Drive device for a vehicle axle of a vehicle

A drive device for a vehicle axle of a two-track vehicle having a drive unit having in particular an electric machine, which outputs on the output side on at least one driveshaft leading to a vehicle wheel, which driveshaft is divided into a wheel-side shaft section and an axle-side shaft section which can be coupled to one another or decoupled from one another in a driving manner by means of a formfitting clutch, in order to avoid drag losses in the deactivated drive unit in driving operation with deactivated drive unit.

FIELD

The invention disclosure relates to a drive device for a vehicle axle of a two-track vehicle.

BACKGROUND

In a generic all-wheel-drive vehicle having electric drive, the front axle and the rear axle can have at least one electric machine independently of one another. Depending on driving operation, for example, the electric machine of the front axle can be non-energized and solely the electric machine of the rear axle can be energized, so that the vehicle is only driven using the rear axle. In this way, the overall efficiency is increased and the range is extended. However, in the case of such a purely rear axle operation, friction losses occur (air friction and bearing friction, gear teeth friction in the transmission, splashing losses, etc.) due to the entrained, deactivated front axle drive.

A drivetrain for a motor vehicle having a clutch-controlled all-wheel-drive is known from DE 10 2015 210 227 A1. An actuating device for a claw clutch is known from DE 20 2015 000 397 U1. An electromagnetic clutch is known from DE 1 575 783 A.

SUMMARY

The object of the invention is to provide a drive device for a vehicle axle of a vehicle, which is electrically operated in particular, with which, in driving operation, drag losses in a deactivated drive unit can be reduced.

According to the invention, the drive unit outputs on the output side on at least one driveshaft leading to a vehicle wheel. According to the characterizing part of claim1, this driveshaft is divided into a wheel-side shaft section and into an axle-side shaft section, which can be coupled to one another or decoupled from one another in a driving manner by means of a formfitting clutch. In the decoupled state, torque transmission does not occur between the wheel-side shaft section and the axle-side shaft section so that in driving operation and with deactivated drive unit, drag losses can be avoided in the deactivated drive unit. In this way, for example, a vehicle axle (especially the front axle) can be coupled or decoupled as needed, preferably independently of the driving state.

In a technical implementation, the formfitting clutch has a sliding collar, which is arranged in a rotationally-fixed, but axially displaceable manner on plug-in gear teeth of a first shaft section. The sliding collar can be displaceable by means of an axial positioning force generated by an actuator between an open clutch state, in which the sliding collar is moved out of formfitting connection to the second shaft section, and a closed clutch state, in which the sliding collar is moved into formfitting connection with the second shaft section.

With regard to the high package density in the region of the vehicle axle, a compact implementation, which is reduced in installation space, of the formfitting clutch including actuator is of great significance. Against this background, an actuator sleeve can be associated with the actuator, which is arranged on a cylindrical sliding collar outer circumference. For the rotational decoupling from the sliding collar, which rotates in operation, the actuator sleeve can be mounted via at least one roller bearing on the sliding collar outer circumference, specifically so that the axial positioning force generated by the actuator is introduced via the rotationally-decoupled actuator sleeve and the roller bearing into the sliding collar.

In a first embodiment variant, for a positioning force transmission, both the bearing outer ring of the roller bearing can be attached to the actuator sleeve to transmit positioning force and also the bearing inner ring of the roller bearing can be attached to the sliding collar to transmit positioning force.

The above actuator sleeve can be adjusted by means of the actuator between an open position, in which the formfitting clutch is open, and a closed position. For this purpose, the actuator can interact via a gearing step with the actuator sleeve. In an implementation advantageous for installation space, this gearing step can have outer gear teeth on the cylindrical sliding collar outer circumference. The teeth are spaced apart from one another in the axial direction in the outer gear teeth and are in tooth engagement with a gear wheel of an actuator shaft of an electric motor, which forms the actuator.

A formfitting clutch is preferably embodied as a claw clutch, in which the sliding collar and the second shaft section have wheel-side and axle-side shifting claws facing toward one another axially. The cylindrical sliding collar outer circumference can merge into the larger-diameter shifting claws while forming an inner corner region. The actuator sleeve can be situated in a manner favorable for installation space in the inner corner region thus formed.

During the closing procedure of the above claw clutch, the wheel-side and axle-side shifting claws can be opposite to one another tooth on gap in the axial direction, so that a smooth formfitting coupling can take place. In the more probable case, in contrast, first the shifting claws come into contact tooth on tooth during the closing procedure. From reaching the contact tooth on tooth, according to the invention the actuator sleeve is adjusted further into its closed position, specifically while building up a spring force of an overload spring acting axially on the shifting claws, by means of which the wheel-side and axle-side shifting claws are clamped against one another. As soon the shifting claws are brought into a relative location tooth on gap by a slight relative angle pivot of the two clutch halves, the wheel-side and axle-side shifting claws can establish a formfitting connection with dissipation of the spring force.

In one technical implementation, the wheel-side shifting claws can be formed on a carrier ring, which is arranged in a rotationally-fixed and axially-displaceable manner on the wheel-side shaft section via plug-in gear teeth. The carrier ring can be supported on its side axially opposite to the axle-side shaft section via the above-mentioned overload spring against an axial stop of the wheel-side shaft section. Therefore, if the wheel-side and axle-side shifting claws come into a contact tooth on tooth during the closing procedure of the claw clutch, the actuator sleeve including sliding collar is adjusted into the closed position, so that the sliding collar adjusts the carrier ring by a compensation stroke on the wheel-side shaft section while building up the spring force. As soon as tooth stands on gap due to a slight relative angle pivot of the two clutch halves, the formfitting connection takes place, during which the wheel-side carrier ring establishes a formfitting connection with the axle-side shifting claws while consuming the above compensation stroke and while dissipating the spring force.

A second embodiment variant is described hereinafter, in which the actuator sleeve is no longer seated on the bearing outer ring of the roller bearing to transmit positioning force, but rather is seated so it is axially displaceable on the bearing outer ring of the roller bearing. The bearing inner ring of the roller bearing remains axially fixed and rotationally fixed as before, that is to say arranged on the sliding collar to transmit positioning force. A ring gap, in which the overload spring is arranged, can be provided between the actuator sleeve and the cylindrical sliding collar outer circumference. The overload spring is supported in the axial direction between an actuator sleeve axial stop and the roller bearing bearing outer ring. During the closing procedure, the actuator sleeve and the sliding collar can thus be adjusted in a movement-coupled manner until reaching a contact tooth on tooth. From reaching the contact tooth on tooth, the actuator sleeve is adjusted in a movement-decoupled manner from the sliding collar further into its closed position, specifically while building up the spring force of the overload spring. Due to a slight relative angle pivot of the two clutch halves, the shifting claws can be brought into a relative location tooth on gap, so that the sliding collar is brought into formfitting connection together with axle-side shifting claws formed thereon while dissipating the spring force of the overload spring.

DETAILED DESCRIPTION

An electrically operated motor vehicle is shown inFIG.1, which has an electrically drivable front axle VA and an electrically drivable rear axle HA. The front axle VA is equipped with precisely one electric machine EM, which outputs via a front axle differential3onto the left and right driveshafts7,9leading to the right and left front wheel5. The rear axle HA has a drive device, in which, in contrast to the front axle VA, one electric machine EM1, EM2is associated with each of the rear wheels15, which electric machines are connected in a driving manner via transmission steps U1, U2to the driveshafts11of the rear axle HA. As can furthermore be seen fromFIG.1, the front right driveshaft9is divided into a wheel-side shaft section17and into an axle-side shaft section19, which can be coupled to or decoupled from one another by means of a claw clutch21.

With open claw clutch21, therefore only a no-load compensation movement of the compensation bevel gears29in the front axle differential3therefore remains in driving operation. The remainder of the driving unit (that is to say transmission and electric machine) come to a standstill, in contrast, so that friction losses are strongly reduced.

For coupling (i.e., during the closing of the claw clutch21), first the electric machine EM is energized and thus the displaceable part of the claw clutch21is synchronized to the present wheel speed. If synchronization is nearly achieved, the actuator49is activated. As described later, the actuator49acts via gear teeth on a non-rotating actuator sleeve53. This presses via a spring-ball bearing combination on the displaceable part of the claw clutch21.

According toFIG.2, the electric machine EM of the front axle VA is connected in a driving manner via a reduction gearing23to an input-side outer gear wheel25of the front axle differential3. On the output side of the front axle differential3, axle bevel gears27are connected to the two driveshafts7,9. The axle bevel gears27and compensation bevel gears29meshed therewith are positioned inside a compensation housing31of the axle differential3.

The structure and the mode of operation of the claw clutch21according to a first exemplary embodiment is described hereinafter on the basis ofFIGS.3and4. InFIG.3, the axle bevel gear27is extended using an axle hollow shaft, which forms the axle-side shaft section19. A plug-in shaft, which forms the wheel-side shaft section17, led to the front wheel5is rotationally mounted radially inside the axle hollow shaft19. The claw clutch21has axle-side shifting claws33and wheel-side shifting claws35inFIG.3, which are in a formfitting connection with one another when claw clutch21is closed. The axle-side shifting claws33are part of a sliding collar37inFIG.3, which is arranged in a rotationally-fixed, but axially-displaceable manner on plug-in gear teeth39of the axle hollow shaft19. The wheel-side shifting claws35are formed on a carrier ring41, which is mounted in a rotationally-fixed, but axially-displaceable manner via plug-in gear teeth43on the plug-in shaft17. The carrier ring41is supported on its side axially opposite to the axle hollow shaft19by means of an overload spring45against an axial stop47of the plug-in shaft17.

The sliding collar37arranged in an axially-displaceable manner on the axle hollow shaft19is actuatable inFIG.3via an actuator49, which is implemented as an electric motor. The actuator49is in a driving connection with an actuator sleeve53via a gearing step51. The actuator sleeve is arranged on a cylindrical sliding collar outer circumference55. For rotational decoupling from the sliding collar37, which rotates in operation, the actuator sleeve53is mounted via two roller bearings (alternately also plain bearings)57,59on the cylindrical sliding collar outer circumference55. InFIG.3, a bearing outer ring61of the roller bearings57,59is pressed into the inner circumference of the actuator sleeve53, i.e., attached to the actuator sleeve53to transmit positioning force. Moreover, a bearing inner ring63of the roller bearing57,59is pressed onto the sliding collar outer circumference55, i.e., attached to the sliding collar37to transmit positioning force. In this way, an axial positioning force FSgenerated by the actuator49is introduced via the rotation-decoupled actuator sleeve53and further via the two roller bearings57,59into the sliding collar37.

The gearing step51connected between the actuator49and the actuator sleeve53is formed inFIG.3by a drive gear wheel67formed on an actuator shaft, which is in tooth engagement with outer gear teeth69on the outer circumferential side of the sliding collar37. The outer gear teeth69have teeth spaced apart from one another in the axial direction.

A closing procedure of the claw clutch21is described hereinafter on the basis ofFIG.3, in which the wheel-side and axle-side shifting claws33,35are axially opposite to one another tooth58on gap60. In this case, the actuator49is activated to displace the actuator53together with the sliding collar37movement-coupled thereto from the illustrated open position I into a closed position S, in which the wheel-side and axle-side shifting claws33,35are brought smoothly into engagement.

A closing procedure is described on the basis ofFIG.4, in which the wheel-side and axle-side shifting claws33,35are not axially opposite to one another tooth58on gap60, but rather are opposite to one another tooth58on tooth58. In this case, during the closing procedure, the wheel-side and axle-side shifting claws33,35first come into contact tooth58on tooth58. From reaching the contact tooth58on tooth58(FIG.4), the actuator sleeve53together with sliding collar37is adjusted farther by an overload stroke Δh (not shown inFIG.4) into the closed position II, wherein the carrier ring41is displaced by the overload stroke h on the plug-in shaft17while building up a spring force of the overload spring45. As soon as tooth58is opposite to gap60due to a slight relative angle pivot, the carrier ring41is brought suddenly into formfitting connection with the axle-side shifting claws33of the sliding collar37while consuming the overload stroke Δh and while dissipating the spring force of the overload spring45.

A second exemplary embodiment is shown inFIGS.5and6, in which the carrier ring41is pressed onto the plug-in shaft17no longer in an axially-displaceable manner, but rather in an axially-fixed and rotationally-fixed manner. The overload spring45is arranged inFIG.7in a ring gap71between the actuator sleeve53and the cylindrical sliding collar outer circumference55.

In contrast to the first exemplary embodiment, inFIG.5, the actuator sleeve53is no longer arranged to transmit positioning force, but rather in an axially-displaceable manner on the bearing outer ring61of the respective roller bearing57,59. The bearing inner ring63of the roller bearing57,59is still positioned in an axially-fixed and rotationally-fixed manner, that is to say to transmit positioning force, on the sliding collar37. The overload spring45is supported inFIG.5in the axial direction between an axial stop73of the actuator sleeve53and an intermediate disk75. This is positioned loosely within the ring gap71and presses against the bearing outer ring61of the roller bearing57.

A closing procedure of the claw clutch21shown inFIG.5is described hereinafter. InFIG.5, the wheel-side and axle-side shifting claws33,35are opposite to one another tooth58on gap60, so that the actuator sleeve53together with the sliding collar37are adjustable smoothly into the closed position II in a movement-coupled manner, to establish a formfitting connection between the axle-side and wheel-side shifting claws33,35.

A closing procedure is illustrated on the basis ofFIG.6, in which the shifting claws33,35are opposite to one another tooth58on tooth58. In this case, during the closing procedure, the actuator sleeve53together with sliding collar37is first adjusted in a movement-coupled manner, specifically until reaching the contact tooth58on tooth58(FIG.6). From reaching the contact tooth58on tooth58(FIG.6), the actuator sleeve53is adjusted further into its closed position II by the overload stroke Δh—in a movement-decoupled manner from the sliding collar37—specifically while building up the spring force of the overload spring45. The shifting claws33,35are moved by a slight relative angle pivot into a relative location tooth58on gap60, so that the shifting claws33,35can be moved suddenly into formfitting connection while dissipating the spring force.

For the coupling (closing procedure), first the electric machine EM is energized and thus the displaceable part of the clutch is synchronized to wheel speed. If synchronization is nearly reached, the actuator49is activated, which acts via gear teeth on the nonrotating actuator sleeve53. This presses via a spring-ball bearing combination on the displaceable part of the claw clutch.

LIST OF REFERENCE SIGNS