FR2996277A1 - DIFFERENTIAL INTEGRATING A HYDRAULIC DEVICE - Google Patents

Abstract

The present invention relates to an assembly comprising a differential (1) linking a first (16) and a second (17) output shaft, said differential (1) comprising a differential case (11) comprising adapted case gears (12) for cooperating with pinions (14, 15) connected to said output shafts (16, 17) and thereby driving said output shafts (16, 17), said assembly comprising a radial piston hydraulic apparatus coupled to said differential, comprising - a distributor (51) of distribution and a cam (3) multilobe defining a first set, - a cylinder block (4) defining a second set, one of said sets being mounted fixed in rotation relative to the differential case (11), and the other of said sets being rotatably mounted relative to the differential case (11) so as to allow the rotation of the differential case (11) by said hydraulic apparatus.

Description

GENERAL TECHNICAL FIELD The present invention relates to the field of vehicles equipped with hydraulic drive means.

STATE OF THE ART It is known the use of hydraulic devices for carrying out the training of vehicles, including applications for agricultural or construction equipment. The wheels of these vehicles are then individually associated with a hydraulic motor, including on the same axle, to drive them independently at the desired speed. Such a configuration is however cumbersome and expensive in that it requires a multiplication of hydraulic devices on the vehicle. In addition, the addition of multiple components makes the integration of such systems very disadvantageous on light vehicles.

PRESENTATION OF THE INVENTION The present invention thus aims to respond to this problem, and proposes an assembly comprising a differential linking a first and a second output shaft, said differential comprising a differential housing comprising case gears adapted to cooperate with sprockets connected to said output shafts and thus driving said output shafts, said assembly being characterized in that it comprises a radial piston hydraulic apparatus coupled to said differential, said hydraulic apparatus comprising a distributor and a multilobe cam defining a first set - a cylinder block defining a second set, one of said sets being rotatably mounted relative to the differential case, and the other of said sets being rotatably mounted relative to the differential case so as to allow the drive to rotation of the differential case by said hydraulic apparatus ic. Alternatively, said hydraulic apparatus comprises a distributor and a distributor cover, an internal volume being defined by the distributor, the distributor cover, the shaft and the cylinder block, said internal volume being supplied with fluid by a conduit arranged so to allow the lubrication and cooling of this internal volume. The assembly then typically further comprises a casing defining an internal volume of casing bathed in the oil, one of said first and second sets being movable relative to the casing and comprising means adapted for the rotation of said assembly relative to the crankcase causes an oil supply of the internal volume by sampling the crankcase oil via internal conduits connecting the internal crankcase volume and the internal volume.

According to another variant, said mounted assembly fixed in rotation relative to the differential housing comprises a toothing adapted to cooperate with a drive shaft so as to allow a drive of said output shafts by the drive shaft, which constitutes a parallel transmission line. Said toothing is for example arranged on the outer periphery of the cam, so as to cooperate with a driving shaft pinion. Said hydraulic apparatus may be connected to one or more hydraulic accumulators adapted to perform energy storage. It then includes, in addition, a drive shaft adapted to drive the output shafts. The said hydraulic apparatus may also be advantageously used for a low speed transmission mode, while the mechanical input may be advantageously used for a high speed transmission mode. According to another variant, the first assembly is mounted movably on the differential housing and the second assembly is fixedly mounted on the differential housing, said cylinder block comprising a plurality of pistons adapted to be retracted so as to disengage from the cam and thus putting the hydraulic apparatus in freewheel configuration in which said first and second sets are free to rotate relative to each other. According to another variant, said differential case comprises a ring of balls forming a bearing around said differential case and linking said differential case to the other of said sets. The cam can then form a rolling track for said ring of balls. According to another variant, the first and second output shafts 20 each rotate a vehicle wheel. According to another variant, said hydraulic apparatus is supplied with pressure by a variable displacement hydraulic pump adapted to be selectively driven by a primary engine of the vehicle via a transmission. PRESENTATION OF THE FIGURES Other characteristics, objects and advantages of the invention will emerge from the description which follows, which is purely illustrative and nonlimiting, and which should be read with reference to the appended drawings, in which: FIG. an example of a system according to one aspect of the invention, - Figure 2 shows a detailed view of a portion of Figure 1, - Figure 3 shows another example of a system according to one aspect of the invention, - Figure 4 shows a variant of the embodiment shown in Figure 3, - Figure 5 shows a particular embodiment of an assembly combining a differential and a hydraulic apparatus according to one aspect of the invention.

In all the figures, the elements in common are identified by identical reference numerals. DETAILED DESCRIPTION Figure 1 shows a sectional view of a system according to one aspect of the invention. This figure shows a longitudinal axis X-X of the system. The system as shown comprises a shaft 2, a cam 3 typically a multilobe cam, a cylinder block 4, a distributor 5 and a housing 6 thus forming a hydraulic apparatus, the shaft 2 is connected in rotation with a differential 1 shown here by a schematization of differential case. The housing 6 and the shaft 2 are rotatably mounted relative to each other, typically by means of bearings, in this case two conical bearings 21. In the following description, it will be considered that the shaft 2 is rotating and that the housing 6 is fixed to illustrate an embodiment of the invention. The cam 3 is typically formed of an annular ring adjacent to the axially inner face of the casing 6, and comprises on its radially inner surface a series of equi-distributed lobes around the X-X axis. Each of the lobes typically has a generally sinusoidal appearance. The cam 3 is linked and integral in rotation with the casing 6.

The cylinder block 4 is placed inside the ring forming the cam 3. It defines a plurality of cylinders 41 oriented radially with respect to the axis XX and opening onto the outer peripheral face of the cylinder block 4 opposite the 3. A piston 42 is mounted to slide radially respectively in each of the cylinders 41. Each piston 42 bears on the radially inner surface of the cam 3. The cylinder block 4 has a central bore through which it is engaged around the tree 2.

The distributor 51 is adapted to apply in a controlled manner a fluid under pressure successively on each of the pistons 42, more precisely in the internal chamber of the cylinders 41 adjacent to the pistons, so that the successive support of the pistons 42 on the lobes of the cam 3 causes the relative rotation of the cylinder block 4 and the elements which are linked to it with respect to the cam 3 and thus to the housing 6 or vice versa. To this end, there is an asymmetry between the number of lobes formed on the cam 3 and the number of associated pistons 42 located in the cylinder block 4. The distributor 51 is surmounted by a distributor cover 52 according to a well-known architecture of the skilled person. In operation, the cylinder block 4 is supplied with pressure via the distributor 51, which causes successive and alternating movements of the pistons 42 to exit and return in their associated cylinders of the cylinder block 4, and thus causes a relative rotational movement between the cylinder block 4 cam 3 and the cylinder block 4.

The cam 3 being fixed and connected to the casing 6, it is here the cylinder block 4 which is rotated, as well as the elements which are connected in rotation, in this case the shaft 2 and the differential 1.

FIG. 1 shows a schematic example of a differential structure. The differential 1 comprises a differential case 11 already mentioned above, rotating satellites 12 mounted on each axis 13 connected to the differential case 11 and cooperating with each other. with planet gears 14 and 15 each rotatably connected with a shaft, respectively 16 and 17. The differential housing 11 may also be referred to as satellite gate or differential cage terminology. The pinions 12, 14 and 15 are typically bevel gears, cylindrical or helical. FIG. 1 shows a differential with bevel gears; it is well understood that the invention is not limited to such a differential structure, and adapts to other differential structures among which there may be mentioned the differential commonly referred to as "Torsen".

The operation of such a differential is well known and will not be repeated in detail here. However, it is clearly understood that the differential housing 11 is rotated by the hydraulic apparatus, which thus makes it possible to drive in rotation the two shafts 16 and 17, for example two shafts of wheels arranged in the shaft 2 which is typically hollow, while maintaining the advantages of a differential and thus allow different speeds of rotation for the shafts 16 and 17 and thus allow for example a vehicle equipped with such an assembly on the same axle to make turns.

The distributor 51, the distributor cover 52, the cylinder block 4 and the shaft 2 delimit an internal volume 54 comprising fluid supply ducts of the cylinder block, which are therefore necessarily associated with sealing elements, for example, for example dynamic joints. Figure 2 shows a detailed view of a section of Figure 1 on which the internal volume 54 is represented by hatching.

When the hydraulic apparatus is not used to drive the differential 1 in rotation, it is typically not supplied with fluid, which can lead to significant friction and wear at this internal volume and the elements. associated sealing. The system thus advantageously comprises independent oil supply means of this internal volume 54 delimited by the distributor 51, the distributor cover 52 the cylinder block 4 and the shaft 2, making it possible to ensure its lubrication and cooling even when the hydraulic unit is not in operation, which avoids having to drown the system in the oil to minimize losses. Examples of such situations are the case of a hybrid vehicle having a front axle driven by a main engine and a rear axle corresponding to shafts 16 and 17 for which hydraulic assistance can be actuated by means of the apparatus. hydraulic system associated with the differential 1. The lubrication is typically performed via a conduit 55 linking the internal volume 54 to a reserve of oil formed in the housing, the duct may for example be arranged in the shaft 2, in the distributor cover 52 or in the distributor 51. The shape of the duct 55 may vary according to the machining constraints resulting from the geometry of the different parts; one can for example realize a single oblique linear conduit instead of two holes as shown. Several conduits 55 can also be made to improve the lubrication, for example when the shape of the internal volume 54 implies that lubrication via a single point of entry would not be sufficient.

The duct 55 may be supplied with oil, for example by means of a scoop 56 typically made by milling, in order to recover oil projected onto a wall by a rotating part, or by being connected to a housing base, in order to to recover oil that would collect there, or by means of any other suitable oil supply system. The hydraulic apparatus as shown further comprises a groove 57 provided on the shaft 2 or in the center of the distributor 51 so as to provide an oil passage between the distributor 51 and the shaft 2 and thus allow the lubrication of the contact surface between the distributor 51 and the cylinder block 4 called ice plane. In addition, in the embodiment shown, the hydraulic apparatus comprises a positive displacement pump 32 mounted on the housing 6, and configured so that the rotation of a rotating element, in this case the differential 1 or more specifically its housing 11 causes a pumping effect, which takes oil from the bottom of the housing 6 so as to inject it into the internal volume 54 via supply conduits 33 made for example in the housing 6 , the cam 3 and the distributor cover 52. This pumping effect is for example obtained by cooperating a boss or a cam formed on the housing 11 of the differential 1 with a piston of the positive displacement pump 32. It is realized and an oil supply of the internal volume 54 from the start of rotation of the hydraulic apparatus, so as to ensure lubrication. The ducts 55 then allow for example an evacuation of the oil which is injected into the internal volume 54 by the positive displacement pump 32.

The hydraulic apparatus is typically powered by a variable displacement hydraulic pump, which can be selectively driven by a primary engine of a vehicle, typically a thermal or electric engine.

Figure 3 shows a sectional view of another embodiment of a system according to one aspect of the invention.

In this embodiment, the cam 3 is rotatably connected to the shaft 2, the distributor 51 and the differential 1, while the cylinder block 3 is rotatably connected to the casing 6 and the distributor cover 52. the same way as above, the pressure supply of the cylinder block 4 via the distributor 51 will cause a relative rotational movement between the cam 3 and the cylinder block 4. The cylinder block 4 is here fixed and connected to the housing 6, c is the cam 3 which will be driven in rotation, as well as the elements which are connected in rotation, in this case the shaft 2 and the differential 1.

In the same way as before, considering a conventional differential structure arranged in the differential housing and driven in rotation, the hydraulic device can drive in rotation two shafts, for example two wheel shafts, while retaining the advantages of a differential.

In this embodiment, the lubrication and cooling of the internal volume 54 delimited by the distributor 51, the distributor cover 52 and the cylinder block 4 and a rolling joint 23 is achieved by means of two ducts 55 arranged in the cover of FIG. distributor 52 linking this internal volume 54 to the casing 6, so as to collect the oil from the casing 6 to lubricate and cool the internal volume 54. This duct is typically associated with a scoop 58, here made on the outer periphery of the distributor cover 52, for example by milling.

The embodiment shown in Figure 3 further comprises a groove 59 formed in the distributor 51 or shaft 2 so as to provide an oil passage between the distributor 51 and the shaft 2 and thus allow the lubrication of the surface contact between the distributor 51 and the cylinder block 4 called ice plane. This groove 59 thus has a function similar to the groove 57 shown in FIG. 1, the two embodiments being two alternatives.

In the same way as for the embodiment shown in FIG. 1, the supply of oil into the internal volume 54 can be achieved by means of a positive displacement pump taking oil from the bottom of the casing 6. , the pump effect being obtained through the relative rotational movement of the different parts of the hydraulic apparatus. FIG. 3 presents another alternative to this embodiment, in which an internal channel 35 is arranged in the hydraulic apparatus, so that during its rotation, oil from the bottom of the casing 6 is projected into said internal channel 35, and that by dynamic effect of the rotation of the various components, it is conveyed to the internal volume 54. A boss 36 and / or scoop is then advantageously arranged to cause this projection of oil in the internal channel 35 during rotation of the rotating part of the hydraulic apparatus. According to another variant, helical grooves are made on the outer periphery of the shaft 2, so as to connect the internal volume 54 to the internal volume of the housing 6. The shaft 2 is rotating, its rotation will cause a contribution oil from the casing 6 to the internal volume 54, the helical grooves indeed to achieve this contribution by a screw end effect. It is understood that these different variants can also be applied to the structural example shown in Figures 1 and 2. In order to maintain a desired volume of oil in the cam 3 when the system is rotating, a retaining plate oil 31 is advantageously fixed on the open side of the cam 3, that is to say the end opposite the end by which is contiguous and rotatably connected to an element of the system. This oil retaining plate 31 retains a layer of oil in the cam 3 as it starts to rotate, the oil being centrifuged on the walls when the system is rotating, which avoids having to drown the system. in the oil to minimize losses. In addition, in operation, the oil leaks of the pistons come to replenish this restraint.

FIG. 4 shows a variant of the embodiment shown in FIG. 3, comprising additional rotation drive means of the differential 1. The structure of the differential 1 is also shown diagrammatically in this figure in a manner similar to FIG. 1.

In this embodiment, the mobile assembly comprising the shaft 2, the differential 1 and the cam 3 is connected to a drive shaft 7 via a gear 71 cooperating with teeth 72 arranged on the outer periphery of the cam 3.

Thus, the differential 1, and therefore the two shafts 16 and 17 can be rotated by the hydraulic apparatus, by the drive shaft 7, or by the combination of the hydraulic apparatus and the shaft. training 7.

The drive shaft 7 is for example a secondary shaft gearbox. It is well understood that this variant comprising additional rotation drive means of the differential 1 can also be adapted to the embodiment shown in Figure 1; the teeth 72 are then not arranged on the cam 3 which is fixed, but on an element connected in rotation to the differential 1, for example on the differential housing 11, or on a ring mounted on said housing 11. Such a system in which the rotational drive of the differential 1 can be achieved either by means of a hydraulic apparatus or by means of an additional drive shaft also makes it possible to perform a function of energy recovery by means of the apparatus when the latter is coupled to one or more accumulators on a single axle. In addition, such a system also makes it possible to carry out a two-mode transmission, for example a first mode in which the drive speed is slow, which typically corresponds to a working configuration for a construction-type or agricultural machine, and a higher speed mode typically corresponding to a road travel configuration.

Indeed, as previously indicated a hydraulic device can operate as a pump or as a motor. When the drive is performed by the drive shaft 7, the latter then drives the cam 3 or the cylinder block 4 in rotation, which causes an input and output movement of the pistons 42 and causes an operation of the hydraulic apparatus as a pump, which causes a circulation of fluid, which can advantageously be used to charge one or more hydraulic accumulators, and thus perform a function of energy storage.

It is well understood that such energy storage function can also be achieved by means of a hydraulic apparatus as shown in Figures 1 or 3 above, mounted on a driven axle of a vehicle.

FIG. 5 shows a particular embodiment of an assembly associating a differential and a hydraulic apparatus according to one aspect of the invention.

In this figure, there is shown an overview of an axle comprising a differential 1 coupled to a hydraulic apparatus as described above, and two wheel supports 18 and 19 rotated respectively by the shafts 16 and 17.

The differential 1, and more generally the rotating elements are here linked to the housing by means of a ring of balls 61 mounted around the differential housing 11, and thus forming a bearing of the type of four points of contact. The bearing thus formed has a diameter substantially equivalent to the internal diameter of the cam 3, which is therefore much greater than a conventional bearing mounted around the shaft 2. Such an assembly thus has a bearing of large diameter and comprising a significant number of logs, which supports high loads.

The cam 3 can then form a raceway for this ring of balls 61. FIG. 5 also shows for each of the wheels 18 and 19, respectively: a wheel spindle 81, 91 carrying the wheel, a train gearboxes 82, 92, respectively disposed between the shaft 16 and the wheel spindle 81, and between the shaft 17 and the wheel spindle 91. These gear trains 82 and 92 optional make it possible to achieve an advantageous additional reduction ratio. in the case of vehicles having very low speeds of displacement, or a decentering of the wheel with respect to its shaft, for example in order to position the center of rotation of the wheel below the shaft on which it is mounted in order to make a crossing vehicle.

In the embodiments with rotating cam and fixed cylinder block 4, the pistons 42 of the cylinder block 4 can advantageously be retracted into their respective cylinders 41, which has the effect of disengaging the hydraulic apparatus, and passing it in a Freewheel configuration. The differential 1 can thus rotate freely. Other variants to obtain a freewheel configuration can of course be exploited, in particular by separating the cylinder block 4 in its rotational movement relative to the casing 6 in the rotary cam assembly shown in Figure 3, or in the disconnecting from the shaft 2 in the fixed cam assembly shown in Figure 1. The assembly comprising the shaft 2 and the differential 1 can then rotate freely, and is in freewheel configuration relative to the hydraulic device associated. The present invention thus makes it possible to drive several wheels of the same axle by means of a single hydraulic apparatus, these wheels being coupled by means of a differential, which allows the use of a vehicle equipped with a such device in various conditions. Since the hydraulic unit is a radial piston and multilobe cam hydraulic unit, it operates at low speed and produces high torque.

The shafts 16 and 17 are typically driven at the same speed as the differential box 11, and the wheels mounted on the shafts 16 and 17 in the absence of reduction between the shafts 16 and 17 and the associated wheels, which allows to obtain a better yield than a conventional assembly comprising multiple stages of reduction.

In addition, a system according to the invention requires a small footprint compared to conventional systems using independent hydraulic devices for each wheel, and can adapt to differential structures commonly used in the automotive field and low cost.

Claims (9)

REVENDICATIONS1. Assembly comprising a differential (1) linking a first (16) and a second (17) output shaft, said differential (1) comprising a differential case (11) comprising case gears (12) adapted to cooperate with gears (14, 15) connected to said output shafts (16, 17) and thus driving said output shafts (16, 17), said assembly being characterized in that it comprises a radial piston hydraulic apparatus coupled to said differential, said apparatus hydraulic system comprising - a distributor (51) and a cam (3) multilobe defining a first set, - a cylinder block (4) defining a second set, one of said sets being mounted fixed in rotation relative to the differential case (11 ), and the other of said sets being rotatably mounted relative to the differential case (11) so as to allow the rotation of the differential case (11) by said hydraulic apparatus. An assembly according to claim 1, wherein said hydraulic apparatus comprises a dispenser (51) surmounted by a dispenser cover (52), an inner volume (54) being defined by the dispenser (51), the dispenser cover ( 52), the shaft (2) and the cylinder block (4), said internal volume (54) being supplied with fluid by a conduit (55) arranged to allow the lubrication and cooling of this internal volume (54) . 3. An assembly according to claim 2, further comprising a casing (6) defining an internal volume of casing bathed in oil, one of said first and second sets being movable relative to the casing (6), and comprising means adapted so that the rotation of said assembly relative to the housing (6) causes an oil supply of the internal volume (54) by removing oil from the housing (6) via internal conduits connecting the internal housing volume and the internal volume (54). ). 4. An assembly according to one of claims 1 to 3, wherein said assembly mounted fixed in rotation relative to the differential housing (11) comprises a toothing (72) adapted to cooperate with a drive shaft (7) so to allow a drive of said output shafts (16, 17) by the drive shaft (7). 5. The assembly of claim 4, wherein said toothing (72) is arranged on the outer periphery of the cam (3), so as to cooperate with a driving shaft pinion (7). Assembly according to one of claims 4 or 5, wherein said hydraulic apparatus is connected to one or more hydraulic accumulators adapted to perform energy storage. 7. The assembly of claim 6, further comprising a drive shaft (7) adapted to drive the output shafts (16, 17). 8. An assembly according to one of claims 1 to 7, wherein the first set is movably mounted on the differential housing (11) and the second set is fixedly mounted on the differential housing (11), said cylinder block (4). ) comprising a plurality of pistons (42) adapted to be retractable to disengage from the cam (3) and thereby set the hydraulic apparatus to freewheel configuration in which said first and second sets are free to rotate. one with respect to the other. 30 9. An assembly according to one of claims 1 to 8, wherein said differential housing (11) comprises a ring of balls (61) forming a bearing around said differential housing (11) and the binder to the other of said sets .10. An assembly according to claim 9, wherein the cam (3) forms a raceway for said bead ring (61). 11. An assembly according to one of claims 1 to 10, wherein the first and second output shafts (16, 17) each rotate a vehicle wheel. 12. An assembly according to one of claims 1 to 11, wherein said hydraulic apparatus is supplied with pressure by a variable displacement hydraulic pump adapted to be selectively driven by a primary engine of the vehicle via a transmission.