INTEGRATED REDUCTION SYSTEM"

Cross-Reference to Related Applications

This patent application is related to Italian Patent Application No . 102022000009842 filed on May 12 , 2022 , the entire disclosure of which is incorporated herein by reference .

Technical Field

The present invention concerns a wheel hub for an axle of a vehicle , in particular a wheel hub for an axle of a heavy vehicle comprising a reduction system integrated in the hub itsel f .

State of the Art

As is known, it is essential to reduce the torque coming from the drive shaft with respect to the axles in a wheeled vehicle provided at least with an internal combustion engine .

As is also known, vehicles are normally provided with a di f ferential unit configured to di f ferentiate the torque coming from the drive shaft between a pair of hal f shafts of the axle , due to known dynamic requirements during driving of the vehicle .

The above-mentioned torque reduction is normally achieved through known gear devices positioned between the drive shaft and the above-mentioned di f ferential unit .

However, in the case of heavy vehicles , it is known that said reduction ratios are insuf ficient in number to provide an adequate reduction ratio between the torque at the drive shaft and the torque at the wheels of the axle in the various load conditions .

In fact , it is clear that a heavy vehicle , such as a lorry, has to withstand a considerable weight di f ference between the unloaded condition and the maximum load condition and therefore the higher gears available are not necessarily the most suited to the vehicle unloaded condition .

For said purpose , reduction systems integrated in the wheel hubs are known . However, said systems require further improvements to increase their ef ficiency .

Furthermore , the known reduction systems do not allow the gears contained in the system to be engaged while the vehicle is moving and therefore require the vehicle to be stopped, with consequent increase in downtimes .

The need is therefore felt to provide a reduction system for an axle of a vehicle that can solve the above-mentioned problems .

The obj ect of the present invention is to meet the above- mentioned needs in an optimi zed and inexpensive manner .

Summary of the Invention

The above-mentioned obj ect is achieved by a wheel hub for an axle provided with an integrated reduction system and a vehicle as claimed in the attached claims .

Brief Description of the Drawings

For a better understanding of the present invention, a preferred embodiment is described below, by way of non-limiting example and with reference to the attached drawings in which :

• Figure 1 is a schematic section view from above of a vehicle provided with wheel hubs according to the invention;

• Figures 2 to 4 are schematic section views of an axle provided with wheel hubs according to the invention in di f ferent operating phases as shown in figures 5 to 7 ;

• Figures 5 to 7 are section views o f a vehicle hub according to the invention in di f ferent operating phases ; and

• Figure 8 is a schemati zed view of a control system for the vehicle hub according to the invention .

Detailed Disclosure of the Invention

Figure 1 illustrates a commercial or heavy vehicle 1 comprising a frame 2 extending along a longitudinal axis A and movable by means of wheels 3 carried by an axle 4 .

As illustrated in figures 2 to 4 , the axle 4 comprises a casing 5 defining a space 6 adapted to house , at least partially, a pair of hal f shafts 7a, 7b extending along an axis B transverse to the longitudinal axis A of the vehicle 1 .

In particular, the hal f shafts 7a, 7b are operatively connected, at a first end, to a transmission 8 of the vehicle 1 and, on the opposite side , to respective wheel hubs 10 . In the example illustrated, the transmission 8 illustrates a bevel gear, but clearly it could be any torque transmission device , such as a di f ferential , operatively connected to a torque source 9 such as a power train, for example an internal combustion engine .

In particular, the wheel hubs 10 are carried by the casing 5 in a rotationally free manner and are each configured to cooperate with the respective terminal portion of the hal f shafts 7a, 7b as described in detail below .

Concerning the wheel hubs 10 , reference will be made to only one of them for the sake of simplicity, for example the right-hand one , and the considerations below apply in the same way also to the left-hand wheel hub, obviously, since the structure described therein is specular with respect to the longitudinal axis A of the vehicle 1 .

The wheel hub 10 , as said, is supported in a rotationally free manner with respect to the casing 5 , in particular it is hollow and coaxial with respect to the transverse axis B . In the example described, the wheel hub 6 is supported by means of support elements 11 , such as for example a pair of cone bearings and sealing means , such as O-rings .

In particular, the hub 10 comprises a main portion 10a having substantially cylindrical shape carried by the casing 2 and an annular portion 10b housed at a terminal portion of the casing 5 and carried by the main portion 10a . Advantageously, the main portion 10a and the annular portion 10b are coupled through threaded means of known type and, optionally, with the aid of further intermediate parts , according to the assembly required by the vehicle type and weight , therefore said parts are not described in detail .

The cylindrical portion 10a defines with the terminal part of the casing 5 a chamber 13 axially delimited along the axis B by an axial wall 10c of the main portion 10a and on the other side by the terminal part of the casing 5 ; said chamber 13 is radially delimited around the axis B by the internal surface of the main portion 10a of the wheel hub 10 .

The wheel hub 10 is operatively connected to the axle 4 by means of a reduction unit 15 housed inside the chamber 13 and configured to connect the wheel hub 10 to the hal f shaft 7b with three di f ferent transmission ratios , so that the speed/torque at the hal f shaft 7b is di f ferent from the speed/torque at the wheel hub 10 according to three di f ferent speed ratios .

In particular, the reduction unit 15 comprises a gearing 16 configured to cooperate with a toothing 17 integral with the hal f shaft 7b according to a first , a second and a third operating condition characteri zed by di f ferent transmission ratios between hal f shaft 7b and wheel hub 10 .

In particular, the gearing 16 is a planetary gear train comprising a first plurality of satellites 18 ' and a second plurality of satellites 18 ' carried by a respective pin 19 ' , 19' ' integral with a carrier 21 and configured to mesh with a portion 22 integral with the casing 5.

In particular, the carrier 21 is carried rigidly by the hub 10, in detail it is fixed rigidly to the cylindrical portion 10a and has an annular shape extending radially from the cylindrical portion 10a towards the space 13, facing the wall 10c.

In particular, the portion 22 integral with the casing 5 is advantageously in the shape of a bell open towards the chamber 13 so as to face the axial wall 6c. The portion 22 is configured to house inside it the satellites 18' , 18' ' . In particular, the portion 22 defines a toothing 23 configured to mesh with the satellites 18' , 18' ' .

The above-mentioned toothing 17 therefore defines the sun element of the gearing 16 configured to selectively cooperate with one of the satellites 18' , 18' ’ or a toothing 24 provided integral with the carrier 21.

In particular, the second plurality of satellites 18' ’ meshes and cooperates with the toothing 17 by means of a toothed wheel 25 operatively interposed between the satellites 18' ’ and the toothing 17 and defining an external toothing 25' meshing with the satellites 18' ’ and an internal toothing 25' ' meshing with the toothing 17.

Preferably the pins 19' , 19' ’ are rigidly connected to each other and to the carrier 21 and define rotation axes for the pluralities of satellites 18' , 18' ’ parallel to each other with respect to the transverse axis B and radially offset therefrom.

In detail, the second plurality of satellites 18' ’ has a smaller diameter than the first plurality of satellites 18' , due to the presence of the additional toothed wheel 25. Advantageously, the entire hal f shaft 7b is moved along the axis B so as to move the toothing 17 . In particular, the hal f shaft 7b is moved with respect to the transmission 8 as described below .

In particular, the hal f shaft 7b is actuated by an actuator device 30 operatively interposed between the casing 5 and the hal f shaft 7b . In particular, the actuator device 30 is operatively interposed between an outer end 7b' of the hal f shaft 7b defining the toothing 17 described above and an inner end 7b' ' of the hal f shaft 7b cooperating with the transmission 8 .

In particular, the actuator device 30 comprises a sleeve 31 carried free to rotate but linearly integral with the hal f shaft 7b . In greater detail , the sleeve 31 is carried by a pair of roller bearings 32 arranged according to a suitable assembly arrangement .

The sleeve 31 comprises a cylindrical body 31 ' and a flanged portion 31 ' ’ extending radially from the external surface of the cylindrical body 31 ' .

In detail , the casing 5 defines a chamber 33 configured to house the sleeve 31 in a sealed sliding manner , in particular in sliding contact with the cylindrical body 31 ' . The flanged portion 31 ' ’ is si zed so as to be in fluid-tight contact with the inner surface of the chamber 33 , dividing the latter into two portions 33 ' , 33 ' ’ .

The actuator device 30 further comprises elastic means 34 configured to maintain the sleeve 31 in a predefined position in the chamber 33 . In particular, the actuator device 30 is configured to maintain the sleeve 30 in a rest configuration at the centre line with respect to the extension of the chamber 33 along the transverse axis B . In greater detail, the elastic means 34 comprise a first and a second spring 34' , 34' ’ positioned in the respective portions of chamber 33' , 33' ’ and configured to exert a force between the casing 5 and the flange portion 31' ’ .

In greater detail, the first and second spring 34' , 34' ’ are spiral helical springs.

The portions 33' , 33' ' are furthermore fluidically connected to a source of pressurized fluid, such as compressed air, of the vehicle (not illustrated) so as to be selectively positioned under pressure or brought to ambient pressure.

In particular, the first portion 33' is fluidically connected to a first duct 35' and the second portion 33' is connected to a second duct 35' ’ fluidically connectable to the pressurized fluid source.

In detail, with reference to figure 8, the vehicle 1 comprises a source of pressurized fluid 36, such as a tank of compressed air, fluidically connected to the ducts 35' , 35' ’ through, for example, respective valve means 37' , 37' ’ configured to regulate the passage of air through them.

The half shaft 7b is connected, integral with rotation but free to slide, to an operating element 40, for example a bevel gear wheel. In particular, the half shaft 7b is connected to said operating element 40 by means of a grooved coupling between a toothing 41 provided on an inner surface of the operating element 40 and a toothing 42 provided on an outer surface of the operating element 40.

In further detail, the length along the axis B of the grooved coupling is such that the half shaft 7b is in continuous torque engagement with the transmission 8, namely the operating element 40 , throughout the movement of the hal f shaft 7b actuated by the actuator device 30 . Consequently according to the movement of the hal f shaft 7b so that the toothing 17 cooperates with the toothing 24 or with the satellites 18 ' , 18 ' ' , the hal f shaft 7b is continuously engaged due to the length of the grooved coupling .

Advantageously the vehicle 1 further comprises an electronic control unit 50 and a plurality of sensors 51-58 adapted to detect quantities relative to di f ferent vehicle operation parameters ; the control unit 50 comprises processing means electronically connected to the sensors 51-58 to acquire the data detected by the latter and consequently control the passage of pressuri zed fluid 35 ' , 35 ' ’ .

In particular, the sensors 51 -58 can be connected to the control unit 50 by wire or electromagnetically and the control unit 50 is configured to control the valve means 37 ' , 37 ’ ’ which are advantageously solenoid valves .

In particular, the electronic unit 50 contains stored data relative to control of the actuator device 30 and valve means 37 ' , 37 ' ' .

The vehicle 1 can furthermore comprise control means (not illustrated) configured to vary the data stored in the control unit 50 so as to vary the actuation condition of the actuator device 30 and the valve means 37 ' , 37 ' ' .

Preferably the sensor means comprise at least some of the following sensor means :

• A load sensor 51 configured to detect the load of a suspension connecting the axle 4 to the frame 2 , for example a load cell ;

• A clutch sensor 52 configured to detect the opening of a control clutch of the transmission 8 , for example a position sensor connected to the clutch pedal ;

• An accelerator sensor 53 configured to detect the acceleration of the vehicle 1 , for example a pos ition sensor connected to the accelerator pedal ;

• An ignition sensor 54 configured to detect the ignition of the vehicle 1 , for example a movement sensor of the key ignition system;

• A speed sensor 55 configured to detect a rotation speed of the output shaft of the power train 9 , for example a tonewheel ;

• A control sensor 56 configured to detect activation of the possibility of varying the wheel hub ratio , for example a button or an icon on a display;

• A speed sensor 57 configured to detect a rotation speed of the axle 4 , therefore of the half shafts 7a, 7b, such as a tonewheel or an encoder ; and

• A speed sensor 58 , configured to detect a speed of the wheel hub 10 , such as an ABS sensor of the tonewheel or encoder type .

•

The operation of the wheel hub according to the invention described above is the following .

In a first operating condition, at high speed, illustrated in figures 2-5 , the toothing 17 cooperates with the toothing 24 of the carrier 21 since air is introduced through the duct 35 ' into the portion 33 ' of the chamber 33 , compressing the spring 34 ' ’ and therefore bringing the hal f shaft 7b to its position of maximum extension along the axis B . In said condition, the torque provided by the transmission 8 , namely by the operating element 40 , to the hal f shaft 7b is transmitted identically to the wheel hub 10 since the carrier 21 is fixed to it .

In a second operating condition, at medium speed, illustrated in figures 3- 6 , the toothing 17 cooperates with the first plurality of satellites 18 ' , since air is introduced through the duct 35 ' ’ into the portion 33 ’ ’ of the chamber 33 , compressing the spring 34' and therefore bringing the half shaft 7b to its position of minimum extension along the axis B. In said condition, the torque provided by the transmission 8, namely by the operating element 40, to the half shaft 7b passes to the satellites 18' which, by meshing on the toothing 23 of the element 22, rotate the respective pins 19' which drive the carrier 21 at a different speed from the first operating condition .

In a second operating condition, at low speed, illustrated in figures 4-7, the toothing 17 cooperates with the second plurality of satellites 18' ' , since no air is introduced into the chamber 33 and therefore the springs 34' , 34' ’ keep the sleeve 30 in an intermediate position of equilibrium between the above-mentioned minimum and maximum extension of the half shaft along the axis B. In said condition, the torque provided by the transmission 8, namely by the operating element 40, to the half shaft 7b passes to the satellites 18' ’ through the toothed wheel 25. The satellites 18' ' , by meshing on the toothing 23 of the element 22, rotate the respective pins 19' which drive the carrier 21 at a different speed from the first and second operating condition.

According to the above, the present invention also concerns a method for controlling a wheel hub provided with a reduction unit 15 of the type described above.

Said method essentially comprises the following steps:

• Detecting a plurality of physical quantities relative to operating parameters of the vehicle 1;

• Processing said physical quantities detected to identify a vehicular load condition;

• Checking that the vehicular load condition complies with the reduction ratio of the wheel hub 10;

• If so, the ratio is maintained, otherwise the actuator device is controlled to pass to a different reduction ratio. In particular, the control of the actuator device 30 comprises sending a control signal to the valve means 37 .

In particular, the method illustrated above can be stored and processed in the control unit 50 described above and the physical quantities detected can be some of the quantities detected by the sensor means 51-58 .

The vehicular load condition can be checked by checking the quantities detected with respect to physical quantities stored in the control unit 50 , for example by means of lookup tables ( LUT ) deriving from speci fic experimental tests for the particular type of vehicle .

Otherwise , the above-mentioned check can be carried out by comparison with a value deriving from mathematical interpolations between said physical quantities .

From the above , the advantages of a wheel hub for an axle of a vehicle comprising an integrated reduction system according to the invention are evident .

Thanks to the system proposed, it is possible to provide a reduction system integrated in a wheel hub that is versatile , compact , inexpensive and easy to assemble and maintain compared to the known systems .

Thanks to the additional reduction system and the three transmission ratios which can be chosen according to the vehicle type and si ze , it is possible to further reduce fuel consumption and therefore polluting emissions .

In particular, the use of a gearing integrated in the wheel hub provides high transmission ratios through a robust gear suited to the high loads of a heavy vehicle axle . The use of a grooved coupling between transmission and half shaft allows the torque transmission to be continuously maintained while the operational gear in the wheel hub is varied, resulting in a particularly compact and stable arrangement .

Furthermore, the presence of two ducts that selectively inj ect air into two portions of the chamber of the actuator means allows the reduction ratio change to be activated in a quicker and more controlled manner . In particular, it is possible to control said change during the vehicle movement .

In fact, thanks to the control method described, it is possible to engage the gear in the reduction unit 15 when the vehicle is moving .

The control can be automated and stored in the electronic unit and the control variables can be stored or modified in advance by the driver .

Lastly, it is clear that modifications and variations that do not depart from the protective scope defined by the claims can be made to the wheel hub of a vehicle axle comprising an integrated reduction system according to the present invention.

Obviously, as said, the casing 4 and wheel hub 10 can have different forms and be produced in several different pieces .

The toothed wheels and the gears described could vary, and likewise elements not described but known for the assembly of an axle according to the present invention could be provided.

Clearly the above description refers to an air actuation which is the most effective and inexpensive, but equivalent actuator means can also be used such as electromagnetic, mechanical or fluid actuators configured for the sleeve 31 in place of the pressure force of the air described in this application. Furthermore, the method described could comprise different methods for checking the engagement condition of the ratios between wheel hub and half shafts, as said, by checking limit values deriving from mathematical interpolations or table relationships .