Patent Application
20120053002
The invention relates to a coupling assembly for connecting a drive axle in a multi-axle driven motor vehicle. Generally, there are two different drive systems: one where a plurality of drive axles of the motor vehicle is permanently driven and one where a first drive axle is driven permanently, with a second drive axle being connected when required. Such drive systems with an optionally connectable drive axle are referred to as hang-on or on-demand systems.
From DE 103 11 427 A1 there is known a differential drive with a differential carrier. There is provided a first coupling package for producing a torque-transmitting connection from a drive to the differential carrier. Furthermore, there is provided a second coupling package for blocking a relative rotation between the differential carrier and a sideshaft gear. The first and the second coupling package are actuated via a ball ramp setting drive.
DE 103 04 730 B3 proposes a multi-plate coupling for transmitting torque between a coupling hub and a coupling carrier. Between the coupling hub and the coupling carrier there is arranged a plate package which can be actuated via an axial setting device. The plate package is axially supported on a supporting disc. The supporting disc is connected to the coupling hub in a rotationally fixed way and forms a form-locking connection with the coupling carrier.
From DE 39 13 487 A1 there is known a four-wheel drive tractor whose front axle differential and rear axle differential are permanently driven during off-road applications. In order to prevent any distortions between the front axle and rear axle during cornering, there is provided a coupling between the ring gear of the rear axle differential and the differential carrier. The coupling is ventilated via an actuating cylinder and can thus be controlled under conditions of slip.
From EP 0 466 863 B1 there is known a device for connecting a driveline of a motor vehicle. One of the drivelines is permanently connected to a drive unit and a further driveline is designed to be optionally connectable to the drive unit.
DE 38 15 225 A1 proposes a lockable differential drive. For locking the differential, there is provided a friction coupling which can be actuated by a ball ramp assembly. The ball ramp assembly is driven by an electric motor.
From DE 101 60 026 A1 there is known an actuating mechanism for axial setting purposes for a transfer case of a multi-axle driven motor vehicle. The actuating mechanism comprises a central disc which is rotatable relative to two outer discs. Thus, a locking coupling for the differential drive can be actuated on the one hand and a two-stage gearbox can be switched, on the other.
DE 10 2008 037 885.2-21 proposes a drive assembly with a hang-on coupling and a differential unit for a multi-axle driven motor vehicle. The hang-on coupling is provided in the form of a friction plate coupling which is arranged coaxially relative to the rotational axis of the differential carrier of the differential unit.
It is the object of the present invention to propose a drive assembly which permits a secondary driveline to be optionally drivable and a differential to be locked, wherein the drive assembly should comprise a compact design and a low weight and it should be suitable for being easily integratable into a drive concept.
The objective is achieved by providing a drive assembly for a multi-axle driven motor vehicle, comprising a differential unit with a rotational axis A, one input part and two output parts drivingly connected to the input part, wherein the two output parts have a differential effect relative to one another; an externally controllable hang-on coupling for drivingly connecting the differential unit to a driveshaft; an externally controllable locking coupling for restricting the differential movement between the two output parts of the differential unit; wherein the hang-on coupling and the locking coupling are arranged coaxially relative to the rotational axis A. The drive assembly comprises at least one actuator for actuating the hang-on coupling and the locking coupling, wherein, preferably, there is provided exactly one single actuator which serves to actuate both the hang-on coupling and the locking coupling.
The inventive drive assembly is advantageous in that it has two functions, i.e. to optionally drive a secondary driveline and to restrict the compensating movement of the differential unit and in that it comprises a compact design at the same time. Because the hang-on coupling and the locking coupling are arranged coaxially relative to one another and to the differential unit, both couplings can be actuated by one single actuator. To that extent, the inventive drive assembly manages with relatively few components, which has an advantageous effect on the installation space and the production costs. However, in principle, it is also feasible that for the hang-on coupling there is provided a first actuator and for the locking coupling a separate second actuator. A further advantage of the inventive drive assembly consists in that the angle drive by means of which torque is introduced from the propeller shaft into the differential assembly is stationary when the hang-on coupling is open. In this way it is possible to reduce rotational friction losses of the bearings of the ring gear and of the driving pinion which bearings are normally pretensioned with high forces. In addition, it is possible to avoid splashing losses which are caused by the rotation of the ring gear around the rotational axis, which, in turn, advantageously affects the fuel consumption of the motor vehicle.
According to a first embodiment it is proposed that locking coupling is provided in the form of a form-locking coupling. Form-locking couplings are meant to be couplings wherein the transmission of torque is effected by a form-locking engagement between a first coupling part and a second coupling part. As examples, claw couplings, dog clutches or toothed couplings are named. By closing the locking coupling it is ensured that the two sideshaft gears and the carrier element of the differential unit rotate jointly as a block around the rotational axis, i.e. compensating movement between the sideshaft gears cannot take place any more. Said embodiment comprising a form-locking coupling represents a particularly compact solution for providing a differential lock, with the actuation mechanics for the hang-on coupling at the same time being used for actuating the locking coupling.
In a preferred embodiment, the locking coupling comprises a first coupling part which is connected in a rotationally fixed way to a carrier element of the differential unit, as well as a second coupling part which is connected in a rotationally fixed way to a sideshaft of the differential unit, with there being provided at least one actuating lever to cause the first coupling part to engage the second coupling part for transmitting torque. The at least one actuating lever is preferably supported so as to be pivotable around a pivot axis, wherein a first end of the lever is effectively connected to the coupling parts of the locking coupling and a second end of the lever is effectively connected to one of the coupling parts of the locking coupling. In this way, the actuating lever acts as a seesaw, with an axial movement of an actuator component causing the locking coupling to be axially loaded. A particularly advantageous kind of force transmission is achieved if a first lever arm between the force application point of the actuating lever at the actuator and at the pivot bearing is smaller than a second lever arm between the force application point of the actuating lever at the coupling part and the pivot bearing. As a result of this embodiment, a shorter axial setting path of the movable component of the actuator is translated into a long axial setting path at the locking coupling, and it is particularly advantageous if the transmission ratio is approximately 3:1.
The actuator of the first embodiment is preferably designed in such a way that, starting from a unactuated condition in which the hang-on coupling and the locking coupling are open, in a first actuating region, first the locking coupling is loaded and that, in a second actuating region, in addition to the locking coupling, the hang-on coupling is actuated, too. In this way, it is ensured that the form-locking locking coupling is securely closed before torque is transmitted to the axle. The actuator preferably comprises a ball ramp assembly which comprises an axially supported supporting disc and a setting disc which is axially displaceable relative thereto, wherein by rotating the two discs relative to one another, the setting disc is axially displaceable. In this context, a relative rotation relative to one another means that either the supporting disc or the setting disc can be rotated relative to the respective other disc while the respective other disc is held in a rotationally fixed condition. More particularly, it is proposed that the two discs each comprise ball grooves whose depths vary around the circumference and in which there are accommodated balls, wherein the two discs are axially supported relative to one another via the balls. The ball grooves of the two discs are preferably designed in such a way that the hang-on coupling is actuated by relatively rotating the two discs into a first direction of rotation and that, the locking coupling, too, is actuated by relatively rotating the two discs in the opposed second direction of rotation.
In a preferred embodiment, the setting disc, on its radial inside, comprises a form-engaging element which engages a driving element at the first end of the actuating lever, wherein, by axially displacing the setting disc, the actuating lever is pivoted around the pivot axis and wherein the coupling parts of the locking coupling are made to engage one another. More particularly, it is proposed that the first coupling part of the locking coupling is axially displaceable relative to the carrier element of the differential unit and that the second coupling part of the locking coupling is axially supported relative to the sideshaft. For example, the first coupling part can be provided in the form of a switching sleeve which, by means of shaft teeth is held on a sleeve projection of the carrier element in a rotationally fixed and axially displaceable way. The second coupling part can be provided in the form of a toothed shaft rim which, by means of shaft teeth, is connected to the sideshaft in a rotationally fixed way. For torque transmitting purposes, the switching muff and the shaft rim, at their end faces facing one another, can each be provided with a face toothing which can engage one another in a form-locking way. To achieve a compact design, it is advantageous if the locking coupling is arranged radially inside the actuator. In order to ensure that the two coupling parts securely and form-lockingly engage one another, it is proposed in an advantageous way that the at least one actuating lever is designed to be intrinsically elastically resilient. It could be any number of actuating levers, the number depending on the force to be transmitted. To achieve a uniform distribution of force around the circumference, a number of three actuating levers is advantageous.
In a concrete embodiment, the ball grooves of at least one of the discs, in the first direction of rotation, starting from an end position in which the two discs approach one another, comprise a first portion with a first gradient and a second portion with a second gradient, wherein the gradient of the first portion is greater than the gradient of the second portion. When the respective disc is actuated, the actuator stroke initially takes place on the steep first portion in order to quickly close the coupling play and then it takes place on the flatter second portion, which allows an accurate adjustment of the torque to be transmitted. When actuation takes place in said first direction of rotation, the actuating lever is not moved, so that the locking coupling remains unactuated.
In the second direction of rotation, the ball grooves of said disc, starting from the end position, comprise a first portion with a first gradient, a second portion with a second gradient and a third portion with a third gradient, wherein the gradients of the first and of the second portion are each greater than the gradient of the third portion. This embodiment ensures that the setting disc moves and axially displaces the actuating lever, so that the locking coupling is loaded. First, the first portion is passed, which first portion is short and steep in order to ensure that the actuating lever is gripped from behind. There then follows the second portion which is similarly steep like the first portion, as well as the third portion which is flatter than the first and the second portion. This embodiment advantageously ensures that the form-locking locking coupling is securely closed prior to the hang-on coupling reaching its abutment point. It goes without saying that there can also be provided transition portions between said portions.
According to a second embodiment it is proposed that the hang-on coupling is provided in the form of a friction plate coupling. This is advantageous in that the locking effect can be variably set as required by controlling the actuator. Accordingly, by means of the friction plate coupling it is possible to set any desirable intermediate position between an open position in which no torque is transmitted between the coupling input part and the coupling output part, and a closed position in which the coupling parts are fully closed and jointly rotate around the rotational axis. More particularly, a compact design of the second embodiment is achieved in that the hang-on coupling and the locking coupling are coaxially arranged inside one another, with the hang-on coupling preferably being effectively arranged between the input part of the drive assembly and a carrier element of the differential unit and with the locking coupling preferably being effectively arranged between the carrier element and a sideshaft gear of the differential unit.
In both embodiments, the actuator preferably comprises a ball ramp assembly which comprises an axially supported supporting disc, an axially displaceable first setting disc for loading the hang-on coupling as well as an axially displaceable second setting disc for loading the locking coupling. The two setting discs can be loaded by the supporting disc in the same axial direction. More particularly it is proposed that the second disc for actuating the locking coupling is arranged coaxially inside the first disc for actuating the hang-on coupling. At its end face facing the setting discs, the supporting disc comprises circumferentially distributed first ball grooves which are arranged opposite the ball grooves of the first setting disc, as well as circumferentially distributed second ball grooves which are arranged coaxially inside the first ball grooves and opposite the ball grooves of the second setting disc. In the first ball grooves of the supporting disc and in the opposed ball grooves of the first setting disc, there are arranged first balls via which the first setting disc is axially supported on the supporting disc. Accordingly, in the inner second ball grooves of the supporting disc and in the opposed ball groves of the second setting disc there are arranged second balls via which the second setting disc is axially supported on the supporting disc.
At least the ball grooves of the supporting disc are preferably designed in such a way that, starting from the unactuated condition in which the hang-on coupling and the locking coupling are open, in a first actuation circumference, first the hang-on coupling is loaded and, in a second actuation circumference, the locking coupling, too, is loaded in addition to the hang-on coupling. To put the invention into effect, it is proposed that the ball grooves are designed in such a way that, starting from an end position in which the discs are arranged close to one another, by rotating the supporting disc, first only the first setting disc is axially loaded for actuating the hang-on coupling. The torque to be transmitted can be set by controlling the setting angle in accordance with requirements. If the locking function is required, the supporting disc is further rotated, so that, in addition to the first setting disc, the second setting disc, too, is axially loaded for actuating the locking coupling. The hang-on coupling is fully closed. By compressing the locking coupling, the carrier element of the differential unit, also referred to as differential carrier or differential cage, is connected to a sideshaft gear in a friction-locking way. In this way, the compensating effect of the sideshaft gears is restricted, i.e. the differential unit is locked.
According to a preferred concrete embodiment, the first ball grooves of the supporting disc each comprise a first gradient portion within which the actuation of the hang-on coupling takes place. Said gradient portion is followed by a second portion without a gradient in which the balls run when the locking coupling is actuated. The ball grooves of the first setting disc preferably correspond to the first ball grooves of the supporting disc, i.e. they also comprise a portion with a gradient and a portion without a gradient. The second ball grooves of the supporting disc each comprise a first portion without a gradient which, more particularly, is positioned in the circumferential region of the gradient portions of the first ball grooves. These are followed by gradient portions by means of which the locking coupling is actuated. The ball grooves of the second setting disc preferably correspond to the second ball groove of the supporting disc.
According to a third embodiment, in the case of which the hang-on coupling is also provided in the form of a friction coupling, the actuator is axially arranged between the hang-on coupling and the locking coupling. Said embodiment is similar to the second embodiment in that the actuator preferably also comprises a ball ramp assembly. There are achieved the same advantages of a compact design while comprising the possibility of variably setting the locking effect of the differential by means of the friction plate coupling.
The ball ramp assembly of the third embodiment preferably comprises an axially supported supporting disc, a first setting disc for the hang-on coupling, which first setting disc can be axially moved in a first direction, and a second setting disc for the locking coupling, which second setting disc can be moved in an opposed second direction. The supporting disc is axially arranged between the first setting disc and the second setting disc. In this case, too, it is proposed that the supporting disc and the two setting discs each comprise ball grooves with variable depths around the circumference in which there are received balls, with the two setting discs being axially supported via the balls relative to the supporting disc. The ball grooves are designed in such a way that, starting from an end position in which the discs are arranged close to one another, by rotating the supporting disc, initially only the first setting disc is axially loaded for actuating the hang-on coupling and that, by rotating the supporting disc further, in addition to the first setting disc, the second setting disc is also axially loaded for actuating the locking coupling. For this purpose, the first ball grooves of the supporting disc, which are positioned opposite the first setting disc, comprise a first portion with a gradient which is unequal to zero and a second portion with a constant groove depth, with the ball grooves of the first setting disc being of a corresponding design. Furthermore, the second ball grooves of the supporting disc, which are arranged opposite the second setting disc, comprise a first portion without a gradient and a second portion with a gradient.
According to a fourth embodiment, which largely corresponds to the third embodiment, it is proposed that the ball grooves are designed in such a way that, by rotating the supporting disc into a first direction of rotation, the first setting disc is axially loaded for actuating the hang-on coupling, and that, by rotating the supporting disc in an opposed second direction of rotation, both the first setting disc for actuating the hang-on coupling and also the second setting disc for actuating the locking coupling are axially loaded. For this purpose, the ball grooves of the first setting disc preferably comprise a central portion with a greatest groove depth and, adjoining thereto in both circumferential directions, a first gradient portion and a second gradient portion. The second ball grooves of the supporting disc, which are arranged opposite the second setting disc, each comprise a first portion with a greatest groove depth without a gradient, a central second portion with a gradient and a third portion with a smaller groove depth without a gradient.
It applies to all the above-mentioned embodiments that the hang-on coupling is preferably provided in the form of a friction plate coupling, with an outer plate carrier of the hang-on coupling being connected in a rotationally fixed way to an input part of the drive assembly, with an inner plate carrier of the hang-on coupling being connected in a rotationally fixed way to a carrier element of the differential unit.
Preferred embodiments will be explained below with reference to the drawings wherein
The drive assembly comprises a ring gear 7 via which, by means of a pinion (not illustrated), torque can be introduced into the drive assembly 2. The ring gear 7 is firmly connected to a flange of a hollow shaft 8, and via bearing means 9, 9′, is supported so as to be rotatable around a rotational axis A in the housing 10 of the drive assembly 2. At its end facing the differential 3, the hollow shaft 8 comprises splines 11 which, for torque transmitting purposes, are engaged by correspondingly designed splines of a first coupling part 12 of the hang-on coupling 4. The first coupling part 12 is provided in the form of a coupling carrier which is arranged coaxially relative to the axis of rotation A and inside which there is arranged the differential unit 3. It can be seen that the hang-on coupling 4 is provided in the form of a friction plate coupling which comprises an outer plate carrier to which outer plates are connected in an axially displaceable and rotationally fixed way, as well as an inner plate carrier to which inner plates are connected in a rotationally fixed and axially displaceable way. The outer plates and inner plates are arranged so as to axially alternate and jointly form the plate package 14 of the hang-on coupling 4. The inner plate carrier forms the second coupling part 13 of the hang-on coupling 4, which coupling part 13 can also be referred to as the coupling output part.
The second coupling part 13 is firmly connected to an input part 15 of the differential unit 3 and is preferably produced so as to be integral therewith. The input part 15 is provided in the form of a differential carrier 15 which is arranged so as to be rotatingly drivable around the axis of rotation A. In the differential carrier 15, differential gears 16 are supported so as to be rotatable on journals 17 and jointly rotate with the differential carrier 15 around the rotational axis A. The differential gears 16, 16′ engage sideshaft gears 18, 18′ which are arranged coaxially relative to the rotational axis A and which, via abutment discs, are axially supported relative to the differential carrier 15. The sideshaft gears 18, 18′ each comprise a bore with splines into which, for torque transmitting purposes, there is inserted an associated sideshaft 19 of which, in the present embodiment, only the righthand sideshaft is shown. The differential carrier 15 comprises a first carrier part 22 which, via bearing means 23, is supported relative to the hollow shaft 8 so as to be rotatable around the rotational axis A, as well as a second carrier part 24 which is firmly connected thereto and which, at the opposite end, comprises a sleeve projection 25. By means of the sleeve projection 25, the differential carrier 15 is rotatably supported on the sideshaft 19.
The actuator 6 which, inter alia, serves to actuate the hang-on coupling 4, comprises a supporting disc 26 which is axially supported relative to the housing 10 of the drive assembly 2, as well as a setting disc 28 which is arranged opposite the supporting disc 26. In the opposed end faces of the supporting disc 26 and respectively, of the setting disc 28, there are circumferentially distributed ball grooves 29, 30 whose depth varies around the circumference and in each of which there is arranged a ball. The balls are received in pockets of a cage 32 arranged axially between the two discs 26, 28 and are thus held in their circumferential position. For actuating the ball ramp assembly, there is provided an electric motor which is able to rotate the setting disc 28 relative to the supporting disc 26.
When the electric motor (not illustrated) is actuated, the balls held in the ball grooves 29, 30 move into the regions of a lesser depth, which means that the setting disc 28 moves axially towards the hang-on coupling 4. The setting disc 28 is axially supported relative to a pressure plate 34 by means of an axial bearing 33. By rotating the setting disc 28, the pressure plate 34 moves towards the hang-on coupling 4, with the pressure plate 34 axially loading the plate package 12. In this way, torque is transmitted from the first coupling part 12 to the differential carrier 15. In the fully opened condition of the hang-on coupling 4, no torque at all is transmitted, so that the first coupling part 12 including the hollow shaft 8 and the ring gear 7 is stationary, whereas in the fully closed condition of the hang-on coupling 4 torque is transmitted from the ring gear 7 to the sideshafts 19, 19′. Between the pressure plate 34 and the second coupling part 24 there is arranged a returning spring 35 which, in the unactuated condition of the actuator 6, axially loads the pressure plate 34 towards the supporting disc 26.
In addition to actuating the hang-on coupling 4, the actuator 6 has a further function, i.e. the actuation of the locking coupling 5. In the present embodiment, the locking coupling 5 is provided in the form of a form-locking coupling, i.e. the transmission of torque takes place as a result of the form-locking engagement between the two coupling parts 42, 44. It can be seen that the setting disc 28, at its inner end, comprises form-engagement means 36 which cooperate with a plurality of circumferentially distributed actuating levers 37. The actuating levers 37 are supported so as to be pivotable around individual pivot axes S. The radially outer first end 39 of the actuating levers 37 is provided in the form of a yoke which embraces the form-engaging means 36. The radially inner second end 40 of the actuating levers 37 each engages a radial recess 41 of the first coupling part 42.
This embodiment—when the setting disc 28 is moved axially—causes the actuating lever 37 to pivot, with the first coupling part 42 being moved towards the second coupling part 44. It can be seen that a first lever arm H1 between the force application point of the actuating lever 37 at the actuator 6 and the pivot bearing S is smaller than a second lever arm H2 between the force application point of the actuating lever 37 at the first coupling part 42 and the pivot bearing S. In this embodiment, a shorter axial setting path of the setting disc 28 of the actuator 6 is translated into a longer axial setting path at the locking coupling 5. The first coupling part 42 is provided in the form of a switching sleeve which, by means of longitudinal teeth 43, is arranged on the sleeve projection 25 of the differential carrier in a rotationally fixed way and is axially displaceable relative thereto. At its end facing the second coupling part 44, the first coupling part 42 comprises a face toothing 45 which is able to engage a correspondingly designed face toothing 47 of the second coupling part 44. The second coupling part 44 is provided in the form of a toothed shaft rim which, via longitudinal teeth 46, is connected to the sideshaft 19 in a rotationally fixed way. The second coupling part 44 and, respectively, the sideshaft 19 are supported via a rolling-contact bearing 48.
Below, with reference to
If rotation occurs in the opposed second rotational direction R2, the profile of the ball grooves is such that, starting from the lowest point in the central portion 50, there is initially obtained a smaller, relatively steep first groove portion 53 with a circumferential extension c as well as a circumferentially adjoining second groove portion 54 with a greater circumferential extension d and a constant groove depth. When moving over said first and second groove portions 53, 54, it is first ensured that the actuating lever 37 is gripped from behind. The second groove portion 54 is followed by a third groove portion 55 with a circumferential extension e and a fourth groove portion 56, with the fourth groove portion 56 extending around a greater circumferential length f and comprising a smaller gradient than the third groove portion 55. The third groove portion 55 ensures the closing of the locking coupling 5, whereas in the circumferential region of the fourth groove portion 56, the hang-on coupling is actuated. The present profile of the ball grooves 30 in the second rotational direction R2 ensures that the form-locking locking coupling 5 is securely closed before the hang-on coupling 4 has reached its abutment point.
The plate package 114 of the hang-on coupling 104 is axially supported relative to the coupling cage by spring means 160 which are preferably provided in the form of plate springs. In addition to the outer plate carrier, the coupling cage 112 comprises a cover part 161, which cover part 161 is firmly connected to the outer plate carrier, for example by welding. The cover part 161 comprises a flange portion with a plurality of circumferentially distributed first apertures 162 through which first actuating punches 163 are guided, as well as second apertures 165 which are positioned radially inside the outer apertures 162, which are circumferentially distributed around the circumference and through which second actuating punches 166 are guided. The first actuating punches 163 serve to transmit force from the first setting disc to the plate package of the hang-on coupling 104, whereas the second actuating punches 166 serve to transmit force from the second setting disc to the plate package of the locking coupling 105.
The second coupling part 113 of the hang-on coupling 104 is firmly connected to the differential carrier 115 and preferably comprises a sleeve-shaped projection. For supporting the first coupling part 112 relative to the differential carrier 115, there are provided two bearing elements 123, 123′ in the form of radial bearings. The locking coupling 105 is coaxially arranged inside the hang-on coupling 104 such that they at least partially axially overlap each other. The second coupling part 113 of the hang-on coupling 104 simultaneously forms the first coupling part 122 of the locking coupling 105. More particularly, an inner face of the sleeve-shaped projection is provided with form-engaging means in which the outer plates of the locking coupling 105 are held in a rotationally fixed and axially displaceable way. The inner plates which are arranged so as to alternate with the outer plates are connected to a sleeve projection 164 in a rotationally fixed and axially displaceable way, which sleeve projection 164, in turn, is firmly connected to a sideshaft gear 118 of the differential unit 103.
The actuator 106 is provided in the form of a ball ramp assembly. However, in contrast to the above-mentioned embodiment, the ball ramp assembly comprises a supporting disc 126 and two setting discs 128, 128′ which are arranged opposite the supporting disc 126 and coaxially relative to the rotational axis A. The first setting disc 128 which serves to actuate the hang-on coupling 104 is positioned coaxially outside the second setting disc 128′ which serves to actuate the locking coupling 105. Both setting discs 128, 128′ are annular in shape and are axially supported via an axial bearing 133, 133′ relative to the associated actuating punches 163, 166. The supporting disc 126 comprises outer first ball grooves 129 which are arranged opposite the ball grooves 130 of the first setting disc 128, as well as radially inner second ball grooves 129′ which are arranged axially opposite the ball grooves 130′ of the second setting disc 128′. The first balls 169 associated with the first setting disc 128 and the second balls 169′ associated with the second setting disc 128′ are held in a common ball cage 132. The supporting disc 126 is annular in shape and, on its reverse side, comprises a sleeve-shaped projection 170 which receives the outer race of a rolling contact bearing 171 by means of which the supporting disc 126 is rotatably supported relative to the cover part 161. The rolling-contact bearing 171 is axially supported relative to the cover part 161.
First spring means 173 are effectively arranged between the first actuating punch 163 and the cover part 161 which spring means 173, in the unactuated condition of the actuator 106, return the actuating punch 163, i.e. axially load same away from the hang-on coupling 104. Accordingly, between the second actuating punches 166 and the cover 161, there are effectively arranged second spring means 173′ which axially load the second actuating punches 166 towards the ball ramp assembly 106. In the present embodiment the first and the second spring means 173, 173′ are provided in the form of plate springs, but it is also possible to use helical springs or the like.
The special feature of the present embodiment consists in that, in contrast to the first embodiment, the locking value of the locking coupling 105 can be variably set by the motor position of the actuator 106. As in the case of the previous embodiments, for operating the actuator 106, there is provided a motor which generates the axial force for compressing the plate package 114 of the hang-on coupling 104 and also of the plate package 168 of the locking coupling 105. For operating purposes, there is provided a plurality of circumferentially distributed first ball grooves 129 as well as second ball grooves 129′ arranged concentrically relative thereto with different gradients and different angular positions. The first setting disc 128 for actuating the hang-on coupling 104 corresponds to the first ball grooves 129 of the supporting disc 126 and the second setting disc 128′ for actuating the locking coupling 105 corresponds to the second ball grooves 129′ of the supporting disc 126.
Below, there will follow a detailed description of the mode of functioning of the ball ramp assembly 106.
For this purpose, the first ball grooves 129 of the supporting disc 126 and the ball grooves 130 of the first setting disc 128 comprise a first groove portion 151 with a circumferential extension a and with a gradient unequal to zero, which is followed by a second groove portion 152 with a greater circumferential extension b +c and a constant groove depth. The second ball grooves 129′ of the supporting disc 126 and the ball grooves 130′ of the second setting disc 128′ comprise a first groove portion 151′ with a circumferential extension a+b with a constant groove depth and an adjoining groove portion 152′ with a shorter circumferential extension c with a gradient unequal to zero. The gradient of the second groove portion 152′ of the second ball grooves 129′ is smaller than the gradient of the first groove portion 151 of the first ball grooves 129. The planar groove portion 151′ of the second ball grooves 129′ and the planar groove portion 152 of the first ball grooves 129 comprise a certain overlapping region b. There is thus provided a neutral setting region in order to avoid the influence of tolerances.
If the supporting disc 126 is rotated in the direction of the arrow, i.e. anti-clockwise, the gradient of the first groove portions 151 of the ball grooves 129 initially causes the hang-on coupling 104 to be compressed. By controlling the motor position, the effective coupling moment can be varied as required. If the locking function is required, the actuator 106 has to be rotated further so that the subsequent second groove portion 152′ of the supporting disc 126 can act on the locking coupling 105 via the second setting disc 128′. The hang-on coupling 104 is now fully closed. By compressing the locking coupling 105, the differential carrier 115 is connected to the sideshaft gear 118′ in a friction-locking way, so that the compensating movement between the two sideshaft gears 118, 118′ is reduced. The compression of the plate package 168 of the locking coupling 105 can be set so as to be variable, so that the torque to be transmitted between an open position and a fully closed position can also be variably set.
To ensure that the driving moment of the motor is not exhausted and that the maximum coupling moment of the hang-on coupling 104 does not exceed a maximum to be defined, the balls of the first ball grooves 129—prior to the locking coupling 105 being started—run into the second groove portions 152 where the gradient angle is 0°. The maximum coupling moment of the hang-on coupling 104 is defined by the stiffness of the spring means 160.
For certain driving-dynamic requirements it is also conceivable to provide an embodiment wherein, in a first direction of rotation of the motor and of the supporting disc 126 respectively, initially the locking coupling 105 abuts a plate spring assembly and thus sets a defined constant locking value for the differential unit 103. By rotating the supporting disc 126 further, it would then be possible to close the hang-on coupling 104, with a variable coupling moment being settable as required. Furthermore, the ball grooves would be designed in such a way that by rotating the supporting disc 126 in an opposed second direction of rotation, only the first setting disc 128 would be loaded for actuating the hang-on coupling 104.
By rotating the supporting disc 226, the balls in the ball grooves run in regions with a lesser depth, so that the first setting disc 228 is axially moved towards the hang-on coupling 204 and loads the plate package 214 via an axial bearing 233 and a pressure plate 234. It can be seen that the first setting disc 228 is held in a rotationally fixed way by anti-rotation means 276 relative to the housing 210. Analogously, the locking coupling 205 is also actuated; upon rotation of the supporting disc 226, the second setting disc 228′ moves towards the locking coupling 205, with force being transmitted from the second setting disc 228′ via an axial bearing 233′ and a pressure plate 234′ to the plate package 268. The second setting disc 228′ is also secured against rotation, which, however, is not shown here. For returning the first pressure plate 234 and the second pressure plate 234′ respectively, there are provided spring means 273, 273′ in the form of plate springs. The locking coupling 205 comprises a first coupling part 242 which is connected to the differential carrier 215 in a rotationally fixed way, as well as a second coupling part 244 which is connected to the sideshaft 219 in a rotationally fixed way. The first coupling part 242 comprises an inner plate carrier to which inner plates are connected in a rotational fixed and axially displaceable way. The second coupling part 244 comprises an outer plate carrier to which outer plates are connected in a rotationally fixed and axially displaceable way.
The second coupling part 244 is axially supported via an axial bearing 277 relative to the housing 210. The first coupling part 212 of the hang-on coupling 204 is also supported via an axial bearing 278 relative to the housing 210. This embodiment ensures that, depending on the arrangement of the ball tracks, the axial forces between the hang-on coupling 204 and the supporting bearing 275 can partially be compensated relative to one another. When the locking coupling 205 is closed, a reaction force acts on the supporting disc 226 by the amount of which the axial force at the supporting bearing 275 is reduced. By compressing the locking coupling 205, the outer plate carrier is connected to the inner plate carrier in a friction-locking way, which leads to a reduction in the compensating effect between the sideshaft gears 218, 218′ of the differential unit 203.
As in the case of the embodiment according to
If the supporting disc 226 is rotated in direction R1 as shown in the drawing, the balls move along the first groove portion 251 around a circumferential extension a in regions of a smaller groove depth, so that the setting disc 228 is moved away from the supporting disc 226. This leads to the plate package 214 of the hang-on coupling 204 being loaded and, thus, the drive assembly is drivingly connected to the propeller shaft. The balls move in the second ball groove 229′ along the planar groove portion 251′ across an angular range a, i.e. the locking coupling 205 remains unactuated. By controlling the motor moment of the motor of the actuator, the effective coupling moment of the hang-on coupling 204 can be varied in accordance with requirements, i.e. between a position in which the hang-on coupling 204 is fully open and a position in which the hang-on coupling 204 is fully closed.
If the locking function is required, the supporting disc 226 is rotated further beyond the angular range b in direction R1, so that the balls run in the second ball grooves 229 along the groove portion 252′ into regions of a lesser depth. In this way, the second setting disc 228′ is moved towards the plate package 268 of the locking coupling 205, so that the latter is closed. The balls of the first ball grooves 229 run along the first groove portions 252 across the angle of rotation c, i.e. the hang-on coupling 204 remains locked. In this case, too, by correspondingly controlling the angle of rotation of the supporting disc 226 within the angle portion c, the locking moment of the locking coupling 205 can be set in accordance with requirements, with the hang-on coupling 204 always being fully closed.
The special feature of the present embodiment consists in that the ball grooves of the supporting disc 326 and those of the two setting discs 328, 328′ are designed in such a way that, starting from an end position in which the discs approach one another, by rotating the supporting disc 326 in a first direction of rotation R1, only the first setting disc 328 is axially loaded for actuating the hang-on coupling 304 and that, by rotating the supporting disc 326 in a second opposed direction of rotation R2, in addition to the first setting disc 328, the second setting disc 328′ is also axially loaded for actuating the locking coupling 305.
A preferred profile of the ball grooves 329, 329′ for this embodiment will be explained below with reference to
It shows the supporting disc 326 wherein, in
By rotating the supporting disc 326 in a second direction of rotation R2 which is opposed to the first direction of rotation R1, the balls which are held between the supporting disc 326 and the first setting disc 328 initially move in the planar central portion 350 along an angle region b. Accordingly, the balls which are held between the supporting disc 326 and the second setting disc 328′ move in the ball grooves 329′ along the groove portion 350 inside the angle region b in regions of a lesser depth, so that initially, the locking coupling 305 makes only a gentle start, with the supporting disc 326 being lifted off the ball bearing 375. Inside said angle region b, there are arranged the balls for actuating the hang-on coupling 304 within the planar portion 350, so that the hang-on coupling 304 remains unactuated.
When the supporting disc 326 is rotated further in direction R2, the balls move in the first ball grooves 329 along the second groove portions 352 inside the angle region c in regions of a lesser depth, so that, in this way, the hang-on coupling 304 is actuated in addition to the locking coupling 305. In parallel thereto, the balls for the locking coupling 305 run along the third groove portions 352′ which have a constant depth and extend over an angular region c2, i.e. when the ball ramp assembly in operated such that the balls run in the ball grooves 329, 329′ inside the angular ranges c and c2, the hang-on coupling 304 is variably controllable between the open position and a closed position, so that, accordingly, torque can be transmitted to the rear axle according to the requirement.
The present embodiment constitutes a drive assembly which, initially, makes it possible to close the locking coupling 305 against the force of the spring means. By rotating the supporting disc 326 further, it is possible, via the ball portions 352 with a gradient, which are associated with the hang-on coupling 304 only, to initiate the compression of the hang-on coupling 304. Thereby, the coupling moment of the hang-on coupling 304 being proportional to the coupling moment of the locking coupling. In this way it is possible to relieve the load on the supporting bearing 375 because the actuating forces act proportionately on both couplings 304, 305.
All the above-mentioned embodiments are advantageous in that the drive assembly permits a function both for locking the differential unit and a connecting function for connecting the drive axle to a main driveline, with only one single actuator being required. By selecting the suitable gradients and angular positions of the discs of the ball ramp assemblies, it is possible to put into effect different switching sequences. By arranging the ball ramp assemblies at and coaxially to the differential carrier it is possible to advantageously combine the disconnection of the angle drive for increasing the energy efficiency with a locking function in a compact and cost-effective form.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2008 063 904.4 | Dec 2008 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP09/09126 | 12/18/2009 | WO | 00 | 11/17/2011 |
