TECHNICAL FIELD

The invention relates to a method for distributing the number of revolutions between two wheel shafts of a vehicle by means of a differential arrangement according to the preamble of claim 1 . The invention relates to a driving arrangement for distributing the number of revolutions between two wheel shafts of a vehicle by means of a differential arrangement according to the preamble of claim 1 . The invention also relates to a motor vehicle.

BACKGROUND

Driving arrangements with shafts where a transmission device is arranged after the differential on one output shaft, wherein the differential takes part in distributing a change of the ratio relations ship to both output shafts are known. Normally in such driving arrangements the differential is driven by a drive shaft, for example from a combustion engine.

US2009203487 discloses a wheel shaft with a transmission device in the form of a CVT-transmission on one side of and after a conventional differential which is driven by a conventional drive shaft, wherein the number of revolutions of the wheel to which the CVT-transmission is connected is variable by means of the CVT-transmission. Such a differential is self-locking which results in problem when torque is desired to be transferred between the respective side of the vehicle in that the driving arrangement binds and turns hard. US 2003/0203782 discloses an electrical shaft with a transmission device in the form of a multi speed unit arranged inside of the differential on one side of the electric motor. The differential is arranged such that the differential function is located on one side. The electrical shaft comprises a hollow shaft which results in that by low gear the greatest torque need to go in the shaft with the smallest diameter, wherein the weakest shaft takes up the greatest torque which demands the dimensions of the device to be increased, which in turn results in greater dimension on bearings. This results in a less compact and more costly construction.

OBJECTS OF THE INVENTION

An object of the present invention is to provide a method for distributing the number of revolutions between two wheel shafts of a vehicle by means of a differential arrangement which, by means of a transmission unit, facilitates cost efficient and non-space consuming drive torque change of the driving of said wheel shafts.

An additional object of the present invention is to provide a driving arrangement for distributing the number of revolutions between two wheel shafts of a vehicle by means of a differential arrangement which, by means of a transmission unit, facilitates cost efficient and non-space consuming drive torque change of the driving of said wheel shafts.

SUMMARY OF THE INVENTION

These and other objects, apparent from the following description, are achieved by a method, a driving arrangement and a motor vehicle which are of the type stated by way of introduction and which in addition exhibits the features recited in the characterising clause of the appended independent claims. Preferred embodiments of the method and driving arrangement are defined in appended dependent claims.

Specifically an object of the invention is achieved by a method for distributing the number of revolutions between two wheel shafts of a vehicle by means of a differential arrangement, where a drive shaft driven by means of a motor arrangement drives said wheel shafts, comprising the step of, by means of a transmission unit, providing drive torque change of the driving of said wheel shafts, comprising the step of: by means of said differential arrangement distribute the number of revolutions between said two wheel shafts via a differential shaft configuration drivingly connected to the driving of said wheel shafts, wherein said differential arrangement provides distribution without so called self-locking of the differential arrangement, and wherein, by change of number of revolutions of the driving of one of said wheel shafts, the number of revolutions and hereby the drive torque of said wheel shafts is distributed equally between the wheel shafts by the operation of said differential arrangement.

By means of a differential arrangement which thus provides distribution without self-locking cost efficient and non-space consuming drive torque change of the driving of said drive shafts by means on only one transmission unit arranged on one side. Such a solution requires no hollow shaft since driving hereby is effected on both outputs, i.e. both wheel shafts. With such a solution without self-locking torque transfer between the opposite wheel shafts is facilitated. By drive torque change by means of the transmission unit resulting in a change in number of revolutions of the wheel shaft at which the transmission unit is arranged the differential arrangement will automatically see to that the number of revolutions is distributed such that both wheel shafts rotate with the same number of revolutions. By for example a downshift to a fourth of the current number of revolutions on the wheel shaft at which the transmission unit is arranged the differential function of the differential arrangement will see to that the number of revolutions of the respective wheel shaft becomes half of the current number of revolutions.

According to an embodiment of the method said drive shaft of said motor has two opposite outputs, and wherein said wheel shafts are driven by means of a respective output via a transmission configuration, by means of which transmission configurations said differential shaft configuration is drivingly bridgingly connected. Such a differential arrangement facilitates a compact construction. Such a construction requires no hollow shaft since driving hereby is effected on both outputs, i.e. both wheel shafts. Such a construction results in a differential function without self-locking. With such a solution without self-locking torque transfer between the opposite wheel shafts is facilitated.

According to an embodiment of the method said transmission unit is arranged between an output of the drive shaft of the motor and the transmission configuration for one of the wheel shafts. Hereby exactly the same torque is obtained on the respective side by drive torque change by means of the transmission unit. By arranging the transmission unit between an output of the drive shaft of the motor and the transmission configuration for one of the wheel shafts the transmission unit is integrated in the driving arrangement such that the respective side with wheel shaft become the same.

According to an embodiment of the method said transmission unit is arranged between the transmission configuration for one of the wheel shafts and that wheel shaft. Hereby a simple and cost efficient construction is facilitated.

According to an embodiment the method comprises the step of controlling the rotation of said differential shaft by means of a driving unit. Such a driving unit is according to a variant constituted by an electric motor. By thus controlling the rotation of the differential shaft with a driving unit a control transmission suitable for a tracked vehicle is obtained, wherein the wheels may be forced to go in different directions and the torque may be shifted any way you desire.

According to the invention the objects are achieved with a driving arrangement for distributing the number of revolutions between two wheel shafts of a vehicle by means of a differential arrangement, comprising a drive shaft driven by means of a motor arrangement, the drive shaft being arranged to drive said wheel shafts, and means for, by means of a transmission unit, providing drive torque change of the driving of said wheel shafts, wherein said differential arrangement is arranged to distribute the number of revolutions between said two wheel shafts via a differential shaft configuration drivingly connected to the driving of said wheel shafts, wherein said differential arrangement is arranged to provide distribution without so called self-locking of the differential arrangement, and wherein, by change of number of revolutions of the driving of one of said wheel shafts, the number of revolutions and hereby the drive torque of said wheel shafts is arranged to be distributed equally between the wheel shafts by the operation of said differential arrangement.

According to an embodiment of the driving arrangement said drive shaft of said motor has two opposite outputs, and wherein said wheel shafts are arranged to be driven by means of a respective output via a transmission configuration, by means of which transmission configurations said differential shaft configuration is drivingly bridgingly connected.

According to an embodiment of the driving arrangement said transmission unit is arranged between an output of the drive shaft of the motor and the transmission configuration for one of the wheel shafts.

According to an embodiment of the driving arrangement said transmission unit is arranged between the transmission configuration for one of the wheel shafts and that wheel shaft. According to an embodiment the driving arrangement comprises means for controlling the rotation of said differential shaft by means of a driving unit.

The driving arrangement according to above with embodiments shows the corresponding advantages as the advantages mentioned above for the corresponding method with embodiments.

An additional advantage with the present invention is that the transmission unit may be located on only one side of the electric motor and may also be applied externally.

The present invention thus does not affect the design of an electric motor. Instead existing electric motors may be used.

Additionally an advantage of the present invention is that the differential shaft configuration may be used as a part of reduction gears at the drive wheels. These reduction gears are for example said planetary gear configurations. A differential shaft in the differential shaft configuration will thus rotate to a greater extent than in the differential shafts according to prior art. Particularly the differential shaft configuration according to the present invention may also rotate during driving straight ahead during normal driving conditions.

BRIEF DESCRIPTION OF THE DRAWINGS A better understanding of the present invention will be had upon the reference to the following detailed description when read in conjunction with the accompanying drawings, wherein like reference characters refer to like parts throughout the several views, and in which:

Fig. 1 schematically illustrates a motor vehicle according to an embodiment of the present invention; Fig. 2 schematically illustrates a driving arrangement for distributing the number of revolutions between two wheel shafts of a vehicle by means of a differential arrangement according to an embodiment of the present invention; Fig. 3 schematically illustrates a driving arrangement for distributing the number of revolutions between two wheel shafts of a vehicle by means of a differential arrangement according to an embodiment of the present invention; and

Fig. 4 schematically illustrates a block diagram of a method for distributing the number of revolutions between two wheel shafts of a vehicle by means of a differential arrangement according to an embodiment of the present invention.

DETAILED DESCRIPTION Hereinafter the term "transmission unit" refers to any suitable transmission unit for providing a drive torque change of the driving of wheel shafts of a driving arrangement comprising any suitable gear device/torque conversion device. The term "transmission unit" comprises according to a variant a so called H/L-step (High/Low-step), i.e. a so called range gear. The term "transmission unit" comprises any suitable transmission unit for shifting of number of revolutions and torque. The term "transmission unit" comprises according to a variant a torque converter, sometimes called Converter, The term "transmission unit" comprises according to a variant a continuously variable transmission (CVT), according to a variant a hydraulic continuously variable transmission, also called hydrostat.

Hereinafter the term "motor arrangement" refers to any suitable motor arrangement comprising electric motor, hydraulic motor, pneumatic motor or the like. Hereinafter the term "link" refers to a communication link which may be a physical connector, such as an optoelectronic communication wire, or a non- physical connector such as a wireless connection, for example a radio or microwave link. Hereinafter the term "driving" refers to output torque from the electric motor. These torques may reach components described later either directly or via other components which e.g. may change gearshift relationships and thereby number of revolutions. The expression "driving" thereby does not relate to changes of torque or number of revolutions originating from external conditions or changes in external conditions. Such external conditions may e.g. be friction between ground engaging members and the ground.

With reference to fig. 1 a side view of a motor vehicle 1 is shown. The vehicle may be a medium heavy or a heavy vehicle, such as a work vehicle or a military vehicle. The vehicle may be a wheeled vehicle or a tracked vehicle. The vehicle may alternatively be a car. The vehicle 1 comprises at least one driving arrangement according to any of the embodiments below.

Fig. 2 schematically illustrates a cross sectional view of a driving arrangement 10 according to an embodiment of the present invention.

The driving arrangement 10 comprises two wheel shafts 12a, 12b, a first wheel shaft 12a and a second wheel shaft 12b. The driving arrangement is arranged to distribute the number of revolutions between said wheel shafts 12a, 12b. The first wheel shaft 12 is arranged to support and drive a first ground engaging member, not shown. The second wheel shaft 12a is arranged to support and drive a second ground engaging member, not shown. Said ground engaging members may be constituted by wheel based ground engaging members or track based ground engaging members.

The driving arrangement 10 comprises a motor arrangement 20 and a housing 30 in which the motor arrangement 20 is housed. The motor arrangement 20 is according to this embodiment constituted by an electric motor 20. The driving arrangement 10 is hereby according to this embodiment constituted by an electric driving arrangement.

The electric motor 20 comprises a rotor 22 and a stator 24, where said rotor 22 is connected to a drive shaft 26 or rotor shaft 26 and is arranged to rotate said drive shaft 26. The drive shaft 26 is arranged to run concentrically relative to the rotor 22, wherein the rotor 22 is arranged to surround the drive shaft 26. The stator 24 is arranged to surround the rotor 22, wherein the rotor shaft and consequently the rotor 22 are arranged concentrically relative to the stator 24. The drive shaft 26 has two opposite outputs 26a, 26b, a first output 26a and a second output 26b opposite to the first output 26a. Said wheel shafts 12a, 12b are arranged to be driven by means of such a respective output 26a, 26b. The first wheel shaft 12a is consequently arranged to be driven by means of the first output 26a of the drive shaft 26 and the second wheel shaft 12b is arranged to be driven by means of the second output 26b of the drive shaft 26.

The respective wheel shaft 12a, 12b are coaxially connected to the drive shaft 26. The respective wheel shaft 12a, 12b are consequently coaxially aligned with the drive shaft 26. The electric driving arrangement 10 comprises a first transmission configuration 50 and a second transmission configuration 60, the electric motor 20 being arranged between said first and second transmission configurations. The first and second transmission configurations 50, 60 are arranged in the housing. The first transmission configuration is according to this embodiment constituted by a first planetary gear configuration 50 and the second transmission configuration is according to this embodiment constituted by a second planetary gear configuration 60, the electric motor 20 consequently being arranged between said first and second planetary gear configurations 50, 60. The first planetary gear configuration 50 comprises a planet gear 52, a sun gear 54, and a ring gear 56. The second planetary gear configuration 60 comprises planet gears 62, a sun gear 64, and a ring gear 66.

The first and second planetary gear configurations 50, 60 are drivingly connected to each other via the drive shaft 26. The first output 26a of the drive shaft 26 is connected to the first planetary gear configuration 50. The second output 26b of the drive shaft 26 is connected to the second planetary gear configuration 60.

The first planetary gear configuration 50 comprises a first planet gear carrier 52a for carrying said planet gears 52. The second planetary gear configuration 60 comprises a second planet gear carrier 62a for carrying said planet gears 62.

The first planetary gear configuration 50 is connected to the first wheel shaft 12a. The wheel shaft is hereby connected to the first planet gear carrier 52a of the planetary gear configuration 50.

The second planetary gear configuration 60 is connected to the second wheel shaft 12b. The wheel shaft is hereby connected to the second planet gear carrier 62a of the planetary gear configuration 60.

The driving arrangement 10 further comprises a differential arrangement 40. The differential arrangement 40 comprises a differential shaft configuration 52. The differential arrangement 40 is arranged to distribute the number of revolutions between said two wheel shafts 12a, 12b via said differential shaft configuration 42. The differential shaft configuration 42 is arranged in the housing 30 between the jacket surface of the electric motor 20 and the housing wall of the housing 30. The differential shaft configuration 42 is arranged to run in the axial extension of the electric motor 20. The differential shaft configuration 42 is arranged to run essentially parallel to the drive shaft 26. The differential shaft configuration 42 comprises a first gearing 44a and a second opposite gearing 44b. The second gearing is in mesh with the ring gear 66 of the second planetary gear configuration 60.

The differential arrangement 40 comprises a gearing 44c. The gearing 44c is in mesh with the ring gear of the first planetary gear configuration 50 and in mesh with the first gearing 44a of the differential shaft configuration 42.

The differential arrangement 40 is engaged with the ring wheel 56 of the first planetary gear configuration 50 and the ring wheel 66 of the second planetary gear configuration 60 for provision of a differential function. The differential arrangement 40, the first planetary gear configuration 50 and the second planetary gear configuration 60 are according to a variant comprised by a differential means. The differential shaft configuration 42 of the differential arrangement 40 is consequently drivingly bridgingly connected to the first planetary gear configuration 50 and the second planetary gear configuration 60.

The driving arrangement 10 further comprises a transmission unit 70 arranged to provide drive torque change of the driving of said wheel shafts 12a, 12b. Said transmission unit 70 is according to this embodiment arranged between an output 26b of the drive shaft 26 of the second transmission configuration 60, here the second planetary gear configuration 60, for the second wheel shaft 12b. The transmission unit 70 is hereby connected to the planetary gear configuration 60.

The transmission unit 70 is constituted by any suitable transmission unit for providing drive torque change of the driving of wheel shafts of a driving arrangement comprising any suitable gearshift device/torque conversion device such as a so called High/Low step for providing of downshift.

The differential arrangement 40 is arranged to distribute number of revolutions between said first and second wheel shafts 12a, 12b via the differential shaft configuration which hereby is drivingly connected to the driving of said wheel shafts 12a, 12b.

Said differential arrangement 40 is arranged to provide distribution without so called self-locking of the differential arrangement 40, wherein, by change of number of revolutions of the driving of one of said wheels shafts, the number of revolutions and hereby the drive torque of said wheel shafts 12a, 12b is arranged to be distributed equally between the wheel shafts 12a, 12b by means of the operation of said differential arrangement 40. The differential arrangement 40 is thus non-self-locking. The differential arrangement 40 thus does not exert any substantial braking power. Hereby the ability for drive torque to be transferred between the wheel shafts 12a, 12b is created.

By for example a downshift to a fourth of the current number of revolutions on the wheel shaft at which the transmission unit 70 is arranged the differential function of the differential arrangement will see to that the number of revolutions of the respective wheel shaft becomes half of the current number of revolutions. By a downshift by means of the transmission unit 70 the differential shaft configuration will rotate which results in that the same number of revolutions is obtained on the wheel shafts 12a, 12b. The differential shaft configuration 42 is configured to rotate only by differences in number of revolutions of the wheel shafts 12a, 12b and by rotation the differential arrangement 40 will see to that the number of revolutions of the respective wheel shaft becomes the same. The differential arrangement 40 and hereby the first and second planetary gear configuration 50, 60 hereby becomes a part of the transmission function of the transmission unit 70. Due to the fact that said transmission unit 70 is arranged between an output 26b of the drive shaft 26 of the electric motor 20 and the second planetary gear configuration 60 for the second wheel shaft 12b, exactly the same torque is obtained by drive torque change by means of the transmission unit 70. By arranging the transmission unit 70 between an output of the drive shaft of the motor and the second planetary gear configuration 60 for the second wheel shaft 12b the transmission unit is integrated in the driving arrangement such that the respective side with the wheel shafts 12a, 12b becomes the same.

In a self-locking differential unit the self-locking is in most cases performed in spindle gears which are arranged as small bevel gears. These are normally not journalled with more than one oil film. Therefore a self-locking differential shall generally not run with different number of revolutions on the drive shafts continuously as this results in excessive wear. The differential arrangement 40 however does not require any spindle gears but can instead be constructed as a straight gear shift. This straight gear shift may for example be provided with at least one straight or bevel cut gear wheel. The differential arrangement 40 may then easily be journalled for continuous drive.

The driving arrangement 10 may comprise a driving unit 80 for controlling the differential arrangement. The driving unit 80 may be constituted by any suitable unit that may influence the rotational speed of the differential shaft configuration 42. The driving unit 80 is according to a variant constituted by an electric motor 80. The driving unit 80 could according to a variant comprise a brake unit arranged to prevent different speeds between the wheel shafts 12a, 12b. The driving unit 80 controllably connected to the differential arrangement 40 for facilitating forced rotation of the differential shaft configuration 42 such that the wheel shafts 12a, 12b hereby may be forced to rotate in different directions and such that torque may be moved as required. Hereby ground engaging members connected to the respective wheel shaft by means of control by means of the driving unit 80 may be forced to rotate relative to each other as required, alternatively be prevented to rotate relative to each other.

The driving unit is signal connected to an electronic to an electronic control unit 100 via a link. The electronic control unit 100 is via the link arranged to send a signal to the driving unit representing control data for controlling the differential arrangement 40 and hereby controlling the wheel shaft and thereby ground engaging members such as drive wheels or drive tracks.

In the following an example of operation is described if the transmission unit 70 is formed as a so called high/low gear, H/L-gear. This H/L-gear may provide two cases of ratio, high and low, H and L, where the low ratio in an example corresponds to a ratio relationship 1 :1 , i .e. the number of revolutions of the drive shaft 26 corresponds to the number of revolutions of the sun gear 64 of the second planetary gear configuration 60. In this case thus both the first and the second planetary gear configuration 50, 60 will have the same input driving number of revolutions to its respective sun gear 54, 64. This results in that, during normal driving conditions and driving straight ahead, both wheel shafts 12a, 12b will receive the same number of revolutions and the same torque. The differential shaft configuration 42 will in this case not rotate. The expression normal driving conditions relates to for example that sufficient friction exists between e.g. wheels or tracks at both wheel shafts 12a, 12b and the ground. In such a way the wheels or tracks will not spin. During cornering this differential shaft configuration 42 may however rotate and thus allow different number of revolutions between the wheel shafts 12a, 12b. Even by cornering the driving will however be the same to both wheel shafts. Cornering may for example be initiated by changing orientation of steerable wheels at another shaft of the vehicle, e.g. by movement of a steering wheel. In tracked vehicles cornering may e.g. be initiated by the driving unit 80.

When the H/L-gear is put in L-position a ration relationship different from 1 :1 may be provided, e.g. 1 :4. In this position the sun gear 64 of the second planetary gear configuration 60 may be driven by a fourth of the number of revolutions of the drive shaft 26. The sun gear 54 of the first planetary gear configuration 50 is however driven with the same number or revolutions as the drive shaft. Thereby a change in number of revolutions of the driving of one of the wheel shafts, more particularly of the driving of only one of the wheel shafts, in this case during driving of the wheel shaft 12b. During normal driving conditions and driving straight ahead the wheels however "wants to" rotate with the same number of revolutions. This since the differential shaft configuration provides distribution of the number of revolutions without self-locking. Thus the lack of a braking and locking power in the differential shaft configuration 42 will facilitate that the differential configuration 42 is put in continuous rotation. This distribution of the number of revolutions is effected automatically. During normal driving conditions the friction between wheels or tracks and the ground is large enough such that a levelling of torque and number or revolutions is effected in that the differential shaft configuration 42 causes rotational movement in different directions at the ring gears 56, 66 of the respective planetary gear configuration 50, 60. This different rotation of the ring gears 56, 66 allows together with different rotation of the sun gears 54, 65 that the planet gear carriers 52a, 62a and thereby also the wheel shafts 12a, 12b rotate with the same number or revolutions.

Fig. 3 schematically illustrates a driving arrangement 1 10 for distributing the number of revolutions between two wheel shafts 12a, 12b of a vehicle by means of a differential arrangement 40 according to an embodiment of the present invention.

The driving arrangement 1 10 differs from the driving arrangement 10 mainly by the positioning of the transmission unit. The driving arrangement 1 10 according to this embodiment comprises a transmission unit 170 for providing drive torque change of the driving of said wheel shafts 12a, 12b. In the driving arrangement 1 10 according to this embodiment said transmission unit 170 is arranged between the second transmission configuration 60, here the second planetary gear configuration 60, for the second wheel shaft 12b and the second wheel shaft 12b. Hereby a simple and cost efficient construction is facilitated which can be used for an existing driving arrangement where a transmission unit is desired, and which then may be applied in accordance with the embodiment in fig. 3.

Above, with reference to fig. 2 and 3, different embodiments of the driving arrangement 10; 1 10 have been described, where the transmission unit 70 according to the embodiment for the driving arrangement 10 is arranged between an output 26b of the drive shaft 26 of the motor and the second transmission configuration 60, and where the transmission unit 170 of the embodiment for the driving arrangement 1 10 is arranged between the second transmission configuration 60 for the second wheel shaft 12b and the second wheel shaft 12b. According to a not-shown variant the transmission unit could be arranged outside the housing 30 and hereby between the second transmission configuration 60 and the housing 30.

In the following an example of operation is described if the transmission unit 170 is formed as an H/L-gear. Here only the situations that deviate from the description in connection to fig. 2. In the high position the transmission unit 170 shift 1 :1 and thereby during drive straight ahead during normal driving conditions the differential shaft configuration 42 will not rotate. The wheel shafts 12a, 12b will then have the same input driving and thus the same number of revolutions. In low position however, in contrast to fig. 2, both sun gears 54, 64 will have the same number or revolutions as the drive shaft 26 since no transmission there between changes the number of revolutions. Instead the planet gear carriers 52a, 62 will rotate with different speed due to the influence of the differential shaft configuration 42 and thereby the ring gears 56, 66. The transmission unit 170 in this case compensates the difference in number of revolutions between the planet gear carriers 52a, 62a such that the wheel shafts 12a, 12b will rotate with the same number or revolutions. Also in this case the distribution is effected automatically by the differential shaft configuration 42. In contrast to what is described in WO 201 1/065888 A1 the present invention does not require a hollow shaft. The transmission unit according to the present invention is also only located on one side of the electric motor and may also be applied externally. The present invention thus does not affect the design of an electric motor. Instead existing electric motors may be used.

An advantage of the present invention is that the differential shaft configuration 42 may be used as a part of reduction gears at the drive wheels. These reduction gears are for example said planetary gear configurations 50, 60. A differential shaft in the differential shaft configuration 42 will thus rotate to a greater extent than in the differential shafts according to prior art. Particularly the differential shaft configuration 42 according to the present invention may also rotate during driving straight ahead during normal driving conditions. This follows e.g. from the description of the examples of operation in connection to Fig. 2 and Fig. 3.

Fig. 4 schematically illustrates a block diagram of a method for distributing the number of revolutions between two wheel shafts of a vehicle by means of a differential arrangement, where drive shaft driven by means of a motor arrangement drives said wheel shafts according to an embodiment of the present invention.

According to an embodiment the method for distributing the number of revolutions between two wheel shafts of a vehicle by means of a differential arrangement comprises a first step S1 . In this step drive torque change of the driving of said wheel shaft is provided by means of a transmission unit. According to an embodiment the method for distributing the number of revolutions between two wheel shafts of a vehicle by means of a differential arrangement comprises a second step S2. In this step the number of revolutions are distributed between said wheel shafts by means of said differential arrangement via a differential shaft configuration drivingly connected to said driving of said wheel shafts, wherein said differential arrangement provides distribution without so called self-locking of the differential arrangement, and wherein, by change in number of revolutions of the driving of one of said wheels shafts, the number of revolutions and hereby the drive torque of said wheel shafts are distributed equally between the wheel shafts by means of the operation of said differential arrangement.

The foregoing description of the preferred embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated.