14 on the axially displaceable discs la, 2a are added to the forces which act on these discs la, 2a as a result of the pressure existing in the chambers 12,13 for setting the transmission ratio of the gearbox.

Supplying the pressure chamber 12 with pressurised medium is undertaken through a channel 43 which is provided in the shaft A and which is connected through a radial bore 44 to a ring groove 45 formed in the shaft A. At least one channel 46 formed in the ring shaped component part 24 extends from the ring groove 45 and produces a connection with the radial port 47 formed in the sleeve like component part 21 and opening into the pressure chamber 12. In a similar way the pressure chamber 13 is also supplied with oil, namely through the channel 48 which is placed round the channel 38 and communicates through radially aligned connecting channels 49 with the pressure chamber 13. The channels 43 and 48 are supplied from a common pressure source through the interposition of at least one valve 50 through connecting lines 51,52. The pressure source 53 which is connected to the valve 50 or valve system 50 can be formed by a separate pump or can however also be through the already existing pump 34 whereby then a corresponding volume or pressure distribution system 54 is required which can comprise several valves. This alternative solution is shown in

broken lines.

The pressure chamber 23 which in the event of pressure biasing is switched actively in parallel with the pressure chamber 22 is separated from a pressurised medium supply in the relative position of the individual component parts shown in the upper half of the illustration of the pair 1 of cone pulleys, namely because the channels or bores 55, 56,57, 58,59, 60 connected to the pressure chamber 23 are not connected with a pressurised medium source such as in particular the pump 34. As a result of the position of the axially movable disc la the radial bore 60 is fully opened so that the chamber 23 is fully relaxed pressurewise. The axial force exerted by the torque sensor on the cams or cam disc 19 as a result of the torque to be transferred is only taken up by the pressurised oil cushion building up in the pressure chamber 22. The pressure arising in the pressure chamber 22 is thereby higher the greater the torque to be transferred. This pressure is as already mentioned controlled through the areas 26a and the outflow bore 41 which acts as a throttle valve.

With a change of transmission ratio into overdrive the cone disc la is moved to the right towards the cone disc lb. This causes on the pair 2 of cone pulleys the cone disc 2a to be axially removed from the axially fixed cone disc 2b. As already mentioned in the upper halves of the illustrations of the pairs of cone pulleys 1, 2 the relative positions between the discs la, Ib and 2a, 2b are shown which correspond to the extreme position for a

transmission ratio in underdrive whilst in the lower halves of these illustrations the relative positions are shown between r-he corresponding discs la, Ib and 2a, 2b which correspond to the other extreme position of the discs la, lb and 2a, 2b relative to each other for a transmission ratio in overdrive.

In order to change from the transmission ratio shown in the upper halves of the illustrations of the pairs 1,2 of cone pulleys into the transmission ratio shown in the corresponding lower halves the pressure chamber 12 is filled accordingly through corresponding control of the valve 50 and the pressure chamber 13 is emptied or reduced in volume correspondingly.

The axially movable cone discs la, 2a are each coupled rotationally secured by a connection 61,62 through teeth with the associated shaft A or B. The rotationally secured connections 61,62 formed by internal teeth on the discs la, 2a and external teeth on the shafts A and B allow an axial displacement of the discs la, 2a on the corresponding shaft A, B.

The position of the axially movable disc la and chain 3 shown in chain-dotted lines in the upper half of the illustration of the driving pulley pair 1 corresponds to the highest possible transmission ratio of the gearbox in overdrive. The illustration of the chain 3 of the pulley set 2 shown in solid lines is associated with the position of the chain 3 of the pulley set 1 shown in chain-dotted lines.

The position of the axially displaceable cone disc 2a and chain 3 shown in chais-dozed lines in the lower half cf the illustration of the driven pulley set 2 corresponds to the maximum possible transmission ratio of the gearbox in underdrive. The position of the chain shown in solid lines in the upper half of the illustration of the first pulley set 1 is associated with this position of the chain 3.

With the illustrated embodiment the discs la, 2a have radially inside centring areas 63,64 and 65, 66 respectively through which they are housed or centred directly on the corresponding shaft A and B respectively.

The guide areas 63,64 of the axially displaceable disc la housed practically free of play on the sleeve face of the shaft A form in connection with the chains 59, 60 valves wherein the disc la serves in practice as a valve slider in relation to the channels 59, 60. With a displacement of the disc la to the right from the position shown in the upper half of the illustration of the pulley set 1, after a certain travel stretch the channel 60 is gradually closed by the guide area 64 with an increasing axial path of the disc la. This means that the guide area 64 comes to lie radially above the channel 60. In this position the channel 59 is also closed radially to the outside by the cone disc la, namely through the guide area 63. With a continuation of the axial displacement of the disc la in the direction of the disc lb the channel 60 remains closed whilst the disc la or its control and guide area 63 gradually opens the channel 59. A connection is thereby

produced through the channel 59 between the pressure chamber 9 of the piston cylinder unit 4 and the channel 58 whereby in curn a connection is made with the pressure chamber 23 through the channels 57,56 and 55. Since the channel 60 is practically closed and now a connection is provided between the pressure chamber 9 and the two pressure chambers 22 and 23 practically the same pressure is set in the two pressure chambers 22,23 and in the pressure chamber 9 and thus also in the chamber 6 which is in active connection with these through the channel 35 and the pipelines 37, 38-apart from the slight losses which possibly exist in the transmission path. Through the connection between the Two pressure chambers 22 and 23 which is dependent on the transmission ratio the axially active surface of the pressurised medium cushion present in the torque sensor 14 ras been increased, namely because the axially active faces of the two pressure chambers 22, 23 are added together action-wise. This increase in the axially active support face causes in relation to an identical torque the p-essure built up by the torque sensor to be reduced in practice proportional to the increase in surface which means in turn that a correspondingly reduced pressure also occurs in the pressure chambers 9 and 6. Thus by means of the torque sensor 14 according tc the invention a transmissiondependent modulation of he pressure can also be produced which is superimposed on the torque-dependenu modulation of the pressure. The torque sensor 14 illustrated allows in practice a wo-stage modulation of the pressure or pressure level.

With the illustrated embodiment the two channels 59, 60 are arranged and formed relative to each other and to the areas 63,64 of the disc la interacting therewith so char- the change-over from the one pressure chamber 22 to the two pressure chambers 22 and 23 and vice versa takes place at a transmission ratio of about 1: 1 of the cone pulley belt contact gearbox. As already indicated, however such a change-over cannot take place suddenly as a result of the structural design so that there is a transition area where the outflow channel 60 is indeed already closed whilst the connecting channel 59 still does not have any connection with the pressure chamber 9. In order to ensure in this transition area the functioning of the gearbox or of the torque sensor 14 for which an axial displaceability of the cam disc 19 must be ensured, compensating means are provided which allow the pressure chamber 23 to change its volume so that the torque sensor 14 can pump which means that the cylinder component parts and the piston component parts of the torque sensor 14 can move axially relative to each other. With the illustrated embodiment these compensating means are formed by a tongue or lip seal 67 which is housed in a radial groove of the ring-shaped component part 24 and interacts with the inner cylinder face of the component part 25 in order to seal the two pressure chambers 22,23 relative to each other.

The sealing ring 67 is formed and arranged so that this only shuts off in one axial direction or prevents a pressure compensation between the two chambers 22 and 23 whilst in the other axial direction at least with the presence of a positive differential pressure between the pressure chamber 23'and the pressure chamber 22 a pressure

compensation or through flow of the sealing ring 67 is possible. The sealing ring 67 thus acts like a non-return valve whereby a flow from the pressure chamber 22 inca trie pressure chamber 23 is prevented but a flow through the sealing point formed by the sealing ring 67 is possible at a certain excess pressure in the pressure chamber 23 relative to the pressure chamber 22. With a movement of the cam disc 19 to the right pressurised fluid can thus flow from the closed pressure chamber 23 into the pressure chamber 22. With a following movement of the cam disc 19 to the left an underpressure can indeed arise in the pressure chamber 23 and where applicable can indeed form air bubbles inside the oil. This is however not detrimental to the functioning of the torque sensor or cone pulley belt contact gearbox.

Instead of the seal 67 acting similar to a non-return valve it is also possible to provide a non-return valve acting between the two pressure chambers 22,23, and this would then be installed in the ring-shaped component part 24. A seal 67 acting in both axial directions could then be used. Furthermore a non-return valve of this kind could also be arranged so that this acts between the two channels 35 and 58. The non-return valve must thereby be arranged so that a volume flow is possible from the pressure chamber 23 in the direction of the pressure chamber 22 but shuts off the non-return valve in the reverse direction.

From the description of the function above it is apparent that practically over the entire partial area of the

transmission ratio range in which the gearbox is set in underdrive the axial force produced through the ball ramps provided on the discs 18,19 is only supported by che axially active surface formed by the pressure chamber 22 whilst practically over the entire partial area of the transmission ratio range in which the gearbox is set in overdrive the axial force produced by the ball ramps on the disc 19 is taken up by the two axially active surfaces of the pressure chambers 22,23. Thus in relation to an identical input moment, with the transmission ratio of the gearbox in underdrive, the pressure produced by the torque sensor is higher than that which is produced by the torque sensor 14 with a transmission ratio of the gearbox in overdrive. As already mentioned the illustrated gearbox is designed so that the change-over point which causes a connection or separation between the two pressure chambers 22,23 lies in the area of a transmission ratio of about 1: 1. Through a corresponding arrangement and design of the channels 59,60 and the areas 63,64 of the cone disc la interacting therewith it is possible however to move the change-over point or change-over area accordingly within the overall transmission ratio range of the cone pulley belt contact gearbox.

The connection or separation between the two pressure chambers 22,23 can also take place through a special valve provided for this purpose which can be counted in the area of a channel connecting the two pressure chambers 22,23 whereby this valve need not furthermore be operable directly through the disc la or 2a but for example can be operable by an extraneous energy source. To his end for

example an electromagnetically, hydraulically or pneumatically operable valve can be used which can be switched in dependence on the transmission ratio or change in transmission of the gearbox. Thus for example a so called 3/2 valve can be used which causes a connection or separation between the two pressure chambers 22, 23. However pressure valves can also be used. A corresponding valve could be provided in the area of a pipeline connecting the two channels 35 and 58 whereby then the channels 59 and 60 are closed or are not present. The corresponding valve is switched and connected so that with separate pressure chambers 22, 23 the pressure chamber 23 is relieved of pressure through the valve. To this end the valve can be connected to a pipeline leading back to the oil sump.

When using a valve which can be controlled from outside this can still also be operable in dependence on other parameters. Thus this valve can be operable for example also in dependence on torque shocks appearing in the drive. Thus for example a slipping of the chain at least in certain operating conditions and transmission ranges of the cone pulley belt contact gearbox can thereby be avoided or at least reduced.

With the design illustrated in Figure 1 the torque sensor 14 is mounted on the drive side and adjacent the axially movable cone disc la. The torque sensor 14 can however be provided ar any point in the torque flow and suitably adapted. Thus a torque sensor 14 as known per se can also be provided on the output side for example on the output

shaft B. A torque sensor of this kind can then be adjacent the axially movable cone disc 2a-in a similar way to the torque sensor 14. Also as known per se several torque sensors can be used. Thus a corresponding torque sensor can be provided for example on both the drive side and on the output side.

Also the torque sensor 14 according to the invention with at least two pressure chambers 22,23 can be combined with other known measures for torque-dependent and/or transmission-dependent pressure modulation. Thus for example the rolling bodies 20 could, in a similar way to that described in DE OS 42 34 294, also be movable in dependence on a change in transmission ratio in the radial direction along the rolling ramps or rolling paths interacting with same.

With the embodiment described according to Figure 1 the pressure chamber 6 is connected to the torque sensor 14.

However the outer pressure chamber 13 can also be biased with the pressure supplied by the torque sensor 14 whereby then the inner pressure chamber 6 serves to change the transmission ratio. For this it is only necessary to alternate the connections of the two pipelines 52 and 37 at the second pulley set 2 or to change them over.

With the embodiment of the torque sensor 14 according to Figure 1 the parts forming same are made substantially of sheet metal. Thus the cam discs 18 and 19 in particular can be made as shaped sheet metal parts e. g. by stamping.

Figure 2 shows a pair 100 of cone pulleys with an axially fixed first cone disc 101 and a cone disc 102 axially displaceable relative thereto. The axially fixed cone disc 101 is connected axially fixed and rotationally secured with a shaft 104 or is formed integral or in one piece therewith. Teething 103 are provided on an attachment 105 on the cone disc 101 and can mesh for example with teething of a further element. An element of this kind can be for example a drive shaft of a hydraulic pump, as can be driven by the teeth. These teeth can likewise be used as a parking lock to lock the pulley set.

The axially movable cone disc 102 is mounted axially displaceable but rotationally secured on the shaft 104. The rotationally secured connection is carried out by means of internal teeth of the cone disc which engage in external teeth of the shaft 104. The displacement of the axial position of the cone disc 102 and the contact pressure of the belt contact means 112 between the cone discs takes place under deliberate pressure biasing of the two pressure chambers 110 and 111.

The pressure chamber 110 is formed on the one hand by the substantially circular ring shaped element 120a, 120b and on the other by the circular ring-shaped arms 121a, 121b of the axially fixed element 121. The circular ring shaped elements are formed for example as deep drawn parts which are connected together radially on the outside. The element 120a is formed as a component part with C-shaped cross-section whereby the radially extending piece is supported axially on the cone disc. The element 120b of

substantially S-shaped cross-section is connected radially outwards with the element 120a for example through a welding seam. In the radially inner end area of r-he element 120b a sealing element 125 is housed in a socket, such as a circumferential groove and is in sealing contact with the cylinder face 126 of the element 121. At the same time the inner arm of the element 120a is sealingly supported by the seal 131 which is housed in a socket such as a circumferential groove of the arm 121b.

The pressure chamber 111 is formed on the one hand by the shaft 104 and the axially movable cone disc and on the other by the radially inner arm of the circular ring shaped element 120a and by the circular ring shaped element 121 with the arm 121b.

The element 121 is preferably formed as a forged or cast part or a sheet metal part and is held axially by the intermediate member such as bearing inner ring 145 and the retaining means such as nut 146. The bearing inner ring is connected with the shaft 104 with keyed engagement in the circumferential direction, such as rotationally secured. Likewise it can be expedient if the bearing inner ring is connected with the shaft through friction locking by means of a pressed seat. The rolling bearing (not shown) is supported by its bearing outer ring on the housing and thus supports the shaft rotatable in the housing. In the radially outer end areas of the arms 121a and 121b, seals 130,131 are housed with sealing rings 121c, 121d in sockets such as circumferential grooves. The holding means engage by a collar radially inside in a

circumferential groove of the shaft 104 and thus secure the axial position of the element 121. The elements 145 and 146 also serve to support the shaft 104 by means of a sliding or rolling bearing (not shown). These component parts are in an expedient embodiment advantageously provided with internal teething which engages in external teething of the shaft 104 and connects the component parts rotationally secured to the shaft. The bearing inner ring 145 is connected rotationally secured with the shaft 104.

The bearing outer ring (not shown) is thereby housed in a socket in the gearbox housing. The rolling bodies such as balls, cones or cylinders, of the bearing, such as ball bearing or cylinder rolling bearing are advantageously housed between radially extending webs of the bearing outer ring.

The element 121 can be connected to the shaft by means of a positive locking connection by means of teeth and counter teeth. In a further advantageous embodiment it is expedient if the element 121 is connected to the shaft by a friction locking connection such as a pressed seat.

The sealing rings 121c are advantageously formed as twopart sealing rings with a radially inner elastic ring element advantageously of an elastomer and a radially outer substantially shape-stable ring element, for example of PTFE, such as Teflon, whereby the elastic ring element biases the non-elastic ring element as a result of its elasticity against a counter sealing face, see also Figures 6a and 6b.

The pressure chambers are connected through the channels 140, 141 to a pressurised medium supply with valves and hydraulic pump. The channels are formed by bores in the radial direction and communicate with channels, shown in Figure 1, running axially inside the shaft 104. The connection 142 of the part 121 is in fluid communication with the connection 141. The connection 142 is formed by two bores 142a, 142b whereby one bore 142a is closed in the end area by a stopper 143.

The energy accumulator 150 is mounted inside the room area 111 and is mounted under pretension between the axially fixed element 121 and the axially movable cone pulley 102.

The end windings of the energy accumulator are housed in socket areas in which they are axially supported and radially supported.

The upper half of Figure 2 shows a position of the pair of cone pulleys with a low transmission ratio of the gearbox and the lower half of Figure 2 shows a position with a high gear transmission ratio. In the upper half of the figures the energy accumulator is relatively relaxed and only the end windings adjoin the socket areas. In this illustration the contour of the energy accumulator can be clearly seen. The radius tapers to the centre of the spring and widens out again towards the two end areas. In the lower half of Figure 2 the energy accumulator is relatively tensioned and in addition to the end windings a centre winding also adjoins the foot of the cone disc and is centred by same.

Figures 3a and 3b show arrangements of the energy accumulator 150 between the axially movable cone disc 102 12 !. i-the--F Figure 3a the transmission ratio is slight and the two Figure 3a the transmission ratio is slight and the two cone discs 101, 102 stand relatively close together. In the illustration of Figure 3b the transmission ratio is large and the two cone discs 101,102 stand relatively far apart. The energy accumulator 150 ends by an end winding 151 in a socket 152 of the cone disc 102. The energy accumulator 150 is supported there by its end winding 151 axially and radially towards the outside. At its other end winding 153 the energy accumulator 150 is supported axially and radially outside on the fixed element 121 in the area of a socket 154. The socket 152 is formed as a circumferential groove in the cone disc. The socket 154 is formed as an end area with a radially aligned edge.

With the illustration in Figure 3a the second winding is not centred or supported from the right radially inwards whereby in the illustration of Figure 3b it is centred and supported radially inwards in the compressed state at the foot 102a of the cone disc.

The wire cross-section of the energy accumulator is in the embodiment of Figures 3a, 3b substantially round whereby flattened areas can also be provided. Likewise the crosssection of the spring wire can also have in another embodiment an oval or angular, such as square or rectangular cross-section. The spring is preferably in its maximum tensioned installation position when the two cone discs 101,102 are in the position of maximum transmission (overdrive).

Figure 4 shows an energy accumulator 200 in semi-section. The end windings 201 and 202 each have a radius Ri and R3 which is greater than the radius R2 in the centre of the spring. The smallest radius R2 can also be with a length Ii from one edge of the spring or 12 from the other edge of the spring whereby the length of the spring is marked I.

A negative centrifugal force effect on the windings is thereby counteracted so that the windings do not extend excessively radially outwards.

The energy accumulator with tapering and then widening cross-section is advantageously mounted in a pressure chamber of the first pair of cone pulleys on the drive side and/or second pair of cone pulleys on the output side. It is thereby also advantageous if the energy accumulator is mounted outside of a pressure chamber and biases the axially displaceable cone disc. The energy accumulator is advantageously mounted coaxial with the shaft 104 of the axially displaceable cone disc. With cone pulley belt contact gearboxes each having a pressure chamber for pressure biasing for adjusting the transmission ratio and for controlling the contact pressure of the contact means, such as chain or belt, it is advantageous if the energy accumulator is mounted in the radially inner pressure chamber. It is likewise expedient in another embodiment if the energy accumulator is mounted in the radially outer pressure chamber.

In an advantageous embodiment it is expedient if the energy accumulator is mounted on the side of a pair of

cone pulleys on which the input shaft of the gearbox is mounted. In another embodiment it is advantageous if the energy accumulator is mounted on the side of a pair of cone pulleys which lies opposite the input shaft of the gearbox.

It is particularly advantageous if the energy accumulator has only few windings preferably 2 to 8 windings, such as in particular 3 to 6 windings, such as 4 windings.

Figures 5a and 5b show the seals by way of example in the sockets 400 and/or 420 of the arms 121a, 121b or in other advantageous variations of the gearbox according to the invention also on other component parts of the cone pulley belt contact gearbox. The seals are provided for sealing pressure chambers or piston cylinder units. A ring-shaped elastic sealing ring 401,410 is housed in the sockets and is enclosed radially outwards by a substantially nonelastic ring-shaped element 402,411. The substantially non-elastic or substantially shape-stable ring-shaped element 402,411 is biased by the elastic ring against the counter sealing face of the element 120a whereby the corresponding chamber area is sealed. The shape stable ring mounted radially outside can have an extension in the axial direction, see Figure 6b or it can have side cheeks 412 which also extend inwards in the radial direction and hold the elastic ring 410 between same and secure it in the axial direction. The shape-stable rings can thus be formed substantially U-shaped wherein they have radially outside a ring-shaped surface which adjoins a counter

face. The seal can also be designed so that the elastic

ring is mounted radially outside and the shape-stable ring is mounted radially inside the elastic ring. The side cheeks can chereby point radially outwards and the slide faces can be mounted radially inside.

The invention is not restricted to the embodiments of the description. Numerous amendments and modifications are possible within the scope of the invention as defined by the claims, particularly those variations, elements and combinations and/or materials which are combinations or modifications of individual features or elements or process steps contained in the drawings and described in connection with the general description and embodiments and claims.

Claims (9)

Claims

1. A continuously variable cone pulley belt contact gearbox with a first pair of cone pulleys and a second pair of cone pulleys each with an axially displaceable and an axially fixed cone pulley and a contact means mounted for torque transfer between these pairs of cone pulleys, with at least one pressure chamber, characterised in that the pressure chamber is sealed by a seal which has an elastic sealing ring and a substantially shape stable ring element.

2. A gearbox as claimed in Claim 1, wherein the elastic sealing ring is mounted radially inside the substantially shape-stable ring element

3. A gearbox as claimed in Claim 1, wherein the elastic sealing ring is mounted radially outside of the substantially shape-stable ring element.

4. A gearbox as claimed in any preceding claim, wherein at least one energy accumulator is mounted actively between an axially fixed element and an axially displaceable cone pulley, which energy accumulator has a cross-section which deviates from a cylindrical shape and has a cross-section which tapers in a first axial area and widens out again in a second axial area.

5. A gearbox as claimed in Claim 4, wherein he energy accumulator is a compression spring with individual windings wherein at least the axially outer windings have

a larger radius in the radial direction than windings arranged axially further inwards.

6. A gearbox as claimed in Claim 4 or Claim 5, wherein the cross-section of the energy accumulator has a double cone like contour.

7. A gearbox as claimed in any one of Claims 4 to 6, wherein the axially fixed element and/or the axially displaceable cone pulley has a socket in which windings in the end areas of the energy accumulator are housed and supported radially outwards.

8. A gearbox as claimed in Claim 7, wherein a socket in the axially displaceable cone pulley is formed as a circumferential groove which is engaged radially by an attachment and in which at least one winding in the end area of the energy accumulator is housed whereby the winding is supported radially outside on the attachment and is supported in the axial direction on the cone pulley.

9. A gearbox as claimed in Claim 7, wherein a socket in the axially fixed element supports at least one winding of the energy accumulator in the end area of the energy accumulator in the radial direction outwards and in the axial direction.