SE542959C2 - An anti-backlash gear arrangement and a gearbox, powertrain and vehicle comprising such an arrangement - Google Patents

Abstract

The invention relates to an anti-backlash gear arrangement (1) for use in a gear drive, said anti-backlash gear arrangement comprising a main gear (2), wherein a biasing arrangement (6) is arranged to act on the anti-backlash gear (4) towards an off-set position with respect to the main gear (2), in which secondary teeth (5) the anti-backlash gear (4) are off-set with respect to the main gear teeth (3), said biasing arrangement (6) including a first set of apertures (7) arranged in either the main gear (2) or the anti-backlash gear (4), a second set of apertures (8) arranged in the other of the main gear (2) and the anti-backlash gear (4), and biasing units (9), each comprising a first, pin-like end (10) that is tightly fitted inside an aperture of the first set of apertures (7), and a second, resilient end (11) comprising a radially compressible metal spring element (12) arranged to act against an inside surface (13) of an aperture of the second set of apertures (8) to thereby act on the anti-backlash gear (4) towards an off-set position with respect to the main gear (2).

Description

AN ANTI-BACKLASH GEAR ARRANGEMENT AND A GEARBOX, POWERTRAINAND VEHICLE COMPRISING SUCH AN ARRANGEMENT TECHNICAL FIELD The invention relates to an anti-backlash gear arrangement for use in a gear drive.Specifically, the invention relates to an improved anti-backlash gear arrangement with amore controlled function and a better reliability over time. The invention also relates to a gear, a powertrain and a vehicle including such an anti-backlash gear arrangement.BACKGROUND ln the automotive industry gear arrangements are widely used, inter alia in powertrains transmitting a rotational movement from a motor to a drive means, such as wheels.

A commonly used gear arrangement is comprised of meshing gears, typically spur gears,arranged to interact with each other. A gear generally consists of a cylinder or a disc with radially extending teeth arranged to be in meshing contact with the teeth of another gear. ln the interaction between gears there is typically a play between the meshing teeth thatmay produce an undesired noise. This is because the driving of the gear may be at leastpartly intermittent but also due to that the gap between two adjacent teeth needs to begreater than the width of the tooth arranged to be received within said gap. The oversizedgap is inter alia necessary to avoid jamming of the gears. The play thus formed between mating teeth may be referred to as a lash or backlash. lt is desired to keep this backlash to a minimum, withoutjeopardizing the function of thegears. A commonly used solution is an anti-backlash gear, also known as a scissorsgear. The anti-backlash gear involves a secondary gear that is biased into contact withthe back side, i.e. the inactive side, of the teeth. This biasing contact will force the activeparts of the teeth to remain in contact to thereby increase the efficiency of the gearing and, at the same time, decrease its noise level. ln an anti-backlash gear, resilient means are arranged to provide a biasing effect that willstrive to keep the anti-backlash gear off-set with respect to the main gear so as to fill thegap of a mating gear. Thereby, the front of the teeth of the main gear remains in contactwith corresponding front of the teeth of the mating gear. The resilient means may becomprised of a centrally arranged spring. Also, in one conventional prior art embodimenta plurality of pins with rubber tubes or rings are arranged symmetrically around the centre of the main gear and the anti-backlash gear. The inherent resilience of the rubber acts to push the main gear and the anti-backlash gear into an off-set position with respect to each other. ln the international publication WO 2013/190458 A1 an alternative arrangement isprovided, in which leaf-like springs are arranged to provide the desired biasing effect.This is however a relatively complex arrangement in which slits need to be provided inthe gear to hold the leaf-like springs and a screw arrangement is arranged to retain each leaf-like spring.SUMMARY OF THE INVENTION There is a need of an arrangement that is easier to install, and/or implies less machining to implement and that is reliable over time. lt is therefore an object of the present invention to provide an improved anti-backlasharrangement with respect to the prior art, which provides an anti-backlash function that is reliable over time.

According to a first aspect the invention relates to an anti-backlash gear arrangement foruse in a gear drive, said anti-backlash gear arrangement comprising: - a main gear with radially protruding gear teeth, and - a anti-backlash gear with radially protruding secondary teeth, said anti-backlashgear configured to be co-axially arranged around a common axis with the main gear andconfigured to be angularly displaceable with respect to said main gear, wherein a biasingarrangement is arranged to act on the anti-backlash gear towards an off-set position withrespect to the main gear, in which the secondary teeth are off-set with respect to themain gear teeth, said biasing arrangement including: - a first set of apertures arranged in either the main gear or the anti-backlashgean - a second set of apertures arranged in the other of the main gear and the anti-backlash gear, and - biasing units, each biasing unit comprising a first, pin-like end that is arrangedto be attached inside an aperture of the first set of apertures, and a second, resilient endcomprising a radially compressible metal spring element arranged to act against aninside surface of an aperture of the second set of apertures to thereby act on the anti- backlash gear towards an off-set position with respect to the main gear.

An advantage of the inventive arrangement with respect to an arrangement with rubber rings or tubes is that is more feasible to provide a metal spring element with a desired resiliency than it is for a corresponding rubber element. The rubber may easily be toostiff, and/or it may have a too slow expansion rate from a compressed state producing anunwanted hysteresis effect. With a metal spring such properties are more easily custom made, and more reliable over time. ln embodiments of the invention the first, pin-like ends of the biasing units are configuredto be attached by press fitting inside the second set of apertures. This allows for thebiasing unit to be implemented and fastened without the use of specific fastening means.The outside surface of the pin-like end or the inside surface of the second set ofapertures may be rugged in order to further improve the attachment. The rugged surfacemay inter alia be accomplished by machining or by abrasive interaction With a sand paper or the like. ln embodiments of the invention the first set of apertures have a cylindrical portion thatextends over a major part of its length, specifically more than 75% or preferably morethan 90% of its length, wherein the pin-like end of each biasing unit has a correspondinglength and is configured to bear against the inside surface of an aperture of the first set ofapertures over a major part of the length of said pin-like end, specifically more than 75%or preferably more than 90% of the length of said pin-like end. Further, the pin-like end ofeach biasing unit is configured to bear against the inside surface of an aperture of thefirst set of apertures over a major part of the length of the cylindrical portion of saidaperture specifically more than 75% or preferably more than 90% of the length of said cylindrical portion. ln embodiments of the invention the second set of apertures have a cylindrical portionthat extends over a major part of the length of said aperture, specifically more than 75%or preferably more than 90% of its length, wherein the resilient end of each biasing unithas a corresponding length and is configured to bear against the inside surface of anaperture of the second set of apertures over a major part of the length of said resilientend, specifically more than 75% or preferably more than 90% of the length of saidresilient end. Further, the resilient end of each biasing unit is configured to bear againstthe inside surface of an aperture of the second set of apertures over a major part of thelength of the cylindrical portion of said aperture, specifically more than 75% or preferably more than 90% of the length of said cylindrical portion.

The term “corresponding length” used above and in other parts of this specification is to be construed as that a corresponding length is similar to the compared length and specifically that the compared lengths have a deviation of less than 15% with respect to each other.

The length of the interface between the apertures and the respective ends of the biasingunits will improve the mechanical properties of the attachment and minimise thegeneration of shear forces. This may be particularly important in the interface between the resilient ends and the second set of apertures.Each biasing unit is made of one integral piece of metal.

The first, pin-like end of each biasing unit is comprised of a first sheet steel portion bentat least half a lap, and the second, resilient end of each biasing unit may be comprised of a second, longer sheet steel portion bent at least a full lap. ln embodiments of the invention each biasing unit is comprised of a pin arranged toextend into both an aperture of the first set of apertures and into an aperture of thesecond set of apertures, said pin being arranged to fit tightly inside said aperture of thefirst set of apertures, wherein said radially compressible metal spring element is aseparate part that is arranged around the pin inside said aperture of the second set ofapertures to act on the pin towards a centre of said aperture of the second set of apertures. ln embodiments of the invention the metal spring element is comprised of a petal-shaped,cylindrical element comprising a plurality of distal portions, a plurality of proximal portions,and radial web portions arranged to connect the distal and radial portions to each other,the proximal portions are arranged to lie against the pin that forms the pin-like end, andthe distal portions are arranged to abut the inside surface of an aperture of the second set of apertures. ln embodiments of the invention the first set of apertures are cylindrical having a firstdiameter and the second set of apertures are cylindrical having a second diameter beinggreater than the first diameter, wherein the respective axes of the first set of aperturesand the second set of apertures are arranged off-set with respect to each other, andwherein the radially compressible metal spring element is symmetric and arranged to act to push said respective axes towards each other.

According to a second and a third aspect the invention relates to a gearbox and apowertrain, respectively, that comprises an anti-backlash gear arrangement as described above.

According to a fourth aspect the invention relates to a vehicle that comprises an anti- backlash gear arrangement as described above.

Other embodiments and advantages will be apparent from the detailed description and the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Below, specific embodiments of the invention will be described with reference to the appended drawings, of which; Fig. 1 shows a first embodiment of an anti-backlash gear arrangement, Figs. 2-3 are perspective views of a biasing unit according to a first embodiment,Fig. 4 is an exploded view of the anti-backlash gear arrangement of fig. 1,Fig. 5 is a side view of the anti-backlash gear arrangement of fig. 1, Fig. 6 is a sectional view of the anti-backlash gear arrangement taken along the lineVl-Vl in fig. 5, Fig. 7 is a schematic view of a vehicle according to a second aspect of the invention,Fig. 8 shows a second embodiment of an anti-backlash gear arrangement,Fig. 9 is a sectional view of the anti-backlash gear arrangement of fig. 8, Fig. 10 is a perspective view of a biasing unit according to the second embodiment, andFig. 11 is an exploded view of the anti-backlash gear arrangement of fig. 8.

DETAILED DESCRIPTION OF THE SHOWN El\/lBODll\/IENTS ln fig. 1 an anti-backlash gear arrangement according to a first embodiment is shown.The shown anti-backlash gear arrangement 1 is intended for use in a gear drive. ltcomprises a main gear 2 with radially protruding gear teeth 3, and an anti-backlash gear4 with radially protruding secondary teeth 5. The anti-backlash gear 4 is co-axiallyarranged around a common axis with the main gear 2 and is angularly displaceable with respect to said main gear 2.

A biasing arrangement is arranged to act on the anti-backlash gear 4 towards an off-setposition with respect to the main gear 2, ln the off-set position the secondary teeth 5 areoff-set with respect to the gear teeth 3 of the main gear. The off-set position between thefirst and secondary teeth 3 and 5 is illustrated by the gap 3'-5' in fig. 1. This relativelysmall off-set position will make sure that a gap between two teeth of a mating gear (notshown) is filled without play. Hence, when a leading side of a tooth 3 of the main gear 2 isin contact with a first side of the gap between two teeth of the mating gear, a trailing sideof the secondary teeth 5 of the anti-backlash gear 4 will be in contact with the opposedside of the gap between two teeth of the mating gear. Thereby, contact will not be lostbetween the leading side of a tooth 3 of the main gear 2 and the tooth of a mating gear during operation.

Fig. 4 shows an exploded view of an anti-backlash gear arrangement with biasing units 9in accordance with the first embodiment. The main gear 2 comprises a sleeve portion 6,of which the inner surface is arranged to be located around a shaft. The sleeve portion 6extends axially out from the main gear 2 and provides a hub-like support for the anti-backlash gear 4, said anti-backlash gear 4 having in inner diameter that corresponds tothe outer diameter of the sleeve portion 6 such that the anti-backlash gear 4 will fit tightlyaround and be supported by the sleeve portion 6 in a slidable manner so as to allow mutual rotation between the main gear 2 and the anti-backlash gear 4.

As illustrated in fig. 4 the biasing arrangement includes a first set of apertures 7 arrangedin either the main gear 2 or the anti-backlash gear 4, and a second set of apertures 8arranged in the other of the main gear 2 and the anti-backlash gear 4. ln the shownembodiment the first set of apertures 7 are arranged in the main gear 2 and the second set of apertures 8 are arranged in the anti-backlash gear 4.

The biasing arrangement further includes biasing units 9, of which a first embodiment isshown in figures 2 and 3. Each biasing unit 9 comprises a first, pin-like end 10 that isarranged to be tightly fitted inside an aperture of the first set of apertures 7, and asecond, resilient end 11 comprising a radially compressible metal spring element 12arranged to act against an inside surface 13 of an aperture of the second set of apertures8. Thereby, the metal spring element 12 will act on the anti-backlash gear 4 towards an off-set position with respect to the main gear 2. ln the shown embodiment each biasing unit 9 is made of one integral piece of metal. ltcomprises a first, pin-like end 10 comprised of a first sheet steel portion bent at least half a lap, and a second, resilient end 11 comprised of a second, longer sheet steel portion bent at least a full lap. ln the shown embodiment the first sheet steel portion of the first,pin-like end 10 has the shape of a spiral wound approximately two laps. The second,resilient end 11 has the shape of a spiral wound more than two laps, typically about fourlaps, said spiral forming a metal spring element 12 of the first embodiment. Both the first,pin-like end 10 and the second, resilient end 11 are cylindrical to such a degree that they have a similar cross section over their respective full lengths. ln the shown embodiment both the first, pin-like end 10 and the second, resilient end 11are somewhat elastic, the second, resilient end 11 of course having a higher elasticity.The elasticity of the first, pin-like end 10 needs to be limited. Namely, preferably, the first,pin-like end 10 is tight fitted inside an aperture of the first set of apertures 7. Hence, inorder for the pin-like end 10 to be retained inside said aperture the radial force exerted bysaid pin-like end 10 towards the inside surface 13 of said aperture needs to be sufficientlyhigh. The interaction between the first, pin-like end 10 and the inside surface 13 of saidaperture should not be elastic in such a meaning that the first, pin-like end 10 will yield tothe forces exerted on the biasing unit 9. lnstead, the resiliency of the metal springelement 12 will handle such forces, said metal spring element 12 being designed to yieldtowards a position where the first set of apertures 7 are positioned off-set with respect tothe second set of apertures 8 at least up to a point where the teeth of the main gear 2 and anti-backlash gear 4, respectively, are in line with each other. ln a not shown alternative embodiment the pin-like end 10 is a solid part, i.e. a cylindricalpart arranged to be press fitted inside an aperture of the first set of apertures 7. Thesecond, resilient end 11 may in such an embodiment be an integral part comprised of acylindrical helicoidal spring, preferably machined from the same piece of metal as the pin-like end 10. ln fig. 5 the anti-backlash gear arrangement 1 is shown from the side of the anti-backlashgear 4, wherein the main gear teeth 3 may be spotted in an off-set position behind theteeth 5 of the anti-backlash gear 4. Biasing units 9 of the type shown in figs. 2-3 are arranged in the respective apertures of the gears.

Fig. 6 is a sectional view taken along the line Vl-Vl of fig. 5. ln this view it is apparent thatthe first set of apertures 7 are cylindrical and have a first diameter d1 and that the secondset of apertures 8 are cylindrical and have a second diameter d2, which is greater thanthe first diameter d1. The respective axes of the first set of apertures 7 and the secondset of apertures 8 are arranged off-set with respect to each other, and the radially compressible metal spring element 12 is symmetric and arranged to act to push said respective axes towards each other, thereby pushing the respective teeth 3 and 5 of the gears 2 and 4 to an off-set position with respect to each other.

Hence, the rotational orientation of the metal spring element 12 does not affect itsfunctional resiliency during operation. Regardless of its orientation the metal springelement 12 will act to keep the pin concentrically located with respect the axis of the aperture of the second set of apertures 8 in which it is located. ln the shown embodiments both the first and the second set of apertures 7 and 8,respectively, are comprised of through ho|es reaching through the respective gear 2 and4, respectively. The apertures may however comprise abutments in the form of shouldersor a solid wall in order to keep the biasing units at place inside them. ln the shownembodiment the first set of apertures 7 have a cylindrical inside surface 13 inside whichthe pin-like end 10 is attached, preferably by press fitting. They may also be screwed.Specifically, the first set of apertures 7 could comprise threads arranged to receive amating thread provided on the pin-like end 10 of the biasing unit 9. The second set ofapertures 8 have a cylindrical inside surface 14 inside which the metal spring element 12is arranged to exert a force extending radially outwards against a substantial length of the cylindrical portion of said aperture, i.e. not only an annular portion thereof.

As is apparent from the embodiments shown in figs. 6 and 9 both the first set of apertures7 and second set of apertures 8 are cylindrical and of similar lengths. The pin-like end 10of each biasing unit 9 has substantially the same length as the apertures of the first set ofapertures 7 and is arranged to bear against the inside surface 13 of an aperture of thefirst set of apertures 7 over a major part of the length of said pin-like end 10. Preferably,the pin-like end 10 bears against the inside surface 13 over more than 75% of its length,more preferably over more than 90% of its length. lt may however also be arranged tobear against the inside surface 13 at circumferential portions located a part from eachother, wherein the distance between their respective outer portions is more than 75% of the length of the pin-like end 10, more preferably over more than 90% of said length Likewise, the metal spring element 12 of the resilient end of each biasing unit 9 hassubstantially the same length as the apertures of the second set of apertures 8 and isarranged to bear against the inside surface 14 of such an aperture 8 over a major part ofthe length of said metal spring element 12. Preferably, the metal spring element 12 bearsagainst the inside surface 13 over more than 75% of its length, more preferably over more than 90% of its length. ln fig. 7 an embodiment according to a second aspect the invention is shown in the formof a vehicle 100, said vehicle comprising an anti-backlash gear arrangement according tothe first aspect of the invention. The anti-backlash gear arrangement is, however,applicable also in other technical fields, including other kinds of transportation means,such as air and water crafts. The invention is also applicable in fixed installations provided with a motor and a gear box or gears.

Fig. 7 schematically depicts a powertrain of an exemplary vehicle 100. The powertraincomprises a power source 101, which in the present example is exemplified by aninternal combustion engine, which, in a conventional manner, is connected via an outputshaft of the power source 101, via a flywheel 102, to a gearbox 103 via a clutch 106. Thegearbox 103 contains an anti-backlash gear arrangement according to the first aspect ofthe invention. The vehicle may also include anti-backlash gear arrangements at otherlocations of the vehicle than in the gearbox, especially along the powertrain in the transmission of rotating movement between mating gears.

An output shaft 107 from the gearbox 103 propels drive wheels 113, 114 via a final gear108, such as a common differential, and half shafts 104, 105 connected to said final gear108. The final gear 108 may include an anti-backlash gear arrangement according to theinvention. The power source 101 is controlled by the vehicle control system via a controlunit 115, and similarly the clutch and gearbox may be controlled by a control unit 116,which may automatically perform changes of gears. lf the power source is a combustionengine an exhaust pipe 109 is arranged to exhaust combustion gases from said motor via a catalytic converter 110, and preferably a particle filter.

Fig. 7, consequently, illustrates a powertrain of a specific kind, but the invention isapplicable in any kind of powertrain involving power source such as an internal combustion engine, an electric engine, or both. ln figures 8-11 the anti-backlash gear arrangement is shown with biasing units 9 inaccordance with a second embodiment. ln the second embodiment each biasing unit 9 iscomprised of a pin arranged to extend into both an aperture of the first set of apertures 7and into an aperture of the second set of apertures 8. A first end of the pin constitutes thepin-like end 10 of the biasing unit 9 and is arranged to be attached, e.g. by press fitting,inside said aperture of the first set of apertures 7. lt may also be screwed or riveted. lnthis second embodiment the radially compressible metal spring element 12 is comprisedof a separate part that is to be arranged around the pin inside said aperture of the second set of apertures 8. The radially compressible metal spring element 12 is arranged to act on the pin to keep the first set of apertures 7 and the second set of apertures 8 in line with each other.

As is illustrated in figure 9. the first set of apertures 7 are cylindrical and have a firstdiameter d1 and the second set of apertures 8 are cylindrical and have a seconddiameter d2, which is greater than the first diameter d1. The respective axes of the firstset of apertures 7 and the second set of apertures 8 are arranged off-set with respect toeach other, and the radially compressible metal spring element 12 is symmetric andarranged to act to push said respective axes towards each other, thereby pushing therespective teeth 3 and 5 of the gears 2 and 4 to an off-set position with respect to each other.

Hence, for this embodiment as well as for the embodiment shown in figs. 1-6, the biasingfunction of the metal spring element 12 is independent of its rotational orientation.Regardless of its orientation the metal spring element 12 will act to keep the pinconcentrically located with respect to the axis of the aperture of the second set of apertures 8 in which it is located.

As illustrated in figure 10, the metal spring element 12 of the second embodiment iscomprised of a petal-shaped, cylindrical element. Specifically, the metal spring element12 comprises a plurality of distal portions 15, a plurality of proximal portions 16, andradial web portions 17 which are arranged to connect the distal and radial portions toeach other. The proximal portions 16 are arranged to lie against the pin that forms thepin-like end 10 of the second embodiment, and the distal portions 15 are arranged toabut the inside surface 13 of an aperture of the second set of apertures 8. ln the shownembodiment the metal spring element 12 comprises four distal portions 15, four proximalportions 16, and eight radial web portions 17 connecting them. Alternatively, the metalspring element 12 may have fewer, or more, distal and proximal portions 15 and 16. Theradial web portions 17 are arranged to provide resiliency. Hence, the web portions 17 arepreferably arranged to extend in in a slightly inclined direction with respect to the radialdirection from the pin towards the surrounding inside surface 13 of one of the apertures of the second set of apertures 8.

Above, the invention has been described with reference to specific embodiments. Theinvention is however not limited to these embodiments. lt is obvious to a person skilled in the art that other embodiments are possible within the scope of the following claims.

Claims (1)

1. An anti-backlash gear arrangement (1) for use in a gear drive, said anti-backlash geararrangement comprising: - a main gear (2) With radially protruding gear teeth (3), and - a anti-backlash gear (4) With radially protruding secondary teeth (5), said anti-backlash gear (4) configured to be co-axially arranged around a common axis withthe main gear (2) and configured to be angularly displaceable with respect to saidmain gear (2), Wherein a biasing arrangement is arranged to act on the anti-backlashgear (4) towards an off-set position with respect to the main gear (2), in which thesecondary teeth (5) are off-set with respect to the gear teeth (3) of the main gear, saidbiasing arrangement including: - a first set of apertures (7) arranged in either the main gear (2) or the anti-backlash gear (4), - a second set of apertures (8) arranged in the other of the main gear (2) and theanti-backlash gear (4), and - biasing units (9), each biasing unit (9) comprising a first, pin-like end (10) that isarranged to be attached inside an aperture of the first set of apertures (7), and asecond, resi|ient end (11) comprising a radially compressible metal spring element(12) arranged to act against an inside surface (Må) of an aperture of the second setof apertures (8), and vlfnereiaw each biasinc: unit (Q) äs :nade of one inteerai ciiece efrnetaâ. eomnršsšiid the first nšrviike end (iii) and the sefzortd resiiient and (11) andvifnerein the first, pin~lil a full lagg; The anti-backlash gear arrangement (1) according to claim 1, Wherein the first, pin-like ends (10) of the biasing units (9) are configured to be attached by press fitting inside the second set of apertures (8). The anti-backlash gear arrangement (1) according to either of claim 1 or 2, Whereinthe first set of apertures (7) have a cylindrical portion of a specific length, Wherein thepin-like end (10) of each biasing unit (9) has a length that corresponds to said specificlength and is configured to bear against the inside surface (13) of an aperture of thefirst set of apertures (7) over a major part of said specific length of said pin-like end(10). 4. The anti-backlash gear arrangement (1) according to anyone of the preceding claims,wherein the second set of apertures (8) have a cylindrical portion of a specific length,and wherein the resilient end (1 1) of each biasing unit (9) has a length thatcorresponds to said specific length and is arranged to bear against the inside surface 5 (14) of an aperture of the second set of apertures (8) over a major part of said specific length of said resilient end (11). "T T fx -fanfi Éflfar-l/ifw in mn-'er faz-'z-'fazwrcr vn! n? f'1\ -faßfl v *Hmm ff ~ nu fin AF flwn ßifaírnn 'i /É ' “'-'““"” \- J ' d “' “' \ ,“-' “'*'“ -J “m “ - "“ -“ "- 1 _____________ __The anti-backlash gear arrangement (1) according to anyone of the preceding claims, wherein the first set of apertures (7) are cylindrical having a first diameter (d1) 30 and the second set of apertures (8) are cylindrical having a second diameter (d2) being greater than the first diameter (d1), and wherein the respective axes of the firstset of apertures (7) and the second set of apertures (8) are arranged off-set with respect to each other, and wherein the radially compressible metal spring element (12) is symmetric and arranged to act to push said respective axes towards each other. A gearbox (103) for a vehicle characterised in that the gearbox (103) comprises an anti-backlash gear arrangement (1) according to anyone of the preceding claims. \\\\\\\\\\ “A powertrain for a vehicle, comprising a power source (101) and a gear box(103) characterised in that the gear box (103) comprises an anti-backlash gear arrangement (1) according to anyone of the claims 1-§>_§«. __________ __A vehicle characterised in that it comprises an anti-backlash gear arrangement (1) according to anyone of the claims 1-§,~_-ï-š1.