SE1650583A1 - An axle gear system, a driving axle system and a motor vehicle - Google Patents

Abstract

An axle gear system (8) for distribution of torque between a forward driving axle and a rear driving axle in a motor vehicle, comprising an input shaft (11), a forward output shaft (12) for transmitting torque from the input shaft to the forward driving axle, a rear output shaft (15) for transmitting torque from the input shaft to the rear driving axle, a connection wheel (16) connected for common rotation with the rear output shaft, a first tapered rolling bearing (19) supporting the connection wheel, a second tapered rolling bearing (20) supporting the input shaft in the connection wheel, further comprising a connection means (22) movable between an engaged position in which the connection wheel and the input shaft are connected for common rotation, and a disengaged position in which the connection wheel and the rear output shaft are disconnected.(Fig. 3b)

Description

An axle qear system, a drivinq axle svstem and a motor vehicle TECHNICAL FIELD OF THE INVENTION The present invention relates to an axle gear system according tothe preamble of claim 1, to a driving axle system comprising suchan axle gear system, and to a motor vehicle. ln particular, but notexclusively, the invention relates to an axle gear system for use ina driving axle system in the form of a tandem bogie or a tridem bogie, i.e. a bogie with two and three driving axles, respectively.

BACKGROUND AND PRIOR ART A conventional driving axle system in the form of e.g. a tandem ortridem bogie of a motor vehicle comprises two or more drivingaxles arranged to be driven by a single input shaft connected to apower source. ln the case of a tandem bogie, the bogie comprisestwo driving axles which are often referred to as a forward-rear anda rear-rear driving axle. The forward-rear and rear-rear drivingaxle each include a pair of drive shafts on which one or morewheels of the motor vehicle are mounted. Each of the forward-rearand rear-rear driving axles further includes a differential gear setthat allows the vehicle wheels on each driving axle to rotate atdifferent speeds. Further, an axle gear system including means fordistributing torque between the forward-rear and the rear-reardriving axles, such as an inter-axle differential, is usually provided.The inter-axle differential allows the wheels of the two drivingaxles to rotate with mutually different rotational speeds andthereby compensates for slippage, cornering, mismatched tires, etc.

EP2942224 discloses another configuration of a driving axlesystem and an axle gear system. According to this configuration,the forward-rear and the rear-rear driving axles are connected bya shaft, operatively coupled to a slip clutch. The amount of torquewhich is transmitted to the rear-rear driving axle can thereby becontrolled by the degree of engagement of the slip clutch, thereby compensating for slippage etc.

A torque distribution system that compensates for slippage etc. isuseful in many applications, but both of the above mentionedconfigurations are relatively complex and involve a plurality ofcostly components. ln certain applications, such as for cargocarrying vehicles, e.g. long-haulage trucks, intended to transportcargo on relatively smooth roads, such complex torque distributionsystems are superfluous. However, the total weight of suchvehicles may vary considerably depending on the weight of thetransported cargo, and on whether the vehicle is loaded or not.When the vehicle is heavily loaded, it is desirable to use bothdriving axles, while as when the vehicle carries no load, it may bedesirable to elevate the rear-rear driving axle off the ground anddrive the vehicle with only the forward-rear driving axle in order to reduce losses in the powertrain of the vehicle.

SUMMARY OF THE INVENTION lt is a primary objective of the present invention to provide an inat least some aspect improved solution for distribution of torquebetween two driving axles of a motor vehicle. ln particular, it is an objective to provide a robust solution for distribution of torque between two driving axles, which is less complex than the abovedescribed prior art solutions and which is suitable for heavy motorvehicles driven under load conditions that vary over time, such ascargo carrying vehicles travelling sometimes with and sometimes without cargo.

At least the primary objective is according to a first aspect of theinvention achieved by means of the initially defined axle gearsystem, which further comprises a connection means movablebetween an engaged position in which the connection wheel andthe input shaft are connected for common rotation, and adisengaged position in which the connection wheel and the rearoutput shaft are disconnected. Thus, in the engaged position,torque can be transmitted to both driving axles so that both drivingaxles obtain the same rotational speed, while as in the disengagedposition, torque can only be transmitted to the forward driving axleand not to the rear driving axle. ln other words, the input shaft andthe rear output shaft are either connected via the connection wheeland the connection means and in that case rotate as a unit, ordisconnected with no possibility to transfer torque to the rearoutput shaft. The connection means are configured for non-slipengagement, i.e. no intermediate positions between the engaged and the disengaged position are available.

The axle gear system according to the invention constitutes arobust driving unit for use in e.g. a bogie of a motor vehicle. lt hasfewer moving parts, and is thereby less complex and more robustthan a conventional axle gear system comprising an inter-axledifferential. lt is also less space-consuming. lt enables inactivation of a rear-rear driving axle of a driving axle system comprising the proposed axle gear system when the conditions are such that thisis desirable. This may be the case e.g. when the motor vehicle istravelling without load and it is sufficient to use one driving axle.When the rear-rear driving axle is disconnected and therebyinactive in the driving of the motor vehicle, it is possible to eitherelevate the inactive rear-rear axle in order to reduce rollingresistance, or use it as a passive support axle, depending on theconditions. The non-slip configuration of the connection meansoffers a very reliable solution for connecting and disconnecting the rear driving axle using a small number of components.

The second tapered rolling bearing serves to transmit axial forcesbetween the input shaft and the connection wheel, includingpreload forces and gear forces in both the engaged and thedisengaged positions. Axial forces may be further transmitted viathe first tapered rolling bearing to e.g. a housing of the axle gearsystem. The second tapered rolling bearing supports the inputshaft stably and efficiently transfers axial forces using a smallnumber of components and thereby contributes to the robustness of the axle gear system according to the invention.

According to one embodiment of the invention, said connectionmeans comprises a sleeve arranged around the input shaft, saidsleeve being movable along a longitudinal axis of the input shaft.The sleeve offers many possibilities for achieving a reliableselectable connection between the input shaft and the rear outputshafi.

According to one embodiment, said sleeve is provided with internal splines engaging with external splines provided on the input shaft, thus providing an efficient connection between the input shaft and the sleeve such that these rotate as a unit.

According to one embodiment, the internal splines of the sleeveare configured to, in the engaged position, engage on one handwith said external splines provided on the input shaft and on theother hand with external splines provided on the connection wheel.ln the engaged position, the input shaft and the rear output shaft are thereby securely locked together and rotate as a unit.

According to another embodiment, the sleeve and the connectionwheel have end faces provided with teeth configured to engagewith each other when the connection means is in the engagedposition. The sleeve thus functions as one clutch half and theconnection wheel as another clutch half, together forming a non-slip clutch, such as a dog clutch. This is an alternative way ofachieving a reliable non-slip connection between the input shaft and the rear output shaft.

According to one embodiment of the invention, the axle gearsystem further comprises a control device configured to move theconnection means between the engaged position and thedisengaged position upon receipt of a signal. Thus, a driver of themotor vehicle may easily provide a signal, e.g. by pushing a buttonor similar, that it is desired to disengage or engage the connection meanS.

According to one embodiment of the invention, the axle gearsystem further comprises a housing in which the connection wheel and the input shaft are supported and in which the connection means is located. The housing protects the components and thereby prolongs their service life.

According to one embodiment, the axle gear system furthercomprises a third bearing supporting the input shaft in the housing.The third bearing is suitably provided forward of the first andsecond bearings, where the input shaft enters into the housing. ltis preferably in the form of a tapered ro||ing bearing. Together withthe first and the second tapered ro||ing bearings, it is configuredto transmit axial forces arising during torque transmission to the housing.

According to one embodiment of the invention, the forward outputshaft extends in parallel with the input shaft. The forward outputshaft is connected to the input shaft by means of e.g. transfer gearmembers which are always in engagement. A rotation of the inputshaft will thus always lead to a rotation of the forward output shaft.Depending on whether the connection means is in an engaged ora disengaged position, either some or all of the input torque willbe transmitted via the forward output shaft. The amount of torquetransmitted via the forward output shaft will in the engagedposition depend on axial pressure, friction, etc., but will usually be around 50 % of the total transmitted torque.

According to another aspect of the present invention, at least theabove mentioned primary objective is achieved by means of adriving axle system comprising at least one proposed axle gearsystem, at least one forward driving axle driven by the forwardoutput shaft, and at least one rear driving axle driven by the rear output shaft. Advantages and advantageous features of such a driving axle system appear from the above discussion inconnection with the proposed axle gear system. Of course, it ispossible to also have a foremost driving axle, located at a front ofthe motor vehicle, which does not form part of this driving axle system.

According to one embodiment, the driving axle system is a tandemdrive system. Such a system has two driving axles coupled to a single axle gear system.

According to one embodiment, the driving axle system comprisesat least two of said axle gear systems and at least three drivingaxles driven by said at least two axle gear systems. ln this case,a forward axle gear system and a rear axle gear system may beprovided together with a forward-rear, a middle-rear and a rear-rear driving axle. When the connection means of the forward axlegear system is in the disengaged position, the middle-rear and therear-rear driving axles will both be inactive, i.e. all torque will betransmitted from the input shaft to the forward-rear driving axle,regardless of the position of the rear axle system's connectionmeans. When the connection means of the forward axle gearsystems is in the engaged position, torque will be distributed toeither all of the driving axles or to the forward-rear and the middle-rear diving axles, depending on the position of the rear axle gearsystem's connection means. Thus, with this driving axle system, itis possible to alternate between one, two and three rear drivingaxles. Of course, it is also possible to connect one or more additional axle gear systems and driving axles.

The invention also relates to a motor vehicle comprising theproposed driving axle system, preferably wherein the motorvehicle is a heavy motor vehicle such as a bus or a truck, e.g. along haulage truck adapted to transport cargo on a trailer, amilitary truck, a construction or distribution truck, a truck for usein forestry, mining, etc. The motor vehicle may be a motor vehiclepowered by an internal combustion engine, or a motor vehicleentirely or partly powered by an electric power source, such as a hybrid vehicle.

Other advantageous features as well as advantages of the present invention will appear from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will in the following be further described by means of example with reference to the appended drawings, wherein Fig. 1a schematically shows a motor vehicle having a drivingaxle system according to an embodiment of theinvenüon, Fig. 1b schematically shows a motor vehicle having a driving axle system according to another embodiment of the invenüon, Figs.2a-bshow an axle gear system according to a firstembodiment of the invention, and Figs. 3a-bshow an axle gear system according to a second embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THEINVENTION An exemplary motor vehicle 1 according to an embodiment of theinvention is schematically shown in fig. 1a. The motor vehicle 1comprises a front axle 2 configured to steer the vehicle and a pairof front wheels 3 mounted thereon. lt further comprises apowertrain 4 including an engine 5, a transmission 6 and a drivingaxle system 7. The driving axle system 7 comprises an axle gearsystem 8, a forward driving axle 9 and a rear driving axle 10. Toeach driving axle, a wheel assembly including four wheels 3 ismounted, such that the motor vehicle 1 in total includes ten wheels 3 distributed between three axles 2, 9, 10.

Each driving axle 9, 10 may or may not include an axle differentialenabling rotation of the left and right wheel assemblies at mutuallydifferent rotation speeds. Such configurations are well known in the art and will not be further discussed herein.

A motor vehicle 1 according to another embodiment of theinvention is schematically shown in fig. 1b. The motor vehicle 1according to this embodiment differs from the one shown in fig. 1aonly in that it has a driving axle system 7 comprising a forwardaxle gear system 8 and a rear axle gear system 8, a forward drivingaxle 9, a rear driving axle 10, and a middle driving axle 31. Asdescribed above with reference to fig. 1, each driving axle 9, 10, 31 may or may not include an axle differential.

Axle gear systems 8 according to a first and a second embodiment of the invention are shown in figs. 2a-2b and figs. 3a-3b, respectively. ln both embodiments, an input shaft 11 having alongitudinal axis of rotation C is provided for transmission oftorque from the engine 5 to the driving axle system 7. A forwardoutput shaft 12 in the form of a pinion is configured to transmittorque from the input shaft 11 to the forward driving axle 9. Torqueis transmitted from the input shaft 11 to the forward output shaft12 via a transfer gear having a first gear member 13 mounted forcommon rotation with the input shaft 11 and a second gearmember 14 mounted for common rotation with the forward outputshaft 12. A rear output shaft 15 is configured to selectively transmittorque from the input shaft 11 to the rear driving axle 10. Theforward and the rear output shafts 12, 15 both extend in parallelwith the input shaft 11, but the forward output shaft 12 is laterallydisplaced with respect to the input shaft 11, while the rear outputshaft 15 shares the longitudinal axis of rotation C with the inputshaft 11.

A connection wheel 16 is connected for common rotation with therear output shaft 15 by means of mutually engaging splines 17.The connection wheel 16 is supported in a housing 18 surroundingthe components of the axle gear system 8 by means of a firsttapered rolling bearing 19, having cylinder shaped rolling elements19a. lts inner ring 19b is resting against a shoulder provided in theconnection wheel and its outer ring 19c is resting against thehousing 18. The first tapered rolling bearing 19 is tapered from theconnection wheel 16 toward the rear output shaft 15. The inputshaft 11 is supported in the connection wheel 16 by means of asecond tapered rolling bearing 20, which is smaller than the firstrolling bearing 19 but otherwise similar. The second tapered rolling bearing 20 has cylinder shaped rolling elements 20 and its inner 11 ring rests against a shoulder provided in the input shaft 11, whileits outer ring rests against a shoulder provided in the connectionwheel 16. The second tapered ro||ing bearing 20 is tapered fromthe input shaft 11 toward the rear output shaft 15. The input shaft11 is further supported in the housing 18 by a third tapered ro||ingbearing 21, arranged in a front portion of the housing 18. The thirdtapered ro||ing bearing 21 is tapered from an inside of the housing18 toward the input shaft 11.

A connection means in the form of a sleeve 22 having internalsplines is arranged around an externally splined section 23 of theinput shaft 11. The sleeve 22 and the input shaft 11 may thus rotate as a unit, due to the mutually engaging splines. ln the first embodiment, shown in figs. 2a and 2b, the sleeve 22has an axial end face 24 directed toward an axial end face 25 ofthe connection wheel 16. Both end faces 24, 25 are provided withteeth 26, 27. The sleeve 22 is movable along the longitudinal axisC between a disengaged position, shown in fig. 2a, and anengaged position, shown in fig. 2b. ln the engaged position, theend faces 24, 25 are in contact and the teeth 27 provided on theend face 25 of the connection wheel 16 interlock with the teeth 26provided on the end face 24 of the sleeve 22, such that theconnection wheel 16 and the input shaft 11 rotate as a unit.Thereby, also the input shaft 11 and the rear output shaft 15 rotateas a unit. ln the disengaged position, the teeth 26, 27 on the endfaces 24, 25 are not in mutual engagement. The connection wheel16 and the input shaft 11 are thus not connected for commonrotation, and no torque is thereby transferable to the rear outputshaft 15. 12 3a and 3b, theconnection wheel 16 is designed with an externally splined section ln the second embodiment, shown in figs.28, having splines adapted to engage with the internal splines ofthe s|eeve 22. The s|eeve 22 is movable between a disengagedposition, shown in fig. 3a, and an engaged position, shown in fig.3b. ln the disengaged position, the internal splines of the s|eeve22 are only in engagement with the external splines of the inputshaft 11. ln the engaged position, the s|eeve 22 partially overlapsboth of the externally splined section 23 of the input shaft 11 andthe externally splined section 28 of the connection wheel 16.Thereby, the internal splines of the s|eeve 22 engage with thesplines provided on the input shaft 11 as well as with the splinesprovided on the connection wheel 16, and the input shaft 11, the connection wheel 16 and the rear output shaft 15 rotate as a unit.

The movement of the s|eeve 22 between the engaged and thedisengaged positions is in both shown embodiments effected by acontrol device 29 having an actuator fork 30 adapted to move thes|eeve 22. The control device 29 is configured to receive an inputsignal from a driver of the motor vehicle 1, and based on this inputsignal control the actuator fork 30 such that it takes on one of twopossible positions, thereby moving the s|eeve 22 between theengaged and the disengaged positions. The input signal maycause a control system of the vehicle to send a signal to the controldevice 29. The signal may be an electric signal or a pneumatic orhydraulic pressure signal. ln both embodiments, the s|eeve 22 ismoved toward the rear output shaft 15 in order to be brought intothe engaged position, and in the other direction in order to be brought into the disengaged position. 13 During torque transmission between the input shaft 11 and theforward output shaft 12 and/or the rear output shaft 15, axial forcesincluding e.g. preload forces and gear forces are transmitted fromthe input shaft 11 via the second tapered rolling bearing 20 to theconnection wheel 16, reagardless of whether the sleeve 22 is inthe engaged position or in the disengaged position. The axialforces are further transmitted to the housing 18 via the first andthird tapered rolling bearings 19, 21. This is the case in both of the shown embodiments. ln the motor vehicle 1 shown in fig. 1a, the axle gear system 8distributes torque between the forward driving axle 9 via theforward output shaft 12 and the rear driving axle 10 via the rearoutput shaft 15. ln the motor vehicle 1 shown in fig. 1b, the forward axle gearsystem 8, corresponding to any one of the axle gear systems 8shown in figs. 2a-2b and 3a-3b, distributes torque between theforward driving axle 9 via its forward output shaft 12, and themiddle and rear driving axles 31, 10 via its rear output shaft 15.The rear axle gear system 8, also corresponding to any one of theaxle gear systems 8 shown in figs. 2a-2b and 3a-3b, distributestorque between the middle driving axle 31 via its forward outputshaft 12 and the rear driving axle 10 via its rear output shaft 15.When the connection means of the forward axle gear system 8 isin its disengaged position, torque is only transferred to the forwarddriving axle 9. When the connection means of the forward axlegear system 8 is in its engaged position, torque is transferred to the rear axle gear system 8 via the rear output shaft 15, functioning 14 as the input shaft 11 of the rear axle gear system 8. Dependingon the position of the connection means of the rear axle gearto both of the middle driving axle 31 and the rear driving axle 10, or only to the middle system 8, torque is therefore transferred driving axle 31.

The front axle configured to steer the vehicle may also beconfigured as a driving axle, in which case the vehicle comprises at least three driving axles.

The invention is of course not in any way restricted to the em-bodiments described above, but many possibilities to modifica-tions thereof would be apparent to a person with skill in the artwithout departing from the scope of the invention as defined in the appended claims.

Claims (14)

1 _

1. An axle gear system (8) for distribution of torque between a forward driving axle (9) and a rear driving axle (10) in a motor vehicle (1), comprising an input shaft (11), a forward output shaft (12) configured to transmit torque fromthe input shaft (11) to the forward driving axle (9), a rear output shaft (15) configured to transmit torque fromthe input shaft (11) to the rear driving axle (10), a connection wheel (16) connected for common rotation withthe rear output shaft (15), a first tapered ro||ing bearing (19) supporting the connectionwheel (16), a second tapered ro||ing bearing (20) supporting the input shaft (11) in the connection wheel (16), characterised in that it further comprises

2. a connection means (22) movable between an engagedposition in which the connection wheel (16) and the inputshaft (11) disengaged position in which the connection wheel (16) and are connected for common rotation, and athe rear output shaft (15) are disconnected. The axle gear system according to claim 1, wherein said connection means (22) comprises a sleeve (22) arranged around the input shaft (11), said sleeve (22) being movable along a longitudinal axis (C) of the input shaft (11). 16

3. The axle gear system according to claim 2, wherein saidsleeve (22) is provided with internal splines engaging with external splines provided on the input shaft (11).

4. The axle gear system according to claim 3, wherein theinternal splines of the sleeve (22) are configured to, in the engagedposition, engage on one hand with said external splines providedon the input shaft (11) and on the other hand with external splines provided on the connection wheel (16).

5. The axle gear system according to claim 2 or 3, wherein thesleeve (22) and the connection wheel (16) have end faces (24, 25)provided with teeth (26, 27) configured to engage with each other when the connection means (22) is in the engaged position.

6. The axle gear system according to any one of the precedingclaims, further comprising a control device (29) configured to movethe connection means (22) between the engaged position and the disengaged position upon receipt of a signal.

7. The axle gear system according to any one of the precedingclaims, further comprising a housing (18) in which the connectionwheel (16) and the input shaft (11) are supported and in which the connection means (16) is located. furthercomprising a third bearing (21) supporting the input shaft (11) inthe housing (18).

8. The axle gear system according to claim 7, 17

9. The axle gear system according to any one of the precedingclaims, wherein the forward output shaft (12) extends in parallelwith the input shaft (11).

10. A driving axle system (7) comprising at least one axle gearsystem (8) according to any one of the preceding claims, at leastone forward driving axle (9) driven by the forward output shaft (12),and at least one rear driving axle (10) driven by the rear outputshaft (15).

11. The driving axle system according to c|aim 10, wherein the driving axle system (7) is a tandem drive system.

12. The driving axle system according to c|aim 10, comprising atleast two of said axle gear systems (8) and at least three driving axles (9, 10, 31) driven by said at least two axle gear systems (8).

13. A motor vehicle (1) comprising a driving axle system (7)according to any one of claims 10-12.

14. The motor vehicle according to c|aim 13, wherein the motor vehicle (1) is a heavy motor vehicle such as a bus or a truck.