Abstract:
A vehicle comprises a chassis, a pair of driving wheels, a pair of idle wheels, at least one steering group, and a differential. The steering group is capable of positioning one of the pairs of wheels in a steering geometry where an axis of each of the wheels of the pair of wheels capable of being positioned by the steering group intersects with the remaining axis within a ground-support quadrilateral formed by the pairs of wheels. The differential comprises an outer case, an inner case, a selective engagement, a selective blocking means, and a selective direct gearing means. When the inner case is coupled to the outer case a first half-shaft and a second half-shaft are driven similarly and when the inner case is coupled to the chassis and one of the half-shafts is drivingly engaged with a crown gear the first half-shaft and the second half-shaft are driven opposingly.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an improved vehicle. 
     BACKGROUND 
     The term “vehicle” refers to common automobiles but also elevator trucks, earth-moving vehicles, off-road and non-off-road telescopic trucks, military vehicles, tractors, air platforms, i.e. all vehicles which, during their normal use, effect maneuvers in which the relative wheels have a steering configuration necessary for allowing a movement, for example straight or curved, of the vehicle itself. 
     In currently known vehicles, the steering, i.e. the positioning of a particular desired orientation of at least one pair of wheels, is generally controlled mechanically by means of a rack coupling activated by the movement of the steering wheel or hydraulically by means of a hydraulic auxiliary system again controlled by the rotation of the steering wheel. 
     In particular, the known steering groups act on the wheels of an axle which are constrained to the vehicle by means of structural extensions. 
     In order to effect a turn, when desired, the presence is currently envisaged of a rigid rod element connected at one end to a steering stem by means of a spherical coupling and at the other end to the wheel-holder group by means of a pin, this being the construction solution of the integrated steering cylinder type mainly used for axles to be installed on off-road vehicles. 
     At present, therefore, in order to effect a sudden turn, a user exerts a translatory movement, generally, as already mentioned, by means of the steering wheel, to the above stem of the main cylinder which in turn entrains the other rigid rod element situated in series with the previous stem, into movement. 
     As this rigid rod element, however, is integrally hinged to the wheel-holder supports of the wheels of a common axle, the latter are concordantly put into movement around respective kingpins through which they are rotatingly connected to the structural extensions. Consequently, the rigid rod elements constrain the wheel-holder supports to rotating in the same direction in response to movement of the steering stem. 
     The only turns therefore that a current known vehicle can make through the coupling described above falls within the typologies contemplated by the “Ackermann”-type geometry in which the axes of the steering wheels of a vehicle intersect upon a single point along a line extending from a rear axle of the vehicle when the steering wheels are rotated from a straight advance position. 
     Unfortunately, however, these known groups have various drawbacks and impose kinematic limits to the vehicle itself on which they are assembled. 
     In particular they relate to the limited angular deviation of the wheel-holder support as a result of the limited translatory movement of the steering stem. 
     In other words, unfortunately, the angular deviation of the wheel-holder group around the kingpin is limited within a narrow angular range which cannot exceed what is granted by the translatory movement of the steering stem. Unfortunately the steering mechanism in accordance with Ackermann steering geometry does not allow rotation of the vehicle with respect to a point inside the ground-support quadrilateral of the vehicle. 
     It is not possible, for example, for present known vehicles to rotate around a center of a non-steering axle, for example, nor is it possible to effect a rotation with respect to the center of the vehicle itself for the above-mentioned kinematic reasons of the known steering mechanisms in accordance with Ackermann steering geometry and also because it is not possible for current known vehicles to impose two opposing rotations on a pair of driving wheels of the same axle. 
     SUMMARY OF THE INVENTION 
     An objective of the present invention is to provide a device capable of solving the above drawbacks of the known art in an extremely simple, economical and particularly functional way. 
     A further objective is to provide a vehicle which enables greater steering angles to be obtained with respect to those which can currently be reached. 
     Another objective is to provide a vehicle which enables wide steering angles to be obtained without requiring effort on the part of the user acting on the steering wheel, thus improving the maneuverability of the vehicle in limited spaces. 
     Yet another objective is to provide a vehicle which allows steering around a point inside the vehicle itself such as, for example, the center of a rigid front drive axle or with respect to the center of the vehicle. 
     An additional objective is to provide a vehicle capable of imposing two opposing rotations on a pair of drive wheels of the same axle. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The characteristics and advantages of an improved vehicle according to the present invention will appear more evident from the following illustrative and non-limiting description, referring to the enclosed schematic drawings, in which: 
         FIG. 1  is a sectional view of a differential of a vehicle according to an embodiment of the present invention; 
         FIG. 2  is a view from above of the steering group of the wheels of an idle axle of the vehicle according to an embodiment of the present invention, the idle axle shown in a straight advance configuration; 
         FIG. 3  is a view from above of the steering group of the wheels of the idle axle shown in  FIG. 2  in another possible configuration of use according to Ackermann steering geometry; 
         FIG. 4  is a view from above of the steering group of the wheels of the idle axle shown in  FIG. 2  in another possible configuration of use according to a steering in which the rotation of the vehicle is effected around a center of a drive axle of the vehicle or a vehicle center; 
         FIG. 5  is a schematic view from above of a vehicle according to an embodiment of the present invention in which the wheels of an axle are positioned according to Ackermann steering geometry; 
         FIG. 6  is schematic view from above of a vehicle according to an embodiment of the present invention in which the wheels of an axle are positioned according to a steering in which the rotation of the vehicle is effected around a center of an axle of the vehicle; and 
         FIG. 7  is a schematic view from above of a vehicle according to an embodiment of the present invention in which the wheels of both of the axles are positioned according to a steering in which the rotation of the vehicle is effected around a vehicle center. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIGS. 5-7 , these show an improved vehicle  30  according to the present invention equipped with a differential  10  in driving engagement with the driving wheels  40 ,  40 ′, in a sectional view of an illustrative embodiment in  FIG. 1 , and two steering groups  100  of the wheels of both axles. 
     Said vehicle  30  is, like all known common vehicles, equipped with a chassis  35 , a pair of driving wheels, indicated in the figures with  40 ,  40 ′, and a pair of idle wheels  50 ,  50 ′. 
     As already mentioned, the vehicle  30  is equipped with the differential  10  in driving engagement with the driving wheels  40 ,  40 ′, which comprises, as can be seen in the schematic example represented in  FIG. 1 , an outer differential case  20  and an inner differential case  19 . 
     In particular, the differential  10  comprises an outer case  20 , which can be activated in rotation by a crown gear  15  activated in rotation by a motor, and an internal case  19  in which a first and second end of two half-shafts  11 ,  12  converge, from facing opposite ends. 
     The relative wheel-holder groups of the driving wheels  40 ,  40 ′ are connected to the opposite ends of the two half-shafts  11 ,  12 , those distant from the differential  10 . 
     Two primary toothed gears  13 ,  14 , which communicate with each other for a possible transmission of the movement between two secondary toothed gears  16 ,  17 , are rigidly respectively connected to the ends of the two half-shafts  11 ,  12  converging inside the inner case  19  of the differential  10 . 
     The latter secondary toothed gears  16 ,  17  are in turn rotatingly assembled on a pin  18  of the inner case  19  which  18  is substantially orthogonal to the two half-shafts  11 ,  12 . 
     According to the invention, the differential  10  also comprises selective engagement means  21  of the inner case  19  with the outer case  20 , selective blocking means  24 ,  25 ,  26  of the inner case  19  with respect to the chassis  35 , and direct selective gearing means  22 ,  23 ,  27 ,  28  of the movement coming from the crown gear  15  to one of the two half-shafts  11 ,  12 . 
     In particular, according to the invention, when the inner case  19  is integral with the outer case  20  a concordant rotation is transmitted to the pair of driving wheels  40 ,  40 ′, whereas when the selective blocking means  24 ,  25 ,  26  and the direct selective gearing means  22 ,  23 ,  27 ,  28  are activated, an opposite rotation with respect to the other is transmitted to the same pair of driving wheels  40 ,  40 ′. 
     In particular, according to an embodiment shown in  FIG. 1 , the selective engagement means  21  of the inner case  19  with respect to the outer case  20  comprise a set of engagement balls  21  interposed between the inner case  19  and the outer case  20 . 
     As can be seen in the same example of  FIG. 1 , the selective blocking means  24 ,  25   26  of the inner case  19  with respect to the chassis  35  comprise at least a first moveable piston element  24 , at least a first spring element  26 , and at least a clutch element  25  connected to the framework of the chassis  35  wherein the at least one piston element  24  can be selectively moved to compress the at least one spring element  26  and disconnect the engagement means  21  of the inner case  19  with respect to the outer case  20  bringing the inner case  19  to the chassis by means of the clutch element  25  if said clutch is “packed” with respect to the chassis  35 . 
     In the same preferred embodiment shown, the direct selective gearing means  22 ,  23 ,  27 ,  28  of the movement coming from the crown gear  15  to one of the two half-shafts  11 ,  12  comprise at least a second moveable piston element  22 , at least one front engagement unit whether it be with a first set of straight or helical teeth  23  and at least a second spring element, wherein the at least second piston element  22  can be selectively moved to compress the at least second spring element and engage the at least one front engagement unit with a second set of straight or helical teeth  28  drivingly engaged with one of the two half-shafts  11 ,  12 . 
     From what is described above consequently, once the selective blocking means  24 ,  25 ,  26  and the direct selective gearing means  22 ,  23 ,  27 ,  28  have been activated, i.e. blocking the inner case  19  with respect to the chassis  35  and imposing a rotation directly on one of the two half-shafts  11 ,  12 , due to the coupling of the primary toothed gears  13 ,  14  and secondary toothed gears  16 ,  17 , the two driving wheels  40 ,  40 ′ are activated in rotation following two opposite rotations. 
     Consequently, the differential  10  described above according to a preferred embodiment allows the driving wheels  40 ,  40 ′ to which it is connected to proceed straight with the same angular rate and to effect common curving maneuvers with different and concordant angular rates, when the cases  19 ,  20  of the differential  10  are integral with each other and form a typical differential, and also according to the invention, the differential  10  allows the two driving wheels  40 ,  40 ′ to rotate in opposing directions with respect to each other. 
     Only according to the invention is it consequently possible for the vehicle  30  to effect rotations around its own center in which the two driving wheels  40 ,  40 ′ proceed with opposing rotational rates of the angular half-axes  11  and  12  wherein, as in the example of  FIG. 7 , the right wheel  40  follows the instantaneous trajectory indicated in the figure with F whereas the left wheel  40 ′ follows the instantaneous trajectory indicated with F′. 
     In order to effect said rotation around the center of the vehicle  30  described above, the vehicle also comprises a steering group  100  of the wheels  40 ,  40 ′,  50 ,  50 ′ of each axle which allows the relative wheels  40 ,  40 ′,  50 ,  50 ′ to be oriented so as to allow rotation of the vehicle  30  with respect to a point inside a ground-support quadrilateral of the vehicle  30  shown in  FIG. 7  and also the steering geometries shown in  FIG. 5 , particularly so that the axes of the wheels  50 ,  50 ′ of the vehicle  30  intersect upon a single point along a line extending from the wheels  40 ,  40 ′ of the vehicle  30  when the wheels  50 ,  50 ′ are rotated from the straight advance position. 
     An embodiment example of said steering group  100  of the wheels  40 ,  40 ′,  50 ,  50 ′ of an axle is shown in  FIGS. 2-4  and comprises two structural extensions  111 ,  111 ′ which are respectively connected at one end to a relative wheel-holder group  113 ,  113 ′ and at another end to a portion  112  rigidly connected, or oscillating, with respect to the vehicle  30 . 
     In particular, the wheel-holder groups  113 ,  113 ′ are respectively rotatingly connected to the two structural extensions  111 ,  111 ′ around a relative first pin  114 ,  114 ′. 
     According to the invention, the steering group  100  also comprises steering means  101 ,  101 ′ of the wheel-holder groups  113 ,  113 ′ equipped with two independent telescopic units  115 ,  117 ,  115 ′,  117 ′ capable of steering the relative wheel-holder groups  113 ,  113 ′ having a common axis according to independent steering geometries. 
     Each telescopic unit  115 ,  117 ,  115 ′,  117 ′ is rotatingly connected to the relative wheel-holder group  113 ,  113 ′ by means of a second pin  116 ,  116 ′, and comprises a first sleeve element  115 ,  115 ′ and a first rod element  117 ,  117 ′ which slides inside the first sleeve element  115 ,  115 ′. 
     The relative independent movement of the first rod element  117 ,  117 ′ inside the relative first sleeve element  115 ,  115 ′ modifies, independently of the normal steering geometry ( FIG. 5 ), the angular position of the relative wheel-holder group  113 ,  113 ′ with respect to the structural extensions  111 ,  111 ′ allowing a geometry of the type shown in  FIG. 4 , to be reached. 
     Furthermore, each steering group  100  also comprises a main moveable steering stem  120  in a main steering sleeve  121 , rigidly constrained to the vehicle, from which it at least partially protrudes laterally with relative ends both equipped with an articulated element  118 ,  118 ′. 
     According to the embodiment shown in  FIGS. 2-4 , the first sleeve elements  115 ,  115 ′ are respectively rotatingly connected to the wheel-holder groups  113 ,  113 ′ by means of the above second pins  116 ,  116 ′, the first rod elements  117 ,  117 ′ are respectively equipped with an end which slides inside the two first sleeve elements  115 ,  115 ′ and another end spherically connected to the above articulated elements  118 ,  118 ′, on the opposite part, to the main steering stem  120 . 
     According to illustrative embodiments, the movement of the first rod elements  117 ,  117 ′ with respect to the first sleeve elements  115 ,  115 ′ is hydraulically driven, whereas the movement of the main steering stem  120  is driven by means of specific drives directly connected with the rotation of the steering wheel such as a rack or hydraulic actuator. 
     In particular, the movement of the first rod elements  117 ,  117 ′ with respect to the first sleeve elements  115 ,  115 ′ is independent with respect to the movement of the main steering stem  120 . 
     If there is no relative movement between the first rod elements  117 ,  117 ′ and the respective first sleeves  115 ,  115 ′, the movement of the main steering stem  120  allows the wheel-holder groups  113 ,  113 ′ having a common axle to be steered as required, respecting the geometrical constraints imposed on the mechanism by the Ackermann geometry, so that the axes of the wheels  50 ,  50 ′ of the vehicle  30  intersect upon a single point along a line extending from the wheels  40 ,  40 ′ of the vehicle  30  when the wheels  50 ,  50 ′ are rotated from the straight advance position. 
     This arrangement is shown in  FIG. 3  allows the vehicle  30  to effect curved trajectories such as that shown in  FIG. 5  in which the steering group  100  with wheels  50 ,  50 ′, imposes, as described above, an Ackermann geometry on the relative wheels whereas the arrangement shown in  FIG. 7  equipped with driving wheels  40 ,  40 ′, respectively imposes a curved geometry on the wheels  40 ,  40 ′ around an instantaneous rotation axis  60  of the vehicle  30 . 
     In particular therefore, common-maneuvers which can be effected with the currently known steering devices having an instantaneous rotation center outside the vehicle  30 , are also possible with the object of the present invention. 
     If, on the other hand, the main steering stem  120  is kept in a blocked position and centered with respect to the center line of the vehicle  30  and there is a telescopic movement of the two first rod elements  117 ,  117 ′ with respect to the relative sleeves  115 ,  115 ′ on both the right and left side of the common axle, new angular positions of the wheel-holder groups  113 ,  113 ′ are reached, which are suitable for obtaining geometrical constraints that are such as to impose on the vehicle  30  a rotation around a point positioned on the edge of a side of the ground-support quadrilateral or inside the ground-support quadrilateral, for example, the center of the vehicle  30  itself. 
     In particular, the instantaneous rotation center is preferably situated in the center of the other axle with respect to that in which the wheels  50 , 50 ′ are steered as described above and shown in  FIG. 6 , or, by thus steering all the wheels  40 ,  40 ′,  50 ,  50 ′ of the two axles, the vehicle  30  can also effect rotations around its own center, as shown in  FIG. 7 . 
     The example of  FIG. 6  shows a vehicle  30  in rotation around an axle and this steering is obtained thanks to the arrangement of the wheels  50 ,  50 ′ of an axle, for example the front idle wheels  50 ,  50 ′, according to the geometry of  FIG. 4 , whereas the wheels  40 ,  40 ′ of the other axle, for example the rear axle equipped with driving wheels  40 ,  40 ′, are kept fixed parellelly with the vehicle  30 , as said rear axle is rigid. 
       FIG. 7  shows a vehicle according to the invention in which the driving wheels  40 ,  40 ′ are also arranged according to the geometry of  FIG. 4 . 
     In this case, the driving wheels  40 ,  40 ′ connected to the common axle are advantageously activated in rotation in opposing directions with respect to each other by the differential  10  according to the present invention previously described by imposing on the vehicle  30 , a rotation around its own center  60 , as shown in  FIG. 7 . 
     These opposing angular positions of the wheel-holder groups  113 ,  113 ′ obtained thanks to the movement of the first two rod elements  117 ,  117 ′ with respect to the relative sleeves  115 ,  115 ′ are represented in  FIG. 4 , whereas  FIGS. 6 and 7  illustrate two vehicles  30  in rotation around the center of the other axle, and around the center of the vehicle  30  itself, respectively. 
     Upon observing the figures in fact, these respectively show three possible different steering configurations of the wheel-holder group  113 ,  113 ′ with respect to the relative independent positions of the first rod elements  117 ,  117 ′ and main steering stem  120 . 
       FIG. 2  shows a steering group  100  of the wheels of a vehicle  30 , object of the present invention, with a zero steering angle in which the stem  120  protrudes symmetrically from the main steering cylinder  121  and the first rod elements  117 ,  117 ′ are in such a position, substantially entirely contained, with respect to the relative first sleeves  115 ,  115 ′ as to impose a zero steering angle on the two wheel-holder groups  113 ,  113 ′. 
       FIG. 3  shows a steering group  100  of the wheels of a vehicle  30  in which the main steering stem  120  has undergone a total axial translation towards the left side of the center of the vehicle  30  whereas the first rod elements  117 ,  117 ′—and the first sleeves  115 ,  115 ′ are in an unaltered position with respect to  FIG. 2 . 
     In particular, therefore, this configuration shown in  FIG. 3  can be obtained starting from that illustrated in  FIG. 2  exclusively thanks to the translation of the main steering stem  120  and effects an Ackermann type steering geometry shown in  FIG. 5 . 
       FIG. 4  shows a steering group  100  of a wheel of a vehicle  30  object of the present invention in which the stem  120  is kept in a blocked and centered position with respect to the center of the vehicle  30 , the same position as  FIG. 2 , whereas the first rod elements  117 ,  117 ′ are placed in a fully extended position with respect to each respective first sleeve  115 ,  115 ′. 
     Consequently, in particular, this configuration shown in  FIG. 4 , can be obtained starting from that shown in  FIG. 2  exclusively thanks to the movement of the first rod elements  117 ,  117 ′ with respect to the first sleeve elements  115 ,  115 ′ and allows the vehicle  30  to effect a rotation around the center of the other axle as shown in  FIG. 6 , or to effect a rotation around the center of the vehicle  30  if the vehicle  30  envisages both the two steering axles equipped with the steering group  100  as shown in  FIG. 7 , and at least one of the axles comprising the differential  10  shown in  FIG. 1 . 
     This latter possibility is schematically shown in  FIG. 7 . 
     As can be seen in  FIG. 4 , the movements of the first rod elements  117 ,  117 ′ with respect to the relative first sleeve  115 ,  115 ′, preferably driven hydraulically, allow an extra angular excursion of the wheel-holder groups to be obtained. Further, the stem  120  is shown in a blocked and centered position. 
     Thanks to the steering group  100  of the wheels of a vehicle  30  according to the present invention, it is advantageously possible to place the wheel-holder groups  113 ,  113 ′ in a fully extended position with respect to the relative structural extensions  111 ,  111 ′, as shown in  FIGS. 4 ,  6 , and  7 . 
     This aspect is also advantageous because, as the movement of the wheel-holder groups  113 ,  113 ′ is independent of the movement of the main steering stem  120  and therefore independent of the rotation of the steering wheel, it allows such configurations to be obtained without requiring excessive effort on the part of the user and without the use of the main steering cylinder  121 . 
     The functioning of the device and the object of the invention, can now be easily understood. 
     The vehicle  30  according to the present invention is equipped with steering groups  100  of the wheels  40 ,  40 ′,  50 ,  50 ′ of the two axles and the differential  10  drivingly engaged with the driving wheels  40 ,  40 ′. 
     In particular, these steering groups  100  are equipped with steering means  101 ,  101 ′ which comprise for each wheel-holder group  113 ,  113 ′, a telescopic unit  115 ,  117 ,  115 ′,  117 ′ each equipped with a first rod element  117 ,  117 ′ which slides inside a relative first sleeve element  115 ,  115 ′. 
     At least one telescopic unit  115 ,  117 ,  115 ′,  117 ′ is interposed between the relative wheel-holder group  113 ,  113 ′ and a central portion  112  of the axle, which includes a main steering stem  120 . 
     Thanks to the present invention, the steering of the wheel-holder groups  113 ,  113 ′ is also independent of the movement of the main steering stem  120  in effecting steering geometries which allow the wheels to be arranged so as to allow the vehicle  30  to rotate around the center of the other axle or around the center of the vehicle  30  itself. 
     In this latter case the driving wheels  40 ,  40 ′ are advantageously set in rotation by the differential  10  of the present invention in opposite directions, causing the vehicle  30  to rotate around its own center. 
     The vehicle  30 , through use of the steering groups  100 ,  100 ′, can orient the wheels  40 ,  40 ′,  50 ,  50 ′ as illustrated in  FIG. 7  and, by means of the differential  10 , the vehicle  30  can move around its own center. 
     It can thus be seen that the vehicle  30  according to the present invention achieves the objectives previously indicated. 
     The present invention thus conceived can undergo numerous modifications and variants, all included in the same inventive concept; furthermore all the details can be substituted by technically equivalent elements. In practice, the materials used, as also the dimensions, can vary according to technical requirements.