Differential system for off-road operation and vehicle equipped with such a differential

Abstract

Differential system for off-road operation and vehicle equipped with such a differential A range-doubler differential system for a vehicle, which comprises: a differential cage (3); a differential input toothed ring gear (2) comprising an external toothing (2.1), a first internal toothing (2.2) and a second internal toothing (2.3), the ring gear being arranged freely rotatable on the differential cage; a planetary reduction system, comprising: satellite support shafts (5.1) secured to the differential cage; satellites (5); an inner wheel (6) of the planetary reducer arranged to rotate freely on the differential cage; the satellites being arranged so as to engage both the first inner toothing of the differential input ring gear and the inner wheel of the planetary reducer; a first and a second locking system (7, 4) intended to activate or deactivate a first and a second gear reduction range called off-road speed and respectively normal speed. Abstract figure: fig. 7.

Description

Title of the invention: Differential system for off-road operation and vehicle equipped with such a differential Technical field of the invention

[0001] The present invention relates to the field of automotive technology and, more particularly, to the field of gearboxes for motor vehicles. In particular, the invention relates to a dual-range differential system for a vehicle, to a gearbox containing such a dual-range differential system, to a method of controlling the gearbox and to a vehicle comprising such a gearbox. State of the art

[0002] To be able to drive on the road, off-road vehicles must have several characteristics. One of the characteristics is that off-road vehicles need a very high torque-to-speed ratio when traveling over rough terrain. Most off-road vehicles are equipped with a particularly high torque-to-speed ratio. This allows the operator to make the most of the engine's available power while traveling slowly over difficult terrain. An internal combustion engine coupled with a normal gearbox often has an output speed that is too high. The vehicle is often equipped with one of two devices: either a very low first gear or an additional transmission box in series with the first, called a reduction gear. Some vehicles are also equipped with torque converters to further reduce the gear ratio.Many wheeled off-road vehicles provide power to all wheels to maintain traction on slippery surfaces. For a typical four-wheel vehicle, this is called four-wheel drive. Vehicles designed for both on- and off-road use may be designed to switch from two-wheel drive to four-wheel drive, so the vehicle uses fewer drive wheels when driven on the road.

[0003] However, it is known that off-road gearboxes have poorly spaced gear ratios, which means that the time required to shift from first to second gear is very short, which sometimes means that the vehicle starts directly in second gear. Due to the poorly spaced gear ratios, off-road gearboxes generate a greater amount of CO 2 than a normal-speed gearbox.

[0004] Patent EP 3 530 983 B1 discloses a gearbox comprising a plurality of mechanisms which define forward and reverse gear ratios for motor vehicles, particularly for off-road vehicles. A planetary gearbox meshes with a sun gear, a crown wheel, and several planet gears which are rotated about the axis by a planet carrier. Said wheel is toothed with external teeth, the crown wheel is a cylindrical gear with internal teeth and the planet gears are cylindrical gears with external teeth. The range selection device comprises a first operating condition in which a rotational connection of the first sun gear to the crown wheel is provided, and a second operating condition in which the rotation of the externally toothed wheel is blocked. In the second operating condition of the device, which can be obtained by moving the movable element, the wheel is permanently connected to the fixed element and its rotation is therefore blocked. Presentation of the invention

[0005] The present invention proposes the use of a planetary reduction system mounted on the differential for off-road operation, leading to off-road operation with the advantages of normal operation, namely easier operation when changing gear ratio, lower CO2 than an off-road gearbox and high torque to the wheels when required. Summary of the invention

[0006] The invention relates to a range-doubler differential system for a vehicle, characterized in that it comprises a differential cage; a differential input toothed ring gear comprising an external toothing, a first internal toothing and a second internal toothing, the ring gear being arranged to rotate freely on the differential cage; a planetary reduction system, the planetary reduction system comprising satellite support shafts secured to the differential cage; satellites mounted to rotate freely around the satellite support shafts; an inner wheel of the planetary reduction gear arranged to rotate freely on the differential cage; the satellites being arranged so as to engage both the first internal toothing of the differential input toothed ring gear and the inner wheel of the planetary reduction gear;a first locking system intended to couple or decouple the inner wheel with a fixed element of the vehicle to activate or deactivate a first gear reduction range called off-road mode; a second locking system making it possible to couple or decouple the differential cage with the second toothing of the differential input crown wheel to activate or deactivate a second gear reduction range called normal mode.;

[0007] The present invention allows the use of a single gearbox for both off-road and normal regimes without changing the gear ratios by using a planetary reduction system mounted on the differential. In fact, the planetary reduction has an internally toothed wheel, machined on the current differential crown, arranged on the differential cage by means of a bearing that allows rotation between the two elements. Said cage is also the support for the planetary reduction gear shafts. In addition, to ensure the transmission of high torque, planetary gears with satellites are used. In particular, the number of satellites in the planetary gear is four. Said satellites are mounted on the satellite shafts integral with the differential cage. The internal wheel of the planetary reduction gear is arranged by means of a bearing on the cage, to allow rotation of the planetary reduction gear.

[0008] It would therefore be advantageous to use a single gearbox for both off-road and normal operation without changing the gear ratios. Thus, the gearbox can operate in off-road operation but with the gear ratios of the normal operation.

[0009] The present invention also makes it possible to maintain the architecture of a current gearbox for normal regime, with a minimum of modifications, and to use it for both normal regime and off-road regime. In this way, we will have a minimum diversity because for the same engine, we will use a single gearbox on both versions. The gearbox will be the most efficient from the pollution point of view because the transmission ratios for the off-road regime will be the same as those used for the normal regime, which is well optimized from the point of view of CO2 emissions. For the off-road regime, the system of the present invention will be used integrated in the same gearbox. The advantages are therefore reduced diversity and reduced CO2 emissions.

[0010] In off-road operation (low speed and high torque), the inner wheel of the planetary gearbox must be locked to the gearbox housing using a first locking system and the ring gear must be unlocked from the differential cage using a second locking system. In normal operation (high speed and low torque), the differential input ring gear must be locked to the differential cage using the second locking system and the inner wheel of the planetary gearbox must be unlocked from the gearbox housing using the first locking system.

[0011] Both locking systems cannot be used simultaneously in the locked position. When one system is locked, the other must be unlocked.

[0012] The advantages of using the dual-range differential system of the present invention are as follows: a single gearbox is used for off-road and normal operation, without changing transmission ratios; technical solution has no impact on the current architecture as it is integrated into the current gearbox for normal regime; reduction of CO2 emissions as, generally, the gears for normal regime are better calculated from a pollution point of view. For the gearbox for off-road regime, the lower gears are very short to ensure high torque, which results in higher fuel consumption compared to normal regime and higher CO2 emissions; the transmission ratio is 1.5 - 2, depending on the possibilities and requirements. Increased torque at the output, towards the wheels, with the same gear ratio; the cost is lower than that of another gearbox or other solution to increase the torque.The off-road differential mounted planetary reduction gear system of the present invention can be implemented in gearboxes for manufactured or even aftermarket vehicles with minimal modifications.

[0013] Advantageously, the invention provides a dual-range differential system in which, for off-road operation, the inner wheel of the planetary reducer is locked to a gearbox housing using the first locking system, and the second locking system is in the decoupled position.

[0014] Advantageously, the invention provides a range splitter differential system in which, for normal operation, the differential input ring gear is coupled to the differential cage using the second locking system and the first locking system is in the decoupled position.

[0015] Advantageously, the invention provides a range-doubler differential system in which the first locking system and the second locking system cannot be simultaneously in the coupled position or in the decoupled position.

[0016] Advantageously, the invention provides a range splitter differential system in which the first locking system and the second locking system can be simultaneously in a coupling position to provide a parking brake function.

[0017] The invention also relates to a gearbox comprising the range splitter differential system and a casing, the fixed element with which the first locking system couples the inner wheel is the gearbox casing.

[0018] The invention also relates to a method for controlling the gearbox, comprising the following steps: selection of the normal speed, by moving the second locking system into a position for coupling the differential input crown wheel to the differential cage and the first locking system into a position for decoupling the inner wheel from the fixed element; selection of the speed off-road by moving the first locking system into a position coupling the inner wheel with the fixed element and the second locking system into a position decoupling the differential input crown with the differential cage.

[0019] Advantageously, the invention provides a method in which the movement of the first locking system and the second locking system is carried out using mechanical means.

[0020] Advantageously, the invention provides a method, in which the movement of the first locking system and the second locking system is carried out using electrical means.

[0021] The invention also relates to a vehicle comprising the gearbox mentioned above.

[0022] The subject of the invention is a planetary reduction system intended to be mounted in a conventional gearbox operating in normal mode, with a minimum of changes to the current gearbox, in order to operate in off-road mode with all the advantages of the normal mode: reduction of CO2 emissions due to the fact that the stages in the gearbox are better calculated from the pollution point of view; increased torque to the wheels with the same gear ratio for all stages; reduced cost compared to another solution for increasing the torque; it is a solution that can be used in after-sales because it does not strongly modify the architecture of the current gearbox. Presentation of figures

[0023] Now, a preferred embodiment of the invention will be described in connection with the accompanying drawings in which:

[0024] [Fig-1] [Fig.l] is a sectional view showing the doubling differential system of the present invention mounted in a gearbox which shows the component elements of the range splitter differential system of the present invention;

[0025] [Fig.2] [Fig.2] is a sectional view showing the dual-range differential system of the present invention mounted on a gearbox operating in normal operation (high speed and low torque);

[0026] [Fig.3] [Fig.3] is a sectional view showing the dual-range differential system of the present invention mounted in a gearbox operating in off-road mode (low speed and high torque);

[0027] [Fig.4] [Fig.4] is a sectional view of the range splitter differential system of the present invention;

[0028] [Fig.5] [Fig.5] is a perspective view showing the differential system range doubler of the present invention;

[0029] [Fig.6] [Fig.6] is an exploded side plan view showing the components of the range doubling differential system of the present invention;

[0030] [Fig.7] [Fig.7] is an exploded perspective view showing the dif system range doubler differential of the present invention. Detailed description of the invention

[0031] The invention will be better understood upon reading the following description of a non-limiting example of the invention.

[0032] The differential system according to the invention comprises:

[0033] a differential cage 3; a differential input toothed ring 2 comprising an external toothing 2.1, a first internal toothing 2.2 and a second internal toothing 2.3, the ring being arranged to rotate freely on the differential cage 3; a planetary reduction system, the planetary reduction system comprising satellite support shafts 5.1 secured to the differential cage 3; satellites 5 mounted to rotate freely around the satellite support shafts 5.1; an inner wheel 6 of the planetary reduction gear arranged to rotate freely on the differential cage 3; the satellites 5 being arranged so as to engage both the first internal toothing 2.2 of the differential input toothed ring 2 and the inner wheel 6 of the planetary reducer; a first locking system 7 intended to couple or decouple the inner wheel 6 with a fixed element of the vehicle to activate or deactivate a first gear reduction range called off-road speed; a second locking system 4 making it possible to couple or decouple the differential cage 3 with the second inner toothing 2.3 of the differential input toothed ring 2 to activate or deactivate a second gear reduction range called normal speed.

[0034] In operation, the motive power of the internal combustion engine enters the gearbox via the primary shaft (which is not shown), passes through any gear ratio, enters the secondary shaft and exits the gearbox via the secondary shaft drive pinion to mesh with the differential input ring gear.

[0035] [Fig. 1] is a sectional view showing the split-range differential system of the present invention mounted in a gearbox which shows the component elements of the split-range differential system of the present invention.

[0036] In essence, the dual-range differential system of the present invention comprises a differential input ring gear 2, a differential cage 3, a second locking system 4 for locking the dif- ferentie 2 on the differential cage 3 and activate and deactivate the normal speed, four satellites 5, an inner wheel 6 of the planetary reducer for the mesh with the satellites 5 of the double-range differential system, a first locking system 7 for locking the inner wheel 6 of the planetary reducer on the casing 9 of the BV gearbox, a bearing 13 for supporting the rotational movement between the differential input ring gear 2 and the differential cage 3 and a bearing 14 for supporting the rotational movement between the differential cage 3 and the inner wheel 6 of the planetary reducer.

[0037] In addition to the external toothing 2.1 of the differential input toothed ring 2 intended for meshing with the driven pinion 1 of the secondary shaft 8 of a BV gearbox for normal operation, said differential input toothed ring 2 also has an internal toothing 2.2 provided for meshing with the internal wheel 6 of the planetary reducer when the operation of the BV gearbox in off-road operation is desired.

[0038] [Fig. 2] is a sectional view showing the dual-range differential system of the present invention mounted on a BV gearbox operating in normal operation. The differential input toothed ring 2 is integral with the differential cage 3 and the inner wheel 6 of the planetary reducer is in free movement.

[0039] [Fig. 3] is a sectional view showing the dual-range differential system of the present invention mounted in a BV gearbox operating in off-road mode. The inner wheel 6 of the planetary reducer is integral with the casing 9 of the BV gearbox, i.e. fixed, and the differential input toothed ring 2 is freely movable relative to the differential cage 3.

[0040] [Fig. 4] is a sectional view of the dual-range differential system of the present invention. The driving force enters via the driven pinion 1 of the secondary shaft 8. The driven pinion 1 rotates the differential input ring gear 2 via the external toothing 2.1. At the same time and if the first locking system 7 is activated, the internal toothing 2.2 of the differential input ring gear 2 drives the planetary gears 5 of the planetary reducer which in turn drive the inner wheel 6. Via the pins 7.1 of the first locking system 7 which slide in the casing of the gearbox BV, the force is transmitted to the outputs towards the front wheels 10.1 and 10.2.

[0041] [Fig.5] is a perspective view showing the dual-range differential system of the present invention seen from the side of the second locking system 4. The second locking system 4 is composed of the pin 4.1, the internal toothing 4.2 and the external toothing 4.3. The fork 4.4 slides all the time in the annular groove 4.5.

[0042] [Fig.6] is an exploded side plan view showing the components of the dual-range differential system of the present invention. The first locking system 7 comprises the pins 7.1 which slide in holes which are arranged in the casing 9 of the gearbox BV and which can move in the X or Y direction, to lock or unlock the first locking system 7. In this embodiment, the number of pins 7.1 is seven but other numbers of pins 7.1 can also be envisaged. The pins 7.1 are integral with a crown which has internal teeth 7.2.

[0043] [Fig.7] is an exploded perspective view showing the dual-range differential system of the present invention. When the first locking system 7 is pushed all the way in, the inner toothing 7.2 meshes with the outer toothing of the inner wheel 6 of the planetary reducer,

[0044] For normal operation on roadways, the first locking system 7 is pushed in the Y direction for unlocking, by means of an element which is not shown in the figures and at the same time the second locking system 4 is pushed in the Y direction for locking, by means of an element which is not shown in the figures. Therefore, at this moment, the first locking system 7 is at a certain distance from the inner wheel 6 of the planetary reducer. Due to the fact that the first locking system 7 is in the unlocked position, the driven pinion 1 rotates the differential input toothed ring 2 via the outer toothing 2.1 but does not rotate the satellites 5 of the planetary reducer, which in turn do not rotate the inner wheel 6 of the planetary reducer.At the same time, the second locking system 4 is pushed in the Y direction, by means of the pin 4.1 which is integral with the fork 4.4 which slides in the annular groove 4.5. When the second locking system 4 is pushed to the bottom, the teeth of the external toothing 4.3 will mesh with the teeth of the internal toothing 2.3 of the differential input ring gear 2 and the teeth of the internal toothing 4.2 will mesh with the grooves of the differential cage 3.1. In this configuration, the driven pinion 1 rotates the differential input toothed ring 2 via the external toothing 2.1 and, due to the second locked locking system 4, rotates the differential cage 3. Thus, the front wheels of a motor vehicle will be driven with a torque corresponding to a certain gear ratio of the gearbox BV, via the outputs to the front wheels 10.1 and 10.2. .

[0045] When the motor vehicle leaves the road to drive on rough terrain, it is necessary to couple the off-road mode. The off-road mode is characterized by a reduced speed but a high torque towards the wheels. To func operation in off-road mode, the first locking system 7 is pushed in the X direction, by means of an element which is not shown in the figures. When the first locking system 7 is pushed to the bottom, with the inner face 7.3 of the crown in contact with the outer face 6.1 of the inner wheel 6 of the planetary reducer, the inner toothing 7.2 meshes with the outer toothing of the inner wheel 6 of the planetary reducer. At this moment, the inner wheel 6 of the planetary reducer is locked on the housing 9 of the gearbox BV. Due to the fact that the first locking system 7 is in the locked position, the driven pinion 1 rotates the differential input toothed crown 2 via the outer toothing 2.1, rotates the planetary reducer planetary gears 5, which in turn rotate the inner wheel 6 of the planetary reducer. At the same time, the second locking system 4 is pushed in the X direction, by means of the pin 4.1 which is integral with the fork 4.4 which slides in the annular groove 4.5. When the teeth of the external toothing 4.3 come out of meshing with the teeth of the internal toothing 2.3 of the differential input ring gear 2, the driven pinion 1 rotates the differential input ring gear 2 by means of the external toothing 2.1 and due to the unlocked second locking system 4, rotates the differential cage 3 by means of the planetary reduction system. Thus, the front wheels of a motor vehicle will be driven with a very high torque by means of the outputs to the front wheels 10.1 and 10.2.

[0046] It is obvious to those skilled in the art that for normal operation, when the first locking system 7 is unlocked, the second locking system 4 must be locked, and for off-road operation, when the first locking system 7 is locked, the second locking system 4 must be unlocked, i.e. the first locking system 7 and the second locking system 4 cannot be locked at the same time.

[0047] In a preferred embodiment, the planetary reduction gear system of the present invention comprises 4 planetary gears. In this configuration, the planetary reduction gear system achieves a rotational speed reduction of approximately 1.66 times for off-road operation. Industrial applicability

[0048] The invention is very useful in the motor vehicle industry, particularly in the field of gearboxes to be able to use a single gearbox for both off-road (low speed and high torque) and normal (high speed and low torque) operation without changing the gear ratios. Thus, with the differential-mounted planetary reduction gear system for off-road (low speed and high torque) operation, the gearbox can operate in off-road operation. (low speed and high torque) but with the speed ratios of the normal regime (high speed and low torque). As far as the manufacture of motor vehicles is concerned, the differential-mounted planetary reduction gear system for off-road regime (low speed and high torque) of the present invention results in a minimum diversity of gearboxes because for the same engine, a single gearbox will be used for both regimes. For after-sales vehicles, the differential-mounted planetary reduction gear system for off-road regime (low speed and high torque) of the present invention allows to keep the architecture of the current normal regime gearbox and with a minimum of modifications, to be able to operate the gearbox also in off-road regime.Other advantages of the off-road (low speed and high torque) differential-mounted planetary reduction gear system of the present invention are reduced CO2 emissions and reduced fuel consumption.

Claims

Claims

1. A vehicle dual-range differential system, characterized in that it comprises: - a differential cage (3); - a differential input toothed ring gear (2) comprising an external toothing (2.1), a first internal toothing (2.2) and a second internal toothing (2.3), the ring gear being arranged to rotate freely on the differential cage (3); - a planetary reduction system, the planetary reduction system comprising: - satellite support shafts (5.1) secured to the differential cage (3); - satellites (5) mounted to rotate freely around the satellite support shafts (5.1) - an internal wheel (6) of the planetary reduction gear arranged to rotate freely on the differential cage (3) - the satellites (5) being arranged to engage both the first internal toothing (2.2) of the differential input toothed ring and the inner wheel (6) of the planetary reducer; - a first locking system (7) intended to couple or decouple the inner wheel (6) with a fixed element of the vehicle to activate or deactivate a first gear reduction range called off-road speed; - a second locking system (4) making it possible to couple or decouple the differential cage (3) with the second inner toothing (2.3) of the differential input toothed ring to activate or deactivate a second gear reduction range called normal speed;.

2. A dual-range differential system according to the preceding claim, wherein, for off-road operation, the inner wheel (6) of the planetary reducer is locked to a gearbox (BV) housing (9) using the first locking system (7) and the second locking system (4) is in the decoupled position.

3. A range-doubler differential system according to one of the preceding claims, wherein for normal operation, the differential input ring gear (2) is coupled to the differential cage (3) using the second locking system (4) and the first locking system (7) is in the decoupled position.

4. A range-doubler differential system according to one of the preceding claims, wherein the first locking system (7) and the second locking system (4) cannot be simultaneously in the coupled position or in the decoupled position.

5. A dual-range differential system according to one of claims 1 to 3, wherein the first locking system (7) and the second locking system (4) can be simultaneously in a coupling position to provide a parking brake function.

6. Gearbox comprising the dual-range differential system according to one of the preceding claims and a casing, the fixed element with which the first locking system (7) couples the inner wheel (6) is the casing (9) of the gearbox

7. A method of controlling the gearbox according to claim 6, comprising the following steps: - selecting the normal speed, by moving the second locking system (4) into a position for coupling the differential input ring gear (2) to the differential cage (3) and the first locking system (7) into a position for decoupling the inner wheel (6) from the fixed element; - selecting the off-road speed by moving the first locking system (7) into a position for coupling the inner wheel (6) to the fixed element and the second locking system (4) into a position for decoupling the differential input ring gear (2) from the differential cage (3).

8. Method according to claim 7, characterized in that the movement of the first locking system (7) and the second locking system (4) is carried out using mechanical means.

9. Method according to claim 7, characterized in that the movement of the first locking system (7) and the second locking system (4) is carried out using electrical means.

10. A vehicle comprising the gearbox of claim 6.

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